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World record air cannon upgraded to a piston valve

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: Secret Squirrel » Thu Aug 18, 2011 2:53 am

jackssmirkingrevenge wrote:
Secret Squirrel wrote:It explains why burst disks aren't used, they're against the rules.


I couldn't find any reference to burst disks, care to elaborate?


1. All pumpkins fired must remain intact until they impact the ground to obtain an official measurement.
2. No part of the machine shall cross the firing line.
3. No Wadding (including bean chaff, straw, foam, metal, or any other object.)
4. No explosives are allowed.
...

The burst disc is part of the machine, and it would cross the firing line.
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Unread postAuthor: MrCrowley » Thu Aug 18, 2011 2:54 am

Image

:wink:
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Unread postAuthor: Secret Squirrel » Thu Aug 18, 2011 2:57 am

Well maybe you could get away with it then. I guess I'm only familiar with the fragmenting-flying-out-the-barrel sort of burst disk.

I suppose a pre-scored disk would be allowable.
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Unread postAuthor: jackssmirkingrevenge » Thu Aug 18, 2011 3:03 am

Ah, I thought it was specifically banned.

Using a scored aluminium disk like D_Hall has done in the past would definitely solve the problem:

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Unread postAuthor: jor2daje » Thu Aug 18, 2011 4:26 am

I think burst disks are allowed but not used because it seems to me that they want to control the air flow, too much at once and they blow up the pumpkin.
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Unread postAuthor: jackssmirkingrevenge » Thu Aug 18, 2011 5:17 am

jor2daje wrote:I think burst disks are allowed but not used because it seems to me that they want to control the air flow, too much at once and they blow up the pumpkin.


Fair point but having a fast and efficient valve allows you to achieve the same performance with lower pressure.

Any word on the legality of this ;)
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Unread postAuthor: Secret Squirrel » Thu Aug 18, 2011 3:47 pm

The captive piston may be considered wadding, but I don't see anything specifically banning them.

A while ago I had an idea to win at least the trebuchet class. As far as I know trebuchet simply means its energy is stored in the form of gravitational potential energy. Dropping the counterweight into a tube full of air would compress the air, which would then fire the pumpkin out the barrel. So it would be an air cannon that was technically a trebuchet.
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