Stock Kraton motor hitting 205 degrees - Alternative motor cooling solutions

[cobalt172]

My COMPLETELY STOCK Kraton motor gets to 195 or 200 degrees on every run now. I have not changed a damn thing on this car. using the same pinion, NOT the speed pinion.... I could use some help on this

I wanted to bounce a few ideas around here if anyone is willing to listen:

1.) Motor fans that I have tried all SUCK. They do not blow enough air. Hot racing, dynamite, castle, they all SUCK. What I would like to do is get a high powered CPU cooling fan that moves some serious air, and wire that up to a totally separate Lipo pack (something very small). A server cooling fan moves some serious air, its like a cool hair dryer. This amount of air flow would actually keep your temps down, I have not noticed a damn bit of difference from using these little chicken crap fans.

Anyone know what kind of cpu/case fan would work and how I should wire that up?
https://www.amazon.com/Fugetek-Brus...ral+purpose+cooling+fan&qid=1573960938&sr=8-5

 

[slick2500]

My COMPLETELY STOCK Kraton motor gets to 195 or 200 degrees on every run now. I have not changed a damn thing on this car. using the same pinion, NOT the speed pinion.... I could use some help on this

I wanted to bounce a few ideas around here if anyone is willing to listen:

1.) Motor fans that I have tried all SUCK. They do not blow enough air. Hot racing, dynamite, castle, they all SUCK. What I would like to do is get a high powered CPU cooling fan that moves some serious air, and wire that up to a totally separate Lipo pack (something very small). A server cooling fan moves some serious air, its like a cool hair dryer. This amount of air flow would actually keep your temps down, I have not noticed a damn bit of difference from using these little chicken crap fans.

Anyone know what kind of cpu/case fan would work and how I should wire that up?
https://www.amazon.com/Fugetek-Brus...ral+purpose+cooling+fan&qid=1573960938&sr=8-5

Something is wrong you should not be running that hot stock fans are not the solution to this problem. Something somewhere in the driveline is binding or riding on a dead bearing.

This is what I would do. Remove the motor and make sure that it spins freely and doesn't make any abnormal noise. If that checks out, remove the center diff and ensure that it and the bearings both spin freely. If those are good move on to the front or rear diff then check the other.


But these fans are the fans you want Hobbystar/Trackstar 30mm aluminum fans. I run 2 of these on my 4985 1650kv motor and that thing runs cool as a cucumber. https://www.rcjuice.com/hobbystar-turbo-ventilator-esc-motor-fan-30x30mm-red.html

 

[cobalt172]

It has been running that hot since Day one, I really don't think anything is wrong. The car rolls easy across the ground.
Looked at that fan, and Those fans constantly lose fan blades.
What about wiring up that centrifugal turbine fan on the kraton after I go through the car?

 

[slick2500]

It has been running that hot since Day one, I really don't think anything is wrong. The car rolls easy across the ground.
Looked at that fan, and Those fans constantly lose fan blades.
What about wiring up that centrifugal turbine fan on the kraton after I go through the car?

Trust me something is wrong, it should not run that hot stock, my Outcast didn't even run that hot with the speed pinion on an 80* day. If everything moves freely that means the motor itself is defective.

 

[Surchaufeur]

did you change the bearibgs for rubber sealed? Maybe you have a bad bearing somewhere binding everything everything should spin smootly. If everything is alright call horizon and they rpwill remplace your motor if it is the motor the issue after all the verifications
You have a 2 year warranty on any unjustified failures i will say

 

[3d-rc.myshopify.com]

Yeah something isn't right. 180 is where mine gets doing runs on the high speed pinion.

 

[unclebrudy]

Yes, check the bearings.

My Typhon rolled smoothly, no issues, even when the front shaft bearing was 100% seized and the rear cap bearing was gritty. Rolling it by hand did not reveal anything wrong.

That’s step one. Report back.

 

[olds97_lss]

What about wiring up that centrifugal turbine fan on the kraton after I go through the car?

No they don't. I run them on 2 of my trucks and they hold up far better than plastic framed fans. I have yet to break one or have a blade brake.

205F does sound hot. Are you running stock tires? Are you running 6S? Where do you drive? Tall grass, short grass, sand, dirt, pavement?

I run my outcast on 6S with 13/50 gearing, stock motor/esc and trencher 3.8's which are larger/heavier than stock outcast or kraton tires. I have a hobbywing single 50mm fan cooler on the motor. I run at a grass bmx track and the motor stays below 160F even after an 18-20 minute run on a set of packs.

 

[3d-rc.myshopify.com]

I was just thinking to myself. What size batteries are you running?

 

[cobalt172]

6s, dirt soccer field and short grass

 

[SrC]

From my experience, if you are diffing out a lot, heat will also migrate from the alu. diff carrier to the motormount and ultimately the motor. Also as motor bearings wear out , the motor gets hotter. Even if you oil the bearings once in a while. IMO. Find out with a temp gun what is the hottest part of the motor. By design it should be hottest at the end where the 3 phase wires come out. If its hotter at the pinion side, it may be the diff causing the heat. Take temps of your center diff. cup too. I was getting temps of 250 F before it melted and exploded. I rebuilt the ctr. diff with 200k using the optional Arrma metal diff cup. and my motor cooled down alot. I always fill my diff to the brim, and vacuum out the air with my shock pump as well. I feel the more air that's in the diff, less oil is circulating and cooling the gears. My thoughts.

 

[cobalt172]

Vaccum out air with a shock pump... I'm sorry what??

