Electromagnet build... fence row nails and wire. rScotty

newbury · Apr 4, 2017

Dadnatron said:
<snip>So, my question is, how would you go about making a relatively inexpensive 84" wide electromagnet strong enough to pull crap off/out of the ground (reasonably) in such a manner? I'm not expecting to rip it from 6" down or anything, but what I'm hoping for is something that can pick up loose wire/nails from the ground or which are partially imbedded in/under some dirt. Would I need (I suspect) several of these along the course?
<snip>

What is relatively inexpensive ?

For dragging for nails around construction of an addition I used ten 112 LB Holding Power Neodymium Cup Magnets w/ Thread Stud MCHN-40MT in a piece of plywood about a 2' long. I drilled holes in the plwood and fastened the magnets with a nut. When I was done they became magnets for my LED, refrigerator, whatever.

They are very strong (usually to get them off the fridge I have to slide them to a corner) and picked up a lot when drug through the dirt.

But that's $35 of magnets for about 2 feet, with repurposing in mind. If I was to do that for a 7 foot span I would need another couple of refrigerators

Dadnatron · Apr 4, 2017

rScotty,

Given a desire to have a field strong enough to pull a piece of barbed wire out of a clump of grass, say, requiring 10lbs of lifting force, with the magnet between 6-8" away, how long of a bar, many windings, and power would you guess would be required to perform this task?

I recognize the direction of the field, pull, and the basics of how this sort of thing works. I'm not asking for calculations, unless that is how you prefer to answer. More of a 'ball park' estimate which might help in my decision to proceed.

And one other question, about transference of the magnetic field to an intermittent piece of metal. ie, picking up paper clips with a magnet. You can pick up one directly, then use that one to pick up another, etc etc.

If I used a microwave core that had been turned into an electromagnet with the strength to pick up 100lbs with 12v, and directly applied it to a soft metal strap, say 1/4x4x48". Would the magnetic field be 'transmitted' through the strap thereby, 'elongating' the area of magnetism of the electromagnet? In a similar fashion to the paperclips? If I place 2, 3, or more on the same metal strap? Or would I likely need to rely on the primary field of each magnet, essentially overlapping each other in order to cover the 48" length?