Another Comber / Coomber build

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arnoldb

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I mentioned in my tooling log that I'll be starting another "Elmer" build. Besides all the Elmer engines that I still want to build, two needs immediate attention.

The Kimble engine has been nagging at me for a long time; it WANTS to be built, and I will build that one soon, but once again it's on the back-burner...

Last year at some point, I was in three minds about which engine to build next for my own collection, and after I showed my sister the pictures, she chose the Elmer #46, which I then built. When I asked her what she wanted for her birthday a couple of months ago, she said I owed her a #46 :big:. Mine is a good runner, and I can just give her this engine, but it does not quite run on breath power, so I thought it better to make her a new one, that will easily run on breath power and with a bit of added personalization. I hope this new build will do the job :)

So the rules are "simple" - build a personalized, breath powered, Coomber :big: - I think I'm a sucker for punishment :big:

On to the nitty gritty then...

I'll be building mostly to Elmer's plans except for:
a) Increased cylinder bore size. An increased piston diameter will reduce the pressure needed to power through a stroke. Increasing the bore diameter means increasing the cylinder block dimensions; that means recalculating the bearing block spacings. I'll do that as I go.
b) A flywheel that is fairly light, yet with good rim mass. Light to keep bearing friction down, and outside rim mass will help it keep up rotational momentum.
c) Minimise friction... My existing Comber has quite a bit of friction in the bearings, and some "slapping" on the cam ring. For this build, I'll add a cast-iron insert on the main/port bearing; the brass running in CI compared to brass in aluminium should be an improvement. For the "slapping", well, I'll just to add a bit more clearance to the forks, make the rollers smoother, and make the cam dead-on smooth. I could add a roller bearing on the non-port bearing block, but maybe a CI insert will do that job as well.
d) Metric - all bits are converted to metric; I don't mind working in inches and fractions and thous, but pretty much everything I have access to is in metric, so I machine in metric.

I started off the cylinder block with a bit of 25 x 25 x 40mm brass stock flycut down to get it square:
normal_IMG_3064.JPG

That's the beginnings of the cylinder block.

A bit of marking out - to find the center on both of the long-end faces: with two reference sides marked
normal_IMG_3065.JPG


In the 4-jaw chuck on the lathe - finding center with a dead center... I REALLY need to make a proper pump center :big::
normal_IMG_3066.JPG


That was then center drilled, reversed in the chuck, and the other end's center found the same way, and drilled 7mm to fit a bit of 7mm round brass I have in stock:
normal_IMG_3067.JPG


That 7mm brass bar was a fairly tight fit, but as I wanted to silver solder it in there, it needed a bit of clearance for the solder to wick in, so I filed the end of the bar down a bit in the lathe to make it about 0.1mm under-sized, and then knurled the end:
normal_IMG_3068.JPG


The knurling raises the effective thickness of the brass bar, making it need a good whack to go into the hole in the cylinder block, retaining it fairly straight and square in the hole. It also leaves grooves for the solder to flow (wick) into the joint. I coated the hole inside the cylinder and the knurled bit with silver solder flux paste before whacking together and added a ring of silver solder and additional flux. A bit of "colouring in" with a graphite pencil around that lot followed; the penciled area will prevent flux and silver solder sticking:
normal_IMG_3070.JPG


Then I showed that lot my Sievert torch - LOTS of heat concentrated on the bottom of the cylinder block to make it glow dull red, took a bit longer than I'm used to; about 50 seconds for the flux to flow (it goes from looking like bubbly sherbet, to white crystals, then like burnt and black caramel, then suddenly like water all over the place) and 10 more for the silver solder to wick in properly, but it came together:
normal_IMG_3071.JPG

Heat at the bottom of the cylinder, as that draws (wicks) the solder INTO the joint; if you just heat the outside and top, the solder will melt, but not penetrate into the joint.

