# Single Cylinder 4-stroke machined from bar stock - Westbury's Kiwi Mk II



## Eccentric (Jan 18, 2021)

I am going to be machining Edgar Westbury’s Kiwi Mk II from bar stock.  I thank Model Engineer Magazine for making the articles free to download. They were printed 60 years ago!  I have captured the design in CAD and have made some modifications to ease my fabrication.  I will not be using BA hardware, I moved the engine mount to the bottom of the engine so it will stand on its own and made lots of small modifications to suit CNC machining.   I am starting with the front crankcase half, which will be machined in two operations, one from the back and one from the front, both using a ¼” flat end mill.  I used my 3D printer to print the parts and identify errors in my CAD model, of which there were a few.   I then used Fusion 360 to create the tool paths for my CNC router.  My CNC router is home made mostly from MDF and performs surprisingly well.


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## Brian Rupnow (Jan 18, 2021)

Eccentric--Very interesting. I was thinking about a single cylinder vertical 4 stroke this morning. I am suffering from 'machining burn out' right now, and trying not to start something new until January is over.  If I do go ahead with one, it will all be manual machining. Good Luck!!---Brian


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## Eccentric (Jan 19, 2021)

Thanks Brian, I have digested most everything you have writen on the Webster as it was my first choice for an engine to build.  I compiled a multipaged document of notes and recommendations. But I eventually decided I wanted to make an enclosed crankshaft engine with conventional valves, seats and lifters for the experience.  I know you like Viton rings, but I am considering trying my hand at making my own cast iron rings, again for the experience.  I ultimately would like to build a multi cylinder engine, but am working on building my machining skills.  I spent today machining the front side of the crankcase front. I am pleased with the important dimensions, but I think the surface finish could be better. This is when I wish I had a bead blaster, but I don't have room in my little workshop and can't justify it for how little it would be used, but ....  I will ream hole for the crankshaft bushing.  I use fusion360 to generate my tool paths for the router.  I am not sure what people are interested in seeing, the CAD design?  the CAM and tool path programming? or just the odd shot of me making chips.  If anyone is interested in building this engine, I am happy to supply any of my models or tool path files.   The photos show the aluminum part compared to the 3D printed part I used for initial prototyping.


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## CFLBob (Jan 20, 2021)

Eccentric - your project catches my eye because I see you and I in a similar place as far as our hardware goes.  I have a CNC Grizzly CNC mill and a smaller, CNC Sherline mill, extended work envelope using A2ZCNC (now out of business) parts.  I've just added a 3D printer for the same sort of uses, as well as making little aids for around the shop.  The CNC process seems to make each part harder to do, because you make it at least twice - once in software then watch the machine make it - as opposed to walking up to the machine and turning cranks.  

So I find this all interesting.  I hadn't heard of this engine, but I'm sure there are thousands of designs I haven't heard of. 

Having just gotten my Webster running, I think your preference for "enclosed crankshaft engine with conventional valves, seats and lifters" is a very good choice.  It seems to me that the intake valve design on the Webster relying on the vacuum the engine generates is a weak spot.  In terms of helping teach of us beginners how the piston compression should feel, it's a good choice, but comparing the solid action of the exhaust valve driven by a lifter and the action of the intake valve is a stark example of how much a lifter does for an engine.  I suppose that's really educational for beginners, too.


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## Eccentric (Jan 20, 2021)

Bob,

I agree with your take on the CNC milling.  I use mine as a standard Mill, with the monitor as a DRO, 90% of the time.  But it does open up additional capabilities like this engine case I am making.  I spent several days modeling the engine on the computer, and then a few hours on the machine making it.  I don’t have the skill to machine it manually and with the CNC any shape is game.  The alternative of machining the crankcase from a casting requires much more difficult and innovative fixturing on both a lathe and a mill.  We all work with the equipment we have.  I envy the guys that have, or have access to, massive production quality machine tools.  If you are interested in using your CNC for something more complicated, I’d be happy to help with CAD modeling or CAM tool path creation; I enjoy working on the computer to support machining.  Today I am machining the rear crankcase half.  The internal cutouts are the same as the front, except the crank shaft is 5/16” when it exits the rear case as opposed to 3/8” for the front case half.  Below are the plans and construction articles that Model Engineer has graciously made available for free download for the Kiwi MK2 Engine.

etw-kiwi-mk2-pt1.pdf (model-engineer.co.uk) 
etw-kiwi-mk2-pt2.pdf (model-engineer.co.uk)


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## Eccentric (Jan 22, 2021)

More Machining today.  Finished the mill work on the rear crankcase, reamed the holes and pressed in the bushings.  I will wait to press in the ball bearings until I do more cleanup on the parts, don't want to get swarf in the balls.  the third photo shows the plastic timing gear cover on the rear of the engine, this weekend I hope to machine an aluminum one.  The square feature on the top of the engine will allow me to touch off and determine the center of the cylinder.  I will then machine the cylinder sleeve hole, and the holes for the studs attaching the cylinder. I used a junky chamfer bit to cut the chamfer on the rear case, this will require some hand filing to fix.  Then on to the crank shaft.  








, then m


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## Eccentric (Jan 27, 2021)

Finished the major machining on the rear timing cover and it is starting to look like a crank case. The first picture shows the timing cover with only the inside machined and mounted to the engine.  The second picture shows all of the outside machined. You can see they don't exactly line up, fortunately this is just cosmetic as all of the critical machining was done from the inside such as the alignment of the spigot to the crank shaft and the relative position of the cam shaft to the crank shaft. Need to do the machining from the top, but I am not sure of the best order of operations for the cylinder sleeve (aluminum), sleeve (cast iron) and the crank case as they all need to fit together precisely.  I guess you start with the most difficult operation, which for me is boring of the sleeve.  Also, I would rather re-machine an aluminum cylinder than a cast iron sleeve. All of that machining will be done on the lathe.  I will mount the crankcase base to the face plate and bore the cylinder sleeve hole into the crank case.  Also, I think I want to lower the compression ratio. Westbury says, "The dimensions shown give the highest ratio recommended for general purposes". I am noodling on the best way to reduce the compression ratio, perhaps increase the volume of the combustion chamber milled into the bottom side of the cylinder head.  An engine with a higher compression ratio has better efficiency and can produce more power at the high RPM range, an engine with lower compression starts easier, and is more forgiving of cam profiles and general play in the system due not less-than-perfect machining.  They also run better at the slower RPM (I think).  I could also just put a spacer between the head and cylinder, but then I have one more place to have issues with the sealing of the combustion chamber, but this would provide a less permanent solution. Decisions decisions.


