go kart motor cooling idea

[dfrydman]

hi, i have a 24v 250w motor that is overheating. i wouldnt say it is about to die but it heats up enough to smell some burnt plastic. i am using a 11 tooth gear on the motor and a 55 tooth on the wheel and it gets pretty hot. this might be due to it being almost three yrs old. i recently switched to an 80 tooth gear and it runs cooler but still really hot as well as my top speed being diminished from 14 to 10mph so i would like to go back to the 55 tooth gear but worried about burning out my motor. would putting a heat sink around the motor and either use the oncoming air or a fan, work. im not really overworking it or overvolting so my cooling capability doesnt need to be great.

p.s. my go kart is homemade so it doesn't have the regular shape and the oncoming air gets to the motor practically unhindered

the heat sink i would bend around the motor casing without much dificulty
the motor and battery are missing from the gokart i i was cleaning it up so ill attach a picture of the motor from the internet separately

 

[amberwolf]

There are oil-filter heatsinks that may fit your motor directly. If they don't already have one, a round clamp (hose clamp) would be able to secure it firmly against the curve of your motor housing, as long as you find a heatsink that is very close to the diameter of your motor casing. You'll need to drill a hole (and file it square) on each side of hte motor bracket, right up against the casing curve, to allow passage of the clamp all the way around the casing.

Cyclone motor heatsinks (or other middrive motor heatsinks) are also made to do this job.

You won't be able to bend a flat heatsink to fit your round motor. If it isn't a perfectly smooth match for the curve, it won't really pull much heat out. A flat heatsink on the flat back face of the motor won't help much.

You will also want to put a fan forcing air thru the heatsink, mounted near but not at the back side of the motor, to make it truly effective. There are 24v "computer case" fans that will work fine; use the largest diameter fan you can fit (5" minimum) to move more air for the power used for less noise.

You will also want to open up the front and rear (silver) parts of your motor housing, to allow airflow thru the motor. Without that, the only part you are cooling is the magnets, not the part of the motor generating the heat (which is on the shaft), and you may still burn out the motor if it's really getting hot. So you would remove the front and rear faces of the motor, and drill the largest holes you can make in them without compromising structure. A bunch of small holes is nowhere near as effective as a few very large ones.


It's probably simpler and cheaper to replace the motor with a larger more power-capable motor that won't overheat under your loading conditions. Usually they will be longer than your existing motor, though some are just larger diameter. The MY-series of motors comes in many sizes; you need to make sure you get a brushed motor to be compatible with your controller.

If you really want to upgrade, get a brushless controller and motor instead--it's more efficient and will have less waste heat for the same power to the wheel.

 

[dfrydman]

thank you so much for your prompt and detailed response. a couple questions though

1. i looked into brushless motors and aside from the cost issue i couldnt find any brushless motors that delivered the same or close to the same am mount of power (i have no need for so much power and it will just drain my battery) like 300-400w ballpark at 24v

2. i am planning on upgrading to a 350w motor but first want to make sure i have decent cooling capabilities before i install a brand new motor. i also want to squeeze this one for what its got.

3. i am new to heat sinks and have no idea what your referring to and a quick search online didn't help much. also where would i get them.

4. what is i drill one inlet hole and one outlet hole and stick an air pump on it since the air is concetrate can i get away with just 2 holes the arent so big like 3/8 or so

 

[dfrydman]

also if i use a step down converter like this one and the fan is a 12v .33a fan what will be the curent draw on the 2 12v batteries rerunning in series (because i have a fan from an old power supply that looks like it should do the trick)

 

[amberwolf]

1. i looked into brushless motors and aside from the cost issue i couldnt find any brushless motors that delivered the same or close to the same am mount of power (i have no need for so much power and it will just drain my battery) like 300-400w ballpark at 24v

The motor doesn't control how much power you use. The controller and your throttle does. So it's up to the current limit in the controller, and your hand on the throttle for that.

The motor simply has to be designed to handle *at least* as much power as you need to move the kart around, at max.

If it can't, then it overheats as you see.