 

[SrC]

I use an RC shock vacuum pump to bleed out every bit of air in my shocks and diffs. It allows for more oil volume and less aeration. There is a lot of air inside diffs because of the thick oil when filling. After its pumped. I let it sit. You can see the air bubbles coming to the surface. Eventually all the air is out, then you will find that you can top it off and it takes more oil. Same with shocks. I feel a must have for Bladder type shocks. My current vac pump is by Tamiya. But others make them. I have a large version for bigger 1/8 shocks and diffs. Sometimes they are hard to find and on backorder
https://www.amazon.com/Tamiya-54152...=2025&creative=165953&creativeASIN=B00PUA5BAY

This is a good price right now. I paid more and had to get it from RC Mart in China on the slow boat last year. My old pump was worn out. I find it very useful.

 

[olds97_lss]

6s, dirt soccer field and short grass

So a lot of wide open throttle running? If your esc is doing ok, you could increase the motor pinion which may help by lessening the motors top RPM a bit.

 

[Yonic]

I agree with everyone here, it most likely some binding,
or! a wrong gear mesh, could be that the pinion/spur mesh is too tight? you should have some play when rotating the spur back/forth.

If it's not in the pinion/spur area, it could also be in the input gear/ring gear of the front/rear diffs.

 

[DoNoHarm]

So a lot of wide open throttle running? If your esc is doing ok, you could increase the motor pinion which may help by lessening the motors top RPM a bit.

Idk olds. Not to shoot your point down, because I’ve never done tests side by side, but that point gets brought up a lot. In my experience I’ve never had an under-geared motor ever get hot from being at top rpm 90% of the time. The senton comes with a 14t stock, so my runs with that were basically full throttle on 6s and that only... motor never passed 140. Only times I’ve ever ran into heat is with high amp draw, like now that I have a 19t in it. But I really don’t know. Maybe if the bearings start to go out, the extra rpm will heat it up worse than extra amp draw of higher gearing?

 

[SrC]

Idk olds. Not to shoot your point down, because I’ve never done tests side by side, but that point gets brought up a lot. In my experience I’ve never had an under-geared motor ever get hot from being at top rpm 90% of the time. The senton comes with a 14t stock, so my runs with that were basically full throttle on 6s and that only... motor never passed 140. Only times I’ve ever ran into heat is with high amp draw, like now that I have a 19t in it. But I really don’t know. Maybe if the bearings start to go out, the extra rpm will heat it up worse than extra amp draw of higher gearing?

Depending on how and where you are driving, you absolutely can over drive the motor. Meaning max rpm. Extreme and sustained revs creates heat also. Especially with rigs that have a lower final drive ratio. Because you are peaking at your KV limit. It is the inverse of over gearing. But there is generally less load on the ESC and battery. Running a 4S versus a 6S lipo is a factor as well. It is the motor that gets worked at max. Try it for yourself. I agree with @olds97_lss. An older motor with fairly worn bearings will bear this out and temps will reflect it. Its just something that I observed in the past when I play with gearing. Under gearing can work against you because you cant get your torque curve where you want it. If that makes sense. For motors to work efficiently it is best to gear where your torque is available most of the time. The rollout of every different style rig changes. What applies to SentonSC my not for a Kraton. I hope I explained it well enough. I haven't had my coffee yet.

 

[SrC]

I agree with everyone here, it most likely some binding,
or! a wrong gear mesh, could be that the pinion/spur mesh is too tight? you should have some play when rotating the spur back/forth.

If it's not in the pinion/spur area, it could also be in the input gear/ring gear of the front/rear diffs.

Pinion/spur mesh is the first and easiest place to start. Mesh should be easy for us to understand as AF members. Basic stuff. Remember ,motor mounts can twist and bend ever so slightly too. Mesh can bind if we don't check that . You also have to remove the pinion to check the rest of the drive train and work your way towards the front and rear difs , then the axels to find any binding issues.

 

[DoNoHarm]

Depending on how and where you are driving, you absolutely can over drive the motor. Meaning max rpm. Extreme and sustained revs creates heat also. Especially with rigs that have a lower final drive ratio. Because you are peaking at your KV limit. It is the inverse of over gearing. But there is generally less load on the ESC and battery. Running a 4S versus a 6S lipo is a factor as well. It is the motor that gets worked at max. Try it for yourself. I agree with @olds97_lss. An older motor with fairly worn bearings will bear this out and temps will reflect it. Its just something that I observed in the past when I play with gearing. Under gearing can work against you because you cant get your torque curve where you want it. If that makes sense. For motors to work efficiently it is best to gear where your torque is available most of the time. The rollout of every different style rig changes. What applies to SentonSC my not for a Kraton. I hope I explained it well enough. I haven't had my coffee yet.

I understand what you mean... don’t worry about the explanation lol. I just never thought rotational friction caused enough heat in a good condition brushless motor to cause it to get any heat at all, but at the end of the day, you’re the crawler guy, I’m not, and you know more about low speed vehicles than me, so I’m taking your word for it.

 

[olds97_lss]

I understand what you mean... don’t worry about the explanation lol. I just never thought rotational friction caused enough heat in a good condition brushless motor to cause it to get any heat at all, but at the end of the day, you’re the crawler guy, I’m not, and you know more about low speed vehicles than me, so I’m taking your word for it.

I was thinking more that running WOT a lot is just pushing a lot of current/volts through the motor causing it to heat up more... so in that vein, higher rpm wouldn't really affect it regardless of gearing as even if you geared it taller, it would still pull the amps trying to get there.

I just know I read that if the esc is hot, gear down, if the motor is hot, gear up... but now that I think on it more, perhaps it's not the RPM's that's heating it up but rather the user using WOT because they want speed. With taller gearing, you get more speed so maybe it's suggested to gear up for a hot motor just for the side effect of the user letting off earlier due to hitting a jump or corner at whatever speed without having the motor fully spooled up. By letting off earlier, they are pulling less amps for less time.