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## Mike Ginn (Jan 28, 2021)

Very impressive. work.  I have been thinking of moving to 3D machining but don't have a suitable package.  So far I been using Autocad 2D.  Please can you advise which 3D package you use and which post processor you used for the GCode.  At present I am using CAMBAM.
Many thanks
Mike


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## Jasonb (Jan 28, 2021)

You could also drop the compression ration by taking some material off the top of the piston, Provided you don't leave the top too thin you can start with it as drawn and then take a bit off if you feel the ratio is too high.

To help get the "cast look" to the crankcase think about doing a finish cut using either a ball ended cutter or one with a corner radius(convex) which will leave a small fillet on the internal corners. Also you can add draft angle when drawing the part and use a Ramp or Scallop finishing method with a small stepover to follow around the angled sides. Should then need minimal work with a needle file and abrasive paper to finish off. I used to like using "steep & shallow" in F360 but it's too expensive now that they have changed their pricing.

Your order of work sounds OK, make the liner and use that as a plug gauge for the hole in the top of the crankcase flange and also to gauge the bore on the sleeve and finally make piston to fit inside.


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## Eccentric (Jan 28, 2021)

Mike,

I understand the cost of CAD/CAM is hard to justify.  I am lucky as I use Solidworks at work and my son has a license for Fusion360.  I use Solidworks for CAD and Fusion360 for CAM.  I thought that using Fusion360 for both CAD and CAM was free or inexpensive for the single hobby user for non-comercial purposes.  I have also heard good thing about OnShape for CAD.  You just can't beat Fusion360 for creating G-code for the CNC machine.  My CNC router uses LinuxCNC, which is open source.

Jason,

I like the idea of modifying or simply using a second piston to adjust the compression ratio.  That way I can 1.) put that concern off for later and 2.) build the cylinder and head to print.  I will look into Step and Shallow in Fusion360, I have not used that technique.  Thank you for the ideas to get the casting look.

Thank you for confirming my order of operations.  I will work the crank shaft next, then turn to the cylinder sleeve.


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## a41capt (Jan 29, 2021)

Eccentric said:


> More Machining today.  Finished the mill work on the rear crankcase, reamed the holes and pressed in the bushings.  I will wait to press in the ball bearings until I do more cleanup on the parts, don't want to get swarf in the balls.  the third photo shows the plastic timing gear cover on the rear of the engine, this weekend I hope to machine an aluminum one.  The square feature on the top of the engine will allow me to touch off and determine the center of the cylinder.  I will then machine the cylinder sleeve hole, and the holes for the studs attaching the cylinder. I used a junky chamfer bit to cut the chamfer on the rear case, this will require some hand filing to fix.  Then on to the crank shaft.  View attachment 122402
> View attachment 122403
> View attachment 122404
> , then m
> ...


I have a question regarding the oil holes and channels on the crank.  Will this be a forced oiling system so as to utilize the oil channels, or some type of wet sump and splash oiler?   Not sure how it all goes together I guess.

thanks, and really excellent looking work so far!!!
John W


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## Eccentric (Jan 29, 2021)

I use a technique to locate holes that works very well for me.  I use the 3D printer to print a drill guide, the darn thing is scary accurate.  Here I am making a drill guide to place the two center drilled holes at each end of this chunk of cold rolled that will become the crankshaft. As you can see from the photos I use dowel pins to position the drill guide to the work piece.  Then it is a simple matter of drilling the two holes on each end so I can turn on centers.  The actual drilling is much simpler and I have better results getting the accuracy I want than scribing and punching the hole positions.
























Here you can see that I am at the extreme limit of what my little lathe can do.  I have about 3/16” travel on my cross slide before the tool post hits the part, so I have to make a 3/16” deep cut, wind my cross slide back to the stop, adjust the tool, then take another cut.  It takes forever and I have a hard time keeping the tool in the same position for each cut.  I showed my wife and explained I need a bigger lathe, but she was not too sympathetic, she said, “it seems to work fine”.









The crank pin is the hardest part machining the crankshaft for me, I polished with 320 grit, 600 grit and 1000 grit emery. I am uniformly ½ a thou over, so I’m going to call ‘er done. It is not perfect, the crank webs came out a little dodgy becasue of the way I have to reposition the tool as I cut in, and I should have put a radius on the edges of my cutter, I have pretty sharp corners where the crank pin meets the crank web and I have some stress risers there.  Live 'n learn.


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## Eccentric (Jan 29, 2021)

a41capt said:


> I have a question regarding the oil holes and channels on the crank.  Will this be a forced oiling system so as to utilize the oil channels, or some type of wet sump and splash oiler?   Not sure how it all goes together I guess.
> 
> thanks, and really excellent looking work so far!!!
> John W


 Yes I will use the oil holes and channels in the crank to lubricate the crank pin.  It is a gravity feed system.


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## Jasonb (Jan 29, 2021)

even with your sons license the Steep and shallow is now classed as a manufacturing extension and you have to pay per day or per Month, think it is something like $125 a month. It is/was a very easy way to do 3D milling but with a bit more effort the ramp and scallop can be used to give a fairly similar finish. This was one of the last pieces I did before loosing economical access to steep & shallow



And this is one of the first items I made with my CNC, a half crankcase.



I use Alibre for my drawing as I've had it a number of years and know my way around it so did not really want to change which makes F360 expensive if paying for both so I just use it's free CAM which I like a lot.


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## Vietti (Jan 29, 2021)

When I built Cole's 30 cc single cylinder 45 years ago I came up with a way to recover the oil in a total loss system like this one.
Somewhere I'd read about using a check valve to create negative pressure in the crankcase and prevent oil from being pushed out.  I installed one in the only orifice open to me, the oil drain plug at the bottom, rear of the crankcase.  I noticed that oil was pushed out as the one way valve operated so I ran a hose from the check valve back up to the side of drip oiler reservoir.  Holes were drilled around the cap to allow the air to escape.  Works really well.  When its running you can see the oil moving up thru the clear hose.

Probably not an original idea but it worked for me.


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## Eccentric (Jan 30, 2021)

Finished one side of the crank shaft, here I am test fitting it into both the front and rear crankcase halves.  In the first picture you can see the ball bearing mounted on the crankshaft, then it goes through a long oil barrier bushing.  There is a hole in this bushing that allows oil to flow from a fitting on the front crankcase half and into the oil passage ways in the crank shaft.













Back out to the shop and finish the other half of the crank shaft.


