# Lobo Pup Twin 1.6 cc diesel



## GailInNM (Aug 24, 2009)

NOTICE: A COMPLETE REDRAW WAS DONE WITH MANY CHANGES MADE ON 12/30/09. ALL THE DRAWINGS IN POSTS 1 & 2 HAVE BEEN UPGRADED TO THIS VERSION 2. CONSTRUCTION OF PARTS THAT HAVE MAJOR CHANGES IN THEM BEGINS AT POST #162 AS WELL AS ALL DIALOG REGARDS VERSION 2.


With the PMC IMP project complete I started sketching on a new engine. This one is an original design and all drawings for Lobo Pup Twin will be published in this thread. This will simplify the Work In Progress descriptions as I had to use a lot of text on the IMP project as the drawings were not available for free download. The drawings will be attached as PDF documents on the first three posts of this thread. It takes three posts because of the attachment limitations of this site.

Since this engine has not been built, there will be revisions to the drawings as the build progresses. A record of these changes will be documented in these first three posts as the drawings are updated. The initial release of each drawing will have a REV of --, and later revisions will be A,B......

There are sure to be revisions. I am not a great draftsman, so I know there will be omissions and errors. I have done enough drawings and engine designs that I do not expect that there will be a lot of these. I expect the engine to run as I have not had one of my engine designs that did not run, at least not in the last 15 years or so. Some did take a bit of tinkering however.

After the build is complete, the drawings will be available in DWG or DXF format for anyone who might be interested in using them in CAD to modify for their own purposes.

The drawings carry a copyright notice with the copyright released to the public domain for non-commercial purposes. This means that you can copy, modify, distribute or publish as long as there is no charge or profit from doing so. The only purpose for this copyright is to discourage people from selling copies of them.

Because many of the techniques used for construction as the same or similar to those used on the PMC IMP I will probably make reference to the posts there. This just because I am lazy and would rather build than type. The link to the main thread is:
http://www.homemodelenginemachinist.com/index.php?topic=4422.0
but if I make reference to anything I will provide a direct link to the post involved.

The general specification can be seen in the following photo. It is the same as Page1.pdf that is attached.
Pages 1 to 4 are attached to this post. Pages 5 to 8 are attached to the next post.

Gail in NM








View attachment Sheet1E.pdf


View attachment Sheet2E.pdf


View attachment Sheet3E.pdf


View attachment Sheet4E.pdf


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## GailInNM (Aug 24, 2009)

The general design considerations were to make a fairly low tech twin of fairly small displacement. The design would be considered fairly conventional - if we still lived in 1955. The stroke/bore ratio is 1.17, a little long by todays standards, and a little short for 1955. A 3 piece crankshaft is used to avoid having split big ends on the connecting rods. The center two crankshafts are permanently assembled to form one crankshaft which carries both crank pins. The front crankshaft is driven by engagement with an extended front crankpin. Both crankshafts are running in sealed ball bearing races. The bearings each have two Teflon seals. This is done to isolate the primary compression space of the two cylinders and to seal the front primary compression space from the outside world. Teflon seals were chosen as I did not know how rubber seals would react to the ether in it fuel. They are also a standard bearing in the radio control car world and are readily available at low cost. 

There would be nothing wrong with running both the center and front crankshafts in plain bearings by removing the bearing cavities in the center bearing housing and the front bearing housing. If the crankshafts are well polished, they would be fine in 6061-T6 aluminum. 

The timing is fairly conservative so this is not going to be a high speed engine. Top RPM is expected to be in the 10,000 range. As with all side port designs with the crankshaft on the cylinder centerline, there is no favored direction for the engine to run.

The crankcase is can be switched front to back at assembly so the exhaust and intake can be reversed. This opens up another possibility of extending the rear crankpin so it is the same as the front crankpin and replacing the rear cover with a second front crankshaft and front bearing assembly. Then the engine would be double ended. Direct drive tether car racing anyone?

Gail in NM


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## GailInNM (Aug 24, 2009)

-
Plan Revision Status
12/30/2009 Complete redraw. All drawings updated to REV D, which is Version 2 of the Lobo Pup Twin.
         Version 2 begins at post #162.
01/05/2010 O-Rings added to Front Bearing Housing and Rear Cover to eliminate gaskets.
         Sheets 4,7 & 8 changed to reflect this but Drawings left as REV D
2/09/2010  All drawings updated to REV E dated 2/09/2010. These drawings are the final set for the Mk2 version
         and reflect the "as built" of the Lobo Pup Twin MK2. 

View attachment Sheet5E.pdf


View attachment Sheet6E.pdf


View attachment Sheet7E.pdf


View attachment Sheet8E.pdf


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## GailInNM (Aug 27, 2009)

I think the drawing package is complete. Probably wrong in places, but complete. All the drawings are contained as PDF attachments in posts 1 and 2. Since the first release on 9/24, a general arrangement drawing has been added and a copule more small parts added to page 7. For you CAD experts, please don't laugh too hard. Snickering is OK, but no LOL.

Whats in a Name?
For those not living in the Southwest USA, the Lobo may not be a familiar name. The Lobo is the Spanish name for wolf, and in particular refers to the Mexican Grey Wolf. The Lobo has many of the same traits as model engine builders. It is a solitary animal, seldom seen with others of it's kind except during mating season, or in our case the occasional model engineering show. It is an endangered species, but with it's reintroduction to the wild it is making a little bit of a comeback, although less than 100 exist in the wild. 

As related to my hopes for this engine, the Lobo is known for being a steady runner. Not the fastest, but very steady.

As related to me. When things go wrong in the shop, I go out the top of the sand dune that I call a back yard and howl at the moon when it is up, the stars when it is not, and otherwise just for the fun of it. Unlike the Lobo I almost always have a companion when I do my howling, my 3 year old Papillon shop dog who looks nothing like a Lobo, but does enjoy the howling with me. 

With all the preliminaries out of the way, it is time to start making chips. First up will be the crankcase. I will start it either this evening or in the morning as personal matters are going to eat up most of the rest of today. Then it will be my time to howl.
Gail in NM


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## arnoldb (Aug 27, 2009)

Really looking forward to this combined design/build Gail - Thank you for your effort :bow:

Regards, Arnold


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## GailInNM (Aug 30, 2009)

With the planned personal items out of the way plus two family emergencies (two adult offspring, two emergencies) I finally got started on the crankcase. 

Sawed off a piece of 1-3/4 square 6061 extrusion and then squared it up and face milled it to the major dimension of the crankcase.









After making a rough sketch of the holes on the crankcase, I center drilled, drilled and tapped the 12 0-80 holes and the 8 2-56 holes. The rough sketch is so I would not put the 0-80 hole pattern on the top edge on one end and the bottom edge on the other end. I like to get all the tapping out of the way as early as possible as a broken tap is a difficult to repair error and very irritating if it occurs after a lot of machining is done. It can become a real possibility if you are not used to doing 0-80 holes. I also put a center hole in location for each cylinder and on both ends of the crankshaft bore for setup purposes for boring those holes. All holes were drilled using the DRO on the mill for location.









Off to the lathe to bore the hole for the crankshaft assemblies. The blank was set up in the 4-jaw chuck using a wiggleer and a dial indicator to indicate the center of the hole to be bored. Notice the strips of soft aluminum under the jaws to protect the surface of the part. The bore was rough drilled with a 1/2 inch drill which is the largest I have.









The hole opened up the a short stiff boring bar that would just fit in the 1/2 inch hole and the part is now ready to go back to the mill where I will put the 0.118 hole in the bottom and bore the cylinder mounting holes with a boring head. The crankshaft bore was done first because I did not want any holes into that bore that might distort that bore by having an interrupted cut.









Gail in NM


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## GailInNM (Aug 30, 2009)

Drawing changes:
Page7A replaced Page7 on 8/27/09 with added parts
Page5A replaced Pace5 on 8/30/09 With missing dimensions added and correction to drawing on intake port.

Gail in NM


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## GailInNM (Aug 31, 2009)

Time to do more holes in the crankcase . I started with the holes for the cylinders.

I moved the crankcase from the lathe to the mill. Started by drilling the holes 31/32, which is 1/32 under teh finished hole size. I had my boring head still set up for 1/2 inch hole from the last time I used it, so I bored the holes to 1/2 inch diameter using it. If it had not been set up, I probably would have reamed the holes.









Flipped the crankcase on end and center drilled, drilled and reamed the 0.156 for the fuel distribution passage. The only reason I reamed the hole is that my reamer leaves less of a burr on exit than a drill bit does, so there will be less to deburr in the 1/2 inch holes when I get to that step.






Then on to the clearance hole in the bottom for a 4-40 screw and the counter bore of the hole so the screw will set flat. Counter bore depth is not critical. Calculates out to be about 0.018 deep with a 1/4 inch end mill, so I cut it 0.020 deep. The edge can get blended when the bottom of the crankcase is shaped to a half round.









Gail in NM


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## GailInNM (Sep 3, 2009)

All the holes in the crankcase that can be reached have been bored, drilled and tapped as required. Now it is time to start shaping the outside of the crankcase.

First up is to get rid of the bulk of the extra metal. A 1/2 inch endmill is used to rough out the profile. 
An 1/8 inch endmill is used to cut the exhaust openings.









The venturi mount hole is center drilled, drilled through to the 1/2 inch bore with 0.156, and opened up to 0.228 to almost full depth. Then the hole is tapped 1/4-40. I got about 5 full threads.









I had drawn a step between the mounting lugs and the cylinder block part of the crankcase. It appears on all the initial release drawings. I knew it didn't look good when I was drawing it, but now that it is committed to metal it really looked ugly. I had thought about several ways to blend it using a ball end mill, but wanted something that would not take a special tool in case someone else wanted to build a copy of this engine at a later date. So I decided to just use a simple 45 degree bevel. I put the crankcase in a vee block to hold it at 45 degrees and then milled away the offending bit of metal with a 1/4 inch endmill. I positioned it all by eye for the first side and then flipped the crankcase over and did the other side.









Gail in NM


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## deere_x475guy (Sep 3, 2009)

Gail this is going to be a good one to watch, thanks for posting. I haven't messed with any RC engines for a long time now....maybe someday I will have the time to get back into it. Your plans are easy to read, the only thing I noticed was a misplace hole in the one your your circular patterns (it's sitting outside of the part).

I am looking forward to seeing this one run!!, 

PS page 7a for the gasket


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## GailInNM (Sep 3, 2009)

Thanks Bob.
I found the hole you were referring to and corrected it on the master.

I have several minor corrections on the masters and when I collect enough of them I will update the PDF's. All the corrections to date have been minor, so would not cause any one a problem if they are following along on the drawings.

When it is done I will repost all the drawings "as built"
Gail in NM


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## deere_x475guy (Sep 3, 2009)

Your welcome and good job, I know it's not an easy task to create drawings when you know others will probably be building from them. This at least is true for those of us on the board that are just now getting to do them. I took 4 years of drafting in high school but the lessons are pretty much long gone. They are starting to come back a bit as I do a few more drawings. I kept finding missing dimensions as I went along and then when I built a second one from my own plans I found the rest of the missing dimensions....Maybe someday..


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## cobra428 (Sep 4, 2009)

Nice Gail,
Man you work fast! Interesting build
Tony


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## GailInNM (Sep 4, 2009)

Bob,
I learned a long time ago that I was not a good draftsman. For the last 20 years of my working life I had a several very good design draftsmen, one at a time, working for me who could clean up my rough drawings. That included everything from things on napkins from the pub to mostly ACAD sketches that were to scale, but frequently had only a few dimensions on them for reference purposes. They saved my butt more often than not.

Tony,
Thanks for the interest. 
As far as working fast, it helps a lot when you have spent the previous two weeks drawing the parts. When I design, I am always thinking about how I am going to make the part, and I design the part to suit the tools and tooling that I have. Where possible I try to design so others can build also with a minimum amount of tooling required. So, when I start to make a part, I already have all the processes in mind and the dimensions are firmly embedded in my head. I typically work in imperial fractions where ever possible. Suits the tooling I have and makes dimensions easy to remember. 

Gail in NM


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## GailInNM (Sep 4, 2009)

Now back to the crankcase.

I have been using the bottom of the crankcase as a square reference to clamp everything while I did all the other features. Now it is time to get rid of all the extra metal there. I used a CNC mill to round the bottom of the crankcase, but I have rounded crankcases in the past on manual machines by mounting on an arbor and either using the arbor in a Spindex and milling a bunch of flats to be blended with a file or by planning with a wide parting tool held 90 degrees to the normal mounting and racking the carriage on the lathe to plane the section round while rotating the spindle a little at a time. All three methods take about the same amount of time, but with the CNC I can eat lunch while the mill is doing it's thing.

After the bottom is rounded, it is easy to reach the beams to drilll the mounting holes.









Then on to clean up. There are internal burrs where the cylinder block bores meet the crankcase bore and where the intake passage meets the cylinder bores.  

For the inlet passages I just run a drill bit through with my fingers, first from the end and then from the side of the crankcase. Then repeat a couple of times. 

For the cylinder block bores and crankcase bore, I use a Flex-hone, not as a hone, but as an abrasive brush or file. I use one that is under size and just work it by hand. A piece of abrasive paper of 400 grit or so wrapped around a wooden dowel will work as well. 

I rough cleaned the crankcase at this point, but the plug for the access hole to drill the internal intake passage still needs to be plugged before the final clean up.

At his point the crankcase looks like this.


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## kustomkb (Sep 4, 2009)

Great work Gail,

Nicely laid out WIP too.

Thanks for posting.


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## arnoldb (Sep 5, 2009)

That's coming along great-guns Gail - a very good job :bow:

Thank you, Arnold


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## Maryak (Sep 5, 2009)

Gail,

You do beautiful work. :bow:

Best Regards
Bob


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## PhiberOptix (Sep 5, 2009)

Gail

Another outstanding thread, 
great pics along with the write up and drawings

top notch :bow: :bow:

regards
Andy


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## GailInNM (Sep 6, 2009)

Kevin, Arnold, Bob and Andy,
Thanks for your kind comments and for following along with me on this journey. It means a lot to know that right or wrong there are people who are interested in what I am doing. 

To finish up the crankcase, all that is needed is to plug up the hole in the rear of the crankcase that was used for access to drill the internal intake passage. That plus some work with some abrasive paper later IF I want it to look better.

The plug is just a section of aluminum rod turned to fit the hole with the length so that it does not protrude into the 1/2 inch bore for the cylinder sleeve. Actually it could intrude on the bore a little bit without causing a problem as the sleeve is cut away there for the transfer passage.

With the bit turned, a hole is cut in a piece of thick paper and the paper is marked so the hole in the crankcase is aligned roughly over the hole. The paper is then marked around the crankcase. The paper will act as a spacer so the plug will protrude a little bit from the crankcase when installed. After cleaning both the plug and the hole in the crankcase with solvent so there is no oil on them, a small amount of high strength Loctite is applied to the plug and the plug inserted into the crankcase. Then the crankcase is set on the paper spacer and the plug is pushed from inside the crankcase so it it touching the surface the paper is on. Go do something else for a while as the Loctite cures.









After the Loctite is cured, the plug will be sticking out of the crankcase a little bit because of the spacer. Clean a file and file the offending bit away so it is flush. I use a 6 inch single cut mill bastard file. The a quick rub on 400 and 800 grit abrasive paper with a little bit of water or oil on it and the plug disappears. 









Gail in NM


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## ANIMATE (Sep 6, 2009)

Great Job Gail .......... :bow: keep up the great work


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## GailInNM (Sep 6, 2009)

Thanks for the kind comment Gordy.

With the crankcase finished, it is time to start filling it up. First up is the connecting rod, sheet 3-1. 

The connecting rod is selected as the first item as the holes in it are reamed, and there is not much that can be done about the hole sizes. By making it first, we can offer it up to the crank pins on the crankshafts to test their size, and those we can do something about. 

I made the connecting rods on the CNC mill. If I were making just one I would normally do it manually, rounding the ends with a file and filing buttons. Doing two, it takes about the same time either manual or CNC, but I like to have a spare so that makes three, and now CNC is quicker. Those with keen eyes will notice in one of the photos that I flipped the blank over when cutting the profile, so now I have six. This is because I was sketching on the back of an envelope last night and have an idea that may be able to use a couple more of them. Once I am this far, why not.

The connecting rod and the rounding of the crankcase bottom will probably be the only parts where I use CNC. It is certainly not essential, but since I have it I use it to save time.

The connecting rod is about the only part that I am fussy about the material. It is highly stressed and needs to have good bearing qualities on the unhardened steel crankpin. 2024 aluminum is my material of choice for this.

I started off with a piece of 1/4 X 1/2 a little over 4 inches long. Sitting it on a parallel, I cleaned up the surface and profiled three rods along the edge of the strip and relieved the rod between the ends so the rod will not rub on the crankdisk. Flipped it over and did the same thing to the other edge.










I sawed the rods apart on a bandsaw. A pocket was cut into a softjaw to hold the part. The part was faced off and the rod section between the ends relieved. The holes are "drilled" using a 3/32 and 5/32 end mill. Like most end mills, the ones I have are slightly under size and this leaves a little bit to bring the holes to size with a reamer. 









After reaming, the parts are cleaned up with some 400 grit abrasive paper to remove burrs and each hole is lightly touched with a small hand held countersink to remove any burrs and sharp edges. 

Gail in NM


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## GailInNM (Sep 7, 2009)

Before making the rest of the parts that fill up the crankcase bottom, I made the four jigs and fixtures that are required to machine the parts and assemble them. Two are the split offset collets that are used to machine the crankpins on the center crankshafts. They are shown on sheet 3 of the drawings and are identical except for the bore size. 

On sheet 4 is a simple U channel used to align the crankpins at 180 degrees and the only critical dimension on it is 0.281 depth, so no machining photos are included. 

Last,also on sheet 4, is a tool to position the center crankshaft assembly in the crankcase so the 4-40 screw that locks it in place can be inserted. While it is not necessary, it will probably save time and frustration during assembly. Particularly on the third or fourth time I disassemble and reassemble it. No machining instructions are given for it. The 0.188 slot in the side is to allow the connecting rod to pass through and can be about anything you want as long as it is at least 0.188 wide and full depth.

I am detailing the split collets as many machinists have not made or used them. You can get by with out making them and setting everything up in a four jaw chuck, but I like the collets so I make them. 

Two blanks are turned up from 1 inch diameter stock on the lathe. The lip is just to keep the split collet from sliding into the lathe collet or chuck. Then it is over to the mill where the blank is held in a vee block in the vice and indicated to locate the center. 









The holes are center drilled and drilled in each collet. The 0.188 hole is just for stress relief and could be omitted as the collet will only be used for one or a few parts. The other hole on one was drilled and reamed to 0.250 to hold the rear half of the center crankshaft (3-3). On the other collet, the hole should have been drilled and reamed to 8mm, but i did not have a 8mm reamer, or even an 8mm drill. So I drilled under size with a 5/16 (0.313) drill and then opened the hole up with a letter "O" drill which is about 0.001 oversize. I think that it will work fine, but if I start getting a little bit of chatter when I start turning the crankpin I will just put a slip of thin paper in the hole with the crankshaft to increase the contact area. 






With rods that fit the holes inserted in the holes I shimmed the small rod to make the holes horizontal. A 0.063 shim is needed for the 8mm collet and a 0.031 shim for the 0.250 collet. They are not critical, so any scrap about that thick will work. 

A 0.063 thick by 2.5 inch diameter cutter was positioned over the top of the collet and lowered until a feeler gauge would just fit under it. Never lower the cutter onto the feeler gage as it is easy to damage a cutter. Either lower the cutter until the gauge will not slid under it, or position it low and raise it until the gauge fits. 









The rods are removed and the cutter positioned to the side. The cutter is lowered to the center line of the collet. This distance will be the thickness of the feeler gauge plus half the diameter of the collet plus half the thickness of the cutter. In this case, 0.025 + 0.500 + 0.031, or 0.556 inch. Position the cutter so the center line is at the back edge of the part. This way the cutter will be conventional milling. Unless you enjoy buying new cutters it is not a good plan to climb mill with this type of setup. I fed to depth and then moved along the axis of the collet to complete the cut.









I mark my split collets with the offset and the bore size. I have a box of them and occasionally end up using them for other projects.

Deburr the collets.
Here are the finished collets and the other two fixtures I talked about in the beginning of this post.









With all this shown, I sometimes just band saw the slot in. Does not look as nice, but works as well. 
Gail in NM


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## GailInNM (Sep 9, 2009)

First off, the drawing for the crankshaft assembly jig built in the lat post is wrong. I corrected the drawing before I made the part, so the photo is correct. I will wait until I have made the rest of the parts on sheet 4 before I post the corrected drawing. That way I can correct the other things I probably have messed up.

Next up is the Center Bearing Housing, part 4-2.
I started with 3/4 inch diameter 6061 aluminum. The end is faced and turned to 0.719 for a length of 0.75. The 0.719 diameter is sized to be a close slip fit into the crankcase using the crankcase as a gauge.

Now a 1/2 diameter hole is drilled to a depth of 0.75 to the point. The hole is opened up to 0.531 with a boring bar to a0.68 depth and the end if further opened up to 0.630 diameter for a depth of 0.197 for the bearing. Use a bearing to check for a close slip or light push fit.









The notches are milled in the end of the housing with a 1/16 end mill. Nothing critical about them. They are just to engage the prongs of the center bearing installation tool on sheet 4 so the housing can be rotated in the crankcase to line up the tapped hole.









Using a metal rule or strip of sheet metal, the housing is clamped in the mill vice with the rule inserted into the 0.063 notches and resting on the front jaw of the vice. I pressed it against a vice stop while clamping. Then the housing is center drilled, drilled and tapped 4-40.









After deburring and cleaning the housing, the bearings are started into the housing. A small amount of Loctite is applied to each bearing. I use Loctite 680, and put a drop on my work surface and then use a wire probe to transfer a small amount to each bearing.

The assembly was inserted into the milling vice and the bearings pressed into the housing. It does not take much pressure, but the vice jaws keep the bearing square while they are being pressed into place. The photo shows the bearings above the vice jaws surface, but that was only for photo purposes. The assembly was inserted deep enough in the jaws that the entire surface of teh bearing was in contact with the jaws.









After removing from the vice, any excess Loctite is cleaned off both the assembly and the vice jaws. 






Gail in NM


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## arnoldb (Sep 10, 2009)

Gail, thank you for the update 

A question/observation if you don't mind:

Near the start of the post you mentioned that the bearing fit must be close slip/light push, but when you install the bearings using the vice, you say "... the housing. It _does take much pressure_, but the vice jaws keep the bearing square while they are being pressed into place."
Is this a spelling mistake or did I drop off the wagon somewhere ?

Once again, thank you for this thread; I'm enjoying it very much.
Kind regards, Arnold


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## GailInNM (Sep 10, 2009)

Thanks Arnold,

I am glad you are enjoying the thread.

The post was in error. It should have read "it does NOT take much pressure...". I have corrected the post.

Never hesitate to ask questions or make comments. I make more than my share of errors. Corrections are the order of the day. So far, every drawing that I have built a part from on this project has at least one correction. Most have been minor. Some have been of the "You idiot, what were you thinking" class, and some to make the part easier to build. Input, like yours, is very valuable. When I am making a part, I know what I intended to draw, so that is the way I make the part. But, it may not be clear to anyone who might try to follow along.

I once had a fellow engineer who sent a drawing out to the shop to have a prototype part made. About an hour later the drawing came back with an envelope full of chips. He had dimensioned a hole larger than the part. 

Gail in NM


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## arnoldb (Sep 10, 2009)

Thank you Gail ;D



> I once had a fellow engineer who sent a drawing out to the shop to have a prototype part made. About an hour later the drawing came back with an envelope full of chips. He had dimensioned a hole larger than the part.


 Rof}

Regards, Arnold


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## Krown Kustoms (Sep 10, 2009)

looking good
I know I dont have to go far for a laugh. :big:
If I went by my plans Some of my parts would be all chips.
-B-


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## GailInNM (Sep 11, 2009)

Yesterday was supposed to be a LOBO building day. I had allocated 6 hours in the shop, and except for an hour to do a simple repair on a steam engine for someone else it was supposed to be all for the LOBO. As it turned out, someone else had "repaired" the engine before me and instead of turn and install one bushing, the engine had to be torn down twice to take care of all the damage. Seven hours into my six hour allotment of time it was all finished. Feeling severely abused, I ordered in dinner instead of cooking and then made up the blanks for the center crankshaft while waiting for delivery.

The center crankshaft is made of two parts, 3-2 and 3-3. After machining, they telescope together. One from each end of the center bearing assembly. They are Loctited to each other to form one piece. The blanks are simple turning jobs and one of them is drilled and reamed. The other is only center drilled. The only dimension that is critical at this point is the 0.315 diameter of 3-2. It is to fit the 8mm ID of the bearing, and should be tested with the bearing to be a close fit. Hard to see in the photos, but there is a 0.375 diameter 0.005 step next to the crankdisk to keep the crankdisk from rubbing the outer race of the bearings.









The center hole in 3-3 is not used and in only there to facilitate disassemble of the center crankshaft/bearing assembly in a later life of the engine should it ever be necessary. The hand written dimension in the background drawing are because I changed my mind on how everything will be assembled, and will be changed on the updated drawings. Either set of dimensions would work, the updated ones will just be a little bit neater.









Gail in NM


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## GailInNM (Sep 12, 2009)

With the center crankshaft blanks done it is time to do something a little bit more exciting, turn the crank pins. The only cardinal rule is the same one that is used anytime that off center work is being done. Never run the lathe under power until you have turned it over at least one rotation by hand. If we follow that rule it will save a lot of excitement.

First a blank is inserted into the split collet. If the split collet was made from any kind of cold rolled steel other than 1144 stressproof, then it probably closed up some when it was split. This is the natural action when the stresses are relieved on cold rolled steels. To insert the blank, it will be necessary to insert a wedge into the split to open up the collet. These wedges are more commonly known as flat blade screwdrivers. I like to leave a little space between the part and the collet to make it easier to measure the part with calipers while it is being held in the collet. The split collet is gripped in the lathe. If I am using a collet in the lathe to grip the split collet, the split on the split collet is lined up with one of the splits on the lathe collet. If gripping with a 3 or 4 jaw chuck, the split is positioned between two of the jaws. This is easily visible in the fourth photo.









After turning the lathe over by hand, the part is faced off to a thickness of the crank disk plus the length of the crank pin. The crankpin is then rough turned to about 0.010 oversize. I use a VBMT carbide insert with a 0.015 tip radius. I started out at about 1000 RPM and can take 0.050 depth of cut (0.100 on the diameter) with a slow feed on the lathe carriage. My lathe is quite rigid so it may be necessary to reduce this depth of cut on a light lathe. I cut the pin short by about 0.002 on these passes. My insert is set so the side cutting angle is at -2 degrees so the cutting edge angles away from the part. 









After measuring the pin diameter, I cut one half of the remaining stock one the pin using the same tool. Measuring again, I cut the remaining pin diameter away and continue the cut to the finished length of the crank pin. Then I retract the tool to face off the crank disk. At this point the connecting rod should just fit on the crank pin, but be a little bit stiff to turn. Then I use a parting tool with a square tip to clean out the radius left by the turning tool. I mark the radius to be cut out and the adjoining section of the crank pin with a permanent marker and then machine by inspection until the marker just starts to disappear on the shaft. I polish the crank pin with 600 grit abrasive paper supported by my 6 inch machinist rule. If the paper is flexible enough, it is easier to wrap the paper around the edge of the rule rather than to try to support the edge of the paper with the rule. After polishing, the connecting rod should just be able to hang like a pendulum from the crank pin under it's own weight. 






Second verse - same as the first. Just use the other split collet and change the length of the crank pin.









Gail in NM


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## arnoldb (Sep 12, 2009)

Gail, good progress 

And thanks for the handy tip about the rule and emery paper! 

Kind regards, Arnold


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## Maryak (Sep 12, 2009)

Gail,

Great work as usual. :bow:

Best Regards
Bob


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## GailInNM (Sep 12, 2009)

Thanks again for following along, Arnold and Bob.

At this point I test fitted the center crankshafts into the center bearing housing. The points to look for were that everything turned smoothly and that the rear center crankshaft did not protrude through the front center crankshaft. It should be slightly recessed or worst case be flush. 

Since all looked OK I inserted the mess into the crankcase from the rear and installed a connecting rod on the front, then slid the assembly forward and put on the other connecting rod. I approximately centered the assembly and rotated the rear crankshaft to top dead center. Then I engaged the crankshaft installation tool with the bearing housing and rotated it until the screw hole in the housing lined up with the hole in the crankcase. A visual inspection showed that the rods were centered in the cylinder bores and that at top dead center there was enough clearance to insert the piston wrist pin. So at least I don't have any major busts on dimensioning. No photos of all this as most everything takes place inside the crankcase where it is hard to see and near impossible to photograph.

The next post will be the assembly of the center crankshaft assembly and have photos of it. 

One small problem did show up. The Crankshaft installation tool worked, but it would have been much easier if the slot for the connecting rod were wider and on both sides. So the slot was changed from 3/16 to 7/16 wide and a second slot put on the other side. I also milled a small flat on the handle so I had a reference as to where the rotation was without having to look down into the cylinder bore. A swipe with a permanent marker would have worked as well, but I was already working on the tool in the mill.

I have updated tha master, but have not published it yet. I hope to publish all the current updates by next weekend. 

This is how the business end of the tool looks now.






Gail in NM


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## GailInNM (Sep 12, 2009)

Assembly of the center crankshaft assembly.

First a word about the use of Loctite to hold things together. Generally I make it a rule not to Loctite any parts together that might have to be disassembled later. This part only half violates this rule. The assembly can be dissasembled using heat as the Loctite gives up it's strength at 350 degrees F. This much heat will probably destroy the seals and/or grease in the bearings. In any event it won't do them any good. But, I consider this OK as the only reason that I can think of that this assembly would ever need to be disassembled is to replace the bearings. So if I am going to replace them anyway I am not going to worry about damaging them.

First clean the inside of the front half and the shaft of the rear half with solvent. Acetone or alcohol work fine. Notice the cotton swab in the second photo. Thats what it looked like after cleaning the bore of the front half of the crankshaft.

The front half of the crankshaft is inserted into the bearing assembly. I put it in the side of the bearing assembly that does not have the notches, but it really does not make any difference. 

Apply a high strength Loctite, I use 680, to the inside of the front half, being careful not to get any on outside or the bearing. I wiped a small amount of Loctite on shaft of the rear half and wiped all of it off that I could. This is to prime the shaft. I don't know if this does any good, but I do it anyway. The rear half is inserted into the front half with a twisting motion to distribute the Loctite. I hold a paper towel over the far end ot the front half to soak up any excess Loctite as it is forced out. Makes it easer to clean up. Before the rear half is inserted all the way I look to make sure there is no excess Loctite on the shaft that might get squeezed out and into the bearing. If there is any, wipe it off with a swab before seating the two crankshaft halves together. 









Now place the assembly int he crankshaft assembly jig and press the crankpins down on the flanges while pressing the bearing housing down against the bottom of the notch. At the same time make sure the crankshafts are fully inserted in each other. The crankpins are now at 180 degrees to each other. Take a break while the Loctite cures. After removing from the jig, it will look like the last photo.









Gail in NM


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## GailInNM (Sep 15, 2009)

I made the front crankshaft next. If I were building a plain bearing version, I would have made the front bearing housing first and then turned the crankshaft to fit the reamed hole in it. 

The Front Crankshaft starts off as a standard turning operation from 5/8 diameter steel bar. The only close tolerance section is the 0.236 diameter that fits the ID of the MR106-2TS bearing. That section should be polished to a close fit on the bearing. The transitions between the 0.203 to the 0.236 diameters and the 0.236 to 0.266 diameters has to be be squared up so the prop driver and a bearing will seat. I used a parting tool with a square tip the same way I did on the center crankshafts. A small center drill is used to create a center in the end of the shaft to facilitate removal of the thrust washer with a gear puller should it ever be needed. A bevel is machined on to the end of the shaft for starting the die to cut the threads.

A straight knurl is used to cut a spline on the 0.203 diameter, raising the diameter to between 0.206 and 0.209. It will depend on what your knurling tool is like. The knurl does not have to reach the shoulder of the 0.236 transition. The 10-32 thread is cut with a die for 14 full turns. With the jaws of my tailstock drill chuck retracted, I use the face of my drill chuck in the tailstock to keep the die square, advancing the drill chuck as I cut the thread.









After parting off with an allowance left to clean up the crankdisk to thickness, the crankshaft is reversed and the crankdisk is faced off to 0.094 thickness.









Moving to the milling machine, I put the crankshaft in the vice using a small aluminum vee block that I have made up with different size vee's to for jsut shuch a purpose. It's height is the same as my vice jaw height. The crankshaft needs to be clamped firmly, but not so tight that the hardened vice jaw might put a flat on the crankshaft. I have never had a problem doing this, but if it is a concern, but a piece of aluminum between the hard jaw and the crankshaft.

After indicating the crankshaft to locate the center, the crankshaft slot is milled to be a close fit on the center front half crankshaft crankpin. I used a 5/32 end mill and found that the slot was too tight so I offset the y axis by 0.001 inch and took a second pass. The crankpin then fit the slot smoothly. 









After deburring, the front crankshaft looked like this.









Gail in NM


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## arnoldb (Sep 15, 2009)

Good progress Gail 

Kind regards, Arnold


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## GailInNM (Sep 17, 2009)

Thanks for your continued interest and support Arnold.

The Front Bearing Housing carries the two 6 X 10 mm ball bearings that support the crankshaft. It is a straight turning job with the ends bored to fit the bearings and some mounting holes drill in it. The length needs to be fairly close so it will match the front crankshaft.

I started off with a one inch diameter bar of 6061 aluminum, faced it and drilled a 1/4 inch hole 3/4 inch deep. This is just a clearance hole for the 0.239 (6mm) crankshaft, so other than being centered it has no real requirements. Then the 1/2 inch nose diameter and the major diameter were turned. 









The end was bored for the ball bearing, using the bearing as a plug gauge. A small bolt with a nut on it that would fit through the ball bearing ID was used to remove the bearing as it was being test fitted.









After parting off with about 0.01 extra length to allow facing, the part was reversed in the lathe and faced off to length. The hole for the second bearing was then bored to size. 









Finally the housing was moved to the milling machine and indicated to zero. The part was supported on parallels for this. Clamping had to be done gently as the vice will deform the outside diameter if clamped firmly. Since the holes were only going to go through the 0.063 flange, I used a 1/16 end mill to drill the holes. This way I did not have to center drill and drill the holes. The holes were drilled using the coordinates on the drawing dialed into the milling machine. 









Just a little deburring of the holes and the housing is finished.

Gail in NM


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## vlmarshall (Sep 17, 2009)

Great work! I'm always glad to click on this thread when I see a new update.  ;D


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## zeeprogrammer (Sep 17, 2009)

I've been in such awe...I haven't been able to say anything.
Still can't come up with something to say.
Very interesting thread...well more than interesting...I'm learning a lot here.
Thanks Gail.
Gosh I hope I can make such good stuff someday.


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## GailInNM (Sep 18, 2009)

Vernon, 
I am glad that you are following along.

Zee,
Thank you for your kind comments.

I have been following your progress ever since you first started posting on HMEM. You have come along way since then. The only difference between you and me is that I have made a lot more mistakes (and scrap) than you have. I started hobby machining young and well before the internet. So, my beginner mistakes were private as I did not know any other hobby machinists. You make your mistakes public, and thanks to your sharing them you get immediate feedback as to what others think you might have done incorrectly. But ultimately, the way you learn is to keep at a part until you get one that works for you. Then move on to the next part.  Because you share your experiences, many others learn from you. I sometimes get caught up in the number of replies to my posts, but it is worth noting that there are about 30 to 40 times as many views on a thread as there are replies. And, most of the time, there are as many guests as members viewing a thread and online in the forum. 

Gail in NM


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## GailInNM (Sep 18, 2009)

While the 1 inch aluminum stock was in the lathe for the front bearing, I also turned the blank for the rear cover. So, they were sort of made at the same time, jumping back and forth between them since many of the operations were similar.

Started the rear cover by turning the two outside diameters and cleaning up the radius left by the tool using a parting tool so the cover would fit all the way into the crankcase.










After cutoff, leaving a bit to cleanup, the part was reversed in the lathe and the flange faced to thickness and the recess in the rear was bored. Then over to the mill where the six mounting holes were put in with the same setup used for the front bearing housing, and using the same method of using a 1/16 end mill and coordinate drilling for location.









d

A little clean up and the rear cover is finished.






Gail in NM


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## cobra428 (Sep 18, 2009)

As usual Gail,
Beautiful Thm:
Tony


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## arnoldb (Sep 18, 2009)

Thank you for the update Gail - lovely work Thm:

Regards, Arnold


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## cobra428 (Sep 18, 2009)

Diymania  said:
			
		

> Will be interesting to see how you´ll make the injectors and the injection pump.



 Rof} Rof} Rof} Rof} Rof} Rof} Rof} Rof} Rof} Rof}

Maybe I shouldn't laugh knowing Gail
Tony


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## GailInNM (Sep 18, 2009)

Thank your for the kind comments Tony and Arnold.

Diymania,
This is not a Diesel engine. It is a compression ignition engine. In the USA, Japan and several other countries model aircraft engines of this configuration are almost universally referred to as being a Diesel.  Since this is a model aircraft engine, I referred to it as a Diesel. If I go into a hobby shop that deals with model aircraft and ask for a can of fuel for a compression ignition engine I will get a blank stare. If I ask for a can of Diesel fuel, I will get what I want, because that is the way it is labeled. It's not right, but that's the way it is.

Most of the time I refer to them as compression ignition engines. I intended to put this information in my initial post, but forgot. 

And the real reason I called it a Diesel is because compression ignition would not fit on the subject line in the recent post column on this forum. As it turned out, neither did Diesel.

Gail in NM


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## vlmarshall (Sep 18, 2009)

GailInNM  said:
			
		

> And the real reason I called it a Diesel is because compression ignition would not fit on the subject line in the recent post column on this forum. As it turned out, neither did Diesel.


Ha, you're right... it does look like sad news, now that you mention it. ;D


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## cobra428 (Sep 18, 2009)

Diymania 
Sorry to laugh so hard. I work with a guy that has a sail boat with a diesel engine. I show him this site because he's an engineer and interested in all mechanical things. His comment to me was "they have carb's that's not a diesel you have to have injectors and they could never be made in that scale" My comment to him was "diesels where around long before injectors"
So Sorry again it just struck my funny bone
Tony
PS the engine was invented and named after Rudolph Diesel 1897 so to me it's a diesel if it runs on using compression for ign.


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## cobra428 (Sep 18, 2009)

Diymania,
My tougths exactly. I googled compression ign eng and it took me to diesels and a HCCI eng. HCCI does it with Propane. What exactly do they mean by "injecting" Carb is an injector or sorts  I've mess't with Radials and Opposed Aircraft eng (full size and models) 2 and 4 ciy's in model a/c, turbines and many car eng the same way. I never played with a Diesel in a truck, ship or train to know. 

Did Mr diesel have injectors in the 1870's????

Gail
Please.....Please.... A history leason! stickpoke

Tony


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## GailInNM (Sep 18, 2009)

Tony,
I do have a couple of good books in my library on the early Diesel engines, but would have to look for them. But from memory, and remember that I am an old man with CRS, here are some of the facts.

The first patent was issued to Rudolph Diesel in 1893 and his first operational demonstration engine was shown in 1897.

The patent was for direct fuel injection into the already compressed air in the cylinder, with the heat of compression providing the ignition. No air was injected with the fuel. The patent also covered the gradual injection of the fuel to give a more constant pressure in the cylinder providing a more uniform power stroke. 

