Mini(sorta) triggered burst disk cannon

[A-98]

this weekend it was raining and i went to the hardware store to buy some supplies for a new cannon. i had never made a burst disk cannon, and wanted to try one out.

everything is currently 3/4". the chamber is 12" long and the barrel is 36" long. i use thick aluminum foil for the burst disks and pressurise the primary chamber to 80 psi, and the secondary to 20 psi.

i was originally going to have a 2" by 12" chamber, but my hardware store was out of the proper couplers

and here are the images

[experament-u2]

smart design iv never seen it before tho

great gun

[A-98]

i was going to paint it but it has been raining

[StealthSpud]

Very nice looking gun and a unique design! Can't wait to see it with a paint job!

[A-98]

have half days right now... just painted my other gun

post them up in a sec

[Insomniac]

You should use some hose or some fittings so the blowgun vents into the barrel. Someone (might have been killagorrila) said they made a sprinkler valve's blowgun vent into the barrel and it significantly improved performance.

[A-98]

really?
hmm. might have to try that out this weekend.

[Insomniac]

Oh and whats the C:B ratio on that?? Looks like the chambers too small.

[medievalman]

looks nice, if i ever make a burst disc cannon, it would be like that one.

Oh and whats the C:B ratio on that?? Looks like the chambers too small.

The c:b ratio is 0.333:1 the most EFFICIENT c:b ratio for a pneumatic is 0.2:1 but the most powerful is 1:1 or higher, so adding a larger chamber would increase performance, ALOT!

[Hotwired]

The c:b ratio is 0.333:1 the most EFFICIENT c:b ratio for a pneumatic is 0.2:1 but the most powerful is 1:1 or higher, so adding a larger chamber would increase performance, ALOT!

I've been waiting for someone to bring this up since I posted my own C:B ratio on my pneumatic and then thought about it for a bit.

A ratio can't possibly be the same for all cannons. A cannon running on 60psi has to have a vastly different optimum ratio to one running at 200psi because of the difference in the stored energy.

With a 1:1 ratio in both cases the first would have 30psi behind the projectile as it left the barrel and the second would have 100psi behind it.

[A-98]

ya, im aware that the CB ratio is really small. it was going to have a 2" chamber, but they were out of the proper couplers.

[medievalman]

before you paint it, you should get a 24" long 1" chamber. and why is it sch 80 pipe? sch 40 is plenty strong for pneumatics and combustions, just not hybrids

[A-98]

its sch 80 because its threaded on both ends at my hardware store. and the unions are sch80...because they are....im going for a 2" by 12" so the same thing

[Pneumatics]

so, why is there 2 diffrent burst valves. is it so you can get higher pressures. Because i thought that maby between the burst valves the the 80 psi gets relief on the foil because the 20psi on the other side? is thais what it does?

[MrCrowley]

Its so he can trigger them instead of waiting and praying for it go boom once it hits the burst discs pressure.