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## Eccentric (Feb 1, 2021)

Whew.. My crankshaft is going to be a keeper.  It spins like a dream and no noticable end play.  I had two issues with it, first the spacer I put between the crank web while I was machining the two main shafts was a bit loose and when I cranked down on the tail stock live center, it cause a little flex and the two sides of the crank shaft were not machined exactly colinear.  when I spun the crankshaft in the crankcase, there was a discernable difference in the way it felt as I spun it with my fingers throughout a revolution.   I set it up running in only one crankcase half and put a test indicator looking at the run out and sure enough the crank web sprung open ever so slighly.  I placed one half of the crank web on an anvil and lightly tapped the other with a hammer until I got the dial indicator to run true.  the second issue wasn't really an issue, but as I tightened down the two crankcase halves, the crankshaft got tight.  the crankshaft runs on two ball bearings pressed into each half of the crankcase and the distance between the inner races was a few thou greater than the distance between the two shoulders on the crankshaft that ride on them.  I put the crankshaft back in the lathe and just turned down the sholders a tad, it took three trips in and out of the lathe before I was happy with the end play and the crankshaft spins smooth as butter with the two crankcase halves bolted tight.


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## nj111 (Feb 2, 2021)

I shall follow with interest as I made a Kiwi over many years (actually decades!). It's a great little engine.  But I wasn't happy with the commercial castings I had bought in 1976 so I started again around 2003 and this time made my own crankcase patterns.  After months of casting failures I eventually learnt how to make nice castings but I failed to cast the head successfully so I milled it from the solid.  At the time 3D CAD /CAM in the home workshop was more limiting than it is today but it came out quite well.  

came out pretty good.


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## Eccentric (Feb 2, 2021)

Your engine is beautiful, a real inspiration. Your castings really look nice and I hope my cylinder head comes out half as well as yours.  I will continue to look back on those pictures as I build, that is what I am aming for.  thanks.


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## a41capt (Feb 2, 2021)

nj111 said:


> I shall follow with interest as I made a Kiwi over many years (actually decades!). It's a great little engine.  But I wasn't happy with the commercial castings I had bought in 1976 so I started again around 2003 and this time made my own crankcase patterns.  After months of casting failures I eventually learnt how to make nice castings but I failed to cast the head successfully so I milled it from the solid.  At the time 3D CAD /CAM in the home workshop was more limiting than it is today but it came out quite well.
> 
> came out pretty good.View attachment 122685
> 
> ...


Does the Kiwi utilize a float type carb? Interesting looking carb, and exceptional work! Congratulations on a beautiful engine!

John W


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## nj111 (Feb 2, 2021)

Yes it's a float carb by E T Westbury.   I learnt so much making the Kiwi, including piston rings (Trimble method), making a camshaft grinder, honing accurate bores, getting small valves to seat properly etc.   I tried to do a lost wax casting for the head, but I didn't source the correct wax and so it was a disaster. Eventually I milled the head but made sure all the fins were tapered in thickness. The toolpath options for CNC milling were pretty limited to me around 17 years ago but with some handwork it was a pleasing result.  The second set of crankcase castings you see above went to the late Ron Chernich at MEN, who liked to have plenty of castings in stock under the bench!  Sadly, Ron never did get to make a start on those.  Nick


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## a41capt (Feb 2, 2021)

nj111 said:


> Yes it's a float carb by E T Westbury.   I learnt so much making the Kiwi, including piston rings (Trimble method), making a camshaft grinder, honing accurate bores, getting small valves to seat properly etc.   I tried to do a lost wax casting for the head, but I didn't source the correct wax and so it was a disaster. Eventually I milled the head but made sure all the fins were tapered in thickness. The toolpath options for CNC milling were pretty limited to me around 17 years ago but with some handwork it was a pleasing result.  The second set of crankcase castings you see above went to the late Ron Chernich at MEN, who liked to have plenty of castings in stock under the bench!  Sadly, Ron never did get to make a start on those.  Nick


Thanks Nick, excellent info!  You’re right, every engine built provides so much education and grey matter expenditure that I feel like I’m in a Master’s degree program all over again!

Yours is some very beautiful work, and shows just what can be accomplished through motivation and persistence!

Thanks again,
John


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## MrMetric (Feb 3, 2021)

Those castings are really nice, nj.  In fact, I don't think I've seen many that I would consider to be nicer.  Out of curiosity, what alloy of aluminum did you use for this?  Or was it just melted aluminum from your junk pile?  I know 356 is very common in die casting, but I don't know if people use that (or another specific alloy) for sand casting.


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## nj111 (Feb 3, 2021)

I cut some of these up and recycled them into Kiwi crankcases!   The camshafts run in them on BMW straight six engines (from the 80's and 90's). There was a BMW dismantler next door and he had loads!  Generally for work like this I would advise to use something from a previous casting.


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## MrMetric (Feb 3, 2021)

nj111 said:


> View attachment 122726
> 
> I cut some of these up and recycled them into Kiwi crankcases!   The camshafts run in them on BMW straight six engines (from the 80's and 90's). There was a BMW dismantler next door and he had loads!  Generally for work like this I would advise to use something from a previous casting.



Thanks nj111.  I agree that it is a good practice to use old, high quality, castings as stock.  I do have to wonder if that still applies with modern castings tough.  My association with that life is now over, so I really haven't kept up.  But the auto industry seems to have moved far more "exotic" over the last few decades.  Have the alloys done the same, to the point where you cannot recycle them as easily/safely?


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## nj111 (Feb 3, 2021)

I'd be inclined to agree with you. Fortunately we only cast small parts for this hobby so its usually possible to source something old that's damaged or worn out! The biggest problem I had was caused by myself overheating the alloy, it then absorbs hydrogen and the castings are full of holes and porosity. Once I had figured that out, and also plunged a tablet into the molten alloy to expel gasses and refine the grain  I started to get really good results, but there were many poor results initially!


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## MrMetric (Feb 3, 2021)

Yeah, de-gassing is a critical step in minimizing porosity.


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## Eccentric (Feb 3, 2021)

Here I have attached the 3D models I created for the KIWI MKII crankcase. I have included both the STL files and the IGS files.  These are enough to 3D print and to machine the engine case.

If you open them you will see I took a lot of liberties and redesigned the parts for ease of machining.  They all can be made with a ¼” flat end mill with a .75” cut length.  I have radiused the parts for this end mill and have made other modifications, for example the timing cover is more than .75” deep, but if you look at my model, I have the depth below .7” .020” inside so the tool does not hit the side wall as it goes deeper.  I also used a ¼” ball end mill and a ¼” chamfer bit, but these were for cosmetics.

