SpudFiles

I have a 2" X 78" air chamber and an 86" X 1.5" Golfball barrel, 1.5" porting piston valve, the angle iron estimated at around 1.5kg.

So in GGDT I put in 2" piston diameter and 1.5" sealing face and 1.68" for the barrel. I think its overestimating it though, do I actually measure the pipe or put in what the pipe says it is?

You put in what the pipe actually is. GGDT doesn't have anything built in to automatically convert to the real pipe measurements.

I guess I was right about the massively oversized chamber though.

Ok I measured a piston that was on my desk, got 1.59 sealing face and 1.75 piston diameter. That gave it 1149 ft-lbs with a 1.5kg projectile.

DYI wrote:I guess I was right about the massively oversized chamber though.

And I even though of putting a 3" chamber on it