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Magnetic repulsive golfball launcher

A place to ask general spud cannon related questions.
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Unread postAuthor: benstern » Sun Mar 02, 2008 11:28 pm

except that neodymium magnets chip and turn to powder easily with moderate force. also you would never get them apart.
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Unread postAuthor: ammosmoke » Wed Mar 05, 2008 1:02 am

GAHH that is why there is the rubber bumper with space in front! I'll draw you an image when I have more rest if you like.
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Unread postAuthor: jimmy101 » Wed Mar 05, 2008 12:56 pm

Benstein:

I think you are under estimating how much Lenz affects are going to bite you in the butt.

I don't think you will be able to get the magnet moving very fast through any type of a metal cylinder (plastic perhaps, but not metal).

Heck, just dropping a rare-earth magnet through a copper tube (slightly larger ID than the OD of the magnet) gives nearly a G of retarding force on the magnet. That's at speeds of less than 1 FPS.

(Dropping powerful magnets through copper pipe is very interesting.)

Edit: because I spell like a second grader.
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Unread postAuthor: Fnord » Wed Mar 05, 2008 1:36 pm

I think you are under estimating how much Lenz affects are going to bite you in the butt.


Holy crap, that's totally right.
I can feel the resistance just by moving a magnet along a strip of copper.

But, couldn't you(in theory) run a wire from the front to the back of the tube to reduce this effect?
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Unread postAuthor: jimmy101 » Wed Mar 05, 2008 4:09 pm

_Fnord wrote:But, couldn't you(in theory) run a wire from the front to the back of the tube to reduce this effect?

What would a wire do? The pipe is already conductive, adding a wire would just make it more so.

The Lenz affect is kind of important, without it electric motors wouldn't work.

Here is a link to a guy studying the dropping of magnets through copper tubes. He was trying to minimize the eddy current that retard the movement of the magnet by slicing and dicing the copper.
http://users.hubwest.com/hubert/mrscience/eddy.html

more interesting links;
http://www.16pi2.com/eddy_currents.htm
http://www.coolmagnetman.com/magpipes.htm

Edit: because my forum code useage is even worse than my spelling.
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