After a pickle in citric acid for the part while I had a bite to eat (~ 30 minutes) I chucked up the 7mm end in the collet chuck on the lathe, and with the tailstock support in the previously-drilled center, I turned down the end to 12mm with a 14mm shoulder:
normal_IMG_3073.JPG


Flipped in the chuck, and clamping down on the 12mm bit, I VERY carefully turned down the 7mm round bit to 6mm. It has a fair bit of overhang, so a sharp HSS toolbit is the order of the day:
normal_IMG_3074.JPG


Then I set up that lot in the mill, using a dial test indicator (DTI) to check for squareness. Obviously, the mill needs to be in near-perfect tram for this and the following machining steps:
normal_IMG_3077.JPG


Then I drilled and bored out the cylinder with a couple of successive drill sizes -3mm, 7mm, 13mm and then the boring head to take it up to 16mm. A blurry action photo; as the boring head was running nicely balanced, this shot is at about 800 RPM, and very fuzzy as I was paying more attention to the feed than the camera :big::
normal_IMG_3079.JPG


I checked for the final 16mm bore size with a telescoping gauge:
normal_IMG_3080.JPG

Well, not entirely true... :big: - the sizes measured are all OK, but I know that that digi caliper of mine is inclined to measure 0.05mm under size... - so that hole is actually 15.95mm :big:

I ended up with this lot for today's work:


If you click on the last photo and have look down the left side of the non-perfect bore, you'll see the slight oval where the shaft joined the body; at least the silver solder job went exactly as planned :)

I wanted to be a bit further along today, but a neighbour popped in with a a gift and his young 'uns in tow. The gift is a very drinkable bottle of Scotch in return for fixing his wife's treadmill last weekend, and the young 'uns wanted to see some of my engines running. It's just as much fun as machining - if not more so - showing off my simple engines to a four and six year old... They seem to like the Elbow engine , the Comber, and of course the half-finished Cracker... pft pft pft ;D

Kind regards, Arnold
 
Off to another great start Arnold!!!

I missed your previous build of this engine, so i will be following this one carefully!!

Andrew

Oh and how do i place my request for an engine??
My Birthday is in August so you have some time! :big: ;D :big:
 
Nice work Arnold! I totally understand when you say some engines must be built. I will be following along.
Brock
 
Thanks Andrew, Brock & Robert :)

Andrew, I also have my birthday in August... And I like giving myself presents, so I guess you're out of luck :big:. But one never knows what might happen if you come and visit Namibia ;) I think my previous build of this engine is my engine build with the most scrapped parts :-[ - I hope this time it will go better though.

Robert, have you bought a mill yet ? - would make things a bit easier. Having said that though, I think it is entirely doable on the lathe. The biggest problem will be the cam profile, but if you follow Elmer's method that should not be a problem.

Had an hour and a half in the shop after work today :)

Layed out for the ports on the cylinder block:
normal_IMG_3083.JPG


As I made the cylinder dimensions bigger than on the plan, I left enough meat to drill the passages square rather than at the angles as on the original plans. I also increased the passage bore to 2mm from the original 1.6mm. Drilling the first passage:
normal_IMG_3084.JPG


Flipped the block and drilled the second passage, then milled out clearance 2mm deep into the cylinder bore:
normal_IMG_3085.JPG


While I had the milling cutter set up, I milled the port slots on the main axle as well:
normal_IMG_3086.JPG


The connection ports followed; I used a "wiggle wire" to feel for break-through into the steam passage:
normal_IMG_3088.JPG


Cleaned things up a bit and stopped for today. Time really flies when one is having fun! :
normal_IMG_3089.JPG


Regards, Arnold
 
Looks like that vise stop is coming in very useful already!!
I like the idea of setting it up and just flipping the part and carrying on!
Saves a lot in set up times!

Great looking cylinder block!

Andrew
 
Thanks Andrew :) - Yes, the vise stop is really handy; it saves a lot of time !

Today's bit; I wanted to have more done by now, but time has a way of running out...