As far as finding them, there's quite a few versions of the Unite and MY series motors out there, both brushed and brushless, that are essentially bolt-on replacements for yours (except for length, usually). I'm sure there's some in the medium power range, but if there arent', there's plenty of other motors out there that would be.

But as noted, a bigger motor than you need is perfectly fine.

3. i am new to heat sinks and have no idea what your referring to and a quick search online didn't help much. also where would i get them.

Pretty simple to find with a google search "oil filter heatsink"
https://www.google.com/search?q=oil+filter+heatiink&source=lnms&tbm=isch
you just have to pick one that matches the circumference of your motor, so the curve is the same. If it does not, it will not seat against the casing, and it will not be useful as a heatsink since it won't be able to pull heat out of the casing (it will actually make the problem worse, as the air gap between heatsink and casing will prevent quick heat transfer, and no airflow will pass that casing area because the heatisnk is in the way).

Same thing for others like "cyclone heatsink" or "rc motor heatsink":
https://www.google.com/search?q=cyclone+motor+heatsink
https://www.google.com/search?q=rc+motor+heatsink
etc. Maybe even "round motor heatsink" would find stuff.

You can look around this forum itself to find examples of motor heatsinks, too, and probably RCgroups and other RC motor forums.

4. what is i drill one inlet hole and one outlet hole and stick an air pump on it since the air is concetrate can i get away with just 2 holes the arent so big like 3/8 or so

It would have to be one hell of an air pump to move much air thru a hole that size, and may use more power than your whole kart to do it, and is going to sound like a jet engine, and probably be larger than your whole motor.. Something like an EDF turbojet fan.

If you're talking about somthing like an aquarium air pump, even the largest one you can get wouldn't move all that much air. it would be better than *no* airflow thru it, but not nearly as good as you could get the way I described. The battery-powered (DC) air pumps I've seen and used are pretty basic, the big ones run on AC (wall voltage) can cannot run off a battery directly.

If you want to move a lot of air with little power and noise, you must use the largest possible holes and hte largest possible diameter fans, and also duct the air. I recommend using the fan in "pull" mode, so that it pulls air thru the motor, rather than trying to push it. And again, use the largest physically possible holes in the motor cover at each end, that dont' compromise the stuff inside the covers (bearings, brushholders, wiring, supports).

 

[amberwolf]

also if i use a step down converter like this one and the fan is a 12v .33a fan what will be the curent draw on the 2 12v batteries rerunning in series (because i have a fan from an old power supply that looks like it should do the trick)

That depends on the current from whatever step down converter you use. You say "this one" but you don't give a link to one or any information about it, so I can't help you there.

If you have to buy a converter, you might as well buy the 24v fan instead, with the highest CFM rating you can get. If it has a thermistor built into it for controlling fan speed, even better, cuz you can put it with the thermistor against the motor casing....

 

[dfrydman]

thank you so much for your help

i looked into those heat sinks you mentioned and couldn't find one that would fit my motor

i also opened up the motor and the rear plate has no chance of getting a hole drilled into it while the front plate i can drill most of it out as it only houses a bearing in the center. will only drilling holes in the front help because the shaft kind of gets in the way

i am planning on buying a 24v 400w motor (150w increase) and i would keep the same gear setup puting me at an estimated (according to the esp calculator (https://electricscooterparts.com/drivetrain-parts-selection-guide.html)) 14.5 mph and the calculator estimates that i could run it at a 1:4 ratio withg a speed of almost 18mph so in theory i wouldnt need much cooling power and could get away with a heat sink and fan, right????

 

[dfrydman]

also with regard to brushless i threw out that idea as the smallest i could find was 48v 1800w for 150$ and i would need two more batteries (50$) and a controller that can provide that power as i sawby the electric scooter parts that you could easily fry a controller that is rated less than the motor is and that was by like a 250w plus difference so after i buy all that it would come to close to 300$ and way out of my budget but thanks for the suggestion it was a much better one than mine in theory and budget allowing

 

[dfrydman]

also i just realized the the motor casing has 4 magnets and in between each magnet is like a 1/2 wid space so i coul drill like 2 or 3 on one side and another 2 or 3 and maybe some in the front piece

 

[amberwolf]

i also opened up the motor and the rear plate has no chance of getting a hole drilled into it while the front plate i can drill most of it out as it only houses a bearing in the center. will only drilling holes in the front help because the shaft kind of gets in the way

If you can set things up with ducting that sucks air out of half the front of the motor, then yes, because air will flow into the other half as you do that. Since the fan can't go directly in front of the motor you'd have to make a duct that fits behind the sprocket/chain against the motor face, and then goes to the side where the fan is, and expands outward to let the fan's entire intake surface suck aire from the motor and not from the area around the fan.

