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Fully Automatic potato cannon project.

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: Conrad2468 » Mon Aug 23, 2010 11:08 pm

Okie dokey, im back lol. were using a venturi effect nipple to siphon air into the system AKA a ton of holes. Ive got pictures of the (now outdated) gas injection/ignition system. Heres how it goes from RIGHT to LEFT.

<a href="http://www.flickr.com/photos/45850538@N08/4921949383/" title="0821180605 by Conrad2468, on Flickr"><img src="http://farm5.static.flickr.com/4143/4921949383_da59c59f9b.jpg" width="500" height="375" alt="0821180605"></a>


Propane tank> Vinyl hose (rated for 3X less pressure than it is under)>two solenoids (for backup/redundancy)> Several reducers to get from 1/2 to 1/4" (hardware store was out of direct stuff if they make it)> propane regulator>reducer>Special nipple*> screw cap/ignition system**

*We took a brass plug (the tip of the torch) and drilled a larger hole through it. We later surrounded it in JB weld and stuck it in the 1/4" nipple (http://en.wikipedia.org/wiki/Injector we have method to our madness) After that we drilled a hole through the nipple and angled it so we could get a more direct flow (this was just straight intuition). I can get a pretty large flame 1-3' fireball and its sucking in air because the flame is right at the end of the nipple.

**Not pictured but upgraded tonight with an ignition coil (thanks dad!) and a spark plug. Not yet tested.
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Unread postAuthor: ramses » Tue Aug 24, 2010 9:20 am

Nice!

I have those same shoes I think. :D

It is worth noting that venturies generally don't perform well with much back pressure. Someone on here filled a homemade stirrup pump from a venturi and used it for hybrid metering. If I remember right, it worked!
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Unread postAuthor: Technician1002 » Tue Aug 24, 2010 12:01 pm

Slightly off topic. 2 minute edit with a free photo editor fixes the toes quickly.

If you can't afford Photoshop, The Gimp is free.
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Unread postAuthor: Conrad2468 » Tue Aug 24, 2010 6:34 pm

The "toes" were sort of a size estimation. And I figured out about the backpressure thing when we had the second solenoid hooked up to the end of the chamber (right next to our venturi nozzle) thats why i moved it back.
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