I started on the cylinder heads; some 25mm square Aluminium bar clocked up relatively on center in the 4-jaw chuck:
normal_IMG_3091.JPG

Remember, when centering up square stock, make sure you have enough travel on the dial indicator to clear the edges, and manually push in the tumbler when rotating the stock ;)

Faced off - I like it when I get a near-mirror finish like this:
normal_IMG_3094.JPG


Then some more taken off to leave a 0.5mm thick step.
normal_IMG_3092.JPG

The step is a nice push fit in the cylinder bore to keep the head concentric, and one needs a nice sharp point on the toolbit to prevent rounding in the corner, otherwise the head will not sit flat against the cylinder face.

The workpiece was then center drilled with a 1mm center drill, and drilled about 8mm deep with a sharp 2mm drill that I know does not drill over size. This hole should actually have been reamed to about 2.02mm, but I don't have a 2mm reamer, so I'll lap the hole out later. I just made a point of retracting the drill bit slowly from the hole; a sharp drill can leave a fairly good finish in the hole if this is done.

Then I used the parting tool (after a quick hone on it) to remove a fair bit of material on the other side:
normal_IMG_3093.JPG

Just a couple of straight-in parting cuts to the same depth; have I mentioned how much fun parting plunge cuts can be through the square section? ::)

The other cylinder head followed, using the same method. The one on the left shows the face that points into the cylinder, and the gory one on the right what it looked like after the parting off on the other side. Not quite as bad as it looks; it's got some cutting oil stains on it as well:
normal_IMG_3096.JPG


To clean up the messy face, I just chucked up a bit of 2mm rod in the collet chuck, leaving a short length protruding to engage the holes in the cylinder heads, and took a bit of carton and stuck it over that:
normal_IMG_3095.JPG


Then I used the revolving center in the tailstock to tightly press the cylinder head to the front of the chuck, and with light cuts turned the face and boss to final sizes:
normal_IMG_3098.JPG


To clean up the face of the boss was another matter; one cannot get close enough without damaging the center; something I REALLY do not want to do. So I moved away the tailstock, and with a narrow strip of emery pressed against the face with the forefinger of my right hand, I started the lathe; the pressure keeps the cylinder head engaged against the collet chuck, and because the contact area against the paper is larger than that of the emery on the face, there's sufficient drive to finish it. NOT the best way to do things; it would be better to stick the cylinder head to a mandrel (with superglue or double sided tape) or clock it up in the 4-jaw against a backstop to finish machining.

A piece of 2mm rod passes easily yet closely through both holes with very little binding. A Little lapping will sort the binding out in just minutes:
normal_IMG_3099.JPG


Next I set up to drill for the cylinder mounting screws. I marked one side of the cylinder out just for visual reference, then found the left back edge of the cylinder block, dialled in the location of the first hole, and set the X and Y dials to 0. A quick check locating the other hole locations on the handwheels turned out well:
normal_IMG_3100.JPG


Then I clamped one cylinder head to the block and drilled the four 1.6mm holes needed to tap for M2.
normal_IMG_3102.JPG

I really need to invest in some spotting drills... I'm still using a center drill to spot the holes before drilling.
Flipped the block, and did the same on the other side using the other cylinder head clamped down.

On to tapping the holes in the block. For tapping M2, I use the cruddy-looking tapping handle and tapping guide shown:
normal_IMG_3104.JPG

I'm a big old wimp - When I get around to tapping holes in a cylinder block, I religiously follow through the holes with each tap in the set; cleaning the tap after each hole. It may take much longer, but after having put a lot of time, material and effort into the cylinder block, the last thing I want is to have it ruined by breaking a tap in it!

One thing I have found to be really convenient is to use a countersink to lightly countersink around each hole before tapping. I just do it by twirling the countersink between fingers until there's a spot just slightly larger in diameter than the thread size:
normal_IMG_3105.JPG

This serves multiple purposes. On a cylinder face, it prevents tapping from raising a burr above the level of the face, keeping it nice and flat. It also seems to help to make the tap start easier into the hole. And last, the tangent surface of the countersink reflects some light when looking through the hole of the tapping guide, making it easier to locate over the hole.

