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Coiled Barrel

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Coiled Barrel

Unread postAuthor: goose_man » Mon Oct 01, 2007 5:05 pm

I came up with an idea for a barrel used to shoot spherical projectiles (not sure how it would work with others) and I'm not sure if it's any good, so I'd like some input before I build.

This idea is based off the premise that the longer the barrel is, the faster the projectile will go (up to a certain length of course). So, why waste space having a barrel that is completely straight? This new barrel would be like a rigid coil going around and around (maybe around the chamber) and then be straight for maybe two feet or so. It would have to have the straigt part at the end to ensure the ammo takes a straight path.

The theory is that the projectile will reach about the same speed as if the barrel was straigtened out, because the acceleration is independant of the barrel's straigtness (assuming it's a tight-fitting projectile). Also, since the straight part at the end is there, the projectile will go just as straight as if the coil wasn't there.

Opinions are very much appreciated!

-goose_man
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Unread postAuthor: babyJ » Mon Oct 01, 2007 5:44 pm

I wouldn't think that the velocity would be the same. It would be less because of it constantly changing directions the projectile would waste alot of energy. not for sure . if u do it i would like to know the answer!
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Unread postAuthor: jackssmirkingrevenge » Mon Oct 01, 2007 5:46 pm

Also, since the straight part at the end is there, the projectile will go just as straight as if the coil wasn't there.


That's certainly true.

The theory is that the projectile will reach about the same speed as if the barrel was straigtened out, because the acceleration is independant of the barrel's straigtness (assuming it's a tight-fitting projectile)


In a straight barrel, accelearation is in one direction. In a coiled barrel, the projectile is constantly changing direction, surely there must be some frictional losses.
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Unread postAuthor: Pilgrimman » Mon Oct 01, 2007 6:07 pm

It's intriguing, but I doubt it would work. First of all, keeping a consistent barrel diameter would be nigh impossible, which is critical for projectiles with a good fit, and second, the barrel would absorb much of the force behind the projectile, as the projectile is under centripetal (I think) acceleration. I hope you keep ideas coming, though! That was original and interesting! :D
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Unread postAuthor: jackssmirkingrevenge » Mon Oct 01, 2007 6:08 pm

First of all, keeping a consistent barrel diameter would be nigh impossible, which is critical for projectiles with a good fit


I buy my 0.177 (and I mean true 0.177) copper barrel as a 10 metre long coiled pipe that's less than 2 feet in diameter, job done :D
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Unread postAuthor: Marco321 » Mon Oct 01, 2007 6:11 pm

Its a good idea, but yeah, the bends will alter the shape of the pipe, unless you can find a way bend the pipe and still keep a consistent ID with a circular shape.
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Unread postAuthor: MrCrowley » Mon Oct 01, 2007 6:13 pm

@JSR

And how do you go about straightening that?
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Unread postAuthor: jackssmirkingrevenge » Mon Oct 01, 2007 6:20 pm

And how do you go about straightening that?


with difficulty :roll:

Seriously though, it's not that hard - I do it manaually and though the result is not 100% straight, it works well enough - certainly better than my other option of 5mm I/D pipe, have a look here.

here's an example on my ball-valve strafer:

Image
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Unread postAuthor: tyguy2000 » Mon Oct 01, 2007 6:24 pm

I think that in a perfect, frictionless system this theory would work out great. But because there is friction it will be many times greater in your coiled system where the projectile will experience a huge force with one side of the pipe (the force that gives it the centripetal motion). So unless you are able to eliminate most of the friction by lubing it with something I doubt it would work.
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Unread postAuthor: Hotwired » Mon Oct 01, 2007 6:27 pm

I have doubts on a coiled barrel.

You'll have a great deal of energy loss from the projectile constantly changing direction and being pushed against the side thus getting a large minus against the rather lower friction and single directional force of a straight tube.

Incidentally bending tube causes the passage to become oval - promoting gaps for gas to escape at best and jamming the projectile at worst.
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Unread postAuthor: MrCrowley » Mon Oct 01, 2007 6:32 pm

@JSR

Lookin' good :D

What do you do? Cut a section off, roll it around on the floor or chuck it in a vice or something?
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Unread postAuthor: Blackett » Mon Oct 01, 2007 6:41 pm

This is like one of those words that you spell and then ask yourself several times if you spelled it correctly, but no matter what you do you can't get it to look right.

this is how I am looking at this. I suppose it would work if you could eliminate the friction factor through some stroke of genius.

In general the coil seems less aerodynamic, which would be bad enough without the constant alteration of velocity. (remember velocity is also direction) ex. going 15mph east and swerving around a bend to go north will result in a greater energy loss than going north in the first place.


but i would love for you to prove me wrong and show me some mad scientist type stuff.
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Unread postAuthor: jackssmirkingrevenge » Mon Oct 01, 2007 6:49 pm

MrCrowley wrote:What do you do? Cut a section off, roll it around on the floor


That's pretty much it, longest I've done so far is around 40 inches.
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Unread postAuthor: ammosmoke » Mon Oct 01, 2007 6:52 pm

This would definitely not get the result you are looking for. The longer barrel might give you more velocity than one of comparable length if you didn't stretch out the coils, but the changes in direction amount to massive energy loss. The bb scrapes against the side, the air goes around it because the pipe becomes deformed, the air must change direction, etc. But, hey, if you can prove me wrong, it won't hurt me any lol.
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<img>http://www.speedtest.net/result/309559995.png</img>
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Unread postAuthor: jackssmirkingrevenge » Mon Oct 01, 2007 6:56 pm

This one's cortesy of the Beeman Collection, proof that it's how the projectile leaves the muzzle that affects accuracy:

Image

After one of the big SHOT trade shows, the owners of the Westinger & Altenburger Co. (Feinwerkbau) of Germany presented us with this amazing feat of airgunsmithing - a Beeman/Feinwerkbau Model 2 CO2 pistol with the barrel making a complete twist around the gas cylinder! The gun actually shoots quite well! Note that the all-important final inch(25 mm) or so is straight - that and the crown are the only really important parts of the barrel as far as accuracy is concerned. When some shooter would say " I think I see some little defect in the rifling way down inside my barrel, or the middle is a little off, or the barrel is not quite straight, and that is why I am not shooting well" , the airgunsmiths loved to bring out this gun and ask if his gun was more off line than this one! Beeman collection.
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