brushed motor max temp

[shaunjohnson]

my new slash needed a power plant.
have a few summit batts that i could use and a XL5 ESC lying about.
went to the LHS and got me a cheap-o venom motor and broke it in properly.
melted the comm on that

so this time i did it better and went for an LRP 17x2 spec 4 motor.

it's a low better power wise and temps SO FAR are cooler.

what would you guys recommend be the max temp for a BRUSHED motor? since BL is usually 170 - <200.
i'm only running a 6 cell nimh pack and it's pretty quick.
the destructions recommend a gear ratio of 8:1 and ive got it at 13:1 (19/90 gearing) according to brianG's calc. will this increase temps?
if i move up to a 21t pinion then it's geared for 40mph (29200 rpm motor) but that's still only 11:1 final reduction.

any thoughts/tips appreciated

[E-Revonut]

I would still be looking for max temps no more than 170-180 the heat kills the magnets and there are still magnets inside a brushed motor. They are just in a different location and are most likely lower quality so idealy temps should be kept cooler. The biggest issue with the stock traxxas brushed motors is the lack of bearings and the brushes aren't replaceable. I just went BL with my E-maxx cause the stock motors wore out in 2 months, the bushings and brushes are both shot, my batteries where only lasting about 5 minutes because of all the added drag.

[shaunjohnson]

heat causes the magnetic fields to align in one direction dosent it?
rendering the motor useless?

yeah these are just iron magnets, nothing like the special neodymium ones we get in the BL motors.

the traxxas titans were alright if treated nicely.
we correctly broke in a titan 12T (the worst motor ever) and ran it on 3s lipo for about 3 hours!!
pretty good i'd say

this motor also has the adjustable timing and stuff...i have it set to 2* advance as it can be very bad to use reverse with an advanced motor.

[coolhandcountry]

I didn't think brushed had the problem of heat build up if geared to low.

[What's_nitro?]

Brushed is pretty linear as far as load-->temp goes. Less load = lower temp, higher load = higher temp. So if you gear faster it will get hotter. Timing advance in brushed motors raises the kV rating which is just like gearing up, so it will get hotter then, too. The magnets in those motors are a ceramic material which (I think?) is less prone to magnetic loss at high temps.

*edit* Found this handy info http://www.magnetsales.com/Design/Matlprop.htm

[Metallover]

I think the magnets aren't much of an issue. I would go by the laminations and insulation. You probably won't melt anything until something like 400f. I saw someone had a brushless hub motor on an e-bike up to around 400f at the windings and it still worked.

[shaunjohnson]

had it out again today at the track in between races.
roasted the rear bearing in the LRP, that caused the end bell to melt around the bearing housing.

so i asked the local guru on brushed motors, he's been racing RC for years so he's an information bank on brushed setups.

he pointed out the fecked BB and hence i made a franken-motor out of the dead venom's end bell and bearing and used the LRP can and armature and brushes.

works good now and the venom end bell runs cooler.

but i'm still geared way low so i figured that i could see what the max temp would be.
under race conditions it got to 150-160 and very slowly rose/fell in that area.
then i did a few high load doughnuts on the road and temps saw 175 so i stopped.

so i guess this is normal. i just dont wanna melt the end bell.
it's gotta last until the 10th of jan when we have a big ass race at a mates private track (22 cars on a backward track FTW!!)

will be upgrading to a MMpro and 1450kv motor and running 6s later on, geared for 40 of coarse