Rudolph Diesel's engines did not use diesel fuel as we know it. All his engines ran on peanut oil, and it was not until after his death that petroleum oil was used as a fuel. I probably did try petroleum oil in his experiments as he tried many different fuels. I think that it was a powdered coal that he tried that resulted in an explosion that almost killed him. His patent referred to the fuel only as "oil" without defining what kind. One of the reasons for peanut oil was to stimulate the economy in the rural area that he had close ties to. Also petroleum oil was less abundant in his area.

Rather than injection pumps, he used high pressure air to force the fuel into the injectors, but no air was injected into the cylinder.

So, the Lobo Pup is not a Diesel as it does not use injection of the fuel into the compressed air in the cylinder. I use the term Diesel only to conform to the common usage in the model airplane community as practiced by both the manufacturers and end users of the engines. The smallest engine that I know of that has used injection has been about 1 cubic inch displacement (16cc). I don't remember the details on it, but I have the here somewhere.

Tony, I hope that this tell you a little bit about what you wanted to know. 

Back to machining. I am a better machinist than I am wordsmith. Of course that may not be saying much. 

Gail in NM


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## cobra428 (Sep 18, 2009)

Gail,
That said it all. Thank you my friend for the enlightenment. He did use injector from the beginning. I always thought that there was a carb involved somewhere in the history. Well what the heck do I know. Those engines run on marbles anyway :big:
Tony


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## GailInNM (Sep 20, 2009)

Thanks for your clarification Diymania. I pulled one of my favorite books on the subject and refreshed my memory before bed last night. It has a chapter on Diesel's early experiments. He went through a lot before he got any useful power out of an engine. My memory is kind of like dynamic RAM in a computer. If it is not refreshed regularly it loses the stored information.

On to making parts. This time it is the bits and pieces that go on the front crankshaft so it can be assembled with the front bearing assembly for a test fit in crankcase.

The only thing really necessary for this is the prop driver (7-1) but I made the prop washer (7-2) and the prop nut (7-3) also to get them out of the way.

The prop driver is turned from 6061 aluminum. The only critical dimension is the 0.203 bore as it is pressed onto the knurled portion of the crankshaft. My angle on the 0.500 to 0.594 transition does not agree with the drawing, but it can really be any angle. Mine is at 37 degrees because I have a VBMT insert in my tool holder. The insert has a 35 degree included angle and is set in the tool holder at 2 degrees so I can use it for facing as well as turning. By using that angle I could machine all the external surface and the angle with one setting and with out having to use the compound slide on the lathe.

Then the bore was drilled by first center drilling, drilling undersize, and finishing with a 0.203 diameter drill.









The bore was stepped out to 1/32 deep, and as the diameter if this only provides a runout area for the knurling tool in the next step I just set the diameter of this counter bore by eye and did not measure it. I used a straight knurl to face knurl the driver so it would bite into a prop and not slip. You can make different patterns on the driver if desired by running the knurl above or below center, or by using a diagonal knurl. See the article at http://modelenginenews.org/techniques/prop_drivers.html
for more information on this if you are interested.









To cutoff, I first plunged in at the 0.188 long dimension until I reached 0.34 diameter. Retracted the tool and moved over an additional 0.010 inch and to widen the cut. After plunging to the 0.34 diameter I moved back 0.005 inch and cut off, thus leaving a 0.34 diameter shoulder on the prop driver. This step is so the driver will bear against the inner race of the front ball bearing if the crankshaft is pushed back while starting with an electric starter.Otherwise it could rub against the outer race or the bearing housing. 









And a finished driver and a shot of the driver along with the prop washers and prop nut. I made two washers. One of them was chamfered for looks and a second one was made plain to use as a spacer if necessary for thin props. I cheated on the nut and used a commercial brass acorn nut because I had part of a box of them. Just a little bit of polish to knock off the oxidation as I have had them for at least 20 years. 









Gail in NM


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## zeeprogrammer (Sep 20, 2009)

GailInNM  said:
			
		

> Then the bore was drilled by first center drilling, drilling undersize, and finishing with a 0.203 diameter drill.



Hello Gail. I usually see "center drill, drill, and ream" - because drilling is not necessarily true or round. This is the first time I've seen finishing with a drill. Is the 2nd drill then acting as a reamer? Can one depend on that? Thanks.

Thanks for showing the knurling too. For me, that was a tip.


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## GailInNM (Sep 20, 2009)

Zee,
For this part reaming would have been a bit of overkill. Since this part presses on the knurled portion of the front crankshaft it is not necessary to have an excellent finish or even that the hole be round. I did want it to be reasonably to size. Drilling under size, in this case about 0.010 undersize, and then opening it up will size the hole to within about half a thousandth of an inch. Finish will be reasonably good. Not the quality of a reamed hole, but good enough in this case. 

I believe in only working to the tolerance necessary on a part. You probably noticed that I did not measure the counter bore I put in the prop driver. Eyeball accuracy was close enough. Not that I could not have measured it and put in the size I put on the print, but it would have taken extra time without improving the part. I would rather build more toys than expend unnecessary time. The old adage around a manufacturing plant was if you want to know the easiest way to do a job, give it to a lazy person to do. Well, I am one of those lazy persons.

Gail in NM


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## GailInNM (Sep 20, 2009)

With all the parts for the Front Crankshaft Assembly made it's time to put some more part together. 

Before committing to anything that is hard to take apart, one check is necessary. That is that the crankshaft fits through the installed bearings with a little bit showing between the bearing and the knurled portion of the crankshaft. The bearings are slipped or pressed into the front bearing housing and the crankshaft inserted. If the dimensions are spot on, there will be 0.004 inch between the inner bearing race and the shoulder of the knurled section. The actual amount showing should be between zero and 0.010 inch. Mine was about 0.006. 

If the shoulder is inside the bearing inner race the bearings will be in compression after pressing on the prop driver. This is not a good thing for the bearings.

If the shoulder is too far out of the bearing, then the crankshaft could slide back when starting and bind on the connecting rod. It would have to move back about 0.015 inch. This would only be during starting, so it would probably not be serious.

First photo shows the parts ready to test fit and the second photo shows the crankshaft shoulder protruding slightly through the bearing.









To begin the final assembly, if a bearing is slightly loose in the housing, it should be secured with Loctite in the same manner as was done for the center crankshaft assembly.  A sleeve is used to press the prop driver in place. Just needs to have a hole larger than the 3/16 diameter of the crankshaft and be long enough that the crankshaft will not protrude when the prop drrver is seated. Mine came out of the scrap bin and was 1/2 inch diameter. I used my milling machine vice to press the prop driver on to the crankshaft.  









And the assembled front end.





Gail in NM


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## GailInNM (Sep 20, 2009)

With the exception of the fuel system, all the parts below the top of the crankcase are now complete. So I made a test assembly of the parts to check for clearances. It all has to be taken apart so I can clean up the tooling marks and do any polishing that I might want to do, so it is mostly just slipped together.

First photo shows all the parts. The center crankshaft assembly is slid into place and the front connecting rod slid on. Then the center bearing assembly is secured with a 4-40 X 1/4 button head cap screw. The rear connection rod is installed. One area that I have screwed up before is the connecting rod to crankcase clearance. I had checked and double checked on this engine, but I still wanted to check. I could always relieve the crankcase a little bit if need be. Well I lucked out this time. Keeping the connecting rod centered in the cylinder bore, I rotated the crankshaft to the minimum clearance position and all was well as shown in the second photo









The other clearances that I wanted to check were the rear crankpin to the rear cover and the front crankpin to the front bearing housing. Sliding them in place I could look down the cylinder bores to inspect them. Any amount of clearance would be OK as the clearance on both areas will increase by 0.006 on final assembly with the gaskets in place. Then the engine was rotated to make sure there were no tight spots.

It's beginning to look like these lumps of metal might make an engine yet. ;D






Gail in NM


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## arnoldb (Sep 21, 2009)

> It's beginning to look like these lumps of metal might make an engine yet.


Gail, that and if I may add, it is turning into a lovely work of art as well. 
Thank you very much!
Kind regards, Arnold


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## ariz (Sep 21, 2009)

I'm with arnold, great working and documentation on this engine :bow:

thanks gail


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## vlmarshall (Sep 21, 2009)

I'm really enjoying this build... have I said that already? ;D


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## ANIMATE (Sep 21, 2009)

Gail it just gets better awesome job keep it going plzzz :bow: 
wiat till you start her up :big: the smell ................i just love that smell of a model diesel engine .......to me thats a real model engine ,
 thankz again keep it going :bow:


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## GailInNM (Sep 24, 2009)

Arnold, Ariz, Vernon & Animate: Thanks for the encouragement and support. 
I had some personal things to take care of the last couple of days, so not much got done until late this afternoon.

Going up from the crankcase, the cylinders are next. I made the cylinders from 7/8 inch diameter 12L14 steel. Things got started by facing the end and turning the two diameters forming the OD of the fins and the 1/2 diameter that goes into the crankcase. Then the radius of the cutter at the junction was squared up with a cut off tool.









Using the same cutoff tool, the fins were cut. The size of the fins and the spaces between them is not critical. The print dimensions were selected to match up with the 1mm wide cutoff blade I have. I would not reduce the top and bottom fin thickness too much however. Because model compression ignition engines tend to run cool, there is far more cooling fin area than is necessary, so about any fin configuration could be used. 

The cylinder blank was cutoff using the same tool, leaving about 0.020 extra to clean up to bring the cylinder to length.
Reversing the blank in the lathe, I cleaned up the end removing just enough material to get the end flat. The cylinder length was measured to determine how much more material needed to be removed to bring the cylinder to length. Then the cyliner was chucked again and the end blackened with a permanent marking pen. With the lathe running, the tool was brought up to the part until the black just started to be removed. Then the additional material on the length was removed to bring the cylinder to length.









Still clamping on the fins, I reversed the part in the lathe to drill the cylinder. I clamp on the fins as they are less likely to distort they cylinder than clamping on the 0.500 diameter would during the final boring stage. After center drilling, I drilled with a letter "U" size drill, which is 0.007 under size from the finished bore size. I peck drilled 0.2 inch at a time and applied cutting oil every time the drill was withdrawn.









I used a short stiff carbide boring bar to bore the cylinder. The bar was the largest diameter that I had that would fit in the hole and the shortest that would pass all the way through. After loading the hole with cutting oil, the cylinder was bored to about 0.0005 under the desired finished bore size. If the boring bar had not been as stiff, I would have allowed more material for lapping.









I will not lap the cylinder to size until after I cut all the ports into the cylinder.

And what fun would it be if id didn't stuff things together to see how it looks so far.
Gail in NM


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## cobra428 (Sep 24, 2009)

Gail,
Man O Man is that starting to look good
Tony


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## Krown Kustoms (Sep 24, 2009)

That looks great, did you blacken the cylinders or is it the camera angle?
-B-


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## GailInNM (Sep 24, 2009)

Thanks Tony & -B-. 

-B-
It's just the camera angle and my poor lighting. I plan to black oxide them in the oven at 550 degrees just before the final lapping. That way any heat distortion will be lapped out as the final step.

Gail in NM


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## Krown Kustoms (Sep 24, 2009)

They definately look good darker than the rest.
-B-


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## cobra428 (Sep 24, 2009)

Gail,
I have never "Heated" my black oxide stuff. Just solution and protective oil. Heating helps?
Tony


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## GailInNM (Sep 24, 2009)

Tony,
This is done with out chemicals. Just formation of the oxide by heating the part. Some of us played with this a couple of months ago. Details are at:
http://www.homemodelenginemachinist.com/index.php?topic=5514.msg58087#msg58087
Gail in NM


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## cobra428 (Sep 24, 2009)

Thanks Gail,
I've been using gun blue and black ox chems, parkerizing so to say stuff. Is this the heat Blueing's I've been reading about here.....Looking to do the same on the Whittle Cyl.
Tony


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## Krown Kustoms (Sep 25, 2009)

I Found a mix a few years ago using chemicals, I had to modify it a bit but it "blues" really well.
You dont want this stuff in the kitchen it has a strong oxidiser and a lot of caustic lye in it.
After I use it I evaperate the water and put the powder in a air tight can for future use.
It definatly is not the most logical way if all you have to do is heat the metal, There is a duribility issue but most parts I do are cosmetic so just the heat will do for now on and its safer. (well maybe not, if my wife catches me with a bunch of steel in the oven)
thanks for the tip
-B-


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## GailInNM (Sep 26, 2009)

Tony and -B-,
I have had mixed results using chemical blackening. Probably not getting parts clean enough. I have chemicals for parkerizing but have not done anything with them yet. I do like the finished produced from photos I have seen.

This will be the first time I have used the heat only treatment on real parts. Only done test parts so far. I like the blue/black look and durability seems to be OK, comparable to the chemical treating I have done in the past. 

In the meantime, I have to get the cylinders up to the point of finishing first.

The only thing done since the last construction post is to drill the mounting holes in the cylinders and clean up the burrs.
The cylinders were clamped in the mill vice using a "V" block. Worked out just right as the cylinder length is only a little bit shorter than my vice jaws are tall. I have a "V" block that I made up to the same height as the vice jaws for just this sort of thing. I modified a General Hardware "V" block as they are cast iron and not hardened. Easy enough to saw off the extra length and then finish up the sawed edge in the mill. 

After clamping in the vice, I indicated the center of the bore and then center drilled and drilled the mounting holes using the coordinates from the drawing. The drill of course made burrs, so back to the lathe and the burrs were cleaned off on both end fins and between the fins using 400 grit abrasive paper folded around a 6 inch rule. I run the lathe in reverse so the paper is under tension. If you run the lathe in forward and work on the top side of the part the paper can bunch up and grab and try to drive the rule into your hand. Not a good thing. If your lathe cannot be reversed, work from the bottom of the part so the paper is under tension. In either case, do not try to steady the other end of the rule with your other hand. The results can be painful.

Gail in NM


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## GailInNM (Sep 27, 2009)

With the mounting holes in place it is time to put the ports in the cylinder. I used a 5c square collet block to hold the cylinder. The mounting holes were put in first because the ports can be easily aligned to them using a fixture. Actually you can align everything with out a fixture using a couple of rods in the holes and a parallel across the bolts and a level on top of than and then tightening the collet with your fourth hand. I find that it is quicker to make up the fixture, even when only a few parts are involved. 

The fixture is just a piece of scrap plate that is squared up to the same dimensions as my square collet block. I used 0.09 aluminum. An oversize 1/2 inch diameter hole is put in the center of the plate. I used a 1/2 inch end mill to punch the hole through and then bumped the table plus and minus about 0.003 inch in both the X and Y axis. It's just clearance for the 1/2 spigot on the cylinder, so I don't care if it is perfectly round. Then 4 holes were coordinate drilled for tapping 2-56 to match the mounting holes in the cylinder. After tapping, two 2-56 were inserted. I found the screw heads were slightly protruding into the 1/2 hole space, so I touched them with a round file for clearance. This just keeps them from catching on the cylinder when the fixture is slid on the cylinder. 









The fixture is engages with two of the holes in the cylinder and the cylinder is inserted into the collet and the collet is tightened while both the block and fixture are on a flat surface.









A stop is set up on the mill to register on the end of the cylinder. Any kind of stop can be used, but it needs to be below the top of the 1/2 diameter of the cylinder so a flat can be milled on the cylinder with out hitting the stop. I have two vices on my mill, so I used the second vice to support the stop, using a "V" block and a spacer to hold the stop level and position it. I used an edge finder to locate the end of the stop and zeroed the X axis. I put the collet block in the vice and then located the center line of the cylinder using the edge finder and zeroed the Y axis on the center line. I then milled the flat on the cylinder using a 1/2 end mill. 









I had intended to just rotate the collet block to do the work on the second, third, and fourth sides of the cylinder, but quickly realized that I did not have room for the collet chuck holding the small end mills to clear the 5C collet. So I reset the cylinder in the collet block so an additional 1/4 inch or so protruded. The position of the cylinder in the collet block is of no importance, other that support, as all the measurments are referenced to the end of the cylinder as set by the stop on the table. Even if I had set the cylinder in the protruding position first, after milling the flat, the end of the cylinder needs to have the burr removed from the end so it does not affect the position of the cylinder.

The Intake and Transfer ports were "drilled" using a 1/16 end mill and the Exhaust port was milled with a 3/32 end mill. The holes were drilled with an end mill as they are starting on a sloped surface for the intake port as they are off center line. Both end mills have to be center cutting. Also, a end mill leaves less burr on the inside of the cylinder so it is easier to remove prior to lapping the cylinder.

















Gail in NM


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## arnoldb (Sep 28, 2009)

Very good going Gail 

You never mentioned what you use your third hand for  :big: 

Thank you for the updates; they are very much appreciated.

Kind regards, Arnold


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## GailInNM (Sep 30, 2009)

Thanks Arnold. Third hand reserved for scratching head while saying "why did it do THAT."

Finishing up the cylinders.
With all the machining done, all that is left on the cylinders is to finish the bore and blacken them. 
Since I had a Flex-Hone the right size, I ran it in and out of the cylinder one time using a low speed drill. This is to remove the bulk of the burrs caused by machining through the cylinder walls. I used some light oil on the Flex-Hone. When I don't have a Flex-Hone, I just use a bit of 400 grit abrasive paper wrapped around a convenient size rod or wood dowel.

Then I cleaned the bore to remove any oil, swarf and abrasive that might have come from the Flex-Hone. I use a nylon tube brush and mineral spirits.









I rough finished the bore to size using a Cogsdill roller burnishing tool that I bought at the right price at an auction. They work by exerting high pressure on the peaks in a bore and deforming them into the valleys. Very quick and easy, but it will not improve the geometry very much, so the bore has to be round and consistent. Most of the time I lap the bore to get it to this point. For information on how I do the lapping, both rough and finishing, see my PMC IMP thread starting at post #40. It details this stage and the next one also.
http://www.homemodelenginemachinist.com/index.php?topic=4422.msg50150#msg50150









With the bore roughed out, I blackened the cylinders. First they were cleaned with solvent. I used acetone as it drys quickly and leaves no residue. Then they were placed in the domestic oven with the oven set a 550 degrees F. I left them there about 30 minutes after the oven reached temperature. The results are shown below, with a untreated cylinder beside a blackened one. I had made an extra cylinder "just in case" so I had it for the photo.

After they were cool, it was back to the lathe for the final bore finishing. I measured and tested the bore with plug gauges before finishing to see if there was any distortion caused by heating, but could not find any. Finishing was done with a brass lap using 5 micron diamond polishing compound. I ran it through the bore just enough to remove the black oxide coating, and then continued on to taper the bore an additional 0.0002 at the bottom end up to just above the exhaust ports. The reasons and procedure is detailed in the PMC IMP thread referenced above.

The last step is to clean the cylinders very well. I used a brush and mineral spirits, then detergent and hot water. After drying, they were coated with light oil to prevent any rust.
Gail in NM


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## GailInNM (Oct 1, 2009)

With the cylinders finished, it is time to fill them up. Piston, contra piston, and wrist pin.

Before starting the piston and contra piston, I made a pair fo internal expanding mandrels to grip them for the finish polishing and fitting operations. 

They are just a aluminum rod turned to fit the inside dimensions of the piston and contra piston with a chucking section. They are drilled, and the chucking section threaded 4-40 and the mandrel end has a clearance hole for a 4-40 and a counter sink on the end for the flat head of the 4-40 bolt. The bolt is inserted and threaded through and a nut is Locktited on the end of the bolt to make turning it easy. 

Gail in NM


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## GailInNM (Oct 3, 2009)

The pistons are made of cast iron. The smallest easily available cast iron stock is a nominal 5/8 inch diameter. It always comes oversize so it can be cleaned up to the nominal dimension. When I get a new piece in I turn it between centers until it just cleans up to get rid of the scale and bring it round. Then I turn the diameter down to the nearest standard collet that I have. In this case it is 0.672. This gives me nice stock to work with.

I started by measuring the two cylinders ID. Then I turned a little over an inch down to a diameter about 0.0005 larger than the larger of the two cylinders. I bored the stepped inside diameters and then cut off leaving about 0.005 inch long for cleaning up to the length dimension. Repeated the boring and cutoff operations for the second cylinder. This was OK because by two cylinders were only about 0.0003 inch different on the ID. If they had been more than 0.001 I would have dusted off a little bit more with the turning tool for the smaller cylinder. You don't have to do accurate measurements in doing all this. Just turn the stock down until it almost goes into the cylinder. Remember the cylinder is slightly tapered, so check at the bottom end.









