astroud

Thanks for the comments.
The holes were drilled on a rotary table, I have a BCA Mk111 jig borer which is perfect for this sort of work but the machine is a bit light for general milling work and it is my only mill.
Elmer gives dire warnings about making the internal gear PCD x 2 of the pinion otherwise lock ups will occur and this method is probably not as precise as gear cutting so we will see. Back of my mind is build some adjustment possibilities for the centres.

Andrew

I have decided to attempt an engine based on Elmer's No 5, I say based as the detail will be own design.
I do not have gear making equipment in my workshop and inspired by a build over on HMEM I decided to try making the gears by drilling holes.
Sizes and spacing were done on the basis it looks about right, you just need the 2:1 ratio and careful measurement, I have chosen 12/24 teeth.

The external gear was completed by putting it back in the cut off square and then inserting 12 x 6mm dia slugs and soft soldering them in. I was worried the strength might not be enough for subsequent clean up machining but it was quite OK. The gears fit together nicely though there is still a bit of solder to file away.

I then went on and made a couple of main bearing stands and will do the crankshaft next.

Andrew

What a terrific model, its a masterpiece, congratulations !

After playing with the engine I noticed if I unscrew the air valve the engine would slow down so I decided to build another air valve with a variable position valve meaning I would be able to move the ball closer or further away from the piston activating prong. I achieved about 0.15 movement which I had seen from my testing was enough.
The photo below shows the design, basically a moveable spool with the ball and spring within the housing. I found out after testing the air pressure within the spool can push the cap on the opposite end to the ball seat off its seating resulting in a loud clacking sound when running. The only way I see to fix this is either solder or Loctite or a much stronger return spring but it is not a problem if I keep the pressure below 40 psi so I will leave as is for the moment.
I have some smaller diameter ball bearings coming to see what impact they might have.

If you can watch the video to the end it does its party trick and starts oscillating backwards and forwards.

Andrew

https://youtu.be/Tlg3QlicZzg

Quote from: JasonbString wrapped around a flywheel will also get it going as will a rubber faced drum in a cordless drill held against a flywheel rim

A good way to allow for some experimentation is to use a separate wrist/gudgeon pin holder then you can just use shims to alter the position of the piston and also add larger shims to the crown to alter compression ratio.

Thanks Jason, something to remember for the future. My conrod is a 6mm tube with little and big ends stuck on so I can unstick it, make a new shorter central section and stick it back together again.

Andrew