For this engine, I'm going to use 2mm countersink screws to retain the cylinder heads. I just clamped each cylinder head in a loose vise, and on the drill press drilled the holes out to 2mm clearance and then countersunk them, using the drill press depth stop to limit depth:
normal_IMG_3107.JPG


I also milled each cylinder head down to final size on the square ends, and ended up with this:
normal_IMG_3108.JPG


Next I need to start laying out the base. As I'd increased the cylinder dimensions, the bearing posts need to be relocated from the original plans. To get a feel of what things would look like, I compared the cylinder block to my existing Coomber's:
normal_IMG_3109.JPG


I think it will look OK - just a bit chunky maybe, because it's fatter. But I didn't expect one thing... :wall: :wall: The new cylinder was meant to be the same length as the original with the same stroke... It's about 3mm longer! - had a look at the plans, and the fuzzy dimension on the printout says it all... The cylinder block was supposed to be 13/16" long, but on the printout it looks like 15/16" and that's what I made it, so it's 1/8" too long... That means I'll have to increase the size of the cam - the original is already very close in clearance and there's no way I can keep to the original cam size now. Seeing as I have 1/8" more stroke available, I might as well adjust the cam for that as well.
I guess my sister's going to get a bigger engine than I thought :big:

Regards, Arnold
 
A good night's rest makes things look better :)

This morning I re-calculated the dimensions for the cam ring to use the new piston stroke, and added a bit of extra clearance to the connecting rod length in the process. The original dimensions would not have enough clearance on the center height of the bearings, so I had to compensate for that as well... So, one wrong-size cylinder and the original changes to the base are still needed as expected, but the bearing columns had to get the once-over as well. This lot took a surprising amount of time to re-design so that things would (hopefully!) work out.

A fairly quick C-o-C later to put all the new dimensions on one bit of paper:
normal_IMG_3110.JPG

:big: It's not pretty, but it makes sense to me...

A rummage around, and some bandsawing, and I had bits of stock to start with:
normal_IMG_3111.JPG


After some work on the mill with the fly-cutter and end mills, I had those to size and ready for lay-out. The bearing blocks were super glued together early on to allow me to machine them as a pair to maintain a semblance of accuracy:
normal_IMG_3113.JPG


I nearly stopped for the day at that point, but decided to drill and bore the bearing blocks to 16mm to accept bushes:
normal_IMG_3115.JPG


Then I did stop for the day:
normal_IMG_3116.JPG


Not a lot of progress, but things might pick up in the evenings :)

Regards, Arnold
 
A lot of progress Arnold!!! ;D
Good catch with the bigger cylinder bock! That would have been a bugger to catch later on in the build.

Coming along very nicely!!!

Andrew
 
Hi Arnold,

You always seem to make it look so effortless. As usual, well thought out and neat. Your sister will (should) be delighted and thanks for having us along for the ride.

BC1
Jim
 
Nice to see some hand drawn plans, makes me feel better as I was thinking everyone was a CAD expert. That cylinder looks great.
Brock
 
Thanks Andrew :) Yes, Fortunately I caught it; otherwise I would have had to re-make the columns :-\

Hi Jim ;D - Thanks! - it looks like the ride might be a bit bumpy, so hang on :big:. "Effortless" Rof} - I wish ! - but it's a LOAD of FUN ;D

Brock, thanks :) It's just a lot quicker for me to draw what's in my head by hand; I use CAD when I need it but I'm no expert with that!

Stole two hours in the shop after work today :)

I used an old "incorrectly made" needle valve stem to find the location for the first mounting hole to drill in the columns and zeroed the X and Y dials on it:
normal_IMG_3117.JPG


Then I started drilling the holes, just by feeding in the coordinates on the mill. The third hole was a bit of a disaster; the 1mm center drill I was using to spot the hole location before drilling snapped it's tip in the hole:
normal_IMG_3118.JPG


I used the sharp side edge of a pair of needle-nosed pliers to grab on to it and gently tried to reverse it out of the hole. A bit more snapped off, and after poking around in the hole with a sharp scriber I could feel there was a bit left. Out of sheer desperation, I plunged the snapped center drill in rapidly, hoping that it would deflect and then pick up and extract the bit of HSS trapped in the hole together with the swarf:
normal_IMG_3119.JPG


