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I've had the idea for a long long time of making a coin gun. I'd love to shoot some sharpened 5 or 10c peices like frizbies at a few hundred feet per second but just have no idea on what the hell I'm gonna do for a barrel. Does anyone have any idea's?
Apparently not the most efficient ammo in the world, have a look here - though you probably were thinking of launching them sideways...
Last edited by jackssmirkingrevenge on Thu Sep 27, 2007 7:16 am, edited 1 time in total.
Well I was hoping to fire them like disks....but for that, I would need to some how make it spin so it stays level and that will definatly be the hard part. Some sort of rifling that spins it could be an option
If you want them to spin like a frisbee, first you'd need a rectangular barrel of the perfect size. If you could get this, just polish one side of the inside of the barrel for a few inches (a short side), and use some tape to put on the opposing side. If the tape has enough friction the coin will rotate as if rolling on the tape and sliding against the polished side.
All in all, you need a very well machined barrel.
Cheers mate. Thanks alot but all in all.........this idea sounds like more trouble and money then its worth. Would be cool though.
Maybe if you let it roll on the side inside ur barrel, firering the coin vertically aligned and having a frontspin.
BTW your barrel should have a weird shape wouldnt it?
The problem is one of surface area when it comes to firing them on their side. Say a coin is 20mm in diameter and 1.5mm and weighs about 3.5 grams.
A typical steel BB weighs 0.35 grams and has a surface area of 0.159 square cm.
The coin will have almost double the area, but weighs ten times more. This means that velocity will be severely limited, even if using shock pump pressures. Ideally you'd have your air pressure driving a large diameter piston that then pushes the coin out between guide rods (or just make a 1" cannon and load them sideways in a sabot )
Yes, this firing alignment would give you spin, but the coin would exit the barrel in a nose dive, The front spin would make the coin rapidly ark forward, and thus down.
A coin fired on its side with any spin would also ark, but to the side. Assuming a left spin the coin would ark left, a right spin the coin would ark right. It is possible to grind the coin to make a more frisbee or aerodynamic profile for flight which would provide some range, but accuracy would be zilch.
The Navy is said to be messing with disk ammo in its rail guns, but there is actually no contact between the disk and the gun. It is levitating due to magnetism.
I fear we are out of our pocketbook's range on this idea. It would be possible, but not practical, and a waste of good cannon money.
A coin firing gun is probably possible though I think you need to do some "out of the box" thinking to get it to work well.
As others have posted, even if you come up with a way to fabricate a barrel the surface area of the ammo is just too small given it's mass.
So... don't think of the gun like a regular pneumatic (or combustion) where the pressurized gas acts directly on the ammo.
Outside the box... perhaps something like a baseball pitching machine. The ammo is dropped between spinning wheels. Google "Lego CD launcher" for the basic concept specifically designed to launch (with spin) a disk shaped object. Can you use compressed air to spin the launch wheels?
Or come up with a way to use compressed air to swing a launch arm like a skeet throwing machine. This method will also give you spin.
Or, use compressed air to move a large diameter (compared to the coin) piston that pushes a flat blade into the barrel that in turn pushes the coin. Use a hop-up like mechanism to give the coin the spin.
Other possibilites... ?
with a little modification, a cheapo pneumatic nailgun would be more than ideal for this application - and look, you can pick one up dirt cheap!
All you need to do is disable the safety and build a frame to launch the coin from.
Last edited by jackssmirkingrevenge on Thu Sep 27, 2007 10:34 am, edited 1 time in total.
This project would be a good one for that spring air idea that's been in a few threads. Maybe even eliminating the "air" part and have a strong spring strike the coin, like in one of those little disk toys.
Edit: Another thought would be to have a system like a pitching machine. It is essentially a rubber wheel that spins with pretty fast rpm to launch baseballs using friction. This way, you could stack the coins in a tube and have a fully automatic coin gun.
Then make the spinning disk more like a sawblade where coins fit in the gaps.
Coins are feeded from the side and falling in the gaps, take over the disk velocity and sweep out.
williamfeldmann you are wrong about the ammo not touching the gun!!!!
in a railgun there are two metal rails (surprise surprise) and the ammo which must be metal (or at least conductive) touches both of them them a sufficiently high voltage is applied across the rails the current flows through the ammo and the lorenz force propels it down the barrel. unfortunately the high current and small contact area cause a huge amount of heat which then causes the rails to become damaged meaning that the gun can usually only be fired once and then requires servicing!!
He must have meant a Coil gun instead of a railgun
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