electro magnet

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frhrwa
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electro magnet

Post by frhrwa »

what would be an easy build for an electro magnet about 4' long that I could hang on my tractor, power with the 12vdc battery, to drive along with it hanging an inch above the ground to suck up screws, nails, etc.. ? coil wrapped 2X4 or something?
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Robert Reed
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Re: electro magnet

Post by Robert Reed »

Yikes! I hope those tractor tires don't suck them up first :smile:
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jwax
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Re: electro magnet

Post by jwax »

Doubt if you have enough 12 volt power to energize a sizable enough electromagnet.
Why not permanent magnets? Dangling some of those Neodymium doughnuts right in the grass/dirt may be easiest.
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haklesup
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Re: electro magnet

Post by haklesup »

Construction is one thing, you also need to worry about power requirements and cost.

First off, a long coil on a wooden rod isn't going to direct or concentrate the magnetic field the way you want. Most of the magnitism will pour out the ends and not very efficiently with a wooden rod. All you will make is a heater that way. You need to make something more Rake shaped with a coil at each tine. In fact lashing together a few rakes side by side might just work but not great because all the tines are magnetically coupled at one end. Maybe that 2x4 with nails sticking out along its length with a coil on each one. you would need to wrap each coil so the wires don't get cut or shorted as you drag it on the ground. Perhaps an epoxy dip or heat shrink tubing.

While the 2x4 based rake might be an acceptable electromagnet, powering it at 12V could take over 100A maybe a lot more depending on the number of coils. You might need to upgrade the alternator on the tractor and add another battery. Add to that the cost of a whole bunch of copper magnet wire and the cost could be significant.

Personally I would just buy a few (or bunch depending on size) powerful permanent magnets and manually clean them off when done. (an electromagnet would be easier to clean bu just turning it off). It would be very durable, more compact and require no electricity.
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frhrwa
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Re: electro magnet

Post by frhrwa »

true, forgot you coil on metal to get the magnetism.. also was going to hang it on the front loader so not to run over the nails first.. thanks for the info.. the permanent magnets will probably do the job, they have some really STRONG ones now.. wayne
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MicroRem
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Re: electro magnet

Post by MicroRem »

Wayne,

save yourself some trouble cleaning the magnets and put a plastic "tear away" sheet over the magnet befor you use it, then you can just peel away the plastic and keep your magnets from getting fouled with iron filings and such. Little bits of metal are almost impossible to remove once they get stuck to a powerful magnet. Just my .02

Tom
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CeaSaR
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Re: electro magnet

Post by CeaSaR »

My yard magnet is a LARGE magnet assembly from an old 15" woofer - somewhere in the 120 OZ range.
I used the rear mounting screws to secure a rope to it and manually swing it over the yard. This picks up
a lot of the ferrous bits and pieces from the lawn. If I see a piece that it didn't pick up on a "swing by",
I usually set it down on top and it picks the piece up. Obviously, this is a relatively slow process.

Since you want to do this with/on your tractor, you would need a much more powerful magnet. An iron core
of sufficient size along with a goodly amount of wire to create a powerful magnetic field, in addition to a rather
healthy DC power supply (enough V and A to create the field needed). This actually sounds rather ambitious.
Perhaps a search for info on commercial electromagnets used in scrapyards could guide you along.

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Externet
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Re: electro magnet

Post by Externet »

Nice task...
Besides already suggested, I would make the coil over a 3/4" ID PVC pipe, about a couple of feet long, or use one canibalized from a discarded microwave oven transformer, its primary seems is a good candidate after removing the core. Ignore its secondary connections. No need to unwind anything.

Then insert a 1/2" reinforcing iron bar rebar ~14 feet long centered into it. That leaves ~6 feet bare iron ends at each side.

Bend the bar 1 feet down at each arm and then in such way that will form two parallel 4 feet long bars spaced about 1/2" inch hanging below to drag across on top of the soil to pick up metal.

--------------------------coil---------------------- 4 feet

======================== 4 feet x 2

In the figure above, the left end of the upper coiled bar bends down ~1' to become one of the lower bars. Something alike to a huge paper clip :smile:
The right end of the bar bends down also ~1' to become the other lower bar. The magnetic field gap is between the lower bars.

I would say 10 Amperes at 12V will do it. The number of turns and wire gauge will have to come to about that figure.
Turning it off on command will drop the picked metal at the desired 'collecting' spot.
Miguel
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jwax
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Re: electro magnet

Post by jwax »

And, if you don't mind dragging along a 120 VAC extension cord, with this electromagnet you'll pick up brass and aluminum!
http://www.rexresearch.com/mrmagnet/mrm ... #schemabcd
:grin:
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Re: electro magnet

Post by Dean Huster »

Your local farm supply store, tool store, hardware store or lumber yard should have strong magnets designed for picking up nails and screws on shop floors. They're in various shapes and ones that look like push brooms are available. Buy two or three of these and put them in line on a bracket.

I've found that the best thing for finding such stuff in the field is to simply drive around and pick them up in your tires. Works every time.

I had knocked out the plaster walls in the bathroom of a customer's old 1930's house, full of nails and screws from all the lathe. I put the rubble into garbage cans, took it to the house dumped into the driveway in neat plies and ran a 4-inch screw pick-up magnet thoroughly through each pile. Picked up a few pounds of nails and never got one in a tire. Stupid but confident? I'd do it again! Stupid AND confident!
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.
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