9XL headache
 

I have a buddy with a 3905 Maxx, just put in a 9XL with a MMM, running 14 cell.

It is weatherproofed, so there is no airflow around the motor, and he was running in the slop tonight to test things out, I was running my truck and no thinking about temps on his.... end of a run and the motor is at 215!

Wha?

It seems ok, which is probably a small miracle.

But is the main issue here the fact that he's over the happy 30,000 rpm zone on this motor?

The motor heats up very fast even freespinning the driveline, we tried it after cooling again on my lipos (16.8v) and the heat did not seem to be an issue nearly as much.

Gearing is very conservative 20/68, could it also be being underworked at 21v?

I ran 14 GP3300 cells on a 9XL in my converted Revo for a long time and the motor never got any hotter than ~150*F after a battery cycle (~12-13 min). Your buddy's motor might have partially demagged and will get worse as time goes on. I'd stop using it and get a new motor before he toasts the ESC from overcurrent.

Ouch- it is a new motor, maybe it should be a Neu?

This was actually it's first real run, but do you think the over 30k mark was the crux?

I have 2 sinks and 2 fans on the 9XL in my Mute, and run mine up to 25/64 gearing with a MM on 16.8, and I never saw over 140 on my motor even in July.

I've read that the MMM will deliver alot more juice, is that also a big factor?

As I said above there is like no airflow around his motor, but that doesn't account for the temp rising so fast (assuming the motor is ok ust for this example) with only driveline load.

I made the recommendations for the motor and esc, what now?

I need to know what to correct before he just buys another motor... I'm at a loss here.

Sucks! lol

Forgot to add, MMM is V3 w/ new firmware, start power low, 0 motor timing and no punch control, so basically flat across.

I'm gonna take a wild guess that the slop your talking about is this slushy crap in my driveway!!! It cakes onto the wheels and truck and your 10-11Lb E-Maxx becomes 15-18Lbs! The tires and rims load up, lots of rotational mass, and it takes more power to push through the crap!!!!! I don't think it's a component problem. To run in the slop without heat you'd need to gear it for about 30MPH at most.

Could be as simple as too tight on the gear mesh......... I would make sure everything is smooth as it should be as well.

Run it in the street out of the slush and check the temps. I'm positive that staying out of the slush will cure your fever:whistle: I don't want to sound like a know it all here but I had a heat issue with the stock titans when running in the slush. I also had reduced runtime because of the extra load.

Yeah I'm only one county away, same stuff E-Revonut... I had a wheel snowball on me- literally got twice it's normal size with snow haha. Usually it's the dry fluffy and doesn't pile up so bad- but what fun!

No binding anywhere, everything is new on my buddy's Maxx.

Is there any hope the motor survived? Any?

It seems fine, except for the purple anodizing has a weird iridescent effect in the light now.....

The 70 & 80mm Medusas are still not out right?

Gonna have to give it another try tomorrow with my lipos under better controlled testing and report back.

I know it's probably not a great idea to run a possibly damaged motor, but we assume all risk (nervous laugh)

My 7xl heats up pretty fast with only driveline load too. I think thats normal for these motors. I think they are just inefficient and heat up. I added a novak heatsink to keep temps in line. I also added 2 40mm fans for running during summer. Never got above 140 this way. Motor reached 180 without the cooling. I think its the combo of running in snow and no airflow around the motor that made it heat up. I would say given what you said I'm not surprise the motor heated up to 215. Hopefully you havent de-magged it.

just temp check the motor and esc often as you test it, a demaged motor usually feels weak and glitchy, especially off the line, and you are right about the airflow, it is important to have the cooling airflow, otherwise the motor sits in a pool of stagnant heat. 35,000rpm should be fine just check temps, and not over 40,000

also, the sealed design of a feigao make them amazingly resilient to water, I do nothing to my motors when I run in the snow, and they are all still running, my buddy dunked a sidewinder in a lake, still running. IMO i'd be more afraid of overheating the motor due to weather proofing than water damage, on the other hand, sensored brushless hears the word water and fails, i'd go as far as to say my MM is "splash resistant" as it has been wet a time or twelve

any bl motor [ferrous-loss ones like the kontronik tango are excluded] will seriously overheat if run with minimal or no load...

Paralyzed, it's not the motor getting wet we're worried about, it's the MMM.

Ok we did a labcoat test on Wed. night for temp. rise per min without cooling, and the test was run on both my MA 2S 6000 x2 and his IB 4600 7cell x2.

Results were extremely close:

On Lipo:
Motor start temp 65, outside temp 25 on all tests, gearing 20/68
After 1 min- 80
2 min- 104
3 min- 123
4 min- 139
5 min-160

On 14 cell
1 min- 82
2 min- 104
3 min- 125
4 min- 160
5 min- 168

Increased gearing to 20/62 and run on lipo again:
1 min- 95
2 min- 113
3 min- 132
4 min- 142
5 min- 177 (run VERY hard for last minute)

And it was too cold to do the 14 cell test on 20/62, so no data.
But as you see the average temp rise/ min is 20 degrees.

The motor shows no symptoms of damage, has very good power and now has cooling via one 2.5 inch square BB 12v fan running at 21v. After a merciless test last nite at about the same 25 degree outside temp, motor temps were not over 110!

Moral of the story, fans are a must -with these chinese motors at least.

Everything is happy now!