same motors, different kv

[Logan's_Rcs]

Hello everyone,

I am currently in the process of building an insanely over powered big rock. At first I bought a tp 4050 2830kv, and running on 4s it would overheat very fast. It was a D wind and the max amp draw was about 294.

I then saw a tp 4050 2100kv in a y wind varient and its max amps is 153 or so. If I ran both of these motors on 4s would the 2100 run cooler or about the same?

Thank you!

 

[LibertyMKiii]

The 2100 would be slower.... After gearing up it to match the same speed it would pull more amps and run the same temps.

 

[dure16]

The 2100 would be slower.... After gearing up it to match the same speed it would pull more amps and run the same temps.

The 12K RPM decrease wouldn’t help with temps?

 

[LibertyMKiii]

The 12K RPM decrease wouldn’t help with temps?

If you leave all elese equal then yes, but if you gear up to gain the speed back to match the other motor then the heat/temps and amp draw will equal out

 

[Logan's_Rcs]

If you leave all elese equal then yes, but if you gear up to gain the speed back to match the other motor then the heat/temps and amp draw will equal out

So what would you recommend? Im trying for 60-65 mph running 4s with good temps

 

[LibertyMKiii]

So what would you recommend? Im trying for 60-65 mph running 4s with good temps

I would increase your pinion gear tooth count to get more speed.
Look at a gearing calculator for RC cars for just how much to gear up. I'd recommend stopping around 60 mph as the tires won't handle much more as they turn into pizza cutters.

 

[Logan's_Rcs]

I would increase your pinion gear tooth count to get more speed.
Look at a gearing calculator for RC cars for just how much to gear up. I'd recommend stopping around 60 mph as the tires won't handle much more as they turn into pizza cutters.

I have tried those, but i cant find out what the rollout of the car is. Not sure how to calculate it. But also if I gear up the motor will continually get hotter, and i would like to avoid that. Im gine with buying another motor, just not sure what to get. Maybe a lower kv runnin on a smaller 6s pack to help lower amp draw (heat) ?

 

[LibertyMKiii]

I would experiment with the 2100kv more. It may get you there with decent heat output. I really think 6s is going to make that rig heavy and not handle well.

Ideally, you will need a heatsink and fan on any motor running up to around 65mph. My Kraton 6s did 61 mph on the stock motor and ran cool enough with a heatsink and fan on it on 6s. (the 6s motors are 1915 kv on a motor tester despite their being called 2050kv)

No matter how many cells you run there is a need for wattage to make that power to reach 65mph and something like 5-10% of the watts is translated to heat generation.

FYI examples of 4s vs 6s
The imaginary value of 2,500 watts is required to run 65 mph used to help visualize the math.

4s setup - 2500 watts = 16v * 156a
6s setup - 2500 watts = 24v * 104a

Watts convert to hp around 746 watts = 1 hp.

 

[Logan's_Rcs]

I would experiment with the 2100kv more. It may get you there with decent heat output. I really think 6s is going to make that rig heavy and not handle well.

Ideally, you will need a heatsink and fan on any motor running up to around 65mph. My Kraton 6s did 61 mph on the stock motor and ran cool enough with a heatsink and fan on it on 6s. (the 6s motors are 1915 kv on a motor tester despite their being called 2050kv)

No matter how many cells you run there is a need for wattage to make that power to reach 65mph and something like 5-10% of the watts is translated to heat generation.

FYI examples of 4s vs 6s
The imaginary value of 2,500 watts is required to run 65 mph used to help visualize the math.

4s setup - 2500 watts = 16v * 156a
6s setup - 2500 watts = 24v * 104a

Watts convert to hp around 746 watts = 1 hp.

I don't have the 2100 though, i was looking at getting it as a replacement for the 2830. I know they are the same size and theoretically should be drawing the same amount of amps at speed, but the 2100kv is a y wind and the 2830 is a D wind. And i believe d winds draw more amps in general so i thought that would make the 2100 more efficient. Also for reference I tested an old castle 1515 2200kv and it ran cooler than the 2830. I know they are different brands, but it being smaller and having to be geared up i thought it would run as hot or hotter.

 

[dure16]

I’d bet the 2100kv and a 23T pinion solves your problems.

 

[Logan's_Rcs]

Another point i would like to add is that I tried a 1730kv 4060 y wind in the big rock running 5s and It got to 180 degrees after 5 min of running in grass with a 24 tooth pinion. I calculated the amp draw out and that would be drawing about 163 amps. Now with the 4050 2100kv it would be drawing around 158 amps, and that doesn't seem like much of a difference especially if i want cooler temps. At this point im really stuck.
Any ideas?

 

[Moirae]

Another point i would like to add is that I tried a 1730kv 4060 y wind in the big rock running 5s and It got to 180 degrees after 5 min of running in grass with a 24 tooth pinion. I calculated the amp draw out and that would be drawing about 163 amps. Now with the 4050 2100kv it would be drawing around 158 amps, and that doesn't seem like much of a difference especially if i want cooler temps. At this point im really stuck.
Any ideas?

You hit 180f with fans?

 

[Logan's_Rcs]

You hit 180f with fans?

Not with fans, but since the 1730 is a 4092 I thought it would be able to handle that...

 

[Moirae]

Not with fans, but since the 1730 is a 4092 I thought it would be able to handle that...

You need some fans bro or you will be stuck with very small pinion sizes trying to combat heat. Aluminum frame 40mm fans your best bet. Like these https://a.co/d/hk5Dkrl will make your life so much easier