The piston for the larger ID cylinder was mounted on the mandrel. I always start with the largest ID cylinder because if I polish the piston down too far, I can fit it to a smaller cylinder.









After measuring the length of the piston, I faced it off to bring it to drawing length. Then I polished the piston with 1200 grit abrasive paper backed with a 6 inch machinist rule. I would polish a little and then try to fit it in the cylinder. The goal is for the piston to jam with about 2 pounds force when the bottom of the piston just clears the intake ports in the cylinder.









Over to the milling machine, where the wrist pin hole is center drilled, drilled and reamed. I center drill a little deeper than I would on a flat surface as the drill will try to deflect due to the curved outer surface of the piston.









While still clamped in the mill vice, I milled away the bit of the piston that forms the transfer notch on the piston.









Gail in NM


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## zeeprogrammer (Oct 3, 2009)

Continues to be an interesting thread (no surprise there).

Thanks for showing the expanding mandrels. I have seen references to such things but could never figure out what they really were or how they worked. This helped a lot.

In an earlier post you described putting the cylinder in a 550F oven for 30 minutes and that this blackened them. You did nothing else but back them? Was there any oil covering on them? Once blackened is there still concern for rust?

Your pics are top quality. Do you use any special lighting?

Very interesting stuff. I don't say much here but I'm always looking.


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## GailInNM (Oct 5, 2009)

Thanks for the comments Carl,

I have not had much shop time for the last couple of days, but I think I am back on track now. If you look at the last photo in my last post, the piston on the right has a few marks just to the left of the flat on the crown of the piston. I had not clamped the piston tight enough when milling the flat and it rotated. The scars polished out enough that the piston would work OK, and once assembled nobody but me would know they were there. But, I would know they were there, so I mane a new piston to replace it. I also spent a few hours on machine preventative maintainance. I am now set up to start the contra pistons.

Since there is nothing done worthy of a photo, I wanted to answer Zee's questions.

The cylinders had no coating on them when they were put in the oven. They had been cleaned very well and all oils removed. The color is just the natural color of oxidation of the steel. If you Google "steel color temperature" you will find many color charts showing the colors at various temperatures. It gets the darkest at about 550 degrees F. The temperature is fairly critical as the color changes rapidly as you go through the 450 to 600 degree range. If you try it, try some scrap first as domestic ovens are not always calibrated very well. The oxide coating will provide very little, if any, corrosion protection, so the parts need to be oiled afterwards. The same is true of cold chemical blackening treatments. Parkerizing will provide good corrosion resistance, but will not be as black and uses heated solutions which I am not fond of.

For photos, I do not use any special lighting. Photos on the lathe are lighted by a 50 watt halogen work lamp. On the mill I have a 50 watt halogen lamp and a 23 watt fluorescent screw in bulb in articulated lamps. I position the lamps to minimize unwanted reflections. I use a macro setting on the camera, but to get a greater depth of field, I back up until the image only fills about 1/3 of the frame. I use a 10MP camera so there is lots of resolution to throw away. I generally put a white index card in an area outside the area that I will be cropping the image to. I do not set the light color temperature on the camera. It's a pain to do with the camera that I am using. Then I process the photo on the computer. 

I use a simple photo editor called "click 2 crop" It's greatest virtue is that it is quick. I have more capable editors, but they take far more time to use. It is available at: http://www.mazaika.com/click2crop.html
Costs about US$20, but you can download it and try it free for a week or two. 

I mentioned a white card earlier. Before cropping, put the cursor on the white card and right click the mouse and it will adjust for the color temperature of your lighting. There is an auto adjust box that cleans up a lot of contrast problems also. Then I set the output format that I want. For this thread I am using 320 x 240 pixel output. Drag the crop lines around to get what you want on the original, and the follow on the output image shown on the split screen. For most of the images I use a sharpen tool and there are 4 levels of sharpening. If there are dark shadows in an area of interest I tweak the gamma a little bit. It really works on this program, at least I like the look for illustration purposes. I really like the program as you can tell. It has more features that I don't use, but the main thing is that it is fast. On average, I don't spend more than 15 seconds on a photo.

Tomorrow will be contra piston day, and maybe wrist pins.

Gail in NM


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## zeeprogrammer (Oct 6, 2009)

Thank you very much Gail. Excellent information, very helpful, and very much appreciated.


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## GailInNM (Oct 9, 2009)

On to the contra pistons. A couple of days late, but still onward.

Most of the operations are similar to the pistons, but with a couple of exceptions. The contra piston has a very thin wall on the skirt. This is to allow the skirt to be compressed slightly to form a tight seal in the cylinder. To make this work, the contra piston is tapered very slightly so the skirt is slightly larger than the crown. I have not measured the amount because the pressure of the micrometer anvil distorts the skirt. The other special requirement is that the bottom of the recess forming the skirt needs to be fairly flat and smooth so the compression adjustment screw will have a good surface to press on.

Same set up as for the piston except I turned down enough of the cast iron bar to make three contra pistons instead of two pistons. I wanted an extra because it is a little more difficult to polish the contra piston to have the taper than to do the straight sided piston. I turned the stock to about 0.001 oversize from the cylinder bore. 

Next bore it to leave a 0.015 wall. I used a boring bar that was small enough that I could face the bottom of the recess with it.









The part was cut off about 0.010 long to allow some stock to clean up to length. Then the other two contra pistons were made to same point. After mounting the contra piston to the expanded mandrel, the contra piston was brought to length.









Polishing the contra to size is the most difficult part. It is not really difficult, but it does require a little bit of a feel. That's the reason I made three blanks. I did not need the extra blank, but it is comforting to have it in case because it is easy to make the contra too small.

Before starting, remove the piston from the cylinder and mark both the cylinder and piston so they can be kept as a set. During the following operations the cylinder needs to be open so the contra piston can be pressed out while sizing it to the cylinder. It is "awkward" to have the piston in one end and the contra stuck in the other end of the cylinder and no easy way to remove either one of them. 

I started with 400 grit abrasive paper backed with a machinist rule. I put a bit more pressure on the crown end until the the crown would almost enter the cylinder. Then I switched to 1200 grit paper and continued polishing until about 1/3 of the contra piston would enter the cylinder with about a pound of force. Remove the contra piston from the mandrel and test fit it in the cylinder. It should take about 2 to 4 pounds of force to get it to enter the cylinder completely. If it is to tight put in back in the lathe and continue polishing the skirt until it does fit. If (when) the contra piston gets stuck in the cylinder, it can be driven out using a soft rod while supporting the cylinder over an opening. I use the mill vice with the jaws opened up to about 1/2 inch. When finished, mark the contra piston so keep it with the corresponding cylinder and piston. 









Gail in NM


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## arnoldb (Oct 9, 2009)

Coming along very nicely Gail :bow:
Thank you !

Kind regards, Arnold


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## GailInNM (Oct 11, 2009)

Thanks Arnold.

Wrist pins. Whats there to say about wrist pins.They have to be the right size, round, smooth, and tough. 

On most of my engines in this size range, I have used music wire from the local hobby shop. The stuff that is straightened and comes in 3 foot lengths. That is what I intended to use on this engine. But, it is typically slightly under size by a small amount and sometimes not perfectly round. So I run an external lap over it to bring round and reduce the size to 0.0930 from the nominal 0.0938. I have a under size reamer that works well at this size when used on the mating parts. Well, being an old man with CRS syndrome I forgot to use the under size reamer and used my standard 3/32 reamer for the connecting rods and the pistons. Therefore the music wire at hand was under size and unusable.

Two alternatives were available. I could use drill rod (silver steel) and harden, polish and temper it, or I had some 3/32 HSS drill blanks. I went with the drill blanks. Since they are already hard, all work on them was done with a grinder. I use a Proxxon IB/E rotary tool on the lathe. It is their industrial rotary tool with preloaded ball bearings on the spindle. About the same size as a corded Dremel, but rated for continuous duty. The nice thing about it is the nose is all metal, and machined for mounting in a 20mm hole. I have mounts made up for my mill spindle housing and for the QCTP on the lathe. I used a standard Dremel cutoff wheel for all the grinding.

Drill blank was put in the lathe collet and the Proxxon mounted on the QCTP. Note the paper towels covering all the slides and lathe bed to protect them from grinding debris. First operation was to square up the end of the blank (no photo) and then advance the lathe carriage the finished length of the wrist pin plus the thickness of the wheel plus about 0.005 more just in case. 









After cutting almost all the way through the pin, I snapped the pin off pliers after retracting the cutoff wheel. After cutting both pins, they were reversed in the lathe and ground to length. The length needs to be less than the cylinder ID by about 0.005 inch.









Finally each end of the pin is radiused and polished hand holding the rotary tool. If you look closely in the last photo, you can see the radius being developed.









The wrist pins on the Lobo are floating, that is there is no method for retaining them in position. Therefore they can contact the cylinder wall. That is the reason that the ends must be polished so they do not damage the cylinder. Note that when the pin passed the intake and transfer ports on the cylinder, it can ride on the bridge left between the two holes forming each of the ports.

Gail in NM


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## GailInNM (Oct 12, 2009)

All the precision fit parts are done, although there will be some fiddly little parts in the fuel system.

Continuing upward, the cylinder heads are next. They are mostly a straight turning job, and since all the top end sealing is done by the contra piston they don't even need to be gas tight.

Started off with one inch diameter 6061 aluminum bar stock in the lathe. Turned the three diameters down and then cleaned out the tool tip radius where the meets the cylinder so the head would seat on the top of the cylinder. A 0.005 or 0.010 chamfer on the top of the cylinder would have eased this requirement some.










Head is cut off, leaving a few thou for cleanup to thickness, and everything repeated for the second head. Then the head is reversed in the lathe and the top is faced off bringing the head to the finished thickness.









Center drill, drill, tap 10-32 and knock off the burr with a hand held countersink.

















After indicating the head to locate the center, the mounting holes were coordinate drilled on the milling machine. I did not center drill, but mounted the drill in a ER collet with only about 1/2 inch protruding. This is stiff enough when drilling aluminum that no center drilling is needed. Both sides of the holes were deburred with a small hand held countersink, then back to the lathe where a slight chamfer was put on the outside edge with a file and the part sanded with 800 and 1200 grit abrasive paper and hit with just a little bit of metal polish. The chamfer has to be small to keep it from going under the mounting screw heads.









And a finished pair of heads. 
Gail in NM


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## mu38&Bg# (Oct 13, 2009)

Gail, I noticed you are using indexable tooling. I finally bit the bullet and ordered a decent set of indexable turning tools. Mind you, I have a basic import 1/2" set for TCMT 3252 inserts. What kind of tools are you using? I ordered a set of 1/2" tools for CCMT 21 and DCMT 21. I was thinking about getting some for VBMT inserts, but don't know if I'll need them. They do offer some visibility in the small parts.

Oh, one more thing are you using separate inserts for aluminum or just one type for everything?

The engine looks great!


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## GailInNM (Oct 15, 2009)

Greg (dieselpilot),
Since I mostly build small toys, I use small VBMT inserts for most of my turning. For my general purpose use, I use VBMT 2 1.5 1 C2. This is 1/4 inch inscribed circle insert with a 1/64 tip radius for cast iron and non ferrous materials. I use it for 12L14 and 1144 steel, but will switch to C6 grade if I am cutting tougher steel. That is rare for me. In 12L14 I can reduce the diameter by 1/4 inch per pass without problems. See photo in the PMC IMP thread of reducing a crankshaft. 
http://www.homemodelenginemachinist.com/index.php?topic=4422.msg47759#msg47759

My insert holders are brass that I made up. They have a 2 degree negative lead, that is the tip points toward the headstock by 2 degrees. This makes for a nice facing cut from the center of the stock outwards. It is very important that the inserts are are on center line if you are doing small diameter work. I have a dial indicator stand made up just for that purpose.

I buy generic inserts from carbidedepot.com. They are about $2 each, but come in boxes of 10. Carbide depot has given me very good service on both inserts and carbide end mills.


Not a lot has gotten done on the Lobo. I cut the gaskets. No photos, you know what gaskets look like. After sanding out most of the machining marks, I decided to engrave the crankcase. After polishing, I will fill the engraving with black Lacquer-stik. Don't expect too much in the way of polishing. Once I have the machining marks out, I generally just give things a quick rub with some polishing compound. Polishing is not something I enjoy. Besides, when I finish an engine and get it running I am ready for the next project. 









Gail in NM


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## zeeprogrammer (Oct 15, 2009)

Gail,

I haven't built up a like for polishing either...though I do like the end result and know it's a necessary chore.

As for your statement about 'you all know what gaskets look like'...I wouldn't be too sure. I think I do...finally...maybe. But only because I've lived long enough to come across them. I'd be surprised if my kids know what they are.

I liked the 'title plate'...I've been thinking about trying to come up with a logo or something that I can apply to my models (once I'm proud enough of them to show outside the family or to this forgiving and understanding forum ;D.)


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## cobra428 (Oct 15, 2009)

Zee,
I had a logo plate made at a trophy shop $5






The only way you do what Gail did is CNC

Tony


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## GailInNM (Oct 16, 2009)

Tony,
You are half right. I did use the CNC to do the engraving, but it is not the only way to do it. Many years ago I made a pantograph engraver. Made the fonts for it a bit at a time as I needed characters using it and tracing large letters. Later I got a good buy on a commercial engraving machine with a couple of sets of fonts and had it for a long time. I sold it after I got set up for CNC.

I like the laser engraved plate on your engine, but I don't think the finish would take kindly to the ether in the model engine fuel. I have used them on some steam stuff. How did you mark the serial number and build date on your plate. It does not appear to be laser engraved in the photo.

Zee,
Just for you ;D I will throw a photo of the gaskets in my next post. I have been beginning to think that I have been putting more photos in that people will want to see. I just checked my folder on them and it appears that I have 181 photos in this thread. There will be at least 40 or 50 more before it is finished. I have kept them small so they don't take too long to load. Not everyone has a high speed connection. 
Gail in NM


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## cobra428 (Oct 16, 2009)

Hi Gail,
That's a question for the trophy shop but they look stamped. I coated the plate with clear polyU before I mounted it. So hopefully that will protect it.
Tony


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## GailInNM (Nov 10, 2009)

I'm back.  
Sorry about not being around this thread for a few weeks. The doctors decided that I needed a tuneup and so I have not been able to do much model engineering.

The Lobo Pup is about ready for the final assembly of the bottom end. A bit of cleaning of parts and I will start from the bottom up and stop at the compression screws and compression limiters. I need that much assembled to be able to measure and make the limiters. After that the final parts will be the fuel system.

I should be able to start publishing the assembly photos late this week, but in the meantime, just for Zee, here is a photo of the gaskets.

Gail in NM


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## Deanofid (Nov 10, 2009)

Glad to see you back at it, Gail. Hope all is well! Looking forward to another runner.

Dean


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## GailInNM (Nov 11, 2009)

Thanks Dean. Glad to be back at it.

Here are the parts needed for from the bottom of the crankcase to the top of the cylinder head except for the fuel parts. Had to lay them out to refresh my memory. Crankcase has been polished and the lettering filled in with black Lacquer-Stik since the last photo of it. 

The screws are:
12 ea 0-80 x 3/16 Socket head cap screws (1/4 inch long would also work)
 8 ea 2-56 x 3/4  Socket head cap screws (7/8 would be ideal, but 3/4 should be OK. Don't have any 7/8)
 1 ea 4-40 x 1/4  Button head screw. Pan head would work but I like the looks of the button head

Gail in NM


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## LADmachining (Nov 11, 2009)

Good to see the engine coming together! Hope its up and running soon! ;D

Anthony


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## zeeprogrammer (Nov 11, 2009)

Glad you're doing well Gail. Welcome back.


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## ozzie46 (Nov 11, 2009)

Glad your back. Hope its nothing to serious. Great job on the engine. 

 Ron


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## Jadecy (Nov 11, 2009)

Glad to hear you are back in the shop! 

Those is some seriously shiiiinyyyy metal parts!! ;D Very nice!


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## cobra428 (Nov 11, 2009)

Hi Gail,
I was wondering what happened to you. I'm in the same situation, was sick and now starting to fell better. Can't wait to see the shop again. Feel better and I'm hoping to see that little baby purr some!
Tony


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## arnoldb (Nov 12, 2009)

Glad to see you back to it Gail.

And the collection of parts looks very nice indeed. While following a build, one does not often get an "overall" feel, so thank you for putting those together!

Kind regards, Arnold


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## GailInNM (Nov 12, 2009)

Thanks for the comments and the welcome backs from everyone.

It's time to start sticking parts together and make it start to look like an engine.

Starting at the bottom, the first job was to install the center bearing with the rear crankshaft and put the connecting rods on at the same time. It is assembled from the rear of the engine. Since everything is symetrical it can be assembled with the exhaust on either the left or right side as desired. The fuel system will of course be on the the other side. This also means that the engine will run equally well (I hope) in either direction. I chose to put the exhaust on the right side as this is the most common position for model aircraft engines.

Parts for this phase in first photo. Second photo shows the center bearing starting to be slid into place. The front connecting rod needs to be installed before it gets slid all the way in because of the extended crankpin. The rear connecting rod can be installed later.









Using the installation tool, the center bearing assembly is rotated and positioned so the 4-40 screw can be inserted to retain it. 









A gasket is placed on the front crankshaft assembly. I put a single 0-80 screw through it to keep it in position while installing it in the crankcase. The front crankshaft has to be rotated so the slot engages the crankpin on the rear crankshaft. Then the rest of the screws are added. The gaskets are not really necessary if the machined surfaces mate well, but I like them. The drawings are dimensioned so the engine can be built either with or without 0.006 inch thick gaskets with no changes necessary.









Gail in NM


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## GailInNM (Nov 13, 2009)

Before starting the assembly, I should have mentioned the lubrication of the parts as the engine is assembled. I use a light machine oil for everything. As soon as the engine is run for a short period the oil in the fuel will replace all of it. Both ends of the connecting rods get a drop of oil during assembly. The cylinder, piston and contra-piston only get a thin film of oil wiped on. Any excess oil on these parts will make setting the initial compression difficult during assembly. For the cylinder I use a cotton swab with a small amount of oil on it to both clean and lube the cylinder.

Continuing on with assembly. In the next photo notice that I have installed a 3/4 inch diameter knurled knob on the prop shaft. While not necessary for the immediate assembly operations, it is convenient and something to increase leverage on the shaft will be necessary when setting the contra-piston later. The engine will get turned over a lot during assembly as it is important to check for free operation after installing each part.

Each set of cylinder parts are installed at one time to avoid the possibility of mixing up the pistons and contra-pistons for the cylinder.

First the crankshaft is rotated so the front connecting rod is at top dead center. One of the considerations during design was that the small end of the connecting rod would be slightly above the top of the crankcase so the piston and wristpin could be installed. Then the piston is slid over the connecting rod and the wristpin is installed. Note that the transfer notch on both pistons face the center of the crankcase. You have to look close in this photo to see the notch, but it shows up well in a later photo of the rear piston. 









Then the cylinder is slid over the piston and rotated so the transfer passage is facing the center of the crankcase. Then it is seated on the crankcase using at least one bolt to align it. The contra piston is then pressed into the cylinder. I left it only part way in the cylinder for the photo, but I pressed down almost flush with the top of the cylinder. You can also see that I had the rear connecting rod installed in this photo, but it could be installed later.









The cylinder head is installed using the 2-56 x 3/4 screws and the screws tightened. Good time to check that everything is free by turning the engine over. It will take a firm grip on the knurled knob to get past top dead center. Everything is repeated for the second cylinder, making sure the transfer notch on the piston and the transfer passage on the cylinder face the center of the crankcase. 









The rear cover is installed with a gasket the same as the front bearing.
And it is starting to look a little bit like an engine.









Gail in NM


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## Jack B (Nov 13, 2009)

Gail this is the first time I saw this engine. I am amazed at the skill of the people on this site like yourself. You do beautiful work. Jack


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## ozzie46 (Nov 14, 2009)

BEAUTIFUL!!! 

