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Chris Murphy
Posted on Monday, June 7, 2004 - 6:05 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

I'm having quite a bit of trouble with the 10-minute railgun project. To overview what I'm doing:
I have a large plastic board as a base. On it are two strips, not of alumninum foil, but of the fire-retardant duct tape, the shiny metal stuff with a backing you have to peel off. Eliminates the need for messy glue, and I checked with a multimeter (ammeter/voltmeter) and it does conduct fine.
The strips of tape are about 2 inches wide and 21 inches long, including the less-than-an-inch flap off the end. There's about 1/4 inch between the strips of tape, making the whole thing about 4 1/4 inches wide.
The armature is made of about 3 inches of coathanger (which conducts, checked), and two disc magnets. The disc magnets aren't from SciToys, they were found inside some old broken headphones. I'm not sure whether they're neodymium or not, but they're strong enough that it's very difficult to separate them, and they do conduct (also tested). The magnets are roughly 1/2 inch in diameter, and 1/16 inch thick.

Now that I've got it all outlined, and hopefully that's all the information needed and more, the problem: it doesn't work. I hook it up with small alligator clips to a 9V battery, drop the armature on it, and it doesn't move. I flip one magnet around, it still doesn't do anything. I hook up the multimeter to the circuit, and it reads a current...sometimes. I check the pieces individually again - both magnets: work fine, rod: works fine, tape: works fine. And yet, the armature doesn't move.

I don't see what's wrong - is the rod too long, the tape too close together, does it acctually need to be aluminum foil, are the magnets too big or not strong enough...it's quite confusing and frustrating. If anyone has any ideas as to why its not working, it would be much appreciated.

~ Chris Murphy
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Simon Quellen Field (Sfield)
Posted on Monday, June 7, 2004 - 8:08 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Do the magnets have any kind of conductive coating on them?
Neodymium-iron-boron magnets are not all that conductive unless
plated with matal. The most common plating is nickel, which is
not all that conductive, but would probably work. Ours are gold plated,
and conduct quite well.

If the magnets are not NdFeB (neodymium-iron-boron), then they will probably
not be strong enough. Ours are 48 MegaGaussOersteds, the strongest available.

The current required is substantial, and your tape may have too high a
resistance. Mine showers sparks when it starts up, because of the high
current and low resistance.

Start with the project as I described it, and only start changing things
after you get it working. Then change one thing at a time, until you are
happy with your modifications.
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aditya chowdhury (Aditya)
New member
Username: Aditya

Post Number: 1
Registered: 4-2007
Posted on Saturday, April 14, 2007 - 2:08 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

hello.
The magnets in ur catalog cost too much.i cant afford those.is there any other way i can get a magnet for this project.please help me.

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