:) It worked; after that plunge, scratching around in the hole with the scriber I couldn't feel any hard bits in there, so I drilled the hole to size without any further fiasco, and the last hole went well as well:
normal_IMG_3120.JPG


Tapping the holes went well; in the background you can see the bottle with the purple-coloured methylated spirits I use for tapping aluminium:
normal_IMG_3121.JPG


I wasn't in the mood to set up the rotary table to round over the tops of the bearing columns, so I used a 16mm drill bit's shank to support the columns and started milling away facets - a quick job, but just make sure there's no swarf trapped below the drill bit (or supporting rod):
normal_IMG_3122.JPG


This is what the columns looked like fresh off the mill; the glue holding them together came loose in the process, but fortunately they need not be held together any more at this point:
normal_IMG_3123.JPG


Getting rid of the facets is easy - a couple of light strokes (literally about 10) with a sharp file around the outside, and you can see the difference:
normal_IMG_3124.JPG


A quick rub over emery, and that's where I stopped for the day; there's still some tool marks left, but I'll remove those later, as I need to do a bit more work on the one column and also press in the bearings once made:
normal_IMG_3125.JPG


Regards, Arnold
 
This afternoon I had a good solid 4 1/2 hours of shop time :)

Started off on the base, and poked in the mounting holes for the columns:
normal_IMG_3126.JPG


I needed to mill a 2mm wide slot 6mm deep - and re-cutting chips is a problem, so I used a bit of wire to pipe in air from the compressor:
normal_IMG_3127.JPG


That slot would need 10 passes at 0.6mm deep per pass, so I dragged a chair closer and got comfortable. The first pass nearly done:
normal_IMG_3128.JPG


And a little while later, all done without any drama:
normal_IMG_3129.JPG


Then I flipped the base, and countersunk the column mounting holes, and also drilled two 3.3mm holes 10mm deep to tap M4 for the mounting the base to wood later:
normal_IMG_3131.JPG


A trip to the bandsaw, and I got rid of some excess from the base:
normal_IMG_3132.JPG


And milled the rest down to size:
normal_IMG_3133.JPG


I thought I was done, then remembered I still needed holes to mount the cam to - those followed in short order - 2.5mm to tap M3:
normal_IMG_3134.JPG


When it came to tapping the holes, a problem raised its head - my taps are too short:
normal_IMG_3135.JPG


That's not the first time I've had this kind of problem with my M3 taps... So I diverted a bit and made a quickie tapping handle for such cases:
normal_IMG_3137.JPG


It works a treat ;D - I just have to shorten the grub screw a bit:
normal_IMG_3138.JPG


I was thinking of making cast-iron bushes to press into the columns - to give good bearing properties combined with the brass that the cylinder block and shafts are made of. Unfortunately I could not find any in a suitable size, and while I do have some 25mm CI I could turn down, that seems a bit of a waste for such an expensive commodity... My next best choice was phosphor bronze, which I have quite a bit of and can get at a reasonable price, but research indicates that brass and bronze are "similar" metals and not good for bearings... Well, I could use steel then; it would be better... And then my eye fell on the 1m length of 17mm round PTFE I bought more than a year ago at a whim (and very good price).

Well... Why not?... I don't see plastics used a lot on model engines, but it's supposed to be as slippery as snot, so should make good bushes for this application. This engine will never be run on steam, so the issues with heat and water porosity shouldn't be a problem... There are two problems though; a) Would it be acceptable to use a synthetic material in a model like this ? and b) I've never tried to machine PTFE - not to any sort of accuracy anyway.

As to a) - It "feels" wrong, but then again, I wonder what the Verburgs, Duclosses and Spareys would have done; Some of their build specifications seem to use cutting edge materials in terms of what was available when they built their models, so I'm not going to feel too bad to add a bit of new technology...

