Multi-Purpuse Piston Cannon

Build a homemade water gun or water balloon launcher and tell us about it.
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Leprechaun71588
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Multi-Purpuse Piston Cannon

Post by Leprechaun71588 » Wed Mar 29, 2006 2:15 am

This is just a crazy idea I thought up today. It was really brought on by the idea of launching waterballoons/other crap out of dorm room windows.
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It's basically just a giant piston-thing that pumps into a much smaller pipe. If I happen to make it, the pump will be made of 4" PVC and the smaller pipe will probably be 2".

I figure that even if it doesn't quite shoot water balloons as far as I want it to, I can make an attachment with a nozzle on the end and fill it up with water. I imagine that would shoot pretty damn far.

This isn't meant to really be used in a water war, just to have fun shooting crap.
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joannaardway
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Post by joannaardway » Thu Mar 30, 2006 8:59 am

I'm not sure this will work - a pump that big would require massive strength to use practically.

Remember that the force required to pump increases with the area of the pump shaft - so a 4" pump would be unusable.
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"So many people have come and gone, their faces fade as the years go by. Yet I still recall as I wander on, as clear as the sun in the summer sky" - More than a feeling, Boston

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Leprechaun71588
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Post by Leprechaun71588 » Thu Mar 30, 2006 10:24 pm

I had a watergun I built last summer that was a 2" piston. The thing that made it harder the use was when I made the nozzle on the end smaller. This will be going from 4" down to 2", so it will be a whole lot easier than if I were trying to push it all out of a little tiny hole.
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joannaardway
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Post by joannaardway » Fri Mar 31, 2006 4:23 pm

Nonetheless, I think it probably won't work very well.

In truth, the speed of a projectile in the 2" pipe will be 4 times faster than the pump in the 4" pipe (assuming the system is isobaric in use, and equal to barometric pressure), but, to apply a decent pressure, it will be difficult.

Assuming you can bring your arm back at 5 or 6 m/s then the projectile will reach maybe 20 m/s - 44 mph. This is low for a water balloon launcher. Most pneumatic launchers fire at 50 m/s or more (up to the predicted 100 m/s of the Cerberus), but some do get as low as 30 m/s (usually small, or with an inefficent C/B ratio, or low psi)
"Over the hills and far away, she prays he will return one day. As sure as the rivers reach the seas, back in his arms again she'll be." - Over the Hills and far away, Gary Moore

"So many people have come and gone, their faces fade as the years go by. Yet I still recall as I wander on, as clear as the sun in the summer sky" - More than a feeling, Boston

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