This has been a great project. I did change some things, but the basics are still the same.
I made my own gland for the displacer out of brass, because it seemed a shame to waste a perfectly good propelling pencil. The rod for the displacer is still a sewing needle.
I didn't have the tin lids required, so the ends of the chamber are cut from the side of an old steel filing cabinet with tin snips. I broke the cabinet down a long time ago, but it is a useful source of 0.8mm mild steel, pre-painted on both sides.
The chamber is made out of a shorter printed ring, and the caps slide over it trapping the steel discs.
- The top part is all glued with epoxy, and the lower ring and disc are also glued with epoxy.
- The top and the bottom aren't glued together. Instead I used a silicone grease, and made some clips to keep the halves together.
- This change means that I can remove the displacer if ever I need, without damaging the whole engine.