I have also included all of the Fusion360 CAM files for the crankcase front.  You should be able to load them up in the free version of Fusion360 and see how I created all of the tool paths.  I machine the backside (inside) of the crankcase front first.  These are all of the critical dimension, the pocket for the ball bearing, the crankshaft and the pocket that is indexed for the precise placement of the cylinder sleeve.  Then I flip it over and use the hole in the center to set the X=0 and Y=0 and ensure the axis are true horizontal and vertical.  The features on the front of the case are less critical, but you do want the screw and the crankshaft to hit the center of the bosses.

Feel free to use these for your personal use, I can't imagine they would be of any commercial value.


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## MrMetric (Feb 3, 2021)

Thank you!  I really want to try printing them for fun.  I've got a 3d printer, but I really haven't used it.  This will be fun.


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## Eccentric (Feb 6, 2021)

Call me crazy, but I had so much fun making the crankshaft, that I decided to make another one.  I did three things different that I hope will result in a better crank. 1.) I heat relieved the cold rolled steel blank 2.) I milled the center web instead of using the lathe, and 3). I placed a piece of steel in the web to prevent flexing of the crank at the offset crank pin before I turned the main shafts.






I am using a small kiln made from firebrick.  I heated the blank to a dull red, then slowly turned down the heat.  I had additional firebricks at each end to hold in the heat, then let is cool slowly over several hours.






I used the mill to cut out the center web section.  My lathe is small and I can only feed out a small amount of the tool at a time and it is difficult to get a smooth continuous edge.  The milled finish is much better.






So far so good. The crank pin came out well, still need to do some polish work here.






I locked this “precision” steel block into the web, if it is too big it will actually spread the web and if it is too small it doesn’t do any good and the whole shaft will flex under the cutting pressure.  I had to tweak my original crank by whapping the crank web with a hammer to straighten it.






I am going to put the crankcase and crank aside for awhile and work on the cylinder sleeve, cylinder and cylinder head.  They will come out of the aluminum and cast iron sitting next to the engine.  I am going to turn the sleeve first, I think I will use the 4 jaw for additional clamping force.  Probably use the drill press and mill to remove the majority of the material from the sleeve before boring.


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## nj111 (Feb 8, 2021)

I recall making two crankshafts for my Kiwi to get one really nice one. In fact, I pretty much made two kiwi's to get one good one!


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## Eccentric (Feb 8, 2021)

Today I have fabricated the blanks for the cylinder sleeve and the cylinder itself.  I have ordered a ½” boring bar to machine the internal bores, wanted one that was really rigid.  While I am waiting for the Amazon driver, I have started working on the fly cutter to cut the tiny teeth in the timing gears.  The spur gear is 1” in diameter with 40 teeth and the pinion is ½” in diameter with 20 teeth.





Here I am milling the starter hole in the cast iron rod that will become the sleeve.  In hind sight I should have milled out more material.  I milled the hole to a .6” diameter thinking that would be enough for the ½” boring bar, but milling goes so much quicker than boring.  Boring can get quite tedious.  I’ll resist the boring pun.






Here are the blanks for the sleeve and the cylinder.






Using info readily available on the internet, I have created the profile for an 40DP involute cutter, as the spur gear is 1” in diameter and has 40 teeth.






This is the generation of the tool path using a 1/8” end mill to shape the end of an 01 tool steel, 3/16” cutter blank.  After I mill the shape, I will grind relief, then heat treat, temper and sharpen.






Milling








This is my heat treat/temper kit.  I warm the fly cutter in a low flame and dip it in boric acid a couple of times until I have a good build up.  The I turn up the MMAP torch full and heat the tip to a bright red, then plunge it into the vegetable oil.  I then go into the kitchen and use the wife’s tea kettle to boil up some water and rinse off the boric acid.  It prevents the black scale from forming during heat treat.  Then I again use a light flame heating the rod away from the tip and watch the color change from a light straw to a bit darker straw at which point I again plunge it into the vegetable oil.  Finally, I take it to the sharpening stones and finish up with an Arkansas stone to a bright polish.






The result – a DP40 involute gear cutter.  It is tiny, it will be interesting to see how this thing holds up, it could fracture before I finish a gear.  We’ll see.  Oh, and my boring bars showed up.


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## Eccentric (Feb 9, 2021)

I got to get a little machining in this afternoon working on the cylinder sleeve.  My new boring bar works like a dream, I have a consistent 1.000” bore all the way through. It is 2.125” tall with a 1/16” lip at the top and a 1/16” wall.  From that big ole cast iron rod, this is all that is left. Well, not really true, the rest of it is covering my lathe, workbench and workshop in a fine gritty dusty mess.


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## Eccentric (Feb 10, 2021)

Today was spent at the lathe working on the cylinder.  I didn’t have any issues, aluminum is nice to machine after a day of machining cast iron.  I mean, I like the way cast iron machines, but aluminum cleanup is a breeze.  I have a white board right next to my lathe and as I approach the critical internal bore ID, I write down both the lathe cross slide indicator position and the bore measurement.  This helps me visualize where I am so I don’t overshoot.  The math is dead easy of course, but I have messed it up too many times.  SA as they say in the Air Force – Situational Awareness.  I aimed for an interference fit of .001” with the sleeve.  For the outside features, I did all of the math and marked out where they fell on the cylinder blank using Dykem. The machining was pretty straight forward, no super critical dimension except the overall length, but I like to hit the numbers on the print; it is good practice.  I did take a little liberty and free hand machined the fins to give them a taper to the outside.  I machined them square, then turned the tool in the tool post about 10 degrees one way, then the other machining the sides of the fins.





                                                             2.25" aluminum round blank





                                                                                        Cylinder and Sleeve

I need to mill and thread four holes in the top of the cylinder for the cylinder head to mount and I need to mill the bottom of the cylinder into a square with four holes to attach to the crankcase.  Finally, of course, I need to press in the sleeve.  I am having fun with this project.  Next I will do some CAD work on the cylinder head and start researching the fabrication of the cast iron rings.


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## Eccentric (Feb 11, 2021)

Today was a light machining day, but I did the work required to mate the cylinder and the crankcase.





When I machined the two crankcase halves, I put a square feature at the top that I could indicate off of to exactly find the position of the cylinder sleeve so it is centered over the crank.  Here the cylinder sleeve mating hole is being machined centered on this square index hole. 






Here the sleeve hole is complete with the slot for the connecting rod.  I machined the hole to exactly 1.125" diameter, then had to go back and open it up .001" becasue the sleeve didn't quite slip into the hole.





Machining the bottom of the cylinder.  I made a mistake when I designed the crankcase, I intended the pad that the cylinder sits on at the top of the crankcase to be 1.875" square, but I made it 1.875" by 1.375".  So instead of remaking the crankcase, I am going with it and making the base of the cylinder rectangular as well.  The cylinder sleeve extends below the bottom of the cylinder and into the crankcase by .3125" and there is just enough sealing area at the base, I think it will be OK.





