New to the Forum, New Project

[charre]

Ok I've been toying with HGDT this weekend and Ive found a bit of an anomaly that has left me scratching my head. With a chamber length of 8 and diameter 3 I seem to get significantly more power in the simulation from a 1.5" bore compared to any other size bore. I have the barrel length set at 48" for all the simulations just as a constant. If anyone has any idea what is going on I'd like to hear it.

[saefroch]

If anyone has any idea what is going on I'd like to hear it.

Well assuming that still means me, and since D_Hall hasn't replied yet, here's my understanding of the situation: You're reached a sort of balance between the pressure behind the projectile, atmospheric pressure, and the friction in the barrel. By increasing the projectile's friction, you decrease the bore diameter that will yield the highest muzzle velocity and muzzle energy. Graphing projectile acceleration against time helps illustrate this, as well as looking at the barrel pressure when the projectile exits.

[charre]

Well assuming that still means me, and since D_Hall hasn't replied yet, here's my understanding of the situation: You're reached a sort of balance between the pressure behind the projectile, atmospheric pressure, and the friction in the barrel. By increasing the projectile's friction, you decrease the bore diameter that will yield the highest muzzle velocity and muzzle energy. Graphing projectile acceleration against time helps illustrate this, as well as looking at the barrel pressure when the projectile exits.

Yea i think I can see that now. I'm trying to figure out on what side of the curve I want to be. On one hand a smaller diameter gives me more power and higher chamber pressure, but I need a longer barrel to harness that. On the other hand a larger barrel diameter allows me to reach max V with a shorter barrel but with less power and chamber pressure.

[saefroch]

I'm trying to figure out on what side of the curve I want to be.

You mean the x-axis
EDIT:that was terrible...

If you have any ammo in mind you'd like to shoot, it'd be easiest to design a cannon around being able to shoot that efficiently. But on the other hand, if you're still looking for a big bang, you probably don't want to have very close to 0 chamber pressure when the projectile clears the muzzle.

[charre]

I had an idea to fire steel darts in a foam sabot made from polyurethane foam. Other than that i liked the burnt latke guy's idea to fire wooden slugs with rubber gaskets.