Using an electromagnet to disengade a permanant magnet?

[doginabag]

First post here, I am hoping some kind soul will be able to help me with solving a problem that I have.

I am a structural engineer specialising in structural glass. I am setting out to test some glass samples for impacts and for this I am required to drop a steel ball of approx 1kg from a height of 4m.

I am proposing to use an electromegnet for the release mechanism, but there are some obvious dangers that I need to take precaution against.

What I am considering, is to use a permanent magnet to support the steel ball, and than have an electromegnet to disrupt the magnetic field, causing the ball to drop. This ensures that if there is a power failure, the ball will remain safe.

Seems like a nice idea, but I am not knowledgable enough to know for sure that it is possible. Any help would be greatly appreciated.

I have attached a sketch to show the arrangement I am proposing, and links to what I believe will be suitable parts.


Ring magnets.

http://e-magnetsuk.com/magnet_products/neodymium_magnets/ring_magnets.aspx

Electromagnet.

http://www.ebay.com/itm/12V-DC-3W-E...H_DefaultDomain_0&hash=item2c5fda859e&afsrc=1

 

[MJR2]

What you have sketched will not work. There used to be a product called FailSafe that did what you want. They don't seem to list it on their website any more. A PM product called Safehold can be motorized to drop the object. Alternatively use a battery backup to power your electromagnet.

Mike

 

[IRstuff]

One possibility is to have an interposer between the magnet and the ball, such that a sheet of mumetal can be inserted between the two. Mumetal can easily reduce the new field by an order of magnitude.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[EdStainless]

A simple block magnet, with poles oriented horizontal.
Steel pole pieces that run down each side of the magnet and are about 2/3 of the ball diameter apart.
You don't want a real strong magnet, just to hold the ball firm.
A ferrite magnet should be fine.
Coils wrapped around the two pole pieces and wired so that the field that they produce opposes the PM.
A simple pulse should cause release.

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