Here is the result so far.  The cylinder is resting on the crankcase and the sleeve has been pressed in. I have spot drilled the holes at the top of the cylinder for the threaded holes to mount the cylinder head.  That will be the next project, back to the computer for a bit to model up the cylinder head.  I bought my little 10mm spark plug so I can have its actual dimensions in the model.


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## CFLBob (Feb 11, 2021)

Interesting build.  

I've heard of using steel liners, but never looked into details, in particular if they're bonded in place or not.  Is that .001" press fit all you're doing?  Is that good vs. temperature?


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## Eccentric (Feb 12, 2021)

Bob,

I use an interference fit for the sleeve to the cylinder then add wicking Loctite 609 which has good thermal properties.  Also, the sleeve is completely retained by the cylinder head which bears down on it when tightened.  We don’t push these engines very hard so using a cast iron sleeve in an aluminum cylinder works fine.



Cast iron is the perfect material for cylinder walls and piston rings. It is great for high temperature environments, is low friction and has great wear properties.  When I was a kid engine blocks were cast iron.  But it is heavy.  I think the primary reason for using aluminum in engine blocks was weight which is of paramount importance in aircraft and also race cars and to some degree cars designed for fuel economy. Aluminum has better thermal conductivity, three times better, than cast iron.  Aluminum is easier to machine and is less expensive.  So, the two material lend themselves to different areas of the engine.  In my application the aluminum when shaped with lots of surface area on the fins, is better at getting the heat transferred to the surrounding air so works well in the cylinder.



You are absolutely correct about the different coefficient of expansion between the two metals, aluminum expands more at a given high temperature and this can cause problems in engines using cast iron sleeves.  Using a sleeve adds parts and much more machining to the finished cylinder assembly.  Sleeving adds complexity without improving the functionality of our model engines as infrequently as they are run.



My motivation for picking a single cylinder engine with a sleeve was to gain experience, to ease myself into building a twin cylinder engine, one that will require the skills to make cast iron sleeves and rings.

Bob—thanks for the comment, sorry I rambled on.  There is not much dialog or feedback in this forum and it is fun to hear from a fellow engine builder, it is reassuring to know that folks are out there.



--Greg


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## Kasey (Feb 13, 2021)

Eccentric said:


> Bob,
> 
> I use an interference fit for the sleeve to the cylinder then add wicking Loctite 609 which has good thermal properties.  Also, the sleeve is completely retained by the cylinder head which bears down on it when tightened.  We don’t push these engines very hard so using a cast iron sleeve in an aluminum cylinder works fine.
> 
> ...


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## Charles Lamont (Feb 13, 2021)

Eccentric said:


> Bob—thanks for the comment, sorry I rambled on.  There is not much dialog or feedback in this forum and it is fun to hear from a fellow engine builder, it is


Well, I am watching, for one.


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## Eccentric (Feb 13, 2021)

Kasey,

You might look into DOM steel tubing, it is supposed to be very dimensionally accurate and might make a good cylinder sleeve (not as good as cast iron  ).

I feel silly becasue I 3D printed the crankcase, but not the cylinder, if I had I would have noticed the cylinder hole pattern didn't match the crankcase hole pattern.

Today I worked on the cylinder head, did the lathe work including the features on the bottom.  I also worked on the piston, I think before I finish off the cylinder head (I still have some CAD cleanup on the finned top) I am going to make the connecting rod and piston.  How cool is it going to be to see the piston go up and down in the cylinder when I spin the crankshaft?





                                             Can you see where the head ends and the cylinder starts?  Hint, look at the next photo






I have read different things regarding how tight a fit the piston is supposed to be in the cylinder, I decided to leave .005" difference between the piston OD and the cylinder ID.  It falls into the cylinder and I can still get a 'pop' when I pull it out fast.  I am looking forward to try my hand at piston rings.  the rings will have across section of 1/16" X 1/16" and will expand into the 1" diameter cylinder.


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## Kasey (Feb 14, 2021)

Eccentric said:


> Kasey,
> 
> You might look into DOM steel tubing, it is supposed to be very dimensionally accurate and might make a good cylinder sleeve (not as good as cast iron  ).
> 
> ...



Eccentric,
               Thanks for the advice re-cylinder. I'm always looking for alternatives when making just >
research ideas into strange engines to see if its possi_ble. and how to do it. Have just realize in my revised design of the crankcase, I could have left off 2 opposite sides and used the cylinder bases themselves alone as part of that. Would have saved weight, $$$, and time and made things more compact. I missed that on my 3d model also. I've now finished the base and flywheel mounting work and hope to set it up for a start up and a very short trial run this week . I just hope it starts. Have choked down the exhaust and throttle....don't want to risk an accidental rev up yet on the siamesed con rod design.......If ok, I'll will dismantle the engine then get to machine the cooling fins into both the head and cylinders, which will be a slow, patient job._


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## Eccentric (Feb 15, 2021)

Made some rings today.  I made 6 total when I need only 2 in case I break one.  I turned a piece of cast iron to an OD .004” smaller than the cylinder sleeve wall and the ring ID such that the rings are .0625 thick.  I used a razor blade to scribe a line on the inside of the ring, then set it down on the workbench and placed the razor blade exactly in line with the scratch I made, then tapped the back of the razor blade with a machinist’s hammer.  The rings cleaved clean.  Then I used the Les Stone’s method to heat treat form the rings.  I splayed the gap open to .114”, a number calculated using George Trimble’s math and hung the ring and gag piece in front of a fire brick.  I heated it and the brick with a torch as evenly as I could moving the torch the whole time. When the ring is a dull red it takes a set and falls off the gag piece.  Ta-da.  I needs to do a bit of cleanup, but they spring nicely into the cylinder.






                                A mess of rings










             Gap test





              Here you can see both ring gaps when the rings are placed inside the cylinder


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## Eccentric (Feb 15, 2021)

The wife is watching the Austrailian Open, so I snuck out to the workshop and machined one more part before bed.  This is the finished piston sans rings.





Looking at the conrod next, can't wait to see the piston go up and down in the cylinder


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## Eccentric (Feb 17, 2021)

Started work on the conrod today.





I chopped off a piece of aluminum approximatly the size of a conrod and machined the bottom to shape.





Drilled the holes for the cap screws at the base.





Back to the mill to seperate the cap from the connecting rod.





Then over to the surface plate (my band saw table) to wet sand the joint between the cap and conrod.

Tap the holes in the conrod, open up the holes a tad in the cap, screw the cap on with cap screws (of course) then back to the mill.





Machine both holes slightly undersized, one attaches to the crankshaft and the other the piston (of course).





And ream to .001" over.

Now it is time to head over to the lathe and make a couple of fixture pieces.  These will have a hole for a hold down screw and will be sized for a .001" clearance to just fit in the conrod holes.





These will allow me to hold the conrod down to a fixture plate, machine one side of the conrod, then flip it over and machine the other matching side, maintaining precise alignment.






I will clamp a fixture plate to the mill bed, then machine two holes to match the two holes in the conrod.  I will then tap and clean them up them right on the mill bed.  The holes in the fixture will remain aligned on the mill's X axis so when I flip the conrod, precise positioning is maintained.

I have to go back to the computer and work on the model a little before I am ready to finish the outside machining of the connecting rod.  But this will have to wait until I trim the vines in the front yard and fix a leaky toliet tank upstair.


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## Eccentric (Feb 18, 2021)

Wrapped up the machining of the connecting rod today.




Here the connecting rod is being teased out of a stick of aluminum.  Machining the first side here.





Connecting rod off of the machine.  It would be nice to have a bead blasting cabinet and see if I could remove the tooling marks.


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## Eccentric (Feb 19, 2021)

I took the conrod over to a buddy's house and used his blasting cabinet, he had some pretty coarse media, but it really gives the conrod a nice cast appearance.  I am going to do the same thing to the engine case, maybe get some walnut shell media and take a look at how that does.






I just noticed that the two precision pins I had put in the conrod to protect the internal bearing surfaces while sand blasting got pretty chewed up,  and if I just pull them out they will destroy my nice internal bearing surfaces I worked so hard on.  I'll carefully cut them off.  Well not the main mearing, of course, I'll just take the cap off.


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## Eccentric (Feb 19, 2021)

Major Milestone!
Click to View.


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## Eccentric (Feb 21, 2021)

Last week I submitted a post on my techique for making fly cutters to cut gears.  Today I made a second cutter, they are unique to both the pitch and how many teeth a specific gear has.  Today I made a 36DP cutter for a 1" gear blank that has 36 teeth.  This is the Spur gear attached to the camshaft that will, of course,  mesh with pinon gear with 18 teeth on the crankshaft.






First I turn the gear blank to 1.055", then begin cutting teeth .062" deep.





Here you can see both the fly cutter and the teeth is is cutting.





The teeth cuts are almost finished.





The final result. Still need to ream the center hole and put in a keyway.

Next I will cut the pinion gear which is half the size of the spur gear.  It is supposed to be steel, but I am going to cut a brass gear first, then try to cut a steel one.  I don't know if the cutter will be able to handle the steel.  the cutter is hardened and tempered 01 tool steel, so if I run the cutter fast and feed very slowly, it should handle the steel.  Also, I will make several incrementally deepter cuts.  With brass I make the cut in one go.


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## a41capt (Feb 21, 2021)

I’ve never cut a gear, but considered the “fly” cutter approach because it looked like an inexpensive way to get into the process.

I wondered about your statement regarding making multiple passes in steel, thinking that a slow feed into the material would be sufficient. Is this because of the lack of rigidity in the single tooth used in the fly cutting procedure?

Thanks in advance for any thoughts you can share!

John W


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## Eccentric (Feb 22, 2021)

John,

I agree with your assesment that a slow feed would be as good as several increasingly deep passes.  The thing is, when I am cutting teeth, the lathe spindle is controlled by an indexer, not the lathe motor, so since the lathe motor is not running I have to move the carriage by hand.  I am not real steady on the crank and it is difficult for me to maintain a really slow and steady infeed.   In fact I did attempt to make a steel pinion gear and I got about 6 of the 18 teeth made when the tip of the fly cutter fractured.  It is a fine balance when tempering the cutter, too little, say a light straw and the cutter is hard, but brittle.  Too much, say a dark straw, and the cutter is too soft.  In my case, the cutter was too brittle and broke clean off. 

The fly cutters have much less "meat" behind the cutter surface and are much less robust than, say, the commercial cutters with many cutting edges per revolotion.

Everything I know about cutting gears I learned from Chris over at Clickspring.  I have only made single "flute"  fly cutters.  He also explains how to make a much more robust multi-flute cutters, much more like the comercial gear cutters.  I may give that a try, but that is a whole other project.


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## Eccentric (Feb 22, 2021)

Today I made the pinion gear and the camshaft, such as it is.





I made the pinion gear from brass rod as it is smaller and needs to be 3/8" thick. I made a first pass around the gear cutting the teeth to the theoretical depth, then took the spur gear and engaged the teeth. I measured the center to center distance (actually I measured the outside to outside distance and calculated the center to center distance) and found it to be .752” when my actual shaft distance is .750” This would have resulted in overly tight gears. So, I took another pass around the gear cutting .005" deeper. Now the gears mesh nicely.





Here is the resulting gear pair.  The cams will go behind the spur gear.


I went to the metal store today and picked up some bronze and 303 stainless for the valve guides and the valves. I have a bunch of brass, but when I Googled "is brass good for valve guides" I got an emphatic answer back: "No, plain old *brass* would be a bad choice for *valve guides*. Your application (high heat, reducing atmosphere, poor lubrication, dry rubbing, heat transfer, low force reciprocation) requires a material especially suited for it."


So what does Google recommend? "Manganese *bronze* is ideal because it is more compatible with stainless steel. ... manganese-*bronze* is still the *best* choice for *valve guides*. "

Well, if Google says it, it must be true.

Why 303 stainless? there are perhaps harder stainless steels, but 303 has nice machinability characteristics which is important for the home machinist.


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## Eccentric (Feb 23, 2021)

Today I started work on the Cams, got on a roll and didn't think to take pictures of the process.  I still need to cut a keyway in the cam pair, and cut off the end piece that allowed me to chuck it in the lathe.  Then case harden, temper and polish.





The cam pair will sit right here behind the spur gear on the cam shaft.


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## Eccentric (Feb 24, 2021)

Made a little more progress on the cams.  I cut the keyways in the camshaft, cam spur gear and the cam pair.  I am using a 1/16" dowel pin as my key.





                                Camshaft with its keyway and key along with the spur gear and cam pair.










The pen is pointing at another 1/16" dowel pin mounted in the crankshaft, this one engages the pinion gear.  I built the pinon to print, but in hindsight I would have made the collar that engages the pin larger and capture the pin.  I am thinking of adding a sleeve over the crankshaft on the inboard side to cover the pin and retain it.  I will cut down the pin.





Progress so far.


