Keeping your cool (motor)

[airsus]

I searched through old posts and didn't find a ton of info on keeping the motor cool. I got some 1/2" flex tubing that I'm going to route from the headlight or grill back to motor to atleast get some airflow to it. I'm also going to cut some holes in the back of the body/bumper to let more air out. What else have you guys done for cooling?

[RadicalRustler]

follow this link (http://www.radiocontrolzone.com/forums/showthread.php?s=&threadid=102108&highlight=frozen+motor) for a good way to keep your motor cool

[Compudude_y2k2]

What kind of car do you have? wiring tubing to the motor wouldnt do much. Instead, get yourself a motor heatsink made for your car or any if the motor is completely open, or if you cant get one specifically for your car, get a close one and use a dremel tool.:D

Maybe you should look at your gearing or whether you are running it too often, too. Your motor generally shouldnt get so hot that you cant hold your finger on it for more than 5 seconds.

[rocknbil]

Agreed w. Cmp., if you're to hot you have unneccessary resistance or are geared too high.

I used to put a little computer CPU fan on my motor after races, mounted with clips. :D Didn't do much good but everyone came over to check it out. LOL

[airsus]

The thing is my battery and heatsink on my ESC are also pretty hot after I run my car too. Could there some problem in the electronics or with the battery. It's a 2400 NiCd pack that I charge at 4 amps with a peak charger. The heat doesn't seem to have cuased any problmes yet, but I don't really want to fry my motor because I'm not made of $ and can't be replacing it all the time.

[SteveK]

Grearing the motor correctly is the best way to keep the motor from over-heating. Don't rely on a heatsink or other method to cool a motor that's too hot at the end of a run.

[airsus]

It's an HPI Rallly and the stock gearing was 31/91, but I switched the spur gear down so now it's 31/84.

[SteveK]

Whoa, wrong direction dude. The 31 tooth pinion included is all wrong for any motor. I don't know why HPI still includes it, they just do. Any motor is severely overgeared from the start, and going to an 84 tooth pinion makes it even worse.

What type of motor do you use? If it's a stock motor, try the 91 tooth spur with a 25-28 tooth pinion. If it's a modified motor, add 5-7 teeth to the number of turns and use a pinion with that number of teeth and the 91 tooth spur. If you keep the 84 tooth spur, reduce the number of teeth on the pinion you'll use by about 2 teeth (Or do some math to find the right ratio.

[LRSeriesIII]

Also, since it's a rally, if you're running on nice, clean surfaces (and what's the fun in that?:)) you might want to consider removing the inner body. There isn't much airflow with that thing on. You also might want to consider cutting holes in the inner body and putting some sort of screen in it to keep dirt out. You'll be exposing the inside to more dirt so I'd keep more of an eye on your internals. I haven't finished building my rally yet (stupid school, job, other r/c cars, friends, life, everything...), but I've been planning on doing just this to the inner body. I suppose you could even put in intake and exhaust fans (esp. intake). Don't know how much it would help though.

[airsus]

I just run it on the street mostly so I don't even use the inner body. I put only the bottom part on once, but it turned out the rocks that got kicked up into the car would stay in the lower body. On HPI's site they say the stock gearing runs best with a 17 turn motor, so I might stick my 19 turn Trinity Chameleon Pro motor to see what happens.

[rocknbil]

Originally posted by SteveK
....The 31 tooth pinion included is all wrong for any motor.....going to an 84 tooth pinion makes it even worse......

WOW an 84 tooth pinion must be even bigger than the motor, I've never seen one of those!!!! :D

(We all know Steve meant 84 tooth spur. :) )

When I was running onroad touring and pan cars, I used to keep up to 25 tooth pinions around for my pan cars, but threw or gave away anything larger, they are a motor burnout waiting to happen. :D

[airsus]

Haha, I didn't even catch that. My theory in going with the smaller spur is that it'll make the car faster, therefore I wouldn't need to be on the throttle as much so the motor wouldn't be going full blast the whole time.

[paladskee]

There is a good site called Sanj's Yokomo Homepage and its got some good stuff on keeping your motor cool and has great info heatsinks and the like. Check it out.

[rocknbil]

Originally posted by airsus
.....smaller spur is that it'll make the car faster....

Which it will, but will put more stress on the motor from a dead stop or at low speeds, which is where the overheating comes from.

[SteveK]

The HPI site and instruction manual are WRONG: 31/91 is way too high for any motor I can think of. Like I said, stock motors work best at about 27/91, and for modifieds, it's generally about 7 teeth more than the number of turns and the 91 tooth spur.

Frankly it's just stupid that they don't at least include a slip of paper saying "The included pinion will cook any motor". Most kits without a motor don't even include a pinion, so they could leave it out altogether and be done with it. It's a nice pinion, so one of a more appropriate size would be better, but still, what if the buyer won't be a using a motor that would work for?

What HPI could have done is design a simpler chassis cover like the one in the TB01, without the drivers (Which don't look out the windows with the body at off-road height anyway) and decals and everything, leave out the pinion, and that would probably save enough to allow them to include a slipper clutch.

[airsus]

Ok, thanks for the thoughts.

[airsus]

I went to the LHS today and got an 87 tooth spur gear and installed that along with a 26 tooth pinion gera that I already had. The 26/87 combo gives me a gear ratio of 3.35, which is almost the same as the 27/91 mentioned above, which has a 3.37 gear ratio. I have to charge my battery, but then I'll be able to get some testing done :) .

Another thing; Do you think a heat sink motor plate would be worth getting? I'm going to order some parts from Towerhobbies anyways (that my LHS's don't have), so I was thinking I'd throw it in with my order since I'm already getting a bunch of stuff. Any thoughts on this?