Electric motor running hot...solutions?

[Nitomor]

Hello all,

I recently built an Aero Avante and Monsterised it straight away as I do, but unlike the other buggies, the motor in this runs really hot. A few reasons for this I guess, the way the motor is mounted means not a lot of airflow to it or around it. The gearing from the larger wheels, and the fact it is having to drive all four.

I put a temp probe on it and it went of the scale, must be 100 degrees+.

My question, what can I do to get a cooler running motor? I'm not talking about fins or fans, what I mean is, what is it that makes it run hot? Is it purely that its being overworked, or the torque output isn't matched to the load. For example if I ran a more powerful motor, would that run cooler, or hotter because it would be spinning at even faster rpm, I'm guessing hotter? Do I go for a lower turn motor for more torque, would that run cooler?

I'm considering pulling the brushless motor off my hornet and putting it into this as a far more suitable chassis which would likely solve the problem but I'm curious nonetheless but I also have a sport tuned or torque tuned that I can rob off another model if that would help at all?

Aside from this, I'm really pleased with the buggy so far, really nice and robust chassis with sharp handling. It would be nice if the 4wd system had a torque splitter option to give more rear bias and quell understeer but it is an entry level buggy I guess.

Cheers

Nito

[GregM]

Since you're running larger wheels than buggy size wheels, I strongly suggest using a smaller pinion to accommodate the added stress on the motor.

More powerful (less turns) brushed motors will have more RPM, but lack in torque. High turn motors have less RPM, but high torque. This can be also remedied by the gearing, too.

If you're already on the smallest pinion, I'd suggest using a 540-sized brushless motor (usually denoted by a .5 in the turns specifications). They are more efficient, thus lose less power into heat.

If that doesn't work, please step back to a higher turns brushed motor or use smaller wheels. Please also check that all components in the driveline are running good.

[lentner3]

Smaller pinion will help, the biggest problem is likely to be the gearing. Yes a lower turn motor will have the same effect as larger wheels and cause more heat. Also the terrain you are on can have an effect or any resistance to the motor for that matter as it adds a load to it. Your options are smaller wheels or pinion, different motor and other methods to cool the motor such as heat sinks and fans etc. I would suggest a combination depending on what the chassis will accommodate.

[Nitomor]

Thanks chaps,

The ESC hasn't shut down on any run and runs cool. What if I do nothing? What damage would it likely cause? I've made sure there are no wires right next to it and I don't think it's a fire risk based on the runs I have done and the heat in surrounding areas. I don't know what the temp limit is on a brushed motor and what the upper limit is. I think Brushless motors it's about 80 degrees?

It's on the stock pinion, I don't have the manual to hand but believe it's a 19T pinion and 70T spur from looking at a website or two. That temp was taken from deep within the motor too, not the casing, but the casing is too hot to touch for more than a second or so which is clearly 'too hot'!

I may give it a few more runs in the name of science. I'm also running it off a 2S Lipo.

Cheers

Nito

[Darat76]

the heat your getting in the motor is due to the wheels, it has increased your final drive ratio and roll out, as well as rolling resistance that the motor has to over come.

returning to the buggy wheels will bring the motor back into normal operating temp range, as will decreasing the tooth count of the pinion, and increasing the tooth count of the spur.

given how much of a size increase your wheels and tyres have, you'd need to look at twin fan heatsinks for the motor

[MadInventor]

Going back to the original post, and you mentioned using a torque splitter, you can replace the front diff with a TT-01 one way roller unit. I did this with my DF-02 to get better grip from a standing start and it also helped with turn in under full power. It can also cope with large wheels as the one way roller unit now lives in the front axle of my TXT-1, which I run with a 4274 1/8 brushless motor and 3S.

[Nitomor]

Thanks for all the input gents, and MadInventor thanks for that useful info on the front diff also, that may well make it on the to do list.

I'll see how it all goes performance wise. The easy option for me might be to slot the Brushless motor in, if that runs hot then I'll have to look at some cooling as suggested by Darat. I won't be going back to the buggy wheels but pinion would certainly also be an option.

Cheers

Nito

[MadInventor]

I'd certainly drop to the smallest pinion you can fit, and also get a metal motor mount which will help a little with heat dissipation (and also won't go soft and distort when the motor gets hot).