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## Eccentric (Mar 1, 2021)

Today I thought I would show some fails.  I have started work on the valves and rockers, but have not made a useable part yet.  What is the saying?  You usually make about three sets of parts to end up with one good engine?  I have a hard time parting off steel in the lathe.






So not to end on a down note, I have also been working on the cylinder head top machining and am happy with the progress there.  I still have some hand filing to perform, but the head looks to be a keeper.






Maybe I will take a break from the valves and rockers and work on the flywheel.


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## Ghosty (Mar 1, 2021)

When machining the valve stems, machine a 1/3 to size, then the next 1/3 and then then last, a lot less flex in the stem. These were machined out of 316 ss.
Cheers
Andrew


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## CFLBob (Mar 1, 2021)

A couple of years ago, parting off on the lathe suddenly kind of gelled in my mind and now I hardly have any difficulty with it.  (Famous last words.  I probably just jinxed myself)  I always part off by hand, not under CNC.  

If I may add something, if you're parting the thin ends of the valve stems (the first picture looks like it), that's the wrong end.  Face the end you're going to make the stem, then cut 1/3 at a time to about .003 over desired diameter.  When the first third is done, cut the next third and then the final third, like Ghosty says.  Get them to final size with abrasive paper.  When you're done using the full diameter handles you left on, part off the finished valve from the handle.


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## a41capt (Mar 1, 2021)

Eccentric said:


> Today I thought I would show some fails.  I have started work on the valves and rockers, but have not made a useable part yet.  What is the saying?  You usually make about three sets of parts to end up with one good engine?  I have a hard time parting off steel in the lathe.
> 
> View attachment 123508
> 
> ...


On many of my critical small parts, especially valves and cast iron rings, I have taken to holding a pencil die grinder in my tool post and cutting off with a 1/16” thick dremel abrasive cutting wheel.  This leaves a much cleaner surface, especially on skinny rings, and requires almost no further finishing on the face of a valve.

Additionally, when turning sub .125 diameter valve stems, I turn them in 1/3 increments down to a couple thousand of finished and then clean them up with abrasive paper to final polished dimension.  This was a trick Brian Rupnow mentioned, and since I started doing that, my slim turned parts are now looking like a million bucks!

John W


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## Jasonb (Mar 2, 2021)

I tend to make them slightly over length so that I can use tailstock support so the full length can be turned. Also just saw them off and then turn the end with light cuts rather than parting off. These are 3mm


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## bluejets (Mar 2, 2021)

I usually follow this blokes advice for successful outcome.


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## Vietti (Mar 2, 2021)

I have had good luck silver soldering ss heads onto drill rod of the correct size.  The stem goes thru the valve head, silver soldered on both sides.  Chamfer before soldering.  You get a ss valve with a precision stem of strong material.  The valve stem is then held in a  collet and the valve head turned to size.  For the final pass machining the seating surface, the side of a new insert set at the proper angle 45 degrees +/- is used cutting across the entire seat in one go, just polishing the seating surface. The finished valve can the be inserted thru the back of the collet and the stem cut to length and valve retainer grooves added.

Never had a failure.  Wish I could say all my valves were leak free to start with.


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## Vietti (Mar 3, 2021)

Forgot to say when machining the valve head, it is center drilled and a center used to steady the work.


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## Eccentric (Mar 6, 2021)

Thanks everybody.  It took me four tries before I had an acceptable valve, but then I made one this morning and it turned out better than the first.  Using the advice given here I did several things different.  First, I turned it with the top of the valve toward the headstock in the lathe.  I center drilled the end and used a live center to steady the work.







I turned the section of the valve head, .375” in my case, to size, then began turning the stem down toward .125”. I started with larger cuts, .015” off at a time and as I got smaller, I move to .010” cuts, then down to .005”.  I used a live center on the stem end of the valve and noticed that the OD near the headstock was smaller than toward the live center.  I assume this is due to some side play in the live center.  So, as I got close to final dimension, about .030” away, I switched to a dead center and this helped a little but did not totally eliminate the OD difference between the two ends of the stem.  I also used a carbide cutter for the majority of the material removal, but then switched to a rounded HSS cutter as I got close to final dimension.  This gave me a much nicer finish.  I turned down to about .006” over and switched to emery cloth – 320 grit to start with.  This removed material and gave a nice finish, but was taking too long.  So, I went back to the round nose HSS cutter and took the stem down to .003” over.  I also worked from the tail stock toward the head stock turning just enough for me to get the micrometer in there to measure the OD.  As I worked my way toward the headstock I had to move the cross slide out a thou at a time to maintain the constant stem OD.  I marked the stem up with a sharpie and used a fine file to knock down a couple of high spots that formed from the different cutter depths.  I went back to the 320 emery paper and took the OD to just under .001” over, then switched to 600 and finally 1000 to get a really nice shine.  Then I used the round nosed HSS cutter to cut the radius between the stem and the valve top.  I then rotated the cross slide to 45 degrees, locked it into place and cut the 45 degree angle where the valve seats into the valve seat/guide.  Finally, I used a cut off tool to cut the groove for the retaining clip and started to cut the valve at the thick end, but not all the way through.  I used a Dremel cut off wheel to separate the valve from the extra material.  Ground the stem to length, then put the stem in the lathe and faced off the top of the valve to size. The valve guide was much easier as it is simpler and the Bronze cuts really nice.


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## Eccentric (Mar 14, 2021)

I have been working on a few odds and ends.  I turned the fly wheel and mounted it, but did not put a pulley on the front.  I am now thinking I will machine a pulley as I would like to use the engine to do some work, don’t know what yet, at least a generator or magneto.  I have returned for a second go at the rockers.  I cut the shape from mild steel then mounted it on the lathe to create the side profile.  I rather free handed it so the two rockers will probably look a little different, but perfectly functional(I hope).


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## Richard Hed (Mar 15, 2021)

Eccentric said:


> Thanks everybody.  It took me four tries before I had an acceptable valve, but then I made one this morning and it turned out better than the first.  Using the advice given here I did several things different.  First, I turned it with the top of the valve toward the headstock in the lathe.  I center drilled the end and used a live center to steady the work.
> 
> View attachment 123639
> 
> ...


How many of these valves do you need?  It's looking good but sounds almost like a nitemare to do.  Have you checkt your tailstock offset?  I had a problem where I had to shim the tailstock up a thou or two once.


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## Eccentric (Mar 15, 2021)

Richard,

Thanks for the suggestion.  I will google "tail set offset".  It would be great if my problems could be solved by an adjustment to the lathe.  It is a really inexpensive, small 7" X 10" and I would not be surprised if something were off. I am thinking aloud, I could put a long piece of known round stock between centers and run a dial test indicator in the carriage and run it up and down the rod looking at the top and the side to see if the tail stock is off.  Or, I could buy a nice, larger lathe   

P.S. Yes, the engine only has two valves, but I am hoping to build more valves in the future.  This engine building is fun, addictive and very challenging.


