Jump to content
ThunderDragonCy

Hot ESC, cool motor - what to do?

Recommended Posts

On my DF01 with GF01 wheels, i geared it appropriately, running 13.5 brushless on a tble02s. Generally it runs well, and the motor stays almost completely cool, but running on grass a couple of times the esc has thermalled quite quickly despite the motor being cool. I have moved it into the air flow to no avail. Do i need to gear down further? Different ESC? Add a fan? 

Thanks! 

Share this post


Link to post
Share on other sites

I see a TFU-01 in your future.

I had a similar setup in my TT-01: 13.5t motor, TBLE-02, tall but not ridiculous gearing.

I also found that the motor remained cool but the ESC thermalled quite quickly - it wouldn't last a full heat. However with a TFU-01 fitted it runs a full pack without cutting out.

  • Like 1
  • Thanks 1

Share this post


Link to post
Share on other sites

What gears do you have and is it run on grass? The slower the motor turns the higher the current draw and the higher the losses in the ESC. The MOSFET transistors in the TBLE02S are nothing special in terms of on-resistance so they heat up more for a given motor current draw compared to beefier ESCs. You want the motor to be running at 50-100% of it's maximum rpm most of the time you're at full throttle. If it's getting bogged down due to long gearing or terrain (hills, grass, mud) the motor current will be higher on average and things get hot. Just a minor change in gear ratio can make all the difference by both bringing up the motor rpm for a given wheel speed and increasing acceleration which makes it get to the efficient rpm range faster - it works like a square-law so for example a ~20% increase in FDR gives a ~45% reduction in heat. Grass running will require a higher FDR / shorter ratio because of the drag produced.

A fan might be able to manage the heat as-is, only way to know is to try. I wouldn't spend more than $10 retrofitting a fan. The Tamiya ESC fan hopup is almost as expensive as the ESC itself - imo that money would be better spent towards a decent 120A esc which would handle a 13.5t, aggressive gearing and grass running all day long.

  • Like 2

Share this post


Link to post
Share on other sites
17 minutes ago, nbTMM said:

money would be better spent towards a decent 120A esc which would handle a 13.5t, aggressive gearing and grass running all day long.

I'd go for the now tried and tested,10bl120 esc at under £40,  but depends on the budget.

If it's just a fan you're after,  you can get none branded ones real cheap (around £3), I'm running an extra one in the speed run car, but looking at one of these for motor cooling in the race car, 

https://wheelspinmodels.co.uk/i/316796/?gclid=Cj0KCQjwyLDpBRCxARIsAEENsrJdBA5dxgbNW9MmVAWgzws3T2Uj6NjvjfqULF330LH8xs0JmxGFy2oaAtOdEALw_wcB

  • Like 1

Share this post


Link to post
Share on other sites

I haven't had any trouble running the same combo in a 2WD truggy on grass. The gearing is over 10, not that aggressive. I worked it back from buggy race gearing based on the bigger wheels, then went a little lower geared because I had a pinion in the spares box. I've ordered the fan. I'm sure with a little more cooling it will be fine. If not I'll go with the 10BL120. I have them in a bunch of other cars. The TBLE02S in this car doesn't owe me anything and the car itself was supposed to be a cheap fixer upper. We'll see.....

  • Like 1

Share this post


Link to post
Share on other sites

I had a similar thing happen before.  Have you considered the weight of the tires?  

I once lowered the gearing according to the diameters.  But the acceleration was much slower.  It took me days to figure out the 2 problems with the weight of the tires. 

In my case, the mass was almost twice.  I was supposed to lower the gearing a lot more. 

And the 3rd factor: rotational resistance.  There is the leverage factor because a tire's weight is mostly on the tread.  Weight on outer diameter adds leverage against the rotation.  (If you have a 10kg of weight, and if you want to prevent somebody from riding your bicycle, you don't want to add it to the axle.  You want to add it to the tire.  The same 10kg was added, but added to the outer rim would make it much harder to pedal)  

So... this is what I should've done.  

1) gear down according to the diameter of tires. 

2) gear down again according to the added weight. 

3) gear down yet again because most of the weight is on the outer diameter.  

In hindsight, it might explain the pinion difference between the Hornet and the Lunchbox. (same 540 for both, unlike the Grasshopper)  Hornet's tires are 95mm in diameter.  Lunchbox's is 105mm.  That's only 10.5% increase in diameter.  But the pinion went from 18t to 10t.  That's 44% change.  I would have thought 10% larger in diameter called for a 10% lower gearing (16t).   But Tamiya gave us 10t instead, because they calculated for the weight of the tires and for the fact that tread weight is on the outside (resisting rotation).  

I think DF01 uses 86mm tires?  GF01 is 105mm, + they have spikes added.  That's greater difference than Hornet to Lunchbox.  

So... maybe going from 21t all the way down to 16t (about 25% down) might not be low enough?  Then again, 13.5t has a lot more torque than brushed motors, so the lowest gearing might work.  

 

  • Like 1

Share this post


Link to post
Share on other sites

I think a fair bit of the lunchbox low gearing was purely to make it wheelie.

I know a couple of people running 18t with a stock silver can and its fine.

I run 18t, but its not a standard motor.

Share this post


Link to post
Share on other sites

Not much can be done here. Yes you can use a shorter gearing, but you'll also lose a lot of performance. Fact is that your ESC is not up to the job at hand. If the airstream won't cool it, a fan won't help either.

Get the Hobbywing Quicrun 10BL120. It's a tried and true unit that will run well and cool. It also means that you might be able to put an even longer gearing on your car and still have a cool motor. The 10BL120 is cheap and it works, so why mess around with bandaids.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...