 Ron


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## ttrikalin (Nov 14, 2009)

Man 
this is why i got the machining bug. cause i see posts like the current one.
great inspirations for newbies like me.

tom


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## GailInNM (Nov 15, 2009)

Thank you Jack, Ron, Tom and DIY for following along. It's nice to know that I am not just writing a personal diary. I am not much of a wordsmith, but I have fun trying and although I don't expect anyone to duplicate this engine I hope that it gives people ideas to try on their own.

To finish up the top end of the engine is the Compression adjustment screw and compression limiter spacer. Mine is a little more complicated than some, but there is a reason for all of it. I have seen engines that just have a plain screw stuck in the top, but besides not looking very good that does not really work very well. A normal screw is not very flat on the end so it does not make good contact with the contra-piston. This sometimes causes it to change adjustment when the engine is running. Also, a tool of some kind is required to adjust it. Sometimes two tools if a lock nut is also put on. This is awkward and not very safe when reaching over a spinning propeller to make the adjustment.

So, the first thing is to trim the screw to length and face the end. I made a split collet out of aluminum to hold the screw. I started off with a 10-32 x 5/8 socket head cap screw. The threads are relieved down to the minor diameter of the screw so the end is a round where it contacts the contra-piston. A small hole is put in the center of the end to remove any cut off pip that may occur when facing the end and to clear any pip that may be on the contra-piston. Then the end is polished a little bit with abrasive paper to remove any burrs. 














With both screws done, a screw in inserted part way into each cylinder head. From this point on, it is necessary to keep each screw associated with it's respective cylinder. I do this by only working on one screw at a time, and then returning to it's respective cylinder before removing the other screw. The crankshaft is rotated until one of the pistons is near top dead center (TDC). By looking in the exhaust ports it is easy to determine which one is at TDC because the other piston will be below the exhaust port. While rocking the crankshaft around TDC, the compression screw for that cylinder is adjusted until the piston strikes the contra-piston. Back off the adjustment screw a little bit and again rock the crankshaft about TDC. This will force the contra-piston up until the piston and contra piston just touch. The adjustment screw is then rotated back down with fingers until it touches but does not move the contra-piston. The same operation is repeated for the other cylinder. Now the distance from the screw head to the top of the cylinder head is measured on each cylinder and written down. 









The compression limiters can be made up now or later after the adjustment screws are finished. The construction was not photographed, but they are made from 1/4 diameter rod drilled to clear the adjustment screws. They are then parted off to the length that is equal to what was measured plus 0.010 inch. This makes sure that the contra-piston can not be adjusted closer to the piston than 0.010 inch. Calculated piston to contra-piston distance for running is 0.025 inch, so normal operation SHOULD be about a half turn above this, but initial starting trials will be set above this. One end of the limiters needs to be countersunk a little bit to clear the radius that is present between the head and shank of most screws. I countersunk both ends so I did not have to keep track of which way was up.

Gail in NM


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## zeeprogrammer (Nov 15, 2009)

I try to read everything you post Gail. Apart from the occasional question, I find it very difficult to come up with a meaningful comment. Please keep the 'diary' going...I'm sure I'm not the only who's trying to get a word out while trying to pick up their jaw.


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## vlmarshall (Nov 15, 2009)

zeeprogrammer  said:
			
		

> I try to read everything you post Gail. Apart from the occasional question, I find it very difficult to come up with a meaningful comment. Please keep the 'diary' going...I'm sure I'm not the only who's trying to get a word out while trying to pick up their jaw.




...yeah, what HE said. Great stuff, keep it up, please!


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## arnoldb (Nov 15, 2009)

Thank you Gail - once again very well done and documented. 
You are most definitely not just writing a diary; following along on your build is a real treat, and most definitely on my own to-build list.

Kind Regards, Arnold


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## GailInNM (Nov 15, 2009)

Thanks to Zee, Vernon and Arnold. Like you, I read most posts on the forum, but respond to only a small percentage of them.

Re-reading the first part of my last post, it sounds like I was fishing for comments. Actually, I was trying to be humorous (poorly). But, comments are always helpful. It lets me know if I am including enough detail, or too much detail. Too little and the beginners get lost and too much bores the experts. And since this is both a design and build thread, I have tried to explain why I do things as well as just how I do things. 

So without the humor, on to finishing up the top end of the Lobo.

The only thing left topside is to finish off the compression adjustment screws. Note to self: keep the screws associated with each cylinders during these operations.
I faced off the top of the head and turned the knurled part off the head. Then bored to remove the hex part inside so the drill would not be deflected when drilling the cross hole.









The screws were reinstalled in their cylinders and run down with fingers until they touched the contra-piston. I marked the screws with a felt marker with a line from the front to back of the engine. Each screw was installed in a collet block in the mill with the marks vertical and center drilled and drilled.













The handle was cut from music wire with a rotary tool (Dremel) and a cutoff wheel. It was cut a little long and then brought to size on the bench grinder and the ends rounded off and polished so they would not act like a cutting tool on bare finger tips when adjusting on a vibrating engine.

The handle was pressed into the crosshole on the adjusting screw and secured with a little bit of epoxy run down to fill the hole in the head of the adjusting screw. The hole was overfilled so epoxy was above the head. After curing , the epoxy was faced off in the lathe so it was flush with the top of the screw.









With the compression limiters installed on their respective screw, the screws were reinstalled in the cylinders and run down to the compression limiters. The reason for all the effort to align the holes in the adjustment screws was so the handles would be in approximately the same place during the running of the engine. Notice that since the compression limiters are 0.010 longer than where the screws were marked the compression screws are about 1/3 of a turn up in the photo from where they were marked ( 0.01 x thread turns per inch = 0.01 x 32 = 1/3 close enough). It is anticipated that when the engine is adjusted while running that these screws will be about 1/2 further out from here. We will see.






Gail in NM


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## zeeprogrammer (Nov 15, 2009)

Well I can say "It's just right for me!" Excellent pics, good writing, wonderful detail. Very enjoyable.

I know what you mean...hard to judge sometimes if what one is doing is good, acceptable, decent, or whatever.


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## Deanofid (Nov 15, 2009)

I'm watching too, Gail. Though I don't always have a comment for your posts, I am enjoying watching a competent machinist go about his work. 
The engine is quite a piece of work, and I see a lot of good procedure in your write up. All of us can learn something here.
(And I didn't think you were fishing either, but I know what you mean!)

Dean


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## ariz (Nov 16, 2009)

I'm following too. every Gail's post is worth the time to read it carefully 

thanks for sharing!!!


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## Bill Mc (Nov 17, 2009)

Hi Gail - I have been following your thread with great interest and I beleive that you are grossly mistaken in the statement made that "no one will attempt to duplicate this engine". I believe that once the plans are finalized it will just be a matter of time until builds of this engine will start appearing on HMEM as well as many other homepages on the internet. Keep up the good work and I for one will be looking forward to your first successful run. - Billmc


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## mu38&Bg# (Nov 17, 2009)

I've want to build an inline twin for a while. I've yet to build a whole engine. I keep putting it off trying to decide what I want to build. I have plenty of projects modifying model airplane engines. Anyway, this build looks like something I might do. It looks great and I can't wait to hear it run.

Greg


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## NickG (Nov 19, 2009)

Gail,

The engine is looking great. I have learnt a lot from reading your posts. Do you always prefer to use collets rather than a 3 jaw. Suppose once it is set up you have the accuracy and repeatability at your finger tips you won't go back to a 3 jaw?

I agree on the tolerancing - horses for courses. I've just realised recently that I waste a lot of time trying to hit dimensions that don't need to be hit, aren't critical. I think it's maybe an OCD of mine!

Considering you don't like polishing it's looking pretty shiny! Must be the superb workmanship. I'm of the same vane though, a nice engineering finish will do me, not into mirror finishes and bling and it's always more satisfying if it comes from the lathe and you don't need to do anything further! Wish that happened with me all the time but I can't claim that it does!

Nick


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## GailInNM (Nov 20, 2009)

Thanks for all the comments and support.

Zee: I have followed your posts from when you first joined. You are making great progress. You have reached the point where you can question authority in an educated manner and that makes you a good proofreader. If anything is not clear be sure to let me know. It helps both me and others. 

Dean: I don't know about the "competent machinist " part. I am strictly self taught, but I have been at it for a long time so I just know what works for me, and more importantly what does not work for me. 

Ariz: The work you have shown on HMEM speaks for it's self, so I consider the fact that you have been following this thread a great compliment.

Bill: I have been keeping the drawings on my computer updated as I go along. Assuming that the engine is successful, and I think that it will be, I will replace all the preliminary drawings that are posted with a set of "as built" drawings. There are about 20 changes that I have made to them as I went along. None of them serious. Mostly clarifications on dimensions and a few things to make machining easier. And a couple of "what was I thinking" when I drew it that way.

Dieselpilot: It's getting close to the time for you to build an engine from scratch. I know that you have worked on enough engines to know what you want, but I would suggest that you start with a single cylinder for your first engine. After the Lobo Twin is finished, I may do a single cylinder version of it. Nothing definite yet, but I made a few extras of the parts which would be common. 

Nick: As you noticed, I use collets most of the time. Since I build small toys, 5C collets will take care of 95 percent of the lathe work that I do. I have a full set in 1/64 increments plus common size hex and square. For odd small sizes, I have a ER16 holder that I put in a 5C collet. I do have both a 6 jaw and 4 jaw chuck that I use for larger and odd shaped parts and for eccentric turning. Also a faceplate when all else fails. My lathe has a 5C spindle, so there is no adapter to fuss with, and to install a chuck is only a 30 second job including cleaning the mating taper and faces. Ease of change over was one of the things I was looking for when I bought this lathe a few years ago. The 5C collets have served me well over the years. In addition to the lathe, I use them in a Spindex, collets blocks, and my indexing head. I just bought what I needed at the time over many years and then a couple of years ago I filled in the set with low cost collets for the odd sizes. 

Enough small talk. I will start posting the remaining seven parts that are necessary for the fuel system later today. Then I will be approaching the moment of truth. 

Gail in NM


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## NickG (Nov 20, 2009)

Thanks Gail,

Exciting times approaching then, I will be following closely!

Nick


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## GailInNM (Nov 21, 2009)

The last group of parts are for the fuel system. The most visible of these parts is the venturi that everything else mounts to, either directly or indirectly. 

The venturi has no critical dimensions. The 1/4-40 thread has to fit the crankcase and the axial hole in it should be reasonable close. Most of the venturi action is created by the reduced cross section caused by the spraybar passing through the axial hole. The air intake or bell portion of the venturi can be any shape or even left as just the axial hole. On a higher performance engine all these things get far more critical but this engine will probably only reach about 10,000 RPM.

I started the venturi with length of 3/8 diameter aluminum bar. One end was turned down and threaded with a 1/40 die. I use the front of my tail stock chuck with the jaws retracted to start the die square.









After center drilling and drilling, the part is cut off a little long to allow cleaning up to length.














After switching ends, the part is faced off to length. The compound slide is set to 12 degrees for an included angle of 24 degrees and the exterior of the bell is cut using the compound slide. Nothing critical about the angle. It is only for looks. 









The end was opened up with a 60 degree countersink. The shallow angle is just for looks. A standard 87 degree would work just as well. A small boring bar could also be used to generate an angle, or the hole could be left plain but it would not look very good to my eye. I then rounded off the sharp edges and did a light polish with abrasive paper.









After transferring to a collet block in the mill the two sides are faced off to provide flat mounting surfaces for the spraybar. The collet block was positioned by a stop on the vice to make it easy to flip the block 180 degrees to do the second side. The center flat surface is center drilled and drilled for the spray bar. After removal from the collet, the axial hole is deburred on the inside using the same drill that was used to drill it.
















Gail in NM


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## zeeprogrammer (Nov 21, 2009)

What kind of aluminum bar did you use? Did you do something else besides use abrasive paper to get such a finish?

You mentioned setting the component slide 12 degrees for an included angle of 24...would you explain that a little more?

Thanks Gail.


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## mu38&Bg# (Nov 21, 2009)

Gail, Yes, it's time to build an engine, before my second little one comes in March. I'm bringing my Clausing 4904 into service this week. I got the carriage cleaned up and back on the ways last night. I'll finish assembling the top slide and compound tonight. And hopefully finish the backplate for the Sjogren 5C chuck after that. 1" through spindle should come in handy, no more sawing 1" 4340 by hand. I don't think my old Altas will make engines anymore. Now to decide what I'm going to build. The only thing I haven't made yet is rings or a lapped piston/liner. I think I can handle everything else.

I use the tailstock chuck trick for squaring dies too.


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## Deanofid (Nov 21, 2009)

zeeprogrammer  said:
			
		

> You mentioned setting the component slide 12 degrees for an included angle of 24...would you explain that a little more?
> 
> Thanks Gail.



Zee, Gail set the compound slide to cut a 12 degree taper. When he cut that taper on the venturi, it makes a mirror image of the angle on the other side of the piece. In other words, it's cut 12 deg all around. When you measure the complete angle of the venturi bell, it will be 24 degrees in relation to the center line of the piece. 12+12=24.

Prints often say to cut an angle to "XX (included angle)". That's letting you know that you need to cut 1/2X to get the angle call out on the print. 

If you look in the tool sales web sites, and go to the dead centers, you will see the description for the dead center often will say 60 deg (included angle). It lets you know that the complete angle is 60 deg, not just one leg of the angle.

Dean


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## zeeprogrammer (Nov 21, 2009)

Ah. Thanks for that Dean.


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## arnoldb (Nov 21, 2009)

Gail, very well done and shown, as always.

Thanks & Regards, Arnold


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## NickG (Nov 21, 2009)

Nicely done Gail. I can almost feel the compression and hear the few plops before the high pitched whizzing noise. Can't wait!

Nick


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## GailInNM (Nov 21, 2009)

Thanks everyone. It starts to get exciting when the end of a build is in sight. 

Zee: I used 6061 aluminum, but any kind will work. I would avoid the hardware store variety however as it is too soft to cut well. I keep abrasive paper in small 2 x 4 inch pieces near the lathe. It is stepped in grades of 400,600,800,1000 and 1200 grit. On the venturi I rounded the edge with 600 grit and then touched everything with 800 and 1200 grit while running the lathe at about 2000 RPM. Finally, I have a small piece of heavy duty paper towel about the same size that had some Mothers metal polish on it at one time. I used the blackened end of it where the polish was for maybe 15 seconds and then used the clean end for a few seconds. So, it's not really polished up. Just enough work done to make it presentable. Less than 2 minutes all told.

Since Dean jumped in and covered the compound setting vs included angle (Thanks Dean!) I don't have to cover that. One small item on it however. My lathe has the zero degree setting when the compound is operating parallel to the lathe bed. Some lathes have the zero when the compound is in the axis of travel is the same as the cross slide. On them the setting would be 90 degrees minus the 12 degree setting, or 78 degrees.

Two of the parts left are the nuts to lock the venturi to the crankcase and the nut for the spraybar mounting. They are easy, and the operations are the same for both so I will just roll them into one post. Although I used hex stock for these, they could just a well be made of round stock with a flat milled on two opposing sides. I normally make up a few extra as it is very little extra work. 

Starting off, the stock is faced off, center drilled and drilled with a tap drill. Then tapped. If making extras, the tap can be run in deep enough for all of them. Then part off the individual nuts using a narrow parting tool. The one I am using in the photo is ground to 0.018 wide.










The nuts will have a nasty burr on the cutoff side. There is no way to avoid this as the final part of the cut is going into the internal thread which will catch to tool at the final stage. I use a hobby knife to slice off most of this burr. On small nuts, like these, it is helpful to stand it upright against a scrap of metal rather than try to hold it with your fingers. Easier on fingers also.









Fnally I clean up the remaining burrs on both sides of the nut by sliding the nut along a fine file. I set the file on a flat surface and hang the handle over the edge. Slide the nut toward the handle while putting light downward pressure on the nut with your finger tip. On the side that had the nasty burr it will probably take two strokes and only one on the other side. I am using a 6 inch single cut mill bastard file in the photo.






Gail in NM


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## zeeprogrammer (Nov 21, 2009)

Thanks Gail. Great information. Including how many strokes to clean up the nuts. It's that kind of detail that helps people like me out. Also the amount of time spent. Gives people some idea of what's involved and how much is required.


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## NickG (Nov 22, 2009)

Gail,

Thanks for the write up. I would probably have tried something crazy like put the nuts back in the lathe and it all gone horribly wrong! When all it needs is 3 strokes on the file what is the point! it's little tips like this that can save a lot of time etc.

Nick


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## GailInNM (Nov 23, 2009)

Thanks Zee & Nick.
Key to filing the nuts is getting most of the burr off with the hobby knife. If you don't do this the burr will catch in the grooves of the file and all you do is wear out your finger tip. 

Nick: Putting the nuts back in the lathe is not crazy. I did 10 of the 5-40 nuts, so I would have some for stock, and that is about the limit as to what my finger tip can take. If I were making more I would have put a 5-40 bolt in a split collet in the lathe and put the nut on it. Then I would have used a facing tool to remove the excess threads from the screw and cut the burr off. After the first one the reduced thread section is used to get the nut started.

The last complicated part is the spraybar. It is not really complicated, but it does have a lot of operations on a small part. Three of the operations are a little bit difficult, but fortunately dimensions are not critical. They are the drilling of the hole lengthwise through the spraybar with two different size drills and drilling the cross hole through one side of the spraybar.

Starting off with 3/16 hex bar stock, it was turned to 0.125 diameter for 0.625 length, and then threaded for about 7/16 of an inch with a 5-40 die. Thats 16 to 18 turns of the die. 









The section that will be centered up in the venturi is reduced to 0.093 inch using a square nose parting tool. I used a 0.040 tool. Too wide a tool will probably grab and bend the part. Then the part is center drilled and drilled to a depth of 5/8 inch with a 0.063 drill. After the first 0.2 inch or so it was necessary to peck drill in about 0.05 increments to keep the flutes of the drill bit from filling up. Then the part was extended from the collet some additional length and parted off a little bit long to allow cleanup of the end.

















After changing collets in the lathe, the other end of the part was cleaned up to length and turned down to 0.093. A shallow groove was put in to help retain the fuel line and the end was beveled a little bit with a file to make it easier to get the fuel line on. 









The final lathe work is to center drill and drill with a 0.040 drill through to meet the hole from the other end. 









A nut was put on the spraybar and then the spraybar was lightly gripped in a small drill press vice with the hex portion of the nut and spraybar slightly above the top of the vice. Turning the vice over, it was pressed down on a hard surface to bring the points on the hex level with the top of the vice and the vice tightened. A parallel could have been used under the spraybar, but this method is a quick way to get the spraybar level in the vice.









Finally, the cross hole through one side of the spray bar needs to be drilled. Fortunately, the exact position is not critical and neither is the size. The size should be some where around 0.032 diameter, but anything under 0.040 down to about 0.025 should work well. I used a #68 drill because I have a small pile of carbide circuit board drills that size. I put the vice on the drill press table at about a 45 degree angle so by moving my head left and right I could look either length wise of the spraybar or perpendicular to it. I centered the drill on the width of the spray bar and in the center of the reduced diameter section by eye and drilled through one side of the spraybar. I was using a 5 power visor for this. Some people wish for 20 year old eyes. I would settle for 60 year old eyes. So if I can do it most anyone can. Any way, the position if the hole is really not very critical so if it looks about right it will work. 









Finally, using the 0.063 drill, I deburred the inside of the spraybar to remove the burrs left by drilling from the other end and from the cross drilling. I held the drill bit in my fingers, and first turned the drill backwards to break off the burrs and then forward. If you turn forward at first, the drill will try to pull into the hole at the far end when it first engages the burr. Clean out the spraybar with compressed air or blow through it. Any crud in it can really make getting a smooth needle valve setting very difficult.
Gail in NM


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## NickG (Nov 23, 2009)

Nice work Gail, that looks a pretty small part. I've just been doing some fiddley bits and I actually put a 6ba bolt in the lathe and faced the end off to shorten it, and the bolt face as it was galvanised so wanted to get rid of that. Not that crazy afterall, it worked!

