Ideal RPM Range BL-E

Hello,

Got a question which maybe some of you Brushless veterans can answer...On my Maxx, I try to gear it so that at the FASTEST part of the track I'm at FULL throttle. Thus I'm in 1st gear, large spur, tiny pinion. Yet even still my motor temps are WAY high when I finish my 5 mins. I've read elsewhere that many guys run much taller gearing and yet their temps are much lower than mine. All of a sudden I had a thought....

What if running full throttle at Max RPM for my motor/batteries is bad. What if I shouldn't be using all that RPM to spin my low gearing? What if I should have it in 2nd and turn down my EPA (or 1st with a larger pinion/smaller spur)...this would lower the motors RPM to achieve the same speed.

But there is a balance, because running taller gearing will require more power (torque), which could also cause the motor to get hotter...I guess I just can't figure it out and I wonder if anyone with experience can fill me in with their wisdom.

What really drove this home for me was that single speed conversion which locks it in 2nd, I can't imagine my truck in 2nd, it would be a beast. In 1st its one of the fastest at the track.

[coolhandcountry]

On another thread a man was experencing a simaliar problem like you. He geared his down( smaller pinion larger spur) some more and the motor got hotter. He geared it up ( Bigger pinion smaller spur) and the temp come down.

[coolhandcountry]

http://www.rc-monster.com/forum/show...=&threadid=884
Here is where the thread is at.

[Mike_D]

Yep what he said, i have the single speed and was gearing at 16/72 and 14/72 and my temps were way to hot, then mike told me to basically think backwards. I now gear 16/66 and i'm running 170 degrees tops. Most of the time now its around 160 or less. Trust me you have to think different with brushless.

[coolhandcountry]

I had my slipper to loose. It made my brushless run hot as well. I guess it lets the rpms go up to high like you said.
I glad to here it is working out for you mike d.

Originally posted by Mike_D
Yep what he said, i have the single speed and was gearing at 16/72 and 14/72 and my temps were way to hot, then mike told me to basically think backwards. I now gear 16/66 and i'm running 170 degrees tops. Most of the time now its around 160 or less. Trust me you have to think different with brushless.

I have just read the other thread...for you with the single speed, do you have your EPA turned down? Do you ever hit full throttle? I'm going to follow the advice laid out here and goose it up a bit but everything I know (or think I know) about gearing tells me this should not work.

Thanks guys. It's been very helpful.

[Mike_D]

Epa at 125%, and yes i go full throttle a lot. I know i thought the same as you, it still does not make sense to me but it works. If you don't believe me ask monster mike, thats who aided me.

[Serum]

The BL motor works like under no load, when you gear it too low. The motor can get very hot. If the motor rotates at a very high RPM, they get very, very much small pulses from the controller, which is translated into heat. And the motor gets less efficient when it hits the higher RPM range. and when it gets hotter and hotter, it gets less efficient as well.

[coolhandcountry]

I won't to far off. Thanks serum you helped me out to. I understand it better now.

[starscream]

To what end?
How do you figure out how high to gear a BL system? trial and error could end up to be an expensive venture if your not careful ;)
I am running my revo with a center diff. The lowest gear ratio I can achieve is 18.5:1 and at 14 cells the motor temps are high and the speed is low. This is quite contrary to my previous setup with the two speed transmission where the gear ratio was much lower 28.24:1 in 1st and 21.35:1 in second at 20 cells. The top speed of the two speed transmision was much higher.

My experience with my BL system has been that the higher rpm's at lower gearing is where the power, speed and safe operating temps are at. This is in comparision to the stock Revo gear ratio's of 23.85:1 in 1st and 16.54:1 in 2nd. I guess I'll have to experiment to find the sweet spot. The other issue I am experiencing with the center diff is that the drive train does not free wheel like it does with the two speed tranny. I am thinking about fabricating a clutchbell for my motor with low tension springs so that the motor can disengage from the drive train when power is no longer applied. This entails using a manual break but I believe this may also help with motor temps.

[Serum]

trial and error with a good state of mind.. Don't gear your truck to 80 mph or so..

;)

I don't understand why your centerdiff doesn't freewheel with ease. it should behave like a normal geared 18.5 to 1 ratio.. Only thing i can come up with, is that you use a metal spur?

[Dafni]

Serum, maybe with the stock revo transmission you have real freewheeling, with a owb or something?

I myself like the feel of this solid driveline, no freewheeling. If you release the throttle, it's like a faint brake. I can imagine with a center diff it's even fainter. With a oneway front shaft my truck felt (more) freewheeling off-throttle.

[Serum]

Yeah, i misunderstood.. I thought he too used a maxx transmission with his erevo..

It is all a matter of getting used to it. Some people call the smooth faint brake of a bl negative against the harder brake of the brushed motors. (when freewheeling)

[Dafni]

I heard the Plettenberg BL's have a very strong "motorbrake", off-throttle.

I prefer my BL's over the Titans/EVX.

[Serum]

The bigmaxx, it had allmost had no brake when i let go of the throttle.. ? allmost no difference in my 2 speed oneway transmission and the 1 speed shaft. Only the first turn (from 0 RPM) needs some energy.