Too much motor heat - help!

[VintageMA]

I'm not sure what I am doing wrong here, but I have just been having terrible problems with motor heat lately.

Latest problem - been waiting for almost 3 months for a 1512/3.5D to come in for my XB8EC and when it finally does here is my setup:

6S
15/46 gearing
Moab 1/8 buggy tires

Calculator puts me around 40mph. Confirmed with Nomadio speed sensor during running.

Lot's of cooling holes in the body - almost looks like swiss cheese right - motor temps were hitting 170* within 5 minutes.

I was running a 1515/2.5D (faster motor) with the same setup on 14/46 gearing and getting faster speeds with less heat.

Any thoughts? Drivetrain spins very smoothly, gear mesh is nice with just a little looseness for impacts, only thing I can think of is that I replaced the center diff oil and went from 10k up a little bit to around 15k (hard to say exactly as it was a mix of 10k and 20k - a little more 10 than 20 - also increased the front from 5k to 7k to increase on power steering a bit).

Based on all the setups that I read here this doesn't sound like it should run so hot. I could drop the pinion down to 12 or 13, but it'll be much slower and doesn't seem like it should have to be that low.

[suicideneil]

What are/were the esc and battery temps like with both setups?

[BrianG]

First of all, what are you using to read those temps? IR sensors can be sensitive to the emissivity setting, and since black radiates heat better, it could be tricking the sensor into thinking it's hotter than it is. Does the motor actually feel that hot?

Second, you mentioned changing the CD oil. Was there a change in temps before and after the change? I set my Hyper8 (1512/2d on 4s) with 50k diff oil and temps are great.

[VintageMA]

Originally Posted by BrianG

First of all, what are you using to read those temps? IR sensors can be sensitive to the emissivity setting, and since black radiates heat better, it could be tricking the sensor into thinking it's hotter than it is. Does the motor actually feel that hot?

Second, you mentioned changing the CD oil. Was there a change in temps before and after the change? I set my Hyper8 (1512/2d on 4s) with 50k diff oil and temps are great.

Brian - using a Flahpoint set to 77E. Hard to tell how accurate it is, but yes the motor is definitely to hot to touch for more than a brief moment.

MMM is hard to measure through the plastic, but it was registering in the low 100s. Battery was coming in at ~120-125*.

I don't think there has really been a temp change before and after the diff oil change.

Only real difference I can tell is the MMM - my motors seem to be hotter than on the MM with very similar setups. I ran a teckno 1515/2.5d through this exact same setup geared at 14/46 with 6S and it was getting up to 150+ as well.

[magudaman]

The motor might be getting hotter because the MMM is capable of higher current and will have lower resistance while doing it. This means you run you motor hard during your runs now than you used to because the MM is not restricting that current flow.

Did you also up your batteries to 6s too?

remember its summer time the ambient temps are higher my 1515/2.5d is running hotter than it has in the past..I lived in the Boston area back in the 80s and I know it gets hot and humid in the summer time

[pullinteef]

BrianG, I have a quick question for you. I am running a very similar setup to your hyper 8 - except mine is RC8, Quark 125b, 1512/2D, 4S. My motor temps were really high yesterday, higher than previously. I was playing with the quark setup but not sure what is ideal. What settings do you use on your quark? What is your gearing? Even with the truggy diff ratios in the RC8 I went from 12/44 down to 11/44 and then 10/44 and saw the motor temps go down about 10 degrees each time, but it feels slightly undergeared as I'm giving up a hair to the nitros on the straightaways (though I did TQ and win the A for the first time yesterday). ESC temps seem around 145, motor got over 190 and I got a little worried. We ran 10 minute qualifiers and 15 minute main, and it was pretty hot and humid yesterday. Any input is appreciated.