You can also try it without the fan, as it may be possible the holes, if large enough, will allow the air to flow in and out enough to help with cooling anyway (just not as much as with a fan).

i am planning on buying a 24v 400w motor (150w increase) and i would keep the same gear setup puting me at an estimated (according to the esp calculator (https://electricscooterparts.com/drivetrain-parts-selection-guide.html)) 14.5 mph and the calculator estimates that i could run it at a 1:4 ratio withg a speed of almost 18mph so in theory i wouldnt need much cooling power and could get away with a heat sink and fan, right????

Remember that changing the motor itself doesn't change the power available. It *only* changes the amoutn of power the motor is designed to handle, either because the motor is physically larger or because it has better cooling designed into it. (if the motor appears identical in size/shape to your motor, it probably is, and just has a different label on it and is not actually any more capable than your existing motor; this is common).

So, some stuff to think about before upgrading anything:

How hot does your motor get? If it is really so hot that it's smellng like burning plastic, that's probably a lot more than just 150w of extra power capacity needed--you probably need to more than double it's capability. So:

How much power does your system actually need to give you the torque and speed you need to do what you want with it?

If you want 18mph, then depending on aero it will take around 500w to do that. So you should get a motor that can do *at least* 500w continous, preferably more, so that A) it won't heat up much doing what you want with it, and B) it will let you do more with it as you discover you want to.

It will *also* require a 500w+ controller, and batteries that can handle that too. At 24v, 500w takes at least 21A. So the controller must be rated for at least that much continous current.

The batteries must be able to handle that too. If they're lead batteries, and you want them to have a long lifespan, they need to be high Ah, 20 to 40Ah, to keep the strain on them low, and to give you a long enough runtime. (at 21A, a 20Ah battery will last less than half an hour before it is half empty, probably more like 20 minutes or less, and once it is half empty, around 12v for each battery in a 24v pack, you should stop and go recharge them. If you use them below around 12v, it's harder on them and they last a lot less lifetime, so you have to replace them a lot more often. (~10v is dead empty for lead batteries).


If you gear the system to run 18mph, it won't have much startup torque, so acceleration will be low.

If you want more torque, you have to gear it for slower speeds, *or* you have to use a higher power motor, controller, and battery, by enough to do both the speed you want *and* the torque you want.

 

[amberwolf]

also i just realized the the motor casing has 4 magnets and in between each magnet is like a 1/2 wid space so i coul drill like 2 or 3 on one side and another 2 or 3 and maybe some in the front piece

I dont' recommend drilling into the magnet casing. That whole piece of steel is shaped to help the magnets do their job, and changing it's shape changes the operation of the motor. Whether it is a problem or not you won't know till you do it, and you can't undo it.

You can also weaken the glue holding the magnets to the casing in the drilling process, and if they come off they'll hit the armature while spinning and shatter, destroying the motor. (when I've had this happen, it's unrepairable).

 

[amberwolf]

also with regard to brushless i threw out that idea as the smallest i could find was 48v 1800w for 150$ and i would need two more batteries (50$) and a controller that can provide that power as i sawby the electric scooter parts that you could easily fry a controller that is rated less than the motor is

You won't fry a controller rated less than the motor.

You will fry a motor rated less than the controller.

The controller is what controls the amount of power provided to the motor. The motor does not control the amount of power the controller sends it.

(it is more complicated than that, but that's the basics, as long as the controller is correctly designed wtih current limiting to prevent overloading it, which any decent controller will be, but many really cheap, especially brushed, controllers may not be).



