Motor running to hot, not sure what to make of it - RC-Monster Forums

Ola · 10:33 AM

Today i got my new max paddle tires, and had to test them in snow..

i`m running XXL drivetrain, a Tekin RX8/T8 2000kv on 5s, geared for 43mph on these tires.
Temp is approx -1 celcius (30f) outside.

I was driving on a field of snow, hardpacked with 3-5cm on top. Very good traction, wheelied like no tomorrow, almost flipped on throttle..
Did some high speed running, alot of accelleration. No jumping and slo-mo, so it got a hard run so to say..

After 10min, i read temps.. RX8 was 50dg C (122f), ant T8 was reading 75-85dg C (185f) (!) based on where i measured, but all reading was done on the rear plate of motor..
Definitive hottest on top, where the motor cables are soldered...

Since i`ve never run this motor setup this hard ( i mostly bash/jump, never speed run), i have to ask for some opinions..
Am i way out of my league, running this motor on 5s?
Or is it undergeared, since the RX8 isnt nearly as hot as the motor?

Ola · 03.10.2011, 03:27 PM

I thought i maybe had answered my own Q when i read my post over again..

So i re-soldered the motor wires, to elliminate cold-soldering from the previous owner... And suddenly when test driving, the hottest point of the rear plate, was located in the middle and not on top at the soldering points... Guess i found a weak solder job there.

I`ll do some more testing tomorrow, since i only had half-charged packs to test with tonight, but atleast the motor wasnt reading over 71`C (160f) now.. Probably alittle more on fully charged batteries though, but this was approx 10-15min of _really_ hard driving on that open field.. Just about full throttle all the time, only adjusting to avoid flippin over

Several top speed passes.

BUT its still only -1C (30f) outside, so i think its still running to hot.
So any opinions would be interesting. I`ve got 4s, 5s, 6s to test with, but i would prefer 5s minimum as i love the power LOL..
I`m using the highest gearing i`ve got now,making 43mph at 5s, but i got lower gearing to test with.. The LST diffs really lowers the gearing alot..

BrianG · 03.10.2011, 03:57 PM

Just a heads up, but if you are running any motor topped out at max rpm for long periods of time, they will heat up. Motors seem to like partial throttle, while ESCs like full throttle. The trick it to find a gearing for a particular setup so that you only hit and stay at max rpm about 10% of the time. Also, lots of WOT starts will heat everything up since that's when you are pulling lots of current, therefore generating lots of power.

Of course, bad soldering joints does make a difference.

Ola · 03.10.2011, 04:19 PM

Yeah, i guess it`s me that want too much out of the motor..
But i read several people running 6s on MMM 2200kv`s with "no overheating" (at least they claim), and that annoys me when i have issues on 5s on my 2000kv at cold ambient temps...

Ola · 03.10.2011, 04:20 PM

Do you think gearing up alittle would be better then, so i dont stay at those high rpms all the time?

BrianG · 03.10.2011, 05:07 PM

I think maybe gearing up will help. Just be careful not to go so high that the current get too great for the ESC/batteries to handle.

Ola · 03.11.2011, 08:33 AM

Ok, since i didnt have higher gear`s to test right now, i had to test something else..

So i charged a set of 3s batteries to try and run 6s.
Hooked up hotwire, and reduced current limiter to 75% (perhaps i should try even lower?)
Timing is set at 0dg as last on 5s, and throttle curve 2.

After a hard 10-15min drive, allthough less full throttle since the car is ballistic on 6s :D, the temps where lower on 6s than on 5s.. I measured the motor to 150f and rx8 to 113.
The same gearing, making top speed 53mph on 6s.

Is 0dg timing the best to avvoid heat, or is it more effective on 5-8dg?

Ola · 03.11.2011, 03:22 PM

Naah, forget my last post.. After a full pack of 6s of hard bashing tonight, the motor was reading 190f.

So i`m back at 5s, or even 4s

I think the 1717 will get busy real soon.

_paralyzed_ · 03.11.2011, 04:50 PM

are you sure you have a "truggy" tekin motor and not a "buggy" motor? I'm not familiar with the kv's to know the difference.

going to 6s should lower temps, when you up the voltage you should lower the gearing to keep the same top speed(load), that's how you get the lower temps.

Does the truck roll freely? Are you sure there is no binding?

You definitely need to play with gearing to find the sweet spot. Start by making the top speed faster, so you can't run wide open so much. You wills always heat up with prolonged full throttle passes. Watch temps closely, check often.

Ola · 06:04 PM

Yes, it says 4038 2000kv on the motor..

No binding in the driveline.. The paddle tires isnt the easyest tires to throw around i guess, but still..

I doubt gearing is the solution anymore. Hitting 190f at sub 30f ambient temps in snow, when i mostly where bashing, jumping and probably not even once was over 35mph....
This must be way to high temps to even be in the ballpark of gearing?!

I did not change gearing when i went for 6s. I kept the gears, and top speed went from 43mph on 5s, to 55mph on 6s.

_paralyzed_ · 03.11.2011, 07:08 PM

55 is pretty fast actually.

Ola · 03.12.2011, 02:50 AM

It`s way to fast for the car for sure.. I`ll try to lower the gearing and see what it doest to temps, when i get the car back together again.. I seem to have the worst luck on breaking parts this week..

Ola · 03.13.2011, 01:39 PM

Now i tested both 5s and 6s, geared to 40 and 41mph..

Both times i read 165-170f after 20min run in 30`f ambient temp.. As last time in snow, with max paddles rear, badlands front.

When the outside temps hit 75-80,and i got real traction, then what... hmf

Ola · 04.01.2011, 06:19 AM

As an update, i bought myself a 1515 2200kv to try out in the Erbe, and after 25min of bashing, alot of speed runs on asphalt, and some running in heavy deep snow, the RX8 is 115f (showing coolish on the led`s) and the 1515 motor about 140f..

This was on 5s, and 45mph gearing, and higher outside temps than before (45-50f).

So the conclusion must be that my T8 2000kv is either worn out, has a problem, or just to small for the truck/driving style.

scarletboa · 04.01.2011, 04:45 PM

Quote:

Originally Posted by Ola

As an update, i bought myself a 1515 2200kv to try out in the Erbe, and after 25min of bashing, alot of speed runs on asphalt, and some running in heavy deep snow, the RX8 is 115f (showing coolish on the led`s) and the 1515 motor about 140f..

This was on 5s, and 45mph gearing, and higher outside temps than before (45-50f).

So the conclusion must be that my T8 2000kv is either worn out, has a problem, or just to small for the truck/driving style.

There's a chance that you got the motor too hot at one point and partially demagged it. That would cause temps to be higher.