Another Adventure in Hot Air

Quote from: PaulR
Thank you Dave. I've made a similar piston connection for a steam/air engine before but getting the bottom of the hole flat was an issue as it was too big for a d-bit and I don't have a mill - I think I soldered a flat into a tube in the end. 

  There are two methods: 1) grinding the tool bit; or 2) if the hole is 8 mm, drilling it with an 8 mm drill bit, then regrinding  drill bit to a 0-degree angle and drilling again. (I have used both methods; the choice depends on the diameter of the hole.)

Quote from: PaulRMinh Thanh, yes, this a very ugly machine like most of my other builds but I'm not too bothered about looks..

  Your engine is very well built and performs significantly better than my  first engines.

I took the engine apart as I wanted to see what state the displacer etc was in. Turns out it had some brown staining at either end, maybe iron oxide staining from when water was getting in? Decided to check if it was still airtight and found there was a tiny leak at the hot cap end, so I've sealed that. I was also surprised to find that none of the holes on the simple rods were enlarged although there was a very tiny burr around two of them that was probably a remnant of drilling so I removed those with some steel wool - every little helps I guess. While I was at it, I decided to spin the flywheel while it was disconnected to see if I could count the rotations but it's very free running even on simple brass bearings. I don't think I'll bother will ball races for the next engine after all!

https://youtu.be/PLSTZ8NTjyg