Picture of all my toys

[Boomer58cal]

If you wait long enough for the gas to rupture a burst disk you have depleted what little oxygen there is and it would be a dud.

In a carbide Cannon you wouldn't want to wait for the pressure to blow the desk( although that would probably work too ), the burst disk serves to contain the combustion gases during ignition, just long enough for a more complete burn( only a few milliseconds ) This gives the benefits of added power and a bigger bang.

My 2" Pneumatic burst disk cannon at 120 psi is comparable to a 20 gauge in the noise department. Hearing protection recommended.

Chuckit's are a little tight for my barrel. I will try the balls from Walmart. Thanks

[BowerR64]

And your bust disk is just a thin layer of foil?

I think the 4"-3" cannons i have sound about like an M80, back in the day M80s

The only way to do the burst disk is with the screw together coupler right?

Ive shot a few different type and the loudest are those with a taper, even if its only 1"-3/4 or 3/4-1/2" those are louder then say a 1" tee with a 1" barrel. They have a bang but those dont crack near what they do when its necked down.

I want to see yours though.

[Boomer58cal]

And your bust disk is just a thin layer of foil?

I think the 4"-3" cannons i have sound about like an M80, back in the day M80s

The only way to do the burst disk is with the screw together coupler right?

Ive shot a few different type and the loudest are those with a taper, even if its only 1"-3/4 or 3/4-1/2" those are louder then say a 1" tee with a 1" barrel. They have a bang but those dont crack near what they do when its necked down.

I want to see yours though.

Yep just a layer of tin foil. The more layers of tin foil you add the more pressure it holds before the disc bursts. In a combustion cannon you should only need one or two layers of foil. In fact if you made a cannon out of metal, you could pump in a little extra air and have a hybrid carbide cannon. I haven't seen one of those yet.

You could also use a camlock ( pictured below )

I don't know how loud the mentos cannon will be. I just need some 1" sch 40 for the barrel.

[BowerR64]

Did you see the "kid scientists" on the David Letterman show last night? One of them shot a T-shirt form a 2" cannon, well dave shot it but she had it all wired up and ready. He just put water on the carbide, screwed the cap on and pulled the trigger.

It had quite a bit of kick because the shirts are so heavy.

[BowerR64]

Adjustment on the cotton candy cup, 1 .22LR shell full will pop the lid off as if you stomped on the cup with the lid on, exciting but not really a celebration. 2 .22LR shells full you start to hear the bang from the conbustion. 3 .22LR shells (about 15 grains) it will ring your ears a bit. An empty 9mm shell holds about 13 grains so an empty 9mm shell will light the cup up and give everyone a bit of a surprise :bom:

First image is .22LR shell, last 3 is the stills from a 9mm shell. You can see the bottom line is the water level.

[Boomer58cal]

Did you see the "kid scientists" on the David Letterman show last night? One of them shot a T-shirt form a 2" cannon, well dave shot it but she had it all wired up and ready. He just put water on the carbide, screwed the cap on and pulled the trigger.

It had quite a bit of kick because the shirts are so heavy.

kid scientists on Letterman http://www.youtube.com/watch?v=tMfuB4K7 ... ata_player

[BowerR64]

Did you see the "kid scientists" on the David Letterman show last night? One of them shot a T-shirt form a 2" cannon, well dave shot it but she had it all wired up and ready. He just put water on the carbide, screwed the cap on and pulled the trigger.

It had quite a bit of kick because the shirts are so heavy.

kid scientists on Letterman http://www.youtube.com/watch?v=tMfuB4K7 ... ata_player

You better hurry and order your carbide before the prices go up. lol

[Fnord]

Have there ever been any definitive studies relating to PVC guns using acetylene with a projectile?

The safety factor is undoubtedly better when no additional oxygen is used, I just wonder if it's actually 'safe' or just takes a long time to form enough mircofratures to blow up.

[Technician1002]

If the carbide cannon has a chamber fan, the burn rate is fast enough that a burst disk is not needed. A burst disk is of benifit on slower burning fuels. If you search the vortex cannon video online you can see the burn rate is fast enough to not need a disk.

I would not want to be holding a carbide cannon when it failed. I have not seen any info online of PVC carbide cannons failing because they are relatively rare. There are some videos online of ABS cannons taking some punishment and surviviing. Most carbide cannons have the advantage of poor mixing to buffer the discharge. A chamber fan and a proper mix could easly make a PVC cannon very dangerous.

[Boomer58cal]

If the carbide cannon has a chamber fan, the burn rate is fast enough that a burst disk is not needed. A burst disk is of benifit on slower burning fuels. If you search the vortex cannon video online you can see the burn rate is fast enough to not need a disk.

