NEW picts added - Project conclusion

[QVTom]

My conclusion is..............  Large piston face/short stroke is unworkable. The large piston face area makes them prone to bounce and it is impossible to make them heavy enough to overcome the bounce. 

Yes, I know it has been years, but, to quell piston bounce, ponder this idea:

Place a reed-valve inside your breech bolt (as used on some two-stroke bike engine intakes) .  The valve would snap shut due to the pressure differential, just as the pistons start to bounce back.  That would trap the bulk of the air behind the pellet, regardless of what the pistons felt like doing.

I'm sure there are many ways to subdue piston bounce but the increase in complexity at some point becomes untenable.  Slide weights, reed valves, etc. are all good ideas but they need to be applied to a design that is not basically flawed.  The piston face area/stroke ratio must be reasonable from the start.

The Whiscombe with its two pistons mechanically connected has a distinct advantage in the area/stroke department; each piston shares each other's mass.

Thanks for the interest!

Tom   

[QVTom]

Yeah, I guess you can say the Dark Side has consumed me.

Tom

[QVTom]

How did I never see this thread! I love to read these type builds!

Did you ever try any other versions of this concept?

I did design a smaller diameter longer stroke version but never built it.  Instead I went to PCPs

Tom   

[subscriber]

I'm sure there are many ways to subdue piston bounce but the increase in complexity at some point becomes untenable. 

After thinking about this some more, I concluded that to keep the overall rifle weight down, exploring what can be done with a single stroke pneumatic was indicated. (Or at most, two strokes: preferably on opening and closing). 

After all, an air "spring" has very little mass, and requires no piston duplication for inertial jolt cancellation...

[chwillbill68]

Just another gun, I will need if you bring to market! LOL

Bill C!

[chwillbill68]

How did I never see this thread! I love to read these type builds!

Did you ever try any other versions of this concept?

I did design a smaller diameter longer stroke version but never built it.  Instead I went to PCPs

Tom

Tom any prediction on when the Evol will open back up! I check every day! LOL

[ozarkair]

This is amazing!  Love the craftsmanship and design!