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I'm building my second cannon (first used ball valve). I have a rotating shell design similar to Solar's Eclipse. It will be using Davidvaini's burst disk cartridge design. Unlike David's design, i want to trigger by puncturing the disc rather than pressurizing until burst.
My problem is I can't think of or find a way to trigger the puncture. I was thinking of using a nail through the barrel to puncture, but I don't know what to use to push the nail. I must be able to trigger without pushing the nail myself.
Any ideas appreciated, and here's a picture of the shell and barrel assembly for reference. The barrel size is 2 inch.

Have a trigger that is attachted to a spring with the nail, to reload push back(pump action) until the trigger locks into the spring again. or just have the nail attached to a long tigger(for leverage) and use that, far easyer

An electric solenoid mebbe?

TurboSuper wrote:An electric solenoid mebbe?

Now that's a rather spiffing idea!

How about using a syringe system to push a nail through the burst disc? You could have one end in the grip and the other end mounted in the barrel with a nail attached to the plunger. I'm not sure exactly how you could mount the syringe but its something to think about at least. Here's a rough idea of it.

[youtube][/youtube]

@Avatar17
hey you made a very nice diagram and I like your idea

Welcome to Spudfiles

I think that the pump action shotgun design would be the best. perhaps, you have the pump pull back the spring that punctures the disk and you have a trigger to release the spring. the cartridges rotate and you re-pump fire et voila.

Howabout a mini cannon inside to launch something at the burst disk?

You could maybe put something through the PVC on the barrel end with a join, so a simple level to puncture.

avatar17's idea is the best IMO... it would be a good idea to insert a small spring in the 'trigger' syringe to help reset it

Pretty cool idea.

Are you stuck on pneumatic? JSR did some work with combustion cartridges.

You could do something along those lines. Have contacts on the rear of the cartridges, and on the face of the receiver.

Avatar's animation is great, but how do you get around having the syringe in the path of the projectile?

Not to mention, that the syringe would have to push through any projectile as well.

Or am I missing something? (Too many beers does cloud the mind some what. :occasion5: )

I've decided to go with a lever system. Although I might go with a solenoid trigger since it's much less complicated. Where can you buy a solenoid? Here's a diagram of the trigger system. The individual parts have unique colors so it's easier to understand, although it's very simple.

Are you muzzle loading the projectiles?

If not, the first shot will "take out" your piercing device.

The projectile won't be loaded into the burst disc shell, I will either muzzle load or breech load. Sorry for not specifying. Also, the shells will be rotated manually unless I can make something to do it automatically. If anybody has idea's for that, I'd like to her them.

You could also have a sharpened barrel which was fixed. Then you could use something to push the cartridge's burst disk against the back part of the barrel making it rupture.

You could also have a sharpened barrel which was fixed. Then you could use something to push the cartridge's burst disk against the back part of the barrel making it rupture.

How about having the barrel push back?