[TheForge] Krause/Nazel type air hammer

[Steve Smith]

Here are a couple of ideas aimed at minimizing or eliminating machining:

Treadle Valve
This seems like the hardest part to most of us.
Why not make the fit a tiny bit less exact (maybe to 0.001") and fill 
the gaps with grease? I think the pressure is only around 50 psi. 
Inelegant, but it should work fine.
As an alternate idea, how about plastic seals? Can you use a plastic 
that gives a bit and bore the plastic out a little undersize, then push 
the valve center into it?

Stroke pressure relief
Krause follows Nazel in machining air passages in the cylinders. I'm 
thinking it will be a lot easier (not to mention easier to fix if I 
don't get it right) to use electric air valves tripped by microswitches 
on the crankplate. This way you could use a standard double-acting 
cylinder with no machining. Overpressure valves in a couple of places 
sound like a good idea in case the electric valves quit for some reason.

Steve Smith