What Brushless Motor to Upgrade Ruckus 4WD Brushless System on 3S?

[KyleRC]

You will burn something up on big pinions (on 3s) that’s all I have to say. A smaller pinion gives you less heat-more torque....Bigger pinion gives you more heat-higher top speed.
Choose wisely experiment trial and error pinions are cheap—motors are not.

 

[KyleRC]

Unless you are geared too low of course but you would easily be able to tell.

 

[Jerry-Rigged]

Larger pinion will let your motor run cooler on a 3s battery. About 6t bigger.

Bigger pinions need more torque to turn them. More torque needs more amps to feed it. More Amps = more heat.

So bigger pinion = more heat, not less.

Maybe JP1ruckus meant that you should go bigger on the SPUR. Adding teeth to the spur will gear the car down, which takes load off the motor, which lowers heat (assuming you are not currently over-reving the motor.)

 

[Jp1ruckus]

The gear down less heat is what i understand but the guy said gear up on 3s. He said it will stop the motor running to high(rpm) to fast and thus keeping heat down.

 

[Jerry-Rigged]

Yeah, I think I understand what he is saying, but over-speeding the motor due to under gearing will normally heat the ESC before the motor - as the motor speed goes up, the ESC must switch faster, so more heat. On the motor side, you can only get to very high RPM if the load is light. Light load = lower amps, and amps make heat. The big amps come in at mid-to-low RPM and very high load - like acceleration. The taller you gear, the more time you spend in the acceleration zone, the more heat you build, and the more torque you need, which needs more amps which make more heat.

One other thought - we all have a 'comfort zone' for bashing speed. If you are pushing your car to 90%-100% on 2s to move it that speed, and it is overheating, the only thing you can do to lower amps is gear down. Here is where the 3s magic can happen - you switch from 2s to 3s, you speed goes up by almost 50%, and then you can run the same speed at around 60%-70% throttle. Lower throttle = lower amps = less heat. The big BUT, and it is a big but, is that most people will just push the car harder on 3s, so the speeds are higher, loads are higher, etc., which leads to more heat, not less... The 'magic' of volt up/gearing up with the same motor only works if you keep the overall running speed of the car the same by limiting the throttle. In reality, we don't, though, because speed is fun.

so 19 out of 20 time, if you have a heat issue, the answer is a smaller pinion, not a bigger one.