Author Topic: JB Weld epoxy is magnetic  (Read 4864 times)

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TDC

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JB Weld epoxy is magnetic
« on: March 01, 2015, 07:48:46 PM »
I was gluing magnets on with JB Weld and it quickly became obvious that it's magnetic.  Due to that and the viscosity, I was having some trouble filling between the magnet and stainless steel band around the outside,  so I switched to Devcon F-2 liquid.  I have a lot of experience with the Devcon and liked that better.   It's best to have a gap of several thousandths of an inch (.2mm) between the parts, so I mixed some sand blast media in the epoxy to maintain a gap between rotor and magnets.  Some center punch marks on the rotor disc also worked.

I have pictures, but can't post due to the size restriction of this forum.  What's the story on the size limit, I've never had re-size pictures for a forum before?

DamonHD

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Re: JB Weld epoxy is magnetic
« Reply #1 on: March 02, 2015, 02:49:18 AM »
I don't have the limits to hand at this moment (I only work round here, it seems!), but remember that many of the users of this forum are in the Styx on dial-up and/or possibly paying by the byte, which is why we have the limits.

Try getting files sizes down to less than 32kBytes and/or pixels on each side no more than 512.  If you are saving JPEGs then try turning the 'quality' setting down to 70% or less.  Those parameters usually make for decent images but not too bandwidth hungry.

Rgds

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electrondady1

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Re: JB Weld epoxy is magnetic
« Reply #2 on: March 02, 2015, 07:31:27 AM »
so there is a layer of sand between your mags. and the steel rotors ?

Flux

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Re: JB Weld epoxy is magnetic
« Reply #3 on: March 02, 2015, 08:04:28 AM »
This is probably a small enough gap not to bother about. Any gap between the magnets and rotor has to be taken off the physical gap between rotor and stator,  in this case about 0.4mm if it is dual rotor. I suppose the sand is similar to the magnetic powder in the JB weld, which is added to give physical strength.

As long as the devcon is strong enough to hold the magnets it should be ok.

Flux

TDC

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Re: JB Weld epoxy is magnetic
« Reply #4 on: March 03, 2015, 07:58:42 PM »
so there is a layer of sand between your mags. and the steel rotors ?
I wouldn't really call it a layer, just a small pinch mixed in with a 20 gram batch of epoxy.  It seems to have produced a .005- .010 gap.  I'm told they use .2mm glass beads in the adhesive for bonding carbon fiber.  I discovered an "email" setting on my camera, here's a pic of the rotor.  http://www.fieldlines.com/index.php/topic,148618.0.html

JW

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Re: JB Weld epoxy is magnetic
« Reply #5 on: March 28, 2015, 04:52:28 PM »
I have increased the attachment size to 512KB and this should not hurt the forum bandwidth or storage.