Nick


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## arnoldb (Nov 24, 2009)

Very good going Gail 

Kind Regards, Arnold


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## Deanofid (Nov 24, 2009)

Nice work on such a small piece, Gail. Good write up, too. (All of it!)

Dean


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## GailInNM (Nov 25, 2009)

Thanks Nick, Arnold and Dean.

Now I am down to easy parts. 
The needle for the fuel control needle valve is about as easy as it gets.
I started off with a length of 1/16 inch diameter straightened music wire from the local hobby shop. Marked off 2 inches and cut it off by clamping in my small drill press vice and cutting with a abrasive cut off wheel in a Dremel tool. The ends were cleaned up on the bench grinder and one end was rounded and polished for the handle end.






The wire was transferred to the lathe where the taper on the end was ground with a fine grit wheel in the Dremel. Before grinding, the grinding wheel was trued up using the same diamond dressing tool I use on the bench grinder. It was trued up by hand so while it is round the working face is not very flat. By keeping the grinding wheel moving, a reasonable taper is generated. Since I ground the needle by hand the dimensions are eyeball approximations. After grinding to shape, I dressed the needle to a finer finish and more even taper using a EZ-Lap 1/4 inch square 600 grit diamond lap. 









Then it was polished with 1200 grit abrasive paper. When finished I could not feel any roughness with my fingernail. Finally I polished the entire shank of the needle with abrasive paper to remove any surface contamination so it can be soldered into the barrel (to be made next).
Gail in NM


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## ozzie46 (Nov 25, 2009)

Thanks for posting this. Carbs are in my future and I really need this info. Kudos to you and a karma.

 Ron


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## GailInNM (Nov 25, 2009)

Ron: I am glad that this is helping you some.

Next up is the barrel that holds the needle.
A few operations, but all are easy. 3/16 diameter brass stock was cut to length and it turned down for a 1/4 inch so the spring will slide over it. Center drill, drill to tap 5-40 and then tap. Drill through with 1/16 drill bit for the needle. Reverse in the lathe and file the end to round it off just for looks. Where the 1/16 hole broke through, the hole is deburred using a small center drill and counter sunk a little bit (5 to 10 thou) to help guide solder at assembly. I just hold the center drill in my fingers to do this.

























Gail in NM


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## GailInNM (Nov 25, 2009)

Last item (I think) is the spring. It could probably come out of one of the junk drawers or be rescued from a ball point pen, but I have found that I can make three up in the time it takes to find one.

The purpose of the spring is to keep the needle valve from changing position from engine vibration.

I used a long 1/8 inch dowel pin to form the spring on. When the spring relaxes from being wound the ID will be close to the 0.141 dimension that is desired.

Starting off with about 2 feet of 0.018 music wire, I bent a hook on one end and gripped the other end in a locking set of pliers. With the dowel pin gripped in the collet of the lathe, I inserted the bent end in one of the collet splits and put tension on the wire. My lathe goes down to about 40 RPM, so setting at low speed I ran it in reverse to wind the wire on the mandrel. If you are trying this, and your lathe will not go below 100 RPM, I would suggest that you use regular pliers and not locking pliers. This is so you can just let go of the wire. When you let go of the wound spring, it will unwind and the loose end can whip around and cut you. Be careful.

As I close wound the spring, I then stretched it out so 10 turns filled half an inch. Using heavy duty cutters, I snipped off a 10 turn length. Put the spring on the mandrel to provide support and a place to grip and then ground the end off a little bit to flatten it so it would turn smoothly on surfaces it will be bearing on. 





















Gail in NM


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## Deanofid (Nov 25, 2009)

That spring came out nice, Gail, (along with everything else you've made here!)

I've made a few springs, and thought I would just mention this for some who might wonder where to get music wire; Down to a pretty small size can be had a many hobby shops. If you need very small wire, check a music store. You can get really small sizes of music wire in the form of guitar and mandolin strings. Cheap too!

Dean


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## GailInNM (Nov 26, 2009)

Good info Dean. Thanks.
I think that my local hobby shop has wire down to 0.010 diameter. I know they have 0.015 and 0.020 wire, either of which would work for this spring. I was fortunate to buy a box of assorted 1/4 pound spools of music wire ranging from o.005 to 0.047 at a auction of a machine shop that was being liquidated about 20 years ago. I have not even put a dent in this stash yet. 
Gail in NM


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## GailInNM (Nov 26, 2009)

On to the assembly of the fuel system.
First the spray bar was installed in the venturi. The cross hole should be pointed at the side of the tube, but it is not critical. If you can not see the hole looking in the air inlet side then it is OK. Drilling the hole the way I did places the hole in line with one of the points of the hex portion of the spray bar, so alignment is easy. 

The barrel is threaded on the spray bar until it bottoms and then it is backed off one turn. This leaves one turn to make sure the valve can be shut off all the way. The needle is inserted into the barrel and pushed all the way down. Then it is retracted a little bit, about an 1/8 inch and flux applied to the needle next to the barrel. Working the needle in and out of the barrel a little bit to distribute the flux in the hole, the needle is reseated all the way down and the excess flux is wiped off.









A ring of solder is made by winding a short length of 0.015 solder several turns around a piece of 1/16 wire, and then cutting it into rings with a hobby knife inserted into the coil after removing the coil from the wire. One of the rings is then slid on the needle down to the barrel.

















The barrel is heated with a small torch until the solder melts and flows down into the joint. After cooling, I removed the flux residue with a bit of alcohol and a paper towel.














The needle was removed from the spraybar and the end of the needle is bent to about a 45 degree angle to form a handle. The needle was left out at this point as it will not clear the mounting lugs on the crankcase when installing the venturi on the crankcase.

The 1/4-40 nut was installed on the venturi and then the venturi was screwed into the crankcase and turned to the desired poslition and the nut tightened. After sliding the spring on the needle, the needle was reinstalled.





The engine is now finished and ready for a test run.

Gail in NM


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## NickG (Nov 26, 2009)

Wow :bow: looks superb, can't wait for the run!

Nick


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## ttrikalin (Nov 26, 2009)

Wow, that's some progress. I was not checking the post out for a week and the engine is already done!
 th_confused0052 
Please post on the run. Also, if applicable, on any troubleshooting (knock on wood). 

tom


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## Deanofid (Nov 26, 2009)

That's a nice job on the needle/spraybar/venturi assembly, Gail. Very pro looking.
The completed engine looks great! I'm excited to hear it run, too.

Dean


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## LADmachining (Nov 26, 2009)

Will it be test-run today??  

Well done Gail, some excellent work there!

Anthony


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## Twmaster (Nov 26, 2009)

I've been watching this build on and off. What a magnificent engine!

Fire it up!


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## GailInNM (Nov 26, 2009)

Well, it's not going to run today. 

First off my ride to Thanksgiving dinner will be here shortly and I don't expect to be back until late. 

But more importantly, I have something screwed up on timing. It's too early to tell for sure if it is design or I screwed up machining. But it is at least consistent in that it is the same on both cylinders. At bottom dead center, I have a small over lap where the intake, transfer and exhaust are all connected. So, no suction on the intake. Determined by blowing into the venturi while turning the engine over. I just make up a connector to replace the carb with a tube connected to it so I can play. I will put a disc on the crankshaft so I can measure what is opening where so I can try to deduce what is happening before I tear it down. 

I will also go over all the timing calculations for the ports so see what I can find out there. If nothing shows up on the design, then it will be time to tear it down to see what is happening. That should keep me busy tomorrow, and then a day or two (optiminst) to make new parts to correct the error.

So, although I did not plan it that way, we will all get a lesson in trouble shooting a new design.

I still have faith that it will run soon. 

Gail in NM


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## arnoldb (Nov 27, 2009)

Thank you very much for the update Gail.

Sorry to see about the timing issue - but I guess that's all part of our hobby!

A silly question - if you don't mind. Was the solder you used on the barrel just thin "resin core" solder, like normally used for electronics, or something more specific? - I cannot see any additional flux applied to the parts in your photos, so I presume you used a form of flux core solder with very clean parts.

Once again, thank you very much for sharing this build 

Kind regards, Arnold


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## GailInNM (Nov 27, 2009)

Thanks Arnold.
First off, to answer your question. Yes, the solder is regular electronics grade solder with a flux core. The flux core is not necessary however. I used a small amount of regular non-corrosive paste flux and worked it into the joint. Then I wiped off all the excess so only a small film remained. That is why none shows in the photo. Since both parts were mechanically clean that is all that is necessary. If one does not have thin solder, you can clamp a length of thick solder in the mill vice to flatten it and then cut small strips from that.

Got in too late last evening to do anything on the engine, but got started a couple of hours ago. First off, the primary problem is that I can't follow my own drawings. I had the pistons and cylinders installed with the intake and transfer ports reversed (post #100) Not only did it reverse them on installation, I took photos and described how to do it! OK I said. It must have been late. No, the time of the post was 7:30 in the evening. So I guess I just had my head some where that it should not have been. That is the problem when you design something. You KNOW what it should be, so you don't check the drawings. 

So I reassembled it (correctly) and it was more like it should have been. I had made up a fitting to replace the carb and had a length of tubing attached to it. I put the tube in a cup of water and turned the engine over by hand. Suction was there but was not very strong and it bleed off too quickly. More disassembly and reassembly wit some tests during and in between. Too much leakage between the two cylinder crankcase halves is the conclusion. Even though I had tested the bearings for leakage around the seals before I started the project, there is just too much leakage after they have been "exercised" a little bit. I think what happened is that I just tested with pressure on one side of the bearing, but in operation there is pressure and suction alternating each revolution and the seals do not get a chance to seat.

So, back to the drawing board for a little bit. I am replacing the ball bearings with sleeve bearings, which means making a new center bearing housing and a sleeve bearing. No big deal, but as long as I am doing that, I am going to change the crankshafts to make them easier to make. I could get by with out doing that, but I think that by doing so it will take less time overall as I can then ream the sleeve bearings with imperial reamers that I have and get rid of the metric dimensions that I was using to match the metric bearings. Nothing against metric. I just don't like to mix imperial and metric on the same project. I am comfortable with either, but most of my tools are imperial. Also, with the ball bearings gone, I have room to fit an o-ring seal on the center bearing retainer to further reduce leakage betweenthe two crankcase. I wanted to do so on the original design, but there was not enough room. This is probably not necessary, but the o-rings are only a few cents each plus the time to put two grooves in the housing.

Current status is that the drawings are about half way done with the updates. I should be ready to start on the replacement parts later today. They should only take a day or two to make. 

It's all part of bringing a new design to life. That's part of the fun in it. Of course it would be nice to have things work perfect the first time, but.........

Gail in NM


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## kustomkb (Nov 27, 2009)

Great looking engine Gail!

Im sure it will run great too.

Thanks for the great thread and all the best with her maiden voyage! 

 :bow: :bow:


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## GailInNM (Nov 27, 2009)

DIY,
The ball bearing internal seals leaked too much under the alternating pressure/vacuum. There was no room to put additional seals in without making a new crankcase. The bronze bush will get rid of the sealing problem because of the long annular passage. They will have lots of lubrication with the alternating pressure/vacuum and the fuel will have 33 percent castor oil.

Also, with the increased room, I am putting o-rings in to the housing to seal against the crankcase wall. 

At the 10,000 RPM max that this engine should run at, wear will not be a problem. The piston/cylinders will wear out long before the center bearing becomes a problem.

UPDATE: The new center bearing assembly is complete. Photos later. Still deciding what to do about front bearings.

Gail in NM


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## Deanofid (Nov 27, 2009)

Glad to hear you're getting it sorted out, Gail!

The plain bronze bearings ought to last nearly forever with that fuel mix, for sure. 
I've had glow engines that used only one plain bearing (aluminum!) that ran weekend 
after weekend for years.

Thanks again for sharing an excellent build. Looking forward to it's maiden run!

Dean


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## Twmaster (Nov 27, 2009)

Sweet. I'm glad to see you have that sorted out Gail.

I'm watching this thread as I fly RC planes and would love to someday build my own diesel.


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## arnoldb (Nov 28, 2009)

Thank you very much for the answer on the soldering Gail 

And it definitely sounds like you're well on your way to sort out the problems!

Kind regards, Arnold


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## GailInNM (Dec 3, 2009)

The Lobo Pup Twin whimpers into life.
It's been cold here so operation on the test stand outside has been limited. 

Last weekend I put the Pup on the test stand for the first time. No video yet as it was too cold to both set up the camera and play with the Pup. I had changed the center bearing out to a sleeve bearig, but left the front bearings as ball bearings. With the new center bearing I had good suction on the intake. 

The engine started up fairly quickly and was running it rich and at low RPM for the first run. Compression setting was about where I anticipated it would be. But, as the run continued, I had to open up the needle valve and increase the compression some. As expected there was some black oil in both exhausts, indicating that some wearing in was happening. But the black exhaust continued and did not clear up. Soon the RPM started to fall off. After running , I brought the Pup inside for a tear down to check. 

Compression was way down. Pulling a cylinder, the piston to cylinder fit was way too loose. So now I knew the source of the black exhaust grunge. A couple of measurements and test fitting of the piston to cylinder produced and unexpected result. BOTH the cylinder and piston were worn. Why???? I don't know why. I suspect, but don't know, that they are approaching similar hardness.

The cylinder was 12L14 and the piston was cast iron. The same as I had used on the three PMC IMPs a few month ago, and the same as I have used in the past. Same lapping technique followed by careful cleaning. The only differences I can think of is that I as using a different source of cast iron for the piston, and that I has colored the cylinder by heating to 550 degrees F. The heating should not have affected the structure of the 12L14. According to my numbers, it would not have been affected any until about 800 degrees. The cast iron machined the same as what I had been using as near as I could tell. So, it seems that for some still to be determined reason the piston and cylinder materials are not happy with each other. It acts like they are similar in hardness. 

Plan of attack.  To make it easy to experiment, I have fitted the front cylinder position with a dummy plug to replace the front cylinder and removed the piston and connecting rod. The dummy plug is necessary to block off the intake passage for the front cylinder. So now I have a single cylinder engine to play with. I plan to make up several piston/cylinder pairs. They can be switched out easily in just a few minutes. I will try some different material pairs for them to see what happens. The progression is planned as follows.

1. 12L14 cylinder that has not been heated. Cast iron piston.
2. 1144 cylinder. Cast iron piston.
3. 41L40 cylinder. Cast iron piston.
4. 4142 HT cylinder. Assorted pistons.

The new 12L14 cylinder is almost done. I have found some 1144 steel in the box. It is enough harder that if it is a hardness problem the difference should show up. I did not have and 41L40 or 4142 on hand, but it is ordered and should arrive tomorrow. 

If nothing else, I should learn something. Not really looking forward to machining the 41L40 or 4142 steels. Nothing too difficult, but a lot slower than the 12L14 and 1144 steels. The 4142 is prehardened to about 300 Brinell. This is still machinable, but not by much for a duffer like me.  

I will let you know how it goes. 

Gail in NM


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## GailInNM (Dec 3, 2009)

That's a possibility Diy. Thanks. I will add that to my list. I have enough cast iron on hand to do it so I might give it a try early on. Depends on when the shipment of steel arrives tomorrow. I will probably make us several sets of piston-cylinders to try as this cold spell looks like it will hang on for a few days. Then all I will have to do is switch them out when I get so weather warm enough for playing.
Gail in NM


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## Maryak (Dec 3, 2009)

Gail,

Commiserations on the problem after your first run. 

I can't remember what lapping process you used but your description of the massive wear over such a short period of time suggests to me that a residue of the lapping process was still present.

I hope this helps.

Best Regards
Bob


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## Twmaster (Dec 3, 2009)

I hope this is not a question born of ignorance...

Why not aluminum pistons?


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## mu38&Bg# (Dec 3, 2009)

Making lapped piston & liners work is about thermal expansion. The piston runs hotter than the sleeve so you need to have a slightly smaller coefficient of expansion in the sleeve material than the piston. Aluminum pistons work, but not with steel liners. Typically ringless aluminum (high silicon content) pistons are run in chromed or nickel plated brass or aluminum ( different than the piston itself) sleeves.

I thought cast iron and 12L14 was a common combination. Is it possible you ended up with material different than you ordered or thought you had?


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## GailInNM (Dec 3, 2009)

Bob,
It sure acts like it, but they were all cleaned with my regular process. It is to first scrub with solvent, then with hot water and detergent. I use a stiff bristle test tube brushes for the cylinder, different one for each process. The only thing I can think of is that heating the cylinder reduced it hardness, although it should not have, enough that my brass lap embedded some lapping compound in the cylinder. But, this does not explain why the cylinder would also have worn. Only the piston should have worn then. But, because of the possibility, that is one reason why I am going to try a harder steel for the cylinder. But, it is obvious that it has something to do with my process or materials. This is the 7th IC engine in this size range that I have built, and the 5th with 12L14/cast iron. No great amount of running time on any of them, but certainly they were not worn out at 10 minutes. 

Twmaster,
Aluminum has it's own set of problems. It is sometimes used with glow engines, but the normal practice there is to put a brass liner in the cylinder and chrome plate it. For compression ignition engines the coefficient of expansion of the piston and cylinder need to match fairly closely. Due to the high compression ratio, the match between the piston and cylinder needs to be very close. On larger engines where rings can be fitted this can be compensated for. For engines under 1/2 inch bore rings are a real pain.  I don't know of any compression ignition engines in this size range where it has been done. I have seen rings down to 3/8 bore on glow engines, but there the compression ratio is only about 6 or 8 to 1. For compression ignition the normal operation point is about 18:1. 

Dieselpilot.
12L14 and cast iron are what I have used before. The cast iron is a new stick, but from the same supplier. The 12L14 I know is the same as it is the same stick that I used on the last engine, but it was not heated on the previous engine. The heat was low enough that it should not have affected it by my charts, but it may have anyway. That is why I have another one to try that has not been heated. Have to make piston and contra piston to match it yet. 

Making parts is the fun part, so I don't mind making a few different sets of piston & cylinder to try and learn something. It will run properly eventually and hopefully I will find out why I am having problems now.


Gail in NM


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## Twmaster (Dec 3, 2009)

Thank you Gail. I appreciate the education.


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## cobra428 (Dec 3, 2009)

What He Said,

I was thinking of how to make an ABC piston for the Whittle.

Keep the faith

Tony


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## mu38&Bg# (Dec 3, 2009)

Gail, I look forward to see what you find with the new parts. Maybe it was just the heat.

Tony, ABC pistons must have 22-30% silicon to work properly. The interference fit at TDC is like -.0001" which should change to about +.0001 when at operating temperature. Taper is important and I've not yet measured any engines to see what the taper actually is.


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## cobra428 (Dec 3, 2009)

Greg,
I have a few model airplane engines laying around here (in that hobby 50 years). I'll have to take a look see. It will be hard to measure
and even harder to make!

Tony


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## zeeprogrammer (Dec 6, 2009)

Wow. What a great thread.
So much to learn.
I'm looking forward to see what you find out.


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## GailInNM (Dec 19, 2009)

You faithful followers must have given up on me by now. It has been too cold to do much test running, at least for an old man like me. Over the last couple of weeks we have twice tied the record low temperatures gong back 70 years. The highs for the days have not been much better, mostly about 5 to 10 degrees F below my threshold of pain for playing with toy engines. Still nothing like the current snow storm you guys in the NE USA are current experiencing. 

I have made several new cylinders. Tightened up the lapping tolerances a little bit. I don't know what the problem was with the original cylinders, but current ones made of 12L14 seem to be working fine. Although I cleaned the original ones quite well, it sure acted like there was still some lapping compound in them. Just as Bob said. Maybe it was just too late that night and I just thought I cleaned them well and forgot the final detergent/hot water scrub. :shrug: 

Current problem is that the intake fuel draw is still low. I have to open up the needle valve about1 to 2 turns more than I should. And then the setting is more critical than it should be. I think that I am going to have to reduce the venturi ID a bit. I have checked the timing diagram and that looks OK, but I can increase it a little bit, but not much, if need be. Of course that means making new cylinders (again). 

