T-Pain Is On A Boat: Re: [Electric Boats] Etek Motor

Monday, June 22, 2009

Re: [Electric Boats] Etek Motor

Could you describe the conditions which caused your magnet bonding failure? Storage location corrosion, over temp during operation, water intrusion...just curious. Rare earth magnets are extremely susceptible to water, and literally foam with oxidation if (when) the plating develops pinholes. Poor plating protocol by itself will fail the magnet. Bonding magnets results in the plating being well fastened, but the strength of the bond is then only as strong as the plating-magnet interface. To further complicate matters, the magnet has only half the thermal coefficient of expansion as the steel mounting plate, so every thermal cycle works the magnet-plating interface just a little more. My father and I developed a dovetail magnet retention technique, jointly patented with John Deere, that uses mechanical retention. It too suffers the same failure mode such that when the steel gets hot and expands, the magnets become loose in their slots. Now I use screws.
You can re-bond the magnets if they are not trashed by abuse when loosened. (Physical abuse will rapidly deplete the magnetic field in neodymium magnets). I have used Loctite EP-20HP (High Peel) with success. The epoxy has some give, so the shear plane across the bond can yield a little.

Arby

________________________________
From: Monte Gisborne <emotive@xplornet.com>
To: electricboats@yahoogroups.com
Sent: Monday, June 22, 2009 8:46:45 PM
Subject: [Electric Boats] Etek Motor

Does anyone in electric boat land have an Etek motor (the original brushed
type as sold by Briggs and Stratton) available for sale? The permanent
magnets became unbonded from the disc which holds them on the one I have, if
anyone had this part for sale, that would be even better than buying an
entire motor.

Monte Gisborne

(705) 484-1559

(416) 432-7067 (cell phone)

monte@buffalosolarb oats.com

Where Water and Electricity Mix!

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