But you would still need a new controller, because the one you have now wont' run a brushelss motor.

 

[dfrydman]

maybe i should've said this before but i am not use a standard controller but a voltage regulator that can supply like 1000w at 24v so
upgrading my motor would not require updating y speed controller also the motor only started heat up like this recently and never smoked it just got hot to touch for more than a second and smelled faintly of burnt plastic and i assume that when i first bought the motor it wasn't like this as the more plastic the melts the more that melts (exponential growth) so i was thinking that 150w coupled with it being new and a decent cooling system would do the trick

thank you once again

 

[amberwolf]

maybe i should've said this before but i am not use a standard controller but a voltage regulator that can supply like 1000w at 24v so

Yes, you shoudl have said that. Unfortunatley it's really common for people to not tell the whole story, resulting in us giving bad advice. :/

If it is not a controller, but just a voltage regulator, it doesn't have a current limit in a way that's useful to preventing motor damage. (some adjustable power supplies do have current limiting, but they are not usually called "voltage regulators"...VRs typically only control voltage, not current).


So to correct that, this means you need to use a at least a 1000w or higher brushed motor, if you want to not have to keep buying new motors.

If you want to look up how all this stuff works, it may help you understand the dilemma you face. But essentially:

You have to use a motor that is *at least as capable* as the controller being used, if the loading allows the controller to output it's maximum power, becuase the controller is in charge of motor power--not the motor. (it's more complicated than that, but that's the basics--if the load is high enough, as in your case, the controller will output more than the motor can handle, because under the right conditions, a motor will draw nearly unlimited power, but can't use most of it so it ends up as waste heat.

If you use an under-capable motor with an over-capable controller, and then you put a load on the motor that causes the controller to supply more power than the motor was designed to handle, the motor will be damaged or destroyed. It may take time, but it will happen, just as it did to your present motor.

If your controller is capable of 1000w, it will supply that at startup from a stop every time, for however long it takes to get you to a speed where the motor spins fast enough to cause enough backflow of current to cancel some of that out.

If the motor is not designed to handle that kind of power, (or is not cooled sufficiently) it will overheat. If the motor is used at lower RPMs than it was meant for at that power level, it will still overheat even if it is rated for that power level, becuase it will still draw more power than it can handle.

One scenario for such a case, which sounds like what happened to you already:

The overheating will damage the windings, burning the enamel from them, and causing shorts inside the windings, which may either affect the speed/torque the motor can supply, or just plain burn it out by shorting across separate windings.

It will also damage the magnets if it gets hot enough, demagnetizing them a little each time, and causing the motor to spin faster with less torque for the same power it used to do slower and more torque with. So it will take more power to get the same torque, which will cause it to take longer to accelerate, which means more heat for a longer time, which then damages the windings and magnets even further, increasing the spiral of damage until the motor simply fails.



If your controller has a current limit adjustment, you can turn it down to what your motor is rated for, and this will let your motor survive. The kart will not perform like it did before, but at least your motor will survive.

If you want the same performance, but not destroy motors, you need a motor at least as capable as your controller.


Or you need sufficient cooling capacity for the existing motor to remove the 750watts (or however much) of excess heat, which is quite a lot of cooling capacity.

Some cooling is better than none...but you'd have to experiment to find out if any particular cooling scheme will work...if it's not enough, each motor used will continue to overheat....

 

[dfrydman]

this is the controller i use https://www.amazon.com/gp/product/B00K4W4FQO/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

i once tested my amperage and it was a little less than 11amps at full speed and this fits because my new 12a battery pack would run for like 45 minutes so it can be drawing that much watts because using amps x volts = watts 10.7 x 24 = 256.8 which is what my motor is rated for and if i remember correctly when i first got this motor like 3 yrs ago it didn't overheat only recently did it start overheating and when i opened it up i found one of the brushes was defective. so maybe this controller doesn't only regulate the voltage??

 

[amberwolf]

Since the information keeps changing, I don't really know what else I can tell you. I can only make assumptions about what your system does based on what you tell us, and my experience and knowledge of how these systems work.

Garbage in, Garbage out.