Scrap Electromagnet

[Herding Cats]

Anyone have any experience with them? Those 5 on ebay are less than an hour from me and I can call the business directly.

I'm have a fairly good idea on how to test them. A 32" should be around 5.5 ohms for the coil, larger magnets will be less. Should have nothing to the case, I also have a megger I can check from the coil to the case.

As far as a power supply, I'll need at least 50 amps at 230 volt DC which I have plently of components like 150+ amp IGBTs, large diodes, a large varistor and so on. I haven't decided if I am going to run an AC generator and rectify the power or use a DC spindle motor as a DC generator and maybe drive it hydraulically.

Anyway, I'm asking more as a reality check if there is something obvious I'm overlooking?

 

[Mud]

Demolition guy I know rigged a DC generator to the engine of an excavator, just stuck it outside the hood and ran it with a V belt. He had to rev the engine to a minimum RPM to get the magnet to work, that might be awkward on a mobile crane, the AC and rectifier I guess would avoid that?

 

[Herding Cats]

Demolition guy I know rigged a DC generator to the engine of an excavator, just stuck it outside the hood and ran it with a V belt. He had to rev the engine to a minimum RPM to get the magnet to work, that might be awkward on a mobile crane, the AC and rectifier I guess would avoid that?

If I ran a gas powered AC generator that would be avoided. The DC motor could also be spun with a gas engine to achieve similar results. Hydraulically driven would be less dependant on RPM than belt driven but engine driven is sounding like a better choice as it can quickly be removed from the machine.

 

[Doug]

I read that on your other thread (about the crane) and thought the 42" one you mentioned was too big & heavy for the crane.

 

[Herding Cats]

I read that on your other thread (about the crane) and thought the 42" one you mentioned was too big & heavy for the crane.

Something in the 42" range should be under 3000 lbs, closer to the 2200-2500 pound range which the crane can swing with the boom fully extended and laid flat.

While a magnet that size can pick a slab or bloom in the 20K range it can only pull 300-400 lbs of turnings which is mostly what I want it for.

There is a good chance I'll get something in the 30" range but if they don't test well and something larger does, the math seems to compute as far as being able to use it to load chips into a roll off dumpster.

Maybe I'm crazy

 

[Doug]

Something in the 42" range should be under 3000 lbs, closer to the 2200-2500 pound range which the crane can swing with the boom fully extended and laid flat.

While a magnet that size can pick a slab or bloom in the 20K range it can only pull 300-400 lbs of turnings which is mostly what I want it for.

There is a good chance I'll get something in the 30" range but if they don't test well and something larger does, the math seems to compute as far as being able to use it to load chips into a roll off dumpster.

Maybe I'm crazy

Oh....My friend ran an overhead crane with a magnet about that size, and when he would set it down on the ground next to me, the thud
sound made me think it was at least 5 tons empty.

 

[Herding Cats]

Oh....My friend ran an overhead crane with a magnet about that size, and when he would set it down on the ground next to me, the thud
sound made me think it was at least 5 tons empty.

I wouldn't doubt if magnets are like machine tools where similar size machines can have huge weight differences.

From what I've read "mill duty" magnets are the heavy duty deals

 

[Doug]

I wouldn't doubt if magnets are like machine tools where similar size machines can have huge weight differences.

From what I've read "mill duty" magnets are the heavy duty deals

I'll bet it was a Mill Duty, as it was on an outside, travelling crane maybe 60'-70' wide, and 1000' of runway, IIRC 20-30 tons.