Another little change you can make which makes a difference to longevity is to replace the kit 3mmx10 self tapping screws that hold the top gearcase on with 3mmx12 (The default length screws used in vintage cars.) They give an extra bit length for the thread to bite and help to stop the threads stripping

If you are going to stick with the big wheels, I'm going to stick my neck out and say look at a EzRun 4274 brushless motor or similar. They are physically larger than a 540, (42mm diameter by 74mm long, compared with 36mm dia * 56 long for a 540) ,so you would need cut away the chassis under the motor, but they are only 2000KV and have a LOT of torque, especially if run on 3S (I also ran my DF-02 with a large Zippy hardcase LiPo fitted, all I had to do was make some taller posts to accommodate the larger battery). The motor will run on 4S, but I suspect that the power would destroy the DF-02 drivetrain

[Percymon]

The plastic motor mount in the kit provides for pinion sizes of 19t, 18t, 17t, 16t - the kit comes with a 19t pinion and 70t spur - fine for 2.2 buggy wheels but not suited to Vajra wheels and tyres which are ca 2.8" from recollection

You need to be on the smallest 16t, which will go part way to address the increased wheel size - will alter the pinion / spur ratio from 3.684 to 4.375 Not sure whether you can get a bigger spur gear in there ?

There's also the hopup metal motor mount (part #53666) which might help dissipate some heat from the motor - perhaps some cooling slots are needed in the shell to help airflow too (there looks to be a prime area for a cut out and some mesh at the side of the cockpit.

Excessive grease in the drivetrain won't help, and use of antiwear in the diffs will also add drag.

[GregM]

I don't know what the temp limit is on a brushed motor and what the upper limit is. I think Brushless motors it's about 80 degrees?

I don't exactly know either, but I think lowering the temps from "too hot to touch" to "beef medium" should lengthen your motor's life.

[Nitomor]

Haha, very good Greg, I'd prefer Medium Rare

Thanks for all the other suggestions chaps, I think I'm going to enjoy this chassis so they are all good tips. I particularly like the idea of cutting out and meshing the vents! I have a 4300kv HPI brushless 9T (based on a 380 casing but finned out to 540 dimension for extra cooling) which is my preferred Brushless motor. I may give it a go with the stock pinion and check out how hot it gets. If that is 'Too hot' then will look at the other ideas, I like the ally motor mount tip too, thanks for the part #. I'll only be running 2S.

[Darat76]

Haha, very good Greg, I'd prefer Medium Rare

Thanks for all the other suggestions chaps, I think I'm going to enjoy this chassis so they are all good tips. I particularly like the idea of cutting out and meshing the vents! I have a 4300kv HPI brushless 9T (based on a 380 casing but finned out to 540 dimension for extra cooling) which is my preferred Brushless motor. I may give it a go with the stock pinion and check out how hot it gets. If that is 'Too hot' then will look at the other ideas, I like the ally motor mount tip too, thanks for the part #. I'll only be running 2S.

be careful when running that brushless motor, they are more sensitive to high temps than a brushed.

the max temp you want a brushless motor getting to is 90 degrees on the can surface, above that and the glues used in construction start to melt and cause the internals to move and self destruct the motor.

I'd suggest running it like you normally do for a few minutes, then grab the can, if it's warm keep going for a couple more minutes, but once it starts to feel hot (which should be around the 60 degree range), stop and let it cool off, check the battery voltage, if it's close to voltage cut out just get a basic heat sink and keep playing, if it's barely used lower the pinion, increase the spur, and get a good heat sink and fan combo. You can keep testing with different size spurs and pinions until you find the combo that gives you the maximum amount of speed without over heating the motor.

A lot of the racers here use Wild Turbo Fans (I think that's what the name stands for) for both on and off road racing, they are all reasonably priced as far as I've seen, and recommended by all that use them.

Edit: Had to edit due to the brand name of the fans using a known acronym

[Nitomor]

Lol, thanks.

Just checked out front one way diff #53671 and rear ball diff #53663, not cheap though, I'll wait until I've spent some time with it before taking that plunge!

I have an 18T pinion 0.6 left over when I uprated my WT01 (I know its only one tooth less but it should help a little and its in my toolbox!)

[Percymon]

Remember those pinion choices are still based on 2.2 buggy wheels - by all means try the 18t but I think you're wasting your time. Its certainly not going to be any worse but you need a more dramatic change.

You've increased the wheel circumference by (off the top of my head) 50%

[Nitomor]

Thanks, I've put a 16T RW upgraded one in my modelsport basket.

[Nitomor]

Well I ordered the 16T pinion, but the above was based around tearing around the kitchen woth lots of forward brake reverse in quick succssion. Out on the track it was barely tepid so looks like in the real world the motor is fine with the 19T pinion. The buggy was great on track, really impressed with the chassis.