I would not want to be holding a carbide cannon when it failed. I have not seen any info online of PVC carbide cannons failing because they are relatively rare. There are some videos online of ABS cannons taking some punishment and surviviing. Most carbide cannons have the advantage of poor mixing to buffer the discharge. A chamber fan and a proper mix could easly make a PVC cannon very dangerous.

I brought up the burst disk for is noise enhancing capabilities (We were going for loud. :bom: ) and because I am adapting his carbide cannon design into a mento's and diet coke cannon by adding a burst disk. He wasn't yet familiar with burst disks.

I had also though about adding a chamber fan, but didn't think electricity and a water filled cannon was a good combo. I would mostly worry about recoil splashing water on the fan or causing premature ignition. I would think the little hand pump on his howitzer cannon would be the best way to mix the charge in a moist chamber.

[BowerR64]

If the carbide cannon has a chamber fan, the burn rate is fast enough that a burst disk is not needed. A burst disk is of benifit on slower burning fuels. If you search the vortex cannon video online you can see the burn rate is fast enough to not need a disk.

I would not want to be holding a carbide cannon when it failed. I have not seen any info online of PVC carbide cannons failing because they are relatively rare. There are some videos online of ABS cannons taking some punishment and surviviing. Most carbide cannons have the advantage of poor mixing to buffer the discharge. A chamber fan and a proper mix could easly make a PVC cannon very dangerous.

I wouldnt want to be holding any PVC when it failed wether its hairspray, or compressed air, or what ever.

I dont think you need to complicate a carbide cannon by adding a fan. Even with a fan wouldnt there still only be 20% oxygen? I dont see the need for it, other then maybe clear out the spent gasses. Just opening the end to put more carbide in is enough.

I dont understand the poor mixing to buffer the discharge? can you explan that a little more?

[Boomer58cal]

If the carbide cannon has a chamber fan, the burn rate is fast enough that a burst disk is not needed. A burst disk is of benifit on slower burning fuels. If you search the vortex cannon video online you can see the burn rate is fast enough to not need a disk.

I would not want to be holding a carbide cannon when it failed. I have not seen any info online of PVC carbide cannons failing because they are relatively rare. There are some videos online of ABS cannons taking some punishment and surviviing. Most carbide cannons have the advantage of poor mixing to buffer the discharge. A chamber fan and a proper mix could easly make a PVC cannon very dangerous.

I wouldnt want to be holding any PVC when it failed wether its hairspray, or compressed air, or what ever.

I dont think you need to complicate a carbide cannon by adding a fan. Even with a fan wouldnt there still only be 20% oxygen? I dont see the need for it, other then maybe clear out the spent gasses. Just opening the end to put more carbide in is enough.

I dont understand the poor mixing to buffer the discharge? can you explan that a little more?

The purpose of the chamber fan is to give you a homogeneous mixture throughout the chamber. This will give you more power. What I think he means by buffering the discharge is, that if you have a rich mixture you will not get a complete burn, giving lower chamber pressure. Read safer.

[BowerR64]

If the carbide cannon has a chamber fan, the burn rate is fast enough that a burst disk is not needed. A burst disk is of benifit on slower burning fuels. If you search the vortex cannon video online you can see the burn rate is fast enough to not need a disk.

I would not want to be holding a carbide cannon when it failed. I have not seen any info online of PVC carbide cannons failing because they are relatively rare. There are some videos online of ABS cannons taking some punishment and surviviing. Most carbide cannons have the advantage of poor mixing to buffer the discharge. A chamber fan and a proper mix could easly make a PVC cannon very dangerous.

I wouldnt want to be holding any PVC when it failed wether its hairspray, or compressed air, or what ever.

I dont think you need to complicate a carbide cannon by adding a fan. Even with a fan wouldnt there still only be 20% oxygen? I dont see the need for it, other then maybe clear out the spent gasses. Just opening the end to put more carbide in is enough.

I dont understand the poor mixing to buffer the discharge? can you explan that a little more?

The purpose of the chamber fan is to give you a homogeneous mixture throughout the chamber. This will give you more power. What I think he means by buffering the discharge is, that if you have a rich mixture you will not get a complete burn, giving lower chamber pressure. Read safer.

Well im happy with the carbide, its very reliable for me i never have any issues with a failure to ignite like the hairspray. I see why so many have issues with it and always complain about ignition problems its so finiky.

So far using the spray with the rockets ive yet to get 2 shots the same. The carbide i consistantly get the same shots over and over. Even with the little guns, the 3/4" chamber those are even consistant.

[Boomer58cal]

That's exactly why I have metered propane on my combustion cannon. It works every time

[BowerR64]

That's exactly why I have metered propane on my combustion cannon. It works every time

i dono i still kinda like how simple the carbide setup is. Maybe if i was more into shooting projectiles i might get into it.