UKC

Back story is that the girl who shared a field with my mrs for her horses has been evicted by the landlord for causing no end of trouble with the neighbours.
Her parting shot was to throw hundreds of plasterboard screws all over the place which are not only damaging to car tyres when we park outside the stable, but are extremely dangerous to the horses.
We are now tasked with picking up all these screws, but due to their colour it's going to be difficult. The best way i can think of is to make a strong electromagnet, the stronger the better. Is it really as simple as winding copper wire around a metal bar?

In reply to mwr72:

Yes, but it sounds like what you want is one of these: http://www.amazon.co.uk/Silverline-250015-Magnetic-Sweeper-325mm/dp/B002QRY...

In reply to mwr72:

Current. You want a lot of current. The more the better. To get this you need a lot of voltage. The more the better. At some point you start to melt the copper wires, then you switch to copper piping and pump coolant through it. When that melts you switch to cryogenically cooled superconducting tape. You're going to need a beefy power supply. It's not really a very safe of practical thing to be doing in a field to be honest.

I would consider a very strong neodinum permanent magnet. Use this inside a small plastic housing that allows you to scrape the screws off, and prevents them from damaging the magnet when impacting. Put it on the end of a stick, mark out a grid on the field using tape or bailing twine and systematically scan each grid cell.

Modern rare earth permanent magnets are also exceptionally dangerous however.

youtube.com/watch?v=ClkP-QwIOAQ&
youtube.com/watch?v=0t8yDnyOaQ8&

Perhaps a normal magnet would work. Our cat had a little magnet on his collar to open the cat flap, it used to collect little screws and iron filing from flower beds all the time.

In reply to psaunders:

That's cheap enough, thanks.
There are some copper nails laying about though only a few(they used them to felt her stable roof) so it would be better going to the effort of making an electromagnet.(i'll still get the sweeper though, it looks like a great tool.

In reply to mwr72:

I might have the wrong end of the stick here, but you're not thinking an electromagnet will pick up the copper nails are you?

In reply to mwr72:

What about a metal detector?

In reply to mwr72:

neodymium magnets from old hard drive?

In reply to mwr72:

http://www.liveleak.com/view?i=7cf_1375537300

In reply to mwr72:

ht

tp://www.eb ay.co.uk/itm/like/351012679727?clk_rvr_id=668759934715&crlp=1_262531&mt_id=635&sdc_id=1405862469z225514z3e073b0a32090z&mid=424487&fitem=351012679727&linkin_id=8066452&kw=%7Bquery%7D&crdt=0&sortbid=13

You can get them for 30 pounds, a magnet won't pick up copper as far as I know.

In reply to mwr72:


Yes. Making a good one that'd do your nail collecting job is a lot harder. It'd be much cheaper, easier and more effective to use rare earth magnets taped to a few stout pieces of wood you can drag around the paddock. Get long thin magnets, poles each end are likely to be most effective.

If they're in dust/soil rather than grass it might be easier and more effective to sweep/scrape it up and sieve it, that'll get the copper too.

jk