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## Richard Hed (Mar 15, 2021)

Eccentric said:


> Richard,
> 
> Thanks for the suggestion.  I will google "tail set offset".  It would be great if my problems could be solved by an adjustment to the lathe.  It is a really inexpensive, small 7" X 10" and I would not be surprised if something were off. I am thinking aloud, I could put a long piece of known round stock between centers and run a dial test indicator in the carriage and run it up and down the rod looking at the top and the side to see if the tail stock is off.  Or, I could buy a nice, larger lathe
> 
> P.S. Yes, the engine only has two valves, but I am hoping to build more valves in the future.  This engine building is fun, addictive and very challenging.


Yes, the second solution is probably the better one if you have the room.  I have an Enco, 9-20.  It's OK for small, non critical things, but if you want precision or turn threads, it is a dud.  Doesn't even turn LH threads at all.  I could put an idler reverse in it somewhere, but the threads, no matter what, are rather crappy compared to the new lathe  I just got in January, which is a Grizz G4003G.  It does great threads, imperial and metric.  Anyway, your problem.  

I'm not sure if you are familiar with the procedure by your remarks.  I thimpfk Joe Pi, Blondi, and others have utub vids that show the procedure for checking the alignment of your tailstock.  It's not that difficult a test, but getting the thing aligned if it is out, is a bit more need of patience.  First get a good rod, putting counter-sink in each end, put it between centers, then cut a swath about an inch on each end, making SURE the crossfeed settings are EXACTLY the same.  Measure that and this will tell you whether or not your tailstock is offset .  I really hate reading something from someone advising me of something I already know, so I hope this is not preaching to the choir.  utub is full of good stuff.


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## Eccentric (Mar 17, 2021)

The last couple of days I have been working on the cylinder head and its associated parts.  I drilled, created the counterbore and tapped the spark plug hole.  In the first picture you can see the fixture used to align the head at the required 40 degrees on the mill.  I really enjoy creating the fixtures that are some times required in the course of machining.  These are the unsung components that get fabricated, but are never seen by the casual observer of the finished project. There is often some stunning creativity put into fabricating fixtures.






I fabricated the rocker pillar, which has a very interesting shape.  It is threaded into the cylinder head, has a 3/8” round foot tight against the head, then it tapers up at 10 degrees, and flares into a square section where the rockers are mounted.  It is crowned with a semi domed top.



The eccentric rocker bushes are fabricated from bronze.  They serve two purposes, first of course as the bearing for the rocker arms, but secondly, they allow the adjustment of the valve lash.  They are mounted to the pillar through an offset hole that allows them to be turned and provide adjustment to the valve lash.  I cut a 5/16” head to allow a tool to be used in the adjustment.






I found some commercial compression springs that would work for my valve springs, but they are $18 for ten springs.  I figured I would try to make my own in the spirit of building as much as possible.  I found some guitar strings for 78 cents on Amazon that are .022" in diameter.  We will see how it goes.


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## CFLBob (Mar 18, 2021)

Eccentric said:


> I found some guitar strings for 78 cents on Amazon that are .022" in diameter. We will see how it goes.



No reason it shouldn't work.  

Since I have several guitars, I always have strings around.  The first time I made a spring was using a used guitar string.  Last time I made some springs I changed strings on a guitar to get some used music wire.   

Between having wire, some steel wool, a toaster oven and this, it's all you need:


			Making Springs on the Small Lathe


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## olympic (Mar 18, 2021)

Thanks for the link, CFLBob. I found a brand new 800-foot coil of .020 music wire, still in the box, at the dump, so I am ready to spring into action.


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## Eccentric (Mar 18, 2021)

Thanks for the link Bob, you know what I will be up to today.  I have a new spring in my step, I succeded in making an appointments for my Covid vaccine this morning!  I got up before six this morning and pinged the vaccination web site until I got in; they go quick.  It reminds me of when I was a kid and online was a new thing, trying to get concert tickets before they sold out.


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## Eccentric (Apr 1, 2021)

I am running out of parts to machine so I have started to work on preping for assembly.  HereI am sand blasting  the aluminum parts to remove the tooling marks as a result of machining.  Not such a great picture of the front crankcase half in the blast cabinet, but you get the idea.  I am using 80 grit glass beads.






Here are the parts after blasing.  They almost look like they could be sand castings.






And Here are a few shots after assembly.








It is very difficult to get the cylinder retaining screws in, I think I am going to use studs in the crankcase and nuts to hold down the cylinder.





I have the carburetor and points in hand.  I needs to make the intake and exhaust flanges that mount to the cylinder head, collect the rest of the ingition system and see if she will run.

Thanks everyone, I have learned an awful lot building my first 4-stroke IC eninge.  I think I am hooked.


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## bluejets (Apr 2, 2021)

Eccentric said:


> It is very difficult to get the cylinder retaining screws in, I think I am going to use studs in the crankcase and nuts to hold down the cylinder.



Had a similar problem with one of mine and used studs with nuts.
Another option with yours may be to open up the clearance on the holes a little.
You have a lot more room above than I had.

Didn't think of using a 1/4" spark plug ...???
6mm bore carby...might be more suited to something smaller.


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## mu38&Bg# (Apr 2, 2021)

NGK CM-6 is a 10mm plug. A 6mm carb will be plenty, the plans call for a 1/4" throat. The blasted parts look great!


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## kuhncw (Apr 2, 2021)

You've built a very nice looking engine.  The bead blast finish really sets it off.

What is the tube with the black cap that is part of the carb?

Chuck


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## bluejets (Apr 2, 2021)

dieselpilot said:


> NGK CM-6 is a 10mm plug. A 6mm carb will be plenty, the plans call for a 1/4" throat. The blasted parts look great!



Well aware it's a 10mm plug.
6mm carby may well be too large which is why I brought it up.


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## Brian Rupnow (Apr 3, 2021)

Eccentric---that is a lovely engine. I like the blasted finish on your aluminum parts.---Brian


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## gilbycoath (Apr 4, 2021)

CFLBob said:


> No reason it shouldn't work.
> 
> Since I have several guitars, I always have strings around.  The first time I made a spring was using a used guitar string.  Last time I made some springs I changed strings on a guitar to get some used music wire.
> 
> ...


Thanks so much to Dean Williams for an excellent article on small spring making. a subject I am interested in.
The article was well written with simple explanations and very clear photographs.
Thanks again Dean.
Ron


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