DC motors

[Dziadek Jacek]

What kind of glue is being used to attache magnets to steel cylinder case? My DC bilge pump motor failed in dire need, because magnets got loos and jamed the rotor. I fixed it with epoxy glue but knowing that epoxy is getting soft when being heated want to know what glue is heat resistant say up to 200 F?

[Alan Wheeler]

Epoxy once fully cured hard will not go soft again.
200F?? I hope your pump doesn't get that hot. If it does, you have other problems to worry about than the epoxy.

[cal40john]

You made me do a little research, since I had heard that it helps to heat epoxy to remove it.

Epoxy as you stated is thermosetting, but if heated too much can be damaged.

West gives some numbers for their epoxy.
Click on Product Information and Typical physical properties.
WEST SYSTEM Epoxy

Here is shown what a heat deflection test means.

Heat Deflection Temperature Testing of Plastics

And here is another forum discussing the Tg number.

Epoxy Strength [Archive] - The WoodenBoat Forum

So at 200 deg F, if it is an epoxy like West System, it looks like it would definitely fail. Whether the motor should ever get that hot is another question.

There are two part high temp RTVs that I guess would work.

GE - RTV 60 Silicone, High Temp Red, Two-Part, Pourable Paste, SS4004 Primer Required (RTV60-1P)

John

[Dziadek Jacek]

Originally Posted by Alan Wheeler

Epoxy once fully cured hard will not go soft again.
200F?? I hope your pump doesn't get that hot. If it does, you have other problems to worry about than the epoxy.

Thanks for prompt answer, maybe it never gets so hot, but 200F is close to boiling ,the upper temp. of a diesel engine where the bilge pump is mounted - I'll try to move it farther away . To my experience epoxy does get soft when heated... from what temp. I do not know. I often reuse norseman terminals sealed with epoxy heating them a little.

[delmarrey]

Try these guys.....................
http://www.masterbond.com/produse/produse_ht.html

[Alan Wheeler]

It depends greatly on the type of epoxy as to what it's upper limit temp is. Some epoxies have very low upper temp points and others are very high. Some epoxies can handle low exhaust temp for Muffler repair etc. Most fully cured epoxies don't melt, they char. Epoxies are thermosetting as John pointed out. In the very intitial stages of cure, the epoxy may be hard to our touch, but there is enough epoxy that has not cross linked and that when heated, it will soften and allow those chains to continue to form, with the end result of a much harder epoxy. That's why they go soft at first, but will get harder and much harder than a standard room temperature Cure. But fully cured epoxy mostly chars rather than melt.
However, if the motor is getting hot enough to melt or burn epoxy, then your windings are in great danger of failing and any plastic on the pump would have melted. So all in all, Epoxy should withstand more heat than any plastic. The maximum temperature of a motor should be still cool enough to allow your hand to touch it. any hotter and you will melt the winding insulation. There are special insulations used in special high temp motors, but I doubt a bilge pump will be considered that special.

[Dziadek Jacek]

Thanks to all for very satisfying answers on ds motors magnets glue Dziadek Jacek