Total run time on the Pup is probably about 45 minutes total at this point.

Thanks to everyone here who voted the PUP as POM for December. It sure helps to keep the drive up to get it running right.

Anyway, here is a short video of the Pup running with only one cylinder installed. I am creeping up on things a little bit at a time.
Gail in NM

[ame]http://www.youtube.com/watch?v=ez6Si49tfls[/ame]


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## zeeprogrammer (Dec 19, 2009)

Given up? I don't think so.
Very nice Gail.


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## Twmaster (Dec 20, 2009)

Gail...

Are ya sure I can't send you a bunch of this snow??

I've not given up on your thread. I just love little aero engines and diesels!!

Once it warms up a hair I'm sure you'll work the kinks out of that little Wolf....


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## GailInNM (Dec 30, 2009)

Zee, I know you never give up on anything. Thanks for staying with me.

Mike, I grew up in Alaska. Winter time is for building. Summer time is for playing outside. My weather here in NM suits me just fine. Snow a few times a year is plenty. 

The last 10 days have been busy. Santa was good to me and I hope he was good to you also. He brought me a new (to me) Dumore model 14, Tom Thumb, tool post grinder. It is about 40, maybe 50, years old, but except for a rotted with age power cord it is in like new condition. Age is OK because that is about how long I have been wanting one. I have been trying to use a hand held rotary tool on a mount, but it was not rigid enough for deep cylinders. He managed to get it here on the 23d, so I was able to have it running on Christmas day. Made a mount so it fits on my QCTP and some new arbors that will reach down into 3/8 inch bore cylinders. A few tests on Christmas day shows that it will work well in the future, and I already have plans for the first application.

Now back to the Pup.
I only had one good day for running. The engine was complete with both cylinders. It ran OK, but was still a little touchy on the needle valve setting, and a revised venturi did not help. So it was back to check the drawings. 

The problem appears to be that I miscalculated the primary compression at the very beginning of the design. Primary compression is the crankcase compression that is used to induct the fuel mixture and to transfer the mixture to the cylinder. Don't know what I did, but it was way low. That meant that the air velocity in the venturi tube was too low for good fuel draw.

Since there were a number of other little changes from the original concept, a complete redraw was done. The new drawings have replaced the old drawings attached to posts #1 and #2 and are annotated in Post #3 of this thread. I plan to build a Version 2 engine over the next month or so. Version 1 is going into the display case as is. Version 2 will not have much of a photo story going with it as most of the operations are the same as the original, although dimensions will vary some. 

Primary differences from Version 1 to Version 2 are:
1. Crankcase and overall height reduced by 5/32 inch.
2. Connecting rod shortened.
3. All ball bearings replaced by bronze sleeve bearings.

I left the cylinder and piston the same. This changed the timing by less than 2 degrees. Since the original timing was more of an educated guess anyway this should not impact the running enough to measure. 

If the eyes and fingers hold out the target date for next run will be Valentines day, or groundhog day if things go exceptionally well. Construction should go fairly fast as it takes me twice as long to shoot photos and write about things as to build them.

Gail in NM


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## cobra428 (Dec 30, 2009)

Gail,
You had me scared for a while. The long post and the tile to the left.... Lobo Pup twin 1.6cc dies.

I read the title fast and didn't see the .... after dies. Glad to see your still at it!

Tony


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## GailInNM (Jan 3, 2010)

OK. Time to get started on the Lobo Pup Twin Version 2.
I had planned to start on New Years Day, but I could not think of anything I would rather do on New Years eve than start on a new engine. So I sawed up a chunk of 6061 aluminum to make the crankcase. Squared up 4 sides and then did the ends using a squaring stop on the vice. Measured. The ends were not square and now the length was too short on two sides. Removed the squaring stop and removed the errant chip that was under it. Back to the saw. Must have been cross eyed as the second piece was was all ready too short with out any machining. The third piece was a charm and by the time the new year arrived local time I had a piece that was square and to dimension.

Operations were the same as on version 1, but with a few different dimensions as version 2 is 5/32 (0.156) shorter. One additional feature was to add cutouts on the mounting lugs. Because the venturi is located closer to the mounting lugs, the cutout makes it easier to get the fuel line on and not to have too sharp a bend as it heads off to the fuel tank.  

Photos show the crankcase finished up with the rough sanding done to remove most of the machining marks. A little more sanding with finer grits and then polishing still needs to be done. I will reserve those operations until there a TV show or movie I want to watch, or at least listen to. That is when I most often do my hand work. I won't machine with the TV on for safety reasons. I am too easily distracted. 

Gail in NM


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## mklotz (Jan 3, 2010)

> I won't machine with the TV on for safety reasons. I am too easily distracted.



Good onya, Gail. I've been blowing that horn for a long time but in our sports-drugged culture it seems to fall on deaf ears. I can't think of anything that has more potential to cause an accident than a blaring TV when you're running a machine. My pal, three-finger Joe, agrees with me too.


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## vlmarshall (Jan 3, 2010)

Well, the Lobo Mk II is looking good! :bow: I hope you'll post photos of the new completed parts.


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## GailInNM (Jan 3, 2010)

Marv,
The older I get the more easily distracted I have become. Besides the more or less universal CRS syndrome, I also find that I think a lot more about the hereafter. I walk out to the shed to get something and when I get there I find myself saying "What am I here after". But seriously, I find that the more distractions I eliminate the more productive I am as well as being safer.

Vernon,
Never fear. I plan to post photos of all completed parts as I finish them. I just will not be posting in process photos of things that are the same as have been posted in the Version 1 portion of the thread. Things that are new or different I will post in process photos of.

Gail in NM


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## GailInNM (Jan 3, 2010)

The connecting rods are different in that they are shorter and a little bit narrower. The same methods were used to make them as used in version 1. Although the cross section of the rod is smaller, they are still plenty large. Compression ignition engines are hard on rods, so I always make sure they are are on the large side.
Gail in NM


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## NickG (Jan 4, 2010)

Nice work Gail,

Shame about the first one but can't wait to watch Mk 2 materialise now!

Nick


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## GailInNM (Jan 4, 2010)

Thanks Nick,
Nothing to worry about on the Mk1 version. I consider it a success. It runs and has reasonable power. Just not quite as stable as I would like. I learned enough from it to make a better one is all. The Mk2 just has all the chnages in it that should make me happy and the engine suitable for others to build if someone desired. Most notable is the getting rid of special parts (hard to get) like the ball bearings that I used. The rest of the changes just improve things in areas a little at a time and should improve running qualities. 
Gail in NM


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## arnoldb (Jan 4, 2010)

Good going Gail!

And thank you; as this engine is definitely on my future build list, I really appreciate the fact that you are aiming at easier-to-get parts.

Kind regards, Arnold


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## ksouers (Jan 5, 2010)

Gail,
Was there a reason for going with a shorter rod?


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## GailInNM (Jan 5, 2010)

Kevin,
The shorter rod reduces the dead volume in the crankcase by lowering the piston. This increased the compression ratio in the crankcase, which is the primary compression. The higher primary compression will increase the air intake velocity and the transfer velocity. That should make the needle valve less sensitive to RPM variations and fuel level.

I was going to get some more progress posted, but found another area that would make building easier. Just changing the drawings now, so should be able to post them later tonight. These changes will not change performance.

Gail in NM


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## ksouers (Jan 5, 2010)

Thanks Gail. That all makes sense now. 
Are you also going to shorten up the cylinders or use a longer piston?


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## GailInNM (Jan 5, 2010)

I took 0.156 off the top of the crankcase and dropped the intake and exhaust ports in the crankcase down. This let me keep the piston and cylinders the same, and reduced the overall height of the engine. 
Gail in NM


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## GailInNM (Jan 9, 2010)

Just a quick update with no photos.

I turned up the front bearing mount and the center bearing mount and the bronze bearing to go in them. Also the rear crankcase cover.

Then I test fitted them to the crankcase. What is going on?? The front an rear parts hung down over the bottom edge of the crankcase. I don't know how, but I located the bore for the crankshaft 0.015 low. Of course the dozen 0-80 holes moved with it perfectly. I thought about how hard it would be to compensate for it. Gave up and decided it would be less work to make a new crankcase. Between Tony's "setup" crankcases on his Whittle V8 andm my "extras" on the MK2 we are getting a good collection going. This is start #4 for the Lobo MK2. Fortunately on mine the first two were screwed up early when getting a blank squared up. 

Now the #4 crankcase is about 75 percent done. All the critical work is done and double checked. I am just starting to start profiling the outside so should be done machining tomorrow and ready for polish.

Gail in NM


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## Deanofid (Jan 9, 2010)

Thanks for the update on the Lobo, Gail. You're a trooper, and like Tony, a good example for us!

Dean


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## GailInNM (Jan 9, 2010)

Thanks Dean.
Tony and I are just persistent is all. I think that is a trait that all model engineers have. Zee is one of the best examples on this site. 
Gail in NM


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## GailInNM (Jan 11, 2010)

If you have followed this thread from the early days you know that I rounded the bottom of the crankcase using a CNC mill. Outside of the forum some one asked me how to do it with out using CNC. Since I screwed up the last crankcase and was making a new one I decided to take the little bit of extra time to illustrate how I do it without CNC. There are a lot of other methods, but this works for me and I have used it, or a variation, in the past. One other way that is widely used is to mount the crankcase on a mandrel in a dividing head, indexer, or spindex. 

My method uses a variant of filing buttons. Two buttons are made. The outside of both are the same, and the hole through one is a clearance hold and the other has a tapped hole. One end is made to fit the inside of the crankcase bore, 0.718 in this case. The center section is made to match the desired radius of the outside of the crankcase, 0.469 radius or 0.938 diameter for the Lobo. The other end is small diameter. It must be large enough that the bolt head does not protrude, but small enough that the remaining portion can be clamped securely in the vice. I made these 0.312 diameter. This was the same as the 8-32 bolt head that I was going to use, so I had to turn down the bolt head some. The only reason for using 8-32 was that it was the only bolt I had that was long enough.

The first photo shows the two buttons on a bolt. Notice that a relief is cut at the junction between each diameter so any radius on the lathe tool does not interfere with the buttons seating. Barely visible in the photo is a generous countersink on the left hand button, which is the threaded one, to make it easy to start the bolt. The second photo shows the buttons mounted on the crankcase.









The assembly is clamped in the milling vice with the small diameter of the buttons resting on the vice jaws and clamping on the large diameter. You may want to check that the vice jaws are at the same height before doing this. The cutter is set to just clear the filing button and a milling cut is made with an end mill. There will be no need to change this cutter height on the rest of the passes. Turn the spindle off and rotate the part a few degrees, keeping the buttons pressed down against the vice jaws, and then make another cut after clamping. Repeat until the crankcase bottom is a series of flats. The closer the flats are to each other the less filing will have to be done.  The only precaution is to make sure the cutter does not touch the crankcase mounting lugs. 









After the entire bottom is done, finish with a file, filing end to end, until the file just touches the buttons on each end. If you only made a few cuts with the mill, it will take a lot of filing, but if you make a lot of cuts with the mill it will only take a few minutes to file. No photo of the filing is shown. Just the finished crankcase polished and ready to go. 
Gail in NM


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## Deanofid (Jan 11, 2010)

Neat, Gail. I've used filing buttons, but never thought of using them as part of a fixture, too. It's a good idea.
Did you harden the buttons, or are they just CRS or some such?

Thanks for the show.

Dean


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## GailInNM (Jan 11, 2010)

Thanks Dean.

I like this method as it is as quick to machine as using an arbor and takes less material than an arbor. Also it takes a lot less time to set up than using an indexing head and making an arbor.

Another off forum email asked if the Lobo could be made as a glow plug version instead of compression ignition. Fuel for compression ignition is not as easily available as is glow fuel because it is not as popular, at least in the United States. I responded directly to him, but thought others might be interested.

A glow version should be no problem. All the port timing is suitable so no changes would need to be made in the bottom end of the cylinder. The top end of the cylinder would need to be reduced in height to get the glow plug down to the right height because the contra piston would disappear. A standard glow plug is too large in diameter to just recess in a new head. I did a couple of quick calculations, nothing final understand. I appears that to get the compression ratio in to the 6.5:1 area that the cylinder would have to be trimmed about 1/8 inch. This could be accomplished by removing one fin and one fin spacing from the top and by spacing the remaining fins a little closer by thinning the fins down. Glow engines run a little bit hotter than compression ignition engines, but the Lobo has lots of cooling. I can hold on to the cylinder for several seconds before becoming uncomfortable. The crankcase is rather massive and it get rid of a lot of heat also.

Should there be sufficient interest, after the current build is finished I can draw up the changes for a glow ignition engine. I will be ready to move on to something different by that time, so I probably would not build one myself.

Gail in NM


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## GailInNM (Jan 12, 2010)

With a GOOD crankcase in hand it is time to start filling it up.

First off is the Center Bearing Housing. It is quite a bit different from the original version. First off two O-rings have been added to make the fit between it and the crankcase less critical. Next the bore is just a reamed hole to take a sleeve bearing instead of recessing each end to take a ball bearing.

The OD is turned to be a close sliding fit in the crankcase and the O-Ring grooves cut. After cutting off and facing to length it is center drilled, drilled and reamed to take the center bearing. The housing is moved to the mill and drilled and tapped for the 4-40 retaing screw that locates and secures in the crankcase. Run a reamer through the center bore by hand to remove any burrs caused by the tapping operation and also remove any burrs on the OD with abrasive paper. Finally cut the grooves in one end that engage the bearing insertion tool. The grooves should be about 90 degrees from the tapped hole to make alignment easier but the angle only needs to be eyeball precision.
Gail in NM


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## sourdoughsmitty (Jan 12, 2010)

HI Gail ,
I amm the one who asked about glow use ,I just checked back here to the forum and you answered a ? that I emailed you about r/e cyl change for glow thanx that will help a bit I like the upgrade to bronze bush I too used many a motor with them the only caution to others here is make sure that you use castor for the lube instead of the the usual modern stuff as it seems to keep the bearings better ,just my experience with old motors here 
thanx smitty


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## GailInNM (Jan 12, 2010)

Smitty, your comments about lube are appreciated. The major fuel suppliers have different formulations for ball bearing and sleeve bearing engines. Pay your money and take your choice.

Withe the center bearing housing done the center bearing can be made and fitted to the housing. The bearing is made from SAE660 bronze. Other designations for the same material are CDA932 and C93200. The the OD of the bearing is turned to be a slip fit in the housing. The inside is drilled a reamed to 5/16 (0.3125) and the front half of the center crankshaft will be made to match this bore. The length is 0.010 longer than the housing to prevent the crankshaft webs from touching the housing.

Both ends of the bearing have a shallow groove (0.062 wide X 0.005 deep) cut across them for oil passages to the crankshaft. 
Gail in NM


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## GailInNM (Jan 12, 2010)

Installing the bearing in the bearing housing is done using any Loctite retaining compound such as 609,640 or 680.
The only tricky part is that the bearing needs to protrude about 0.005 inch from each end of the housing. A spacer with a notch in it is used to space the bearing. Heavy weight printer paper, 30 pound, is about 0.005. Regular copy paper is only about 0.003. Clean the housing bore and the bearing OD with alcohol, acetone or some other solovent that leaves no residue. Apply the Loctite near one end of the bearing and insert in into the housing with a twisting motion. Place the housing over the spacer so the bearing fits in the notch and push the bearing all the way down. By sliding the assembly around on the spacer you can feel the edge of the notch in the spacer so you know that the bearing is in the correct position.
Gail in NM


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## GailInNM (Jan 13, 2010)

The front bearing housing is regular turning, drilling and reaming job. On the Mk1 I used ball bearings and that is changed to a sleeve bearing on the Mk2 so the bore is just a reamed hole. An irritant on the Mk1 was the gasket between the housing and the crankcase. The flange is not very wide so the gasket was delicate. I broke several while taking the engine apart multiple times to tweak and check things. So, the gasket has disappeared and been replaced by an O-ring in a groove on the bearing housing housing. The same applies to the rear cover which will be coming up shortly. In total the engine uses 4 O-rings and they are all the same--AS568-015. By altering the groove a metric o-ring could also be used.
Gail in NM


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## GailInNM (Jan 13, 2010)

The front bearing is another turning similar to the center bearing. Again bronze (SAE 660) is used. This time it is turned to 0.375 diameter. Length is 0.023 longer than the front bearing housing. The oil passage (0.005 X 0.062) is only put in on one end, and that end will face to the inside of the crankcase. It is reamed to 0.250, which is larger than on the Mk1 which was 6mm to match the ball bearings that have disappeared on the Mk2. After cleaning both the bearing OD and the bore of the housing the parts are Loctited together same as was done on the center bearing assembly. This time however, the bearing wants to be flush on the nside the crankcase with about 0.005 sticking out beyond the front of the bearing housing. 
Gail in NM


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## GailInNM (Jan 13, 2010)

The rear cover is basically the same as the Mk1 except that it has a O-ring groove cut into it to eliminate the gasket. The depth of the of the groove made it necessary to reduce the diameter of the lightning cutout in the back of it by 0.062 inch.
Gail in NM


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## Deanofid (Jan 13, 2010)

The most recent version is looking good, Gail. I like the idea of O-rings, (and thanks for explanations).
Good thinking using paper for your locating spacer on the bearing. I would have been looking through my brass shim stock. Sometimes, or often, the most sensible idea isn't the first one that pops into my head!

Dean


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## GailInNM (Jan 13, 2010)

Thanks Dean,
I use paper for setup spacers like that. Besides the 0.003 and 0.005 for the light and heavy weight copy papers, my 3X5 index cards are 0.0075 so two of them stacked up make 1/64 inch close enough. 

With the front bearing done, the front crankshaft can be made and fitted to the front bearing. It is the same procedure as was done on the Mk1 but a few dimensions have changed. Most notable is the change from 6mm main shaft to 0.3125 to suit the imperial sized 5/16 reamer I used for the front bearing bore.
Gail in NM


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## Powder keg (Jan 13, 2010)

Looks like you are staying busy) Nice job.


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## cobra428 (Jan 13, 2010)

Looking good Gail

Tony


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## GailInNM (Jan 15, 2010)

Thanks Tony and Wes.

The center crankshafts turned and ready to assemble to the center bearing assembly. I had to make up a new crankpin turning fixture as the the main shaft diameter was changed from 8mm to 0.3125 on the front half of the center crankshaft. This was done so I could use an imperial reamer to make the bearing. 
Gail in NM


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## GailInNM (Jan 15, 2010)

A few small parts were made that were unchanged from the Mk1 version. The prop driver, prop washer and prop nut.
Adding a button head 4-40 x 3/16 screw, a dozen 0-80 X 3/16 socket head cap screws and 4 o-rings gives us all the parts necessary to build the bottom end of the Lobo Pup Twin. In addition some Loctite retain compound will be used to assemble the center crankshafts.
Gail in NM


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## GailInNM (Jan 16, 2010)

Before assembly is started, everything was cleaned with alcohol saturated paper towel strips. The crankcase is likely to have traces of polishing compound in various holes and needs to be flushed out.

Assembly is started with inserting the front crankshaft into the front bearing. Before inserting, the crankshaft is lubed using regular 20 weight machine oil. When running it will get replaced with the castor oil in the fuel. The Prop driver is pressed on the crankshaft in my milling vice using a length of bar that has been drilled 3/16 and the ends faced so they are parallel. Then a test knurled knob is attached to the crankshaft to make adjustment easier later. An o-ring is installed on the front bearing housing. 









Assembly of the center bearing assembly with the two center crankshafts requires a bit of care. Most important is that no Loctite get into the bearing. It is easy enough if precautions are taken. I inserted the front half of center crankshaft into the bearing from the end of the bearing housing that does not have the notches used to align the housing in the crankcase. It is lubed with machine oil as it is inserted. After inserting, the inside of the crankshaft is cleaned using alcohol and a cotton swab. This is to make sure that no oil has gotten into the crankshaft. Loctite retaining compound is placed inside the crankshaft, making sure that no compound gets on the bearing. Then the rear half of the crankshaft is inserted with a rotating motion to distribute the Loctite. The assembly is placed into the alignment fixture and every thing pressed down so the bearing housing and both crankpins are touching the housing. Notice the o-rings have not yet been installed on the bearing housing. After the Loctite is set the O-rings are installed on the bearing housing. 
Gail in NM


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## GailInNM (Jan 16, 2010)

Put a drop of oil on each o-ring. Using the insertion tool, insert the center crankshaft assembly into the crankcase and align the 4-40 clearance and tapped hole. Insert the 4-40 x 3/16 screw in the bottom of the crankcase to secure the crankshaft assembly.

