Moonbogg wrote:So hybrid vs pneumatic, it seems that what it comes down to is simply pressure. If all else is equal, then its just whichever has more PSI behind it.
Not quite. The limited speed of sound in the pneumatic cannon does slowly begin to limit efficiency as velocity begins to progress over half the speed of sound - and faster than around 80% of the SOS is still a pretty hefty achievement.
Hence, overly light projectiles are going to lose power
However, dependence on the combustion gas temperature with a hybrid, means that heavy projectiles that accelerate slowly will cause the loss of gas temperature, and thus pressure.
Hence, overly heavy projectiles may lose power.
It's a similar tendency to air rifles, where the springers (which use gas heated by rapid compression, making them similar in ways to a combustion or hybrid) tend to shoot the light pellets more energetically, and the PCP rifles tend to do better with pellets with some more mass in them.
The exact effect of each is a little hard to know. I've been working on doing analysis of pneumatics and mass vs. velocity. For my cannons at least, it seems to hold to the rough rule that up to about ~70-80% of the SOS (and at a given pressure), Mass x Velocity<sup>2.5</sup>
is pretty constant. After that, the numbers start to fall away due to losses near the speed of sound.
I haven't a hybrid to analyse, but I may at sometime do some estimation with HGDT and try and find out if there's a similar work from that.
I love this hobby. When I excitedly tell people I finished a high end spud cannon, they tend to look at me like I have brain damage. If only they knew.
I've had that a couple of times - the famous "You build spudguns?" look.
This is often followed with the "Wait, that's
what you mean by spudgun