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Sitting on a load of cash.......now what should I build?

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: limbeh » Sat Aug 04, 2012 8:22 am

Anyway, after 3 weeks of rushing deadlines......1 more week till finals are over.

I discussed with the 2 MIT professors about what plans they had for spudding, they said they'll probably start experimenting with making rifled barrels.

Therefore, I think I'll probably propose this plan to them.

- Make a small tee barrel seal PVC gun with a 13mm bore or something. Mainly intended for indoor demonstration and teaching purposes.

- Make a steel tee & chamber barrel seal gun with detachable barrels. This allows for testing of rifled barrels.

Now, anyone have any advice on what sort of twists you guys use for rifling? I dug through a couple of old threads on rifling and so far this link http://kwk.us/twist.html seems to be the simplest. Just wanted to find out what the bullet SG value would be for potato.
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Welcome to Singapore.

The laws are stricter concerning spudguns than anywhere in the West.

Even the Aussies for all they complain have it good compared to us.
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Unread postAuthor: Zeus » Sat Aug 04, 2012 8:47 am

I'll be edgy and controversial, and say that rifling will do somewhere between jack sh!t and sweet FA for a potato. It's inconsistant, too soft to engage the rifling without leading(potatoing?) the rifling, and it's close to a square cylinder, which isn't that easily stabilised.

Now, if you use some more suitable projectile, then rifling might help, IMO, there's too many variables in organic products to compensate for. And you'd need some damn high lands to stop the projectile shearing off the engaged material. Then you lose power to friction and blowby.
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/sarcasm, /hyperbole
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Unread postAuthor: limbeh » Sat Aug 04, 2012 9:50 am

Well yeah, the rifling wasn't my idea though, it's theirs. Their purpose for building it as to give freshmen "a taste of the real world" - ie that real world problems aren't as nice and ideal as in say high school physics.

Anyway, you're very right, there's no way that you can make a potato consistent by any means.

Personally I'm not for firing spuds on such a huge scale, methinks it's a huge waste of food and potentially a source of bad press. I'd rather fire darts, even though I'm kinda short of targets to shoot at.
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Welcome to Singapore.

The laws are stricter concerning spudguns than anywhere in the West.

Even the Aussies for all they complain have it good compared to us.
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limbeh
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