Motor running v. hot

[evertonal]

I run a Yokomo B-Max with a Speed Passion 2.0 GT Pro speedo and a Speed Passion V3 6.5 T motor. After running the final heat on wednesday night I measured the temperature of the motor. The temp was 104 degrees C! A friend running a cat SX with an Exceed 6.5 T combo measured his motor temp as 58 degrees C. My gearing is not too much 87 spur, 20 T pinion and the drive train feels fairly free. The timing on the speedo is set to the lowest setting. Any advice on what I could be doing wrong would be gratefully appreciated.

[ianhaye]

check your roll out compard to the guideline stated in the motor intructions or on the website ?

[Big G]

mine tend to thermal out at 85oC / 185oF

I guess there's a variance in our temp guns though. I'm pretty sure mine was down to a terminal on the speedo touching the can of the motor. very close in the durango.

[CODMAN]

Tonal, I know you've benn having this issue for quite sme time... :(.

Have you tried reducing your pinion by 1-2 teeth? Do you see any improvement? With a 20T you get a FDR (Final drive ratio) of 10.22, which might be a bit high for a 6.5T... But also, that depends on your track and driving style...
I'd also check your temp gun with someone elses just to make sure it is accurate.

Have you installed a fan/heatsink on the motor? definetly worth a try as it will save you a few degrees.

Good luck!

[kyfran95220]

I had the same problem with my Yokomo b-max (speedo Tekin RS and SP 6.5t V3).
At this time, I had the 87t spur and 20t/21t pinion.

Now I use the 84t spur and 19 pinion (HobbyWing 120A and SP 6.5V3)
It was better during a month but last week I have smoked the motor (118°C because of too much drag brake).

I will try a LRP 6.5 next week and, in 1 or 2 months, I will install definitively a 6.5 PRT (ptityo)
I will tell you then

[CODMAN]

Kyfran, 84T/19T is almost exactly the same ratio as 87T/20T, so I'm not surprised you smoked your motor. Your change in gears accomplished nothing, except for bringing the center of gravity more towards the center of the car. You should have kept the 87T spur and dropped the pinion by a few teeth... But anyways...

Is it possible that the SP motors run hot and need lower gearing?
I've said it before, and I'll say it again. No matter how many turns you are running, you need to gear your car so you can keep the motor running in the manufacturers recommended temperature range. So either gear down, add a fan heatsink or adjust timing to get it in the range... or change your motor to something milder...

Just for reference, I just ordered a new ESC with a Tekin redline 7.5T. At 6100Kv rating, it should be plenty fast without running too hot. And if ever it's a bit too slow, I should be able to use the dynamic timing advance to add some top speed (as long as I can still stay within the recommended temps).

Just food for thought...

[sosidge]

Back when I had a B-Max, the drivetrain was tight, especially around the centre transmission. I had to file material away to stop the bearings from being crushed.

Check your car because it may be the same thing. The car should roll freely along the floor with the motor out.