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Coilgun Projectile Stabilization

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Coilgun Projectile Stabilization

Unread postAuthor: strangers » Wed Aug 19, 2009 1:40 pm

I'm building a multi-stage coilgun for a science fair project, and am about to add a third stage to it and was wondering if spin could be applied to the projectile without rifleing or modifying the projectile, thats when I came up with this:
http://i790.photobucket.com/albums/yy186/grunt009/Picture001.jpg
But I dont know if the discharge time would be long enough for the rotation to effect the projectile, or if rotating the coil could even make the projectile rotate. I'm also having trouble finding information rotating magnetic fields. If it does work however, I may need to slot the projectile as rotation in the magnetic field could generate eddy currents and slow or reverse the projectile. Any thoughts, suggestions, or random ramblings? Once again, any help is appreciated.

I can explain the picture if neccesary.
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Unread postAuthor: jackssmirkingrevenge » Wed Aug 19, 2009 1:45 pm

I think you'd be better off with a hollow tailed projectile.
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Unread postAuthor: strangers » Wed Aug 19, 2009 2:01 pm

I don't have the tools to make a hollow tailed projectile sadly, or really anything. I have a dremel and a drill to make things with, plus being convoluded is fun. But if I could make them I would.
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Unread postAuthor: jagerbond » Wed Aug 19, 2009 2:14 pm

What size projectile are you proposing?
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Unread postAuthor: strangers » Wed Aug 19, 2009 2:27 pm

24mm long sections of steel nails, almost the exact same diameter as 6mm airsoft bb's, but I can't be exact as I don't have anything to measure them with.
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Unread postAuthor: geardog32 » Wed Aug 19, 2009 2:49 pm

just an idea i cant say it will work but, if when you load the projectile and took care to make sure to load it exactly the same way every time, you could place small permanent magnets on the projectile then place permanent magnets at different places on the barrel and lined them up so that like charges repel in the direction you want it to spin.

here is a very poorly drawn picture
Image[/img]
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Unread postAuthor: tomthebomb137 » Wed Aug 19, 2009 2:52 pm

I cant be sure, as i am not positive about my magnetic knowledge, but im not sure it would add spin as the nail is not North/South discriminant. By this, i mean it is not magnetized, but it is still magnetic (it will stick to a magnet) In order for your idea to work, i believe you would need a nail that was North on one side and south on the other, and have your rotating coil also be North/South.

Again, i cannot be held responsible for the information contained in my post :D
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Unread postAuthor: tomthebomb137 » Wed Aug 19, 2009 2:53 pm

yup geardog, thats exactly what i mean
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Unread postAuthor: Ragnarok » Wed Aug 19, 2009 2:59 pm

Ugh...
I know how to do this. However, it's also something I really want/need to keep under wraps, so I'm afraid I can't tell you any details.

I can however tell you that your idea for spinning the coil won't work, (Nor will your idea geardog - the magnets will just destroy one another)
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: strangers » Wed Aug 19, 2009 3:35 pm

Good thing I didnt build it then, mr. sneaky :p. Can't wait to see what you do though.

Maybe something to do with this?

@ Geardog- I thonk the nail would snap in place with the poles lined up and just come to a complete stop.
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Unread postAuthor: tomthebomb137 » Wed Aug 19, 2009 3:48 pm

im somewhat scared of whatever ragnarok is making now. :D

but yes, thats a good point. perhaps if the coil was spinning fast enough and the projectile was already traveling very fast?
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Unread postAuthor: geardog32 » Wed Aug 19, 2009 3:53 pm

rag, are you saying that the permanent magnets on the projectile will interfere with the accelerator coils? if not why would it not cause it to spin as it is moving forward? the acceleration coils should be exerting a much larger force than the magnets to produce spin.
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Unread postAuthor: Ragnarok » Wed Aug 19, 2009 4:03 pm

strangers wrote:Maybe something to do with this?

Not exactly.

It bears similarity in that it uses electromagnetics for the spin, but that's probably obvious and about as far as the resemblance goes.

EDIT:
geardog32 wrote:rag, are you saying that the permanent magnets on the projectile will interfere with the accelerator coils?

No. Imagine you're making a magnet with another one - you pass it over whatever you're trying to magnetise repeatedly...

What do you think will happen when you fire numerous magnetised projectiles past the barrel magnets? They'll get remagnetised to uselessness.
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Unread postAuthor: strangers » Wed Aug 19, 2009 4:16 pm

But would you say it would work? Because I know that you dont have to have a working idea to get a patent. Do you think a low powered electromagnet would work with an unmagnetized projectile?
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Unread postAuthor: Hotwired » Wed Aug 19, 2009 4:25 pm

*sends out a trawler to sift through the silt of memory*

Causing a conductive object to spin using magnetism eh.

A second thought I'm not sure of but the following is common electrical knowledge.

Grab yourself an AC motor, yoink out the rotor, drop a steel ball bearing in and switch the motor back on.

The ball bearing will start spinning round the inside of the motor. The coils in the motor are turning on and off in sequence, creating a rotating magnetic field. In normal use the squirrel cage rotor inside the AC motor has torque put on it by the rotating magnetic field causing it to spin.

You'd have to (a) have a very specially made projectile (b) use alternating current and (c) probably lose sight of the barrel under all the coils.
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Last edited by Hotwired on Wed Aug 19, 2009 4:52 pm, edited 1 time in total.
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