After applying machine oil to the crankpin, install the front connecting rod through the cylinder hole in the crankcase on the front crankpin. Then insert the front bearing assembly while looking through the cylinder hole to align the slot in the front crankshaft. Secure with 0-80 x 3/16 screws. Install the rear connecting rod with oil and then install the rear cover and secure with 0-80 screws. This completes assembly of everything below the top of the crankcase except the fuel system.
Gail in NM


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## Deanofid (Jan 16, 2010)

A more complicated assembly process than I had figured, Gail. Everything just so, and in order.
Still looking good. Maybe not to far from video time?

Dean


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## GailInNM (Jan 16, 2010)

Thanks Dean,
Assembly is logical. I just detailed it out so it looks more complicated.
I have the cylinder stock by the lathe so I can start on them in the morning. They should go fairly quickly as they are the same as the Mk1 version except for some relief for the con rods has to be added in the skirts.
Gail in NM


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## arnoldb (Jan 16, 2010)

You've been busy Gail  - Well done and shown!

Regards, Arnold


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## GailInNM (Jan 16, 2010)

The cylinders were turned up same as the Mk1 and the porting cut into them. Then they were rough lapped to about 0.0005 under size. By careful planning I was going to cook a brisket in a slow oven for about 5 to 6 hours today to ward off starvation for a few days. So the oven was set to 550 deg F and I went about cleaning all traces of oil off the cylinders. Oven was up to temperature so the cylinders went in the oven for 20 minutes to produce a blue/black oxide coating. In the intervening time I prepared the brisket for the oven. Remove the cylinders and replace with brisket and turn down the oven temperature.

I turned up a dummy piston to an easy slip fit in the cylinders and made up the wrist pins. I knew that the connecting rod was going to hit the bottom of the cylinder skirt. There are three options. One is to countersink the bottom of the skirt with a 60 degree included angle countersink for about 0.050 inches. Second would be to just reduce the length of the cylinder by 0.050 inches. Both of these options leave the bottom of the piston skirt unsupported as it passes bottom dead center. This would not be a problem as there are only very small side loads near BDC, but it just never seemed very neat to leave it that way. The third option, which is what is on the drawing, is to relieve the bottom of the cylinder with a burr with a notch about 0.150 wide by 0.050 deep at about 30 degrees. That is what I did. Carbide burr in the rotary hand tool and 10 minutes later they were finished. The reason for the dummy piston was so I could check that the rods were not touching. Just hold the cylinder in place on the crankcase and turn the engine over. When the rod quits touching, take off an extra 0.005 or so for safety and it's done.

One other thing that could be done is to round the edges of the rectangular cross section of the rod. This almost gives enough clearance. I did not do this.

All that remains on the cylinders is the final lapping and polishing.
Gail in NM


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## kustomkb (Jan 16, 2010)

Nice Job Gail!

Thanks for another very nice build.

And thanks for the detailed explanations.


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## Deanofid (Jan 17, 2010)

So, how was the brisket?

; )


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## ariz (Jan 17, 2010)

thanks for sharing, nice and useful as always!


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## GailInNM (Jan 17, 2010)

Thanks Kevin and Ariz.

Dean, the brisket is good. I did not get to do more than sample it yesterday as I got a better offer for dinner. Went to dinner with my son and his family. Got to see two of the granddaughters that I don't get to see very often. But the brisket made for a fine lunch today.

Gail in NM


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## Deanofid (Jan 17, 2010)

You sound like you have a similar situation to my own, George. Just me and the dog here, so cooking for a few days ahead makes sense. Works for a middle-aged-pushing-ol'-codger kind of guy, like me.

Sunday is pizza day. The dog likes that, too.

Dean


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## Maryak (Jan 18, 2010)

Gail,

Good Brisket, Good Family and a Good Engine as well - not to mention your good dog. :bow: :bow: :bow: :bow: Thm:

Best Regards
Bob


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## GailInNM (Jan 18, 2010)

Dean,
Your are correct. Just me and the puppy dog named Coot. He is the Young Coot and I am the Old Coot. I enjoy cooking and enjoy eating my own cooking so he and I eat quite well. At least I don't hear any complaints from Coot.

Thanks Bob. You are right about everything except not sure about the Good Engine yet.

Busy for the last few days, so did not get too much done on the Lobo. Just the cylinder heads. But all that leaves is final lapping the cylinders, then making and mating the pistons and contra pistons. I need them to make the compression adjustment screws and compression limiter. And,of course the carb, Then wait for a warm day for test runs.

So the cylinder heads is the only progress report. They are unchanged from the Mk1 version.
Gail in NM


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## GailInNM (Jan 21, 2010)

The final lapping of the cylinders is done and the pistons and contra pistons are made and mated to the cylinders. The wrist pins are also done but not photographed.
Gail in NM


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## Deanofid (Jan 21, 2010)

It doesn't look like there could be to much to go on this one, Gail. 
A great effort. How many engines did you actually end up making to get to this point?

Dean


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## GailInNM (Jan 21, 2010)

Getting down to the wire, Dean.

Only the fuel system and compression limiters to go. Thanks for following along to keep me honest.

The limiters will wait until I loosen the engine up a little bit so I can feel the contra piston touch the piston easier. 

I could cheat on the fuel system and steal the carb from the Mk1, but the weather forecast is for it to be to cold to try a test run until next week so I will build a new one. 

With it partially assembled I ran it for a few minutes in the lathe for a few minutes at about 1500 RPM. Lots of suction and sucking sounds from the intake where the carb will go. Big improvement over the Mk1.

Gail in NM


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## cobra428 (Jan 21, 2010)

Looking real nice Gail
Dieing to hear it hummm

Tony


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## GailInNM (Jan 23, 2010)

Dean,

I forgot to answer your how many Lobo's I built to get to this point. This is the second Lobo that is completed. I suppose that if you put all the spare parts in a paper bag and shook long enough another one would fall out. It would probably look a little strange with the changes that have crept in on the two versions.

I finished up the fuel system, so the Lobo Pup is ready to take it's first steps at howling next week. Test stand was covered in snow until about a hour ago. Warm enough for the snow to melt, but not warm enough for an old man to play engine games outside. It will probably be late in the week for the test run. Tuesday is the first day forcast to be warm enough and I have to spend the day humoring the MD's that keep me building toys.

Here is the engine with the fuel system installed and ready to go.
Gail in NM


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## ariz (Jan 23, 2010)

it is very very nice Gail and sure it will run smooth

you have completed another great build, many compliments :bow: :bow: :bow:


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## Maryak (Jan 23, 2010)

Gail,

Great engine. :bow:

Send it here, we have a week of over 30C days. 

Best Regards
Bob


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## Deanofid (Jan 23, 2010)

We'll be watching, listening, for a good bark out of it soon, Gail!

I thought you had built quite a few versions of a few of the parts for this. We all "get" to do some do-overs in this game.

I'll have to try the paper bag trick with some of the stuff in my rejects box. Ought to get a couple of "engines" out of that, at least. ; )

Dean


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## GailInNM (Jan 27, 2010)

The Lobo Pup is alive and running. woohoo1

The weather man is still not cooperating with me. It is still about 5 degrees below my threshold of pain for playing with toys but I could not stand it any longer. Besides the long range forecast shows it being colder for the next week.

So off to the test stand. Full fuel tank and a almost charged battery for the starter and away we go. Open the needle valve about 1-1/2 turns and back off the compression on both cylinders. Hit it with the starter and the fuel jumps right up to the needle valve. Much better than the Mk1 which had weak fuel draw. Bring up the compression on the #1 Jug and it starts to show signs of life. Play with the compression and needle valve setting and it starts to unload the starter and make better noise. Still won't run with out the starter of course as there is nothing but drag coming from the #2 cylinder. Bring up #2 cylinder compression and it starts to run for 5 seconds or so without the starter. Everything is still stiff, but it is loosening up a little bit. I am still running it rich until things wear in a little bit.

The whole 10 seconds of run routine is repeated until the fuel tank is empty. It's a small fuel tank, less than a fluid ounce. Refill the tank and start over again. This time I lean it out a little bit and it runs on it's own. And the first problem shows up. The compression adjustment works loose. To keep it running smooth I have to hold the compression adjust lever in position by hand. This is probably means the contra piston is a little bit too loose and a new one will have to be made. I wont know until I pull the #2 jug off and inspect it but I am pretty sure. It takes less pressure to move the contra piston down with the adjusting screw than it should, and less than #1 cylinder takes.

Second problem is the needle valve spring makes the needle jump during adjustment. Close it a 1/4 turn and it jumps back an 1/8 turn when I let go. I probably need a stronger spring and a smoother grind to flatten the ends.

Third tank of fuel. I start it and let it run the whole tank out. My left hand is frozen holding the #2 compression adjustment in place in the slipstream. I smell of ether my fingers taste of castor oil and the starter battery is low so it's time to call it a day. Remove engine from test stand, clean it up and retire to the shop. Wash hands. They no longer smell of ether, but left hand still has little feeling other than cold. Wash hands again, this time with hotter water. Much better. 

Time to remove the #2 jug and check the contra piston, and probably make a new one. And nake a new spring for the needle valve and maybe put a washer on each end of it to smooth it out.

It will be about another week before the weather warms up enough for another run. I will try to get video then. Could not do so today while holding the compression adjustment in place. 

Gail in NM


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## Maryak (Jan 27, 2010)

Gail,

Congratulations :bow: :bow: Looking forward to the warmer weather and the, (by now), obligatory video.

Best Regards
Bob


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## cobra428 (Jan 27, 2010)

Congrats Gail,
Can't you use a little blue Loctite on the contra to tighten it up a bit?

Tony


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## Deanofid (Jan 27, 2010)

Alright Gail! I just knew you would have a good report for us when I saw the "Lobo" subject line.

It's hard to be patient, but I don't live close enough to come over and prod you. We'll just have to wait for the video. ; )

Dean


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## NickG (Jan 28, 2010)

Great work Gail.


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## ozzie46 (Jan 28, 2010)

WAiting for the Video Gail.


 Ron


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## GailInNM (Feb 6, 2010)

Thanks for the comments everyone. 
A new contra piston was made. The old one was borderline on my rule of thumb test. If I can push it in with my thumb then it is too loose. I just put washers on each end of the spring to stabilize the needle valve. It could use a heavier spring with properly ground ends, but it works OK with the washers.

Video is attached. The Lobo is running about 6900 RPM at the beginning of the video and climbs to about 71oo RPM with a Master Airscrew 8-4 propeller. It is still running rich while I break it in, but these are acceptable numbers for a long stroke engine of this displacement. 

I will have the final updates on the drawings in a few days. All the changes have been made to the files but I want to make one final check before converting to PDF and re-posting them in the early posts for this thread. I will also post the final photos as the engine gets ready to disappear into the dark recesses of my display cabinet so I can start on something new.

Gail in NM
[ame]http://www.youtube.com/watch?v=PtPvTr94_7w[/ame]


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## rake60 (Feb 6, 2010)

Congratulations Gail!

Great runner! Thm:

Rick


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## putputman (Feb 6, 2010)

Gail, that engine really sounds good and smooth.

How do you use to measure the rpm?


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## Maryak (Feb 6, 2010)

Gail,

Congratulations - Fantastic Twin. :bow: :bow:

Not to mention a great build thread and tutorial.

Best Regards
Bob


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## Deanofid (Feb 6, 2010)

Double congrats, Gail! It sounds like it's running great.
You really made the extra effort on all the extra parts that had to be made for this one.

Dean


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## kustomkb (Feb 6, 2010)

Congrats on a great looker/ runner.

Thanks for the drawings and build tutorial.


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## arnoldb (Feb 7, 2010)

Great runner Gail :bow:

And thank you for the build thread!

Kind regards, Arnold


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## ariz (Feb 8, 2010)

great looking and running engine Gail!!!

it's very smooth too, symptom of a well built engine :bow:


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## NickG (Feb 8, 2010)

Great job gail, seems to be running incredibly smoothly despite my jerky computer!

Well done, fantastic engine, thanks for the build log, can't wait to see the next project!

Nick


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## GailInNM (Feb 9, 2010)

FINAL REPORT

First off I want thank everyone who followed along on the Lobo Pup Twin from concept to the final run video. It has been a fun trip and having others follow the progress along has just made it more fun. I think we all welcome positive comments. I know it helped keep me going.

Arv, I measured the RPM using a contact tachometer. The 6900 RPM number came from the last part of the previous run before the video and the 7100 RPM came from the start of the run following the video. At the last run I was measuring about 7300 RPM and I do not expect it to improve from that. The tachometer loads the engine about 100 RPM, but I did not correct for that. I have an optical tach also, but did not use it on this engine.

All the drawings are contained in the first three posts of this thread. They have been updated to reflect the "as built" status of the Mk2 version. They all carry a REV E notation and a date of Feb 9,2010. Any one using these drawing for reference or building should make sure they have the REV E drawings.

Thank you everyone.
Gail in NM

Photos show both the Mk1 and Mk2 versions and the Mk2 version alone. The Mk 1 has the Lobo head on it.


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## GailInNM (Feb 9, 2010)

And a final howl and wishing everyone the best of engine building fun.


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## joe d (Feb 9, 2010)

Gail

Those turned out great. I especially like the hood-ornament!

As always, it was an excellent learning experience following along, thanks for sharing with us.

regards, Joe


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## Deanofid (Feb 10, 2010)

Hey, twin Twins!
Thank you for all the extra work involved in the presentation of this project, Gail.

Dean


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## metalmad (Feb 24, 2010)

Fantastic thread 
I just read it from start to finish and am wondering if it or the whittle v8 will be my next project
love your work 
 :bow:


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## GailInNM (Feb 24, 2010)

Welcome to HMEM Metalmad.
I invite you to put a little introduction to yourself in the welcome section.

Thank you for your comment about the Lobo Pup.  The engine you build should be based somewhat on the level of engine building experience you have. The Whittle V8 is a wonderful engine, but I feel that anyone who builds it should have at least one or two successful 4 stroke engines under their belt before attempting it. Tony (Cobra428) has a very nice thread going on about his Whittle V8 build.

Whatever you decide to build, keep us informed and if possible do a build thread on it.

Gail in NM


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## Tad Wicks (Feb 25, 2010)

GAILinNM,
 I just can't get over the talent that is on this website, I have only been coming here for a few days thanks to gbritnell and all I can say is that I am delightfully impressed with everyone and everything I have seen so far. Major congratulations on a great build and having the tenacity to see it through, thank for the time you took to photograph and explain everything you did.
 Are you far from the town of Reserve, NM? I have a sister that lives there. Thanks Again; Tad


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## GailInNM (Feb 25, 2010)

Thank your for the kind comments Tad. 

There is a lot of talent on HMEM, but most important is that the members are willing to share their talents no matter what level they are at. Everyone has something to contribute at some level and no one has to be afraid of putting forward any build of any level.

Welcome to HMEM. Please share your talents with us.

I live about 200 miles NE of Reserve. I have never been there, but have passed within a dozen miles of there a number of times when I lived in the SW part of New Mexico years ago. It is a little off the beaten path.

Gail in NM


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## GailInNM (Jun 22, 2010)

A few updates on the Lobo Pup Twin.

The complete drawing package has been placed in the Downloads section on page 17. The drawing are in three different formats. PDF, DWG, and DXF. The CAD versions are in the lowest ACAD format that I can generate so should be able to load in most CAD programs that can read either DWG or DXF formats.

Someone in one of the countries that is metric based is converting the drawings to metric standards and building an engine to those specifications. He has contacted the editor of "Model Engine Builder Magazine" about having the plans and an article published after he completes building and running an engine. The editor contacted me for permission to do the spin off article, which I gave. I also sent the editor, at his request, my electronic drawing files. IF the article comes to be, then the editor plans to publish both the Imperial and Metric drawings. He would redraw my drawings to the MEB standards as he does with most submissions. I am not holding my breath on all of this happening as I know how easy it is for most of us to get side tracked on projects and the metric engine may be a long time coming.

For those not familiar with MEB, their website is:
www.modelenginebuilder.com
It is a great magazine. In the beginning it was devoted almost entirely to internal combustion engines, but it is now branching out into other types. 

Ron gave the Lobo Pup a nice plug on his long running website in the March 2010 issue. By his own admission, Ron is a sucker for twins.
http://modelenginenews.org/ed.2010.03.html#t1

The rest of his website is at
http://modelenginenews.org/index.html
and contains the last 8 years of his monthly editorials along with an astounding amount of information about model engines, mostly model aircraft engines. 

Gail in NM


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## GailInNM (Dec 24, 2010)

I received a PM today from an HMEM member who is starting to build a glow plug version of the Lobo Pup Twin. He asked for recommendation on the glow head and cylinder modifications. 

I have sketched a glow head and revised cylinder of what should work OK. I have not tried this, but I have built successful side port induction glow engines following this general layout before. Unless I have overlooked something this should work OK, but no rash promises. Fins were added to the head as glow engines normally run hotter than compression ignition and the additional fins will help make up for the loss of two cooling fins on the cylinder. Everything else should remain the same between the two versions. The drawing is attached as a PDF file. 

I forgot to dimension the counter bore for the head bolts on the drawing. It is 0.156.

Gail in NM 

View attachment GLOWHEAD.pdf


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## ebrathole (Oct 28, 2011)

I ended up completing the glow version of the Lobo and it runs, sort of. It's very tough to get started, then will run for about 30 seconds and not restart. After waiting a while (maybe until it cools) it will restart. It will also only start with a finger flick to the propeller (8x4 plastic prop). Cylinders are 1144 and pistons are cast iron. Fuel's tried have been Patriot R/C supreme 10% nitro 18% oil, and Traxxass top fuel 20% Nitro. Either fuel seems very hit or miss wanting to fire or run. My two theories are either a) the 1144 expands faster than the cast iron and causes a compression loss, or b) starting and not wanting to restart is a fluke and my real problem is a fuel delivery problem. Any tests, ideas, or parts to remake? I think the fact that i've got it to run at all is a success for a first attempt at an IC, but I'd love to have a reliable runner.


Thanks,

   Eric


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## ShedBoy (Oct 28, 2011)

Hi Eric, how about posting some pictures of your engine in a thread in the finished engine section. I am interested in making the glow version of this.
Brock


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## GailInNM (Dec 4, 2011)

Eric,
Sorry to be slow in responding about your build. With lots of life getting in the way about the same time you posted things kind of slipped through the cracks.

My GUESS is that the difference in thermal expansion is not what is giving you problems. 1144 and cast iron are both close to each other with 1144 being slightly greater. This is offset by the cylinder running cooler than the piston anyway so I don't think that should be a problem.

I would guess that the fit and finish between the piston and cylinder is the problem. When hot the lubricant in the fuel is much thinner and will not make as good a compression seal and when cold. 

I have seen this behavior on early 1/2 A class engines as the piston/cylinder became worn and even on some new commercial engines where the piston and cylinder were not properly fitted at the factory. On my engines I make the piston/cylinder initial fit slightly tight and and most often put a slight taper in the cylinder to provide a squeez point at the last 10 percent of the piston travel as it approaches top dead center. In engines of this size it is essential that both the piston and cylinder be lapped with a very fine lapping compound using internal and external laps and very fine lapping compound. I typically use either 5 or 10 micron diamond lapping compound for the final fit.  5 micron is about 3000 mesh and 10 micron is about 1800 mesh.

Never try to lap the piston and cylinder to each other by putting any kind of polishing or lapping compound on the parts and then fitting them together. This will produce a fit that looks nice but will be too loose for good operation. Larger engines, say 3/4 inch bore, can get away with it but not small bore engines.

Gail in NM


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