More renderings

Here is the valve which will probably be used. The two o-ring (well, four) design pressurizes the end of the cylinder the valve is pushed toward.

Here is the 3 o-ring version. It's operation is the reverse of the other, and I believe as designed, it has a slightly longer throw. That can easily be tweaked though. An advantage of this design is it's completely closed, and potentially reversable by swapping the center Input with the two ends (exhaust). Probably more complicated than I want to deal with in this project.

Here is a view WITHOUT the structural / guide rails.

The following is a ghost view of the complete engine so far. If you look closely you can see how the crosshead interacts with the rails, and also the set screws that determine valve throw and end travel. It is likely I will include another set of (adjustable) positive stops for the valve to keep it's momentum from carrying it beyond the mark when pushed by the crosshead.