And as to b) - Well, there's always a first time :)

Decision made, I started; I just used my regular HSS tools that I use on everything; I just made sure all the cutting edges were honed sharp. Cuts easily, though I had some chatter as I didn't add tailstock support right from the start, but even parting off is a breeze ;D - small diameter bush done:
normal_IMG_3140.JPG


Bigger diameter bush in-making:
normal_IMG_3141.JPG


Both bushes were turned on the OD to a press fit in the columns. I'm surprised; it was easy to accurately turn the plastic and get fairly acceptable finishes; I expected to struggle a bit with that, but it turned out rather well. Pressing the inserts into the columns made a fairly significant change on the ID's of their bores.
So I decided to try out my hand reamers on them; the 6mm one for the small shaft went well, and easily cut the bush ID to size again without any complaints.

The 12mm reamer was another matter; it wanted to chatter - severely... I was trying dry cuts, so I decided to try a little lubrication... But what scratch.gif. I settled on a squirt of the synthetic oil/water mixture I use when parting off steel; it worked a treat and the reamer smoothed right out and cut nice even chips out of the hole woohoo1

For today's work, I ended with this lot:
normal_IMG_3142.JPG


I'm surprised by how well the PTFE bushes work ;D:
[ame]http://youtu.be/D8wbTMHXql8[/ame]

The bush on the thin axle looks like cr@p though, so I think I'll make an aluminium insert to press in with a smaller bush that will be hidden by the flywheel hub later on. I can make the ali insert nearly invisible and things should look nicer.

Kind regards, Arnold
 
Arnold,

You may find it easier to separate the tap extension function from the tap torquing function...

EXTENDER.jpg


At only 0.25" diameter, this one will get into fairly tight corners. It has my usual floating alignment pin to keep the tap square to the work. The small tap wrench can be fitted onto it anywhere on the flat; its screw bears on the flat.
 


To clean up the face of the boss was another matter; one cannot get close enough without damaging the center; something I REALLY do not want to do. So I moved away the tailstock, and with a narrow strip of emery pressed against the face with the forefinger of my right hand, I started the lathe; the pressure keeps the cylinder head engaged against the collet chuck, and because the contact area against the paper is larger than that of the emery on the face, there's sufficient drive to finish it. NOT the best way to do things; it would be better to stick the cylinder head to a mandrel (with superglue or double sided tape) or clock it up in the 4-jaw against a backstop to finish machining.



Actually that is an excellent way to face it....even writing paper should have enough grip to do what your doing....

Dave

 
Thanks Marv :) - that's a neat idea; another project for a rainy day then... I'll have to make ones for my smaller taps as well.

Dave, thank you; I won't disagree with you then ;D.

Today's four hour stint was done on the cam ring; it's not finished, but at least some progress.

I printed out the list of machining diameters (Many Thanks goes to Gail Graham for making up the spreadsheet I used), jotted down some notes of things to keep in mind on it, and sawed a bit of 2mm brass plate from some stock I have:
normal_IMG_3144.JPG


The plate was smeared with some permanent marker ink, and laid out for the most important bits:
normal_IMG_3145.JPG


On to setting up for machining, and oh dear; it's too big for my rotary table:
normal_IMG_3146.JPG


But it will fit on the lathe's face plate if I mount that to the RT ;D:
normal_IMG_3147.JPG


I found a bit of wood off-cut from last year's kitchen renovations, and mounted the workpiece to it with some self-tapping screws through the center bit where the screws will be inside the cutting tool path. After that, I drilled holes through the corners where excess will be, but spaced to match up the face plate's slots when the workpiece is centered:
normal_IMG_3148.JPG


Mounted the face plate on the RT, and centered the RT on the mill as well as zeroing the X and Y handwheels - making an additional note on the cutting chart as to which direction I was moving the table when zeroing the handwheels:
normal_IMG_3149.JPG


Then I mounted the workpiece on the face plate, lightly tapping it till I could get it as centered as possible. The mill's X and Y wheels were left strictly alone on zero. The idea is to center the workpiece to the center of the RT here:
normal_IMG_3150.JPG

I also tried to get the base reference as parallel to the X travel of the mill as possible by eye.

Once I was happy that the workpiece was centered, I cranked on X to check on the rotational orientation:
normal_IMG_3151.JPG

I'd eyeballed the rotation to less than half a degree, so I cranked the RT to bring the line on center and zeroed its dial.

