First engine: Elmer's #25

[Trizza]

Well, not technically my first, but the previous was many years ago on a different continent.

So I just received my machines (Sieg Super C3 & Super X1L) last week and figured I'd pick a little engine project to break them in and get some practice. I picked Elmer's #25 because it looked like a nice little design - and I just happened to have suitable stock lying around.

I got a start on it tonight by converting the plans to metric and making the piston (shown upside-down here):

The process used was to face and turn a length of brass bar down to the right diameter, then cut the oil grooves, centre drill, drill through with pilot bit for M3, then drill out the waste from the piston interior. I parted off to length and then tapped the M3 thread manually (I don't have a bottoming tap and I didn't want to run the risk of breaking my through tap). The brass was exceptionally easy to cut on the SC3 - 1mm passes didn't show any signs of struggle at all, and the parting cut was smooth sailling.

I don't have a reamer of the right diameter for the cylinder so I'm planning to use a boring bar to bring it to the right size. Should I plan to lap the cylinder and the piston together? Will I have any problems if I swap the cylinder to aluminium?

 

[mklotz]

For future reference, it's generally easier to make the cylinder first, then make the piston.

Brass on aluminum is not the best of combinations but it will work. A steel cylinder would be better. For reference, here's how the relative friction stacks up...

			Coefficients of Friction

dry (unlubricated) condition
				static		sliding

aluminum	aluminum	1.05-1.35	1.4
steel		brass		0.51		0.44
steel		aluminum	0.61		0.47
steel		steel		0.74		0.57
steel		graphite	0.1
cast iron	cast iron	1.1		0.15



Elmer's #25 calls for a cylinder that has a blind, square top. You may find it easier and more accurate to bore through and cap the top of the cylinder.

 

[Troutsqueezer]

Since the top of the piston is threaded, you can screw a bolt into it and chuck it back onto the lathe. Then you can turn the piston to size after you bore the cylinder to a size slightly smaller than the existing piston diameter.

 

[Trizza]

Hmm, I think I have a bar of mild steel big enough to mill a cylinder from, I'll give that a shot.

Thanks folks.

 

[Trizza]

I rummaged around and found a piece of 18mm steel (FE52 - low carbon) bar and decided to have a go at making a cylinder from it. I adapted the plans to what I had to hand and added some embellishments and ended up with, I think, a nicer looking cylinder. The steel machined OK, and it shined up really nice, but parting was a total no-go - way too much chatter. I ended up just making a groove and hacksawing through.
I also made up the conrod, although I haven't milled & drilled it yet.

This is fun

 

[Trizza]

I've been plodding along with the build and its nearing completion now - I just need to make an M3 nut for the spring and the air connector and I'm done. It turns over nicely, very smooth This has been a really enjoyable build, I've learnt a tonne about my machines and turning. Its fun to compare the most recent parts to the oldest parts and see how much better they are.

 

[ShedBoy]

Looks good, a great first effort and you can onyl get better. Have you run it yet?

Brock

 

[Hat56]

Speaking of Elmers engines I saw a two cylinder wobbler geared to a single shaft presented by Tubalcain on youtube and he suggested it was a number 115? made by Elmer. I would like to get the plans for this if anyone can help.

I have searched the John Tom to no avail.
Cheers Hat