I had a very satisfactory day in the workshop, yesterday. Worked on another mod, to try to improve balance.
The displacer has a balance weight....... But the relatively heavy piston hasn't...... It wags the table from 200 rpm!

I made a quadrant from 1/4" thick brass. Then drilled & tapped the side of the bob weight 4BA......
Huxtable Hot Air Engine.Screwed it into place......
Huxtable Hot Air Engine.And turned it down to crank throw diameter......
Huxtable Hot Air Engine.Now it looks like this. Balancing the piston.......
Huxtable Hot Air Engine.Started up. Much smoother, straight away.
Huxtable Hot Air Engine.Happy top revs now, are 450 to 500.
Any more than
this, it starts to jump around....... Again!
Huxtable Hot Air Engine.It's
never gone over 400 rpm before........ This time it went up to 578rpm!
Almost 50% extra revs, just for improving the balance!

David D