One disadvantage of having screw-on chucks/faceplates is in a scenario like this. In this case, the face plate screwed on with it's slots offset by about 30 degrees, so I couldn't use the RT's own degree scale:
normal_IMG_3153.JPG


Oh well, a permanent pen can make a new scale; I'm going to work without any cutting fluid, so the markings won't be washed off:
normal_IMG_3154.JPG


Next I bodged up a DRO - One day I'll get proper DRO's but for the most part I don't mind reading the handwheels:
normal_IMG_3155.JPG

:big: - I did say "bodged up" :big:

A final check of everything later, then a cup of coffee, pulled up a chair, and started... I'd calculated the cutting path for a 12mm cutter, so I drilled a 10mm hole to start things at the first coordinate after locking both X and Y axes on the mill and the RT's table. The hole is to give the cutter less material to cut away for a start - and prevent things moving:
normal_IMG_3156.JPG


Then I started with the 12mm cutter - same location and drill it out to size, mark the first coordinates on the sheet done. Then the roundabout began... Unlock RT, feed 2 degrees, lock, unlock X, dial in the new coordinate, lock, drill new location, mark as done on the sheet. Repeat. About 60 degrees later:
normal_IMG_3157.JPG


I stopped for the day at 178 degrees:
normal_IMG_3159.JPG


It takes about 45 minutes to do 90 degrees and a LOT of concentration (maybe I'm just a slow worker :big:). One mistake, and I'll get to start all over :-\ And it is a bit of a mind-numbing process, so better to carry on when I'm fresh. That's why I put a new battery in the caliper; so it can "remember" the last reading, and why I meticulously marked off each position as it was done and the state of the mill when I started; at least I can stop and pick up from there later.

Regards, Arnold
 
After a hectic work week and most of my weekend spent on getting an additional data center going for my company I finally got some shop this afternoon.

Finished off the last 180 degrees of the cam:
normal_IMG_3161.JPG


Drilled the two 3mm mounting holes:
normal_IMG_3162.JPG


I nearly forgot to clamp down the outer bit to the wood block before removing the bolts holding everything to the face plate... Fortunately I realised just in time and added a couple of screws through the mounting holes to keep it in place. The whole lot needed to be moved on the face plate to the outer ring center to finish things off, and if it moved it would have lost its place on the center piece that has the center position marked! :
normal_IMG_3163.JPG


Of course, last weekend in a blinding flash of idiocy I didn't drill additional mounting holes offset with the required 8mm from the initial ones, so no mounting holes could align with the face plate slots once I moved the workpiece to the new center :big: - So I grew a forest of clamps to finish the rest of the machining operations:
normal_IMG_3164.JPG


That meant I had to stop during machining to move clamps around to get out of the way - here is one of the stoppages to move a clamp:
normal_IMG_3165.JPG


Finally - all machining done on the cam three hours into the shop session:
normal_IMG_3166.JPG

Not a miss-step or anything, and that's the hardest part of this build done ;D - just some clean-up left to do.

A close-up of the cusps left by the machining process on the inside of the cam:
normal_IMG_3167.JPG


They look worse than they are; a little very light and careful filing with a 250mm fine half-round file brought the roughness down very quickly till all the cusps were barely visible and even in size right around the ring. Then I wrapped some 320 emery around a bit of 50mm pipe, and in careful circular motions around the ring removed the last visible signs of the cusps. All this was done very carefully; things needed to just be smoothed out; the shape mustn't change.

After a bit of file work around the outside of the ring to get rid of tool marks, and a rub over some emery and a quick rub with scotch-brite to give a brushed finish, the cam is done:
normal_IMG_3169.JPG


What do you know? - things fit together and is starting to look like an engine:
normal_IMG_3170.JPG


That's the engine half-way done then; so only 90% to go ;D

Regards, Arnold
 
Nicely done Arnold....and that wasn't bodged up...that was Manufacturing Engineering at it's finest! ;D

:bow:

Dave
 
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