Getting Hot

[DadHav]

I'm reading that some of the magnets are good all the way up to 120-135 degrees, before they suffer some sort of damage, or loss. How can this be? Don't these motors run hotter than that? A car in the sun with the windows closed can get to 135 degrees. I wouldnt expect my motor to be ruined if I left the plane in the car. Is this accurate information. Also I heard that magnets loose their strength over time? I wonder what kind of time? If they don't have to much time, I'll make sure I design so they can be replaced easily.
Any Input?

C YA

[Jay C]

I'm reading that some of the magnets are good all the way up to 120-135 degrees, before they suffer some sort of damage, or loss.
Actually is 80 degrees C so 176 degrees F. But this is the point at which the atoms start to lose some magnetic field. It weakens.
How can this be? Don't these motors run hotter than that? A car in the sun with the windows closed can get to 135 degrees. I wouldnt expect my motor to be ruined if I left the plane in the car. Is this accurate information. Also I heard that magnets loose their strength over time?
Eventually ... but you will be long gone before it's even measureable ;)
I wonder what kind of time? If they don't have to much time, I'll make sure I design so they can be replaced easily.
Any Input?

C YA
No worries. Your motor shouldn't be getting that hot. If they are, I would worry more about what ever adhesive you are using to hold the magnets in place 8)

[DadHav]

Thanks for that. I never thought that they were referring to C degrees. I guess My tons of years using inch system is showing. But thats good to hear. I'm gonna heat em up a bit then.

C YA

[ScubaSteve]

Not to mention the fact that if you're motor gets hot enough to ruin your magnets, you're doing something seriously wrong.

Not to mention you'll likely need a putty knife to scrape whatever's left of your ESC off your plane/bench... :roll:

[DadHav]

Thanks Steve, I won't be scraping anything (I Hope). I'm pretty careful about testing before I put a motor in a plane. Lately I've been using a DC Clamp Meter around one of the battery leads. Man, This seams to work real nice. I also keep an infrared temprature meter close, as well as my tachometer and digital fish scale. Some time I'll have to send you a picture of my test device. You'll get a laugh out of it. I also have a high tech fail safe early warning device built in: I use dental floss to tighten the winding leads to the bushing holder. When you start to smell pepermint, it's time to start checking for over current.

C YA

[Jay C]

I also have a high tech fail safe early warning device built in: I use dental floss to tighten the winding leads to the bushing holder. When you start to smell pepermint, it's time to start checking for over current.

C YA
I did that too ... melted the wax all over my nice neat windings :( Now I cover them in conformal coating.

[DadHav]

What's conformal coating. Won't coating the coils increase the heat?

C YA

[paulvi]

What's conformal coating. Won't coating the coils increase the heat?

C YA

It is a thin polymer based paint that will sweat into the cracks and crevis's to create a bond between the windings you see this used in high current motors like automotive starter motors

Just a way to keep things from shifting.

When we used to rewind slot car motors when i was 10 or so we would dip the whole stator in a bath of thined epoxy 30 minute epoxy cut with denatured acahual then we would let it drip dry contact side high (brushed motors) and when it had cured we would scrap the end shaft and sand the whole thing to take the epoxy off the stator ends and then we would balence the whole mess between to strait edge razors

You may also find the coating in a rubberized format same idea

[ScubaSteve]

Check out www.epoxies.com. They will provide free samples (that'll last forever) of a special thermo-conductive epoxy. Haven't used mine yet, but it may prove to be a good way to "secure" windings AND suck the heat away as well.

Also, before you fly, throw your ROTOR (only the rotor) into your freezer for a few hrs. Your magnets are actually stronger at lower temps than at higher temps. Again, haven't had a chance to try, but that suggestion came straight from George @ Engineering Concepts (where GB gets all their magnets). :wink: