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Old 09-06-2008, 07:34 PM   #1
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Default Brushless motor gearing

I'm wondering if someone can give me a rundown on how to gear brushless motors.

I'm running a B44 with an LRP 13.5, Speed passion GT Speedy and Br00d IB4200 packs.

At a race meeting last weekend, the first heat I had the car geared at 28/84. It was a little slower than most of the other cars but not too bad, still qualified 5th in the round. Brought the car off at the end, motor was only slightly warm. I thought "No big deal, I'll just gear up a few teeth". So I geared at 30/84 and went out for the next round. Car was even slower!!!! I didnít change a thing, pack was fully charged. I was getting overtaken down the straight and couldnít clear any jumps, I could hold full throttle around nearly the whole track. Brought the car off and the motor was stone cold. I think I qualified 18th in that round. It was a 2 day event and the Sunday was washed out so wasn't able to do any more experimentation with gearing.

So Iím completely stumped. I've only gotten back into electric racing in the last few months after a 2 year break, And only went brushless a few weeks ago. So Iím not really up to speed on the brushless side of things.

Any help or advice is appreciated.
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Old 09-06-2008, 07:39 PM   #2
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Default AE.......................IS THE KILLER OF ALL! B4 & B44..

Try going down from your first pinion you had in their! 28 go to a 25 maybe even lower!
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Old 09-06-2008, 07:51 PM   #3
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Originally Posted by losidriver70 View Post
Try going down from your first pinion you had in their! 28 go to a 25 maybe even lower!
Thanks, I'll give that a go.

So with brushless motors, if the car if the car feels as though it's undergeared.... gear down?
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Old 09-06-2008, 08:46 PM   #4
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Thumbs up AE.......................IS THE KILLER OF ALL! B4 & B44.. Both are Brushless! $

Might go up to 36! gear brushless motors up!.............

In my B4 i run 28/78.....13.5............

In my b44 in 19/84 6.5 motor...........

I had my b4 geared 81/28 and it felt really smooth no bottom end and motor was cold.........
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Old 09-07-2008, 07:23 PM   #5
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Default Brushless Gearing Guide

Quote:
Originally Posted by Nehpets View Post
I'm wondering if someone can give me a rundown on how to gear brushless motors.

I'm running a B44 with an LRP 13.5, Speed passion GT Speedy and Br00d IB4200 packs.....

Any help or advice is appreciated.
Check the pic out for a good guide...

The B44 has an internal gear ratio of 2.5:1, so with your 13.5 brushless the manufacturers say you should be running a Final Drive Ratio (FDR) of around 7. If you run the 84t spur then you should use the 30t pinion, maybe down to a 28 if the temps are too high (84/30*2.5=7 FDR).

Both my brother and myself have just started with 13.5 LRP/Novak Brushless Systems on offroaders and we found we had to gear a little lower. Factory reccomends 7, but we have been at 7.4 or 7.6. That would mean your 84/28 or 84/27 might be the best option.

Ben
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Old 09-08-2008, 05:35 AM   #6
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Check the pic out for a good guide...

The B44 has an internal gear ratio of 2.5:1, so with your 13.5 brushless the manufacturers say you should be running a Final Drive Ratio (FDR) of around 7. If you run the 84t spur then you should use the 30t pinion, maybe down to a 28 if the temps are too high (84/30*2.5=7 FDR).

Both my brother and myself have just started with 13.5 LRP/Novak Brushless Systems on offroaders and we found we had to gear a little lower. Factory reccomends 7, but we have been at 7.4 or 7.6. That would mean your 84/28 or 84/27 might be the best option.

Ben

Thanks Ben,

The problem is though I don't get how gearing up could make the car slower in the first place.

As I said, I was running a 28/84 combo. Car had decent speed, a little on the slow side, but my packs have seen better days, while still only slighly warm. So I gear up and even it goes even slower and runs even colder .

Oh well I'll gear down to 27/84 combo and see if it picks up some speed.

Thanks for your help dudes

Cheers
Stephen
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Old 09-09-2008, 06:56 PM   #7
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Originally Posted by Nehpets View Post
Thanks Ben,

The problem is though I don't get how gearing up could make the car slower in the first place.

As I said, I was running a 28/84 combo. Car had decent speed, a little on the slow side, but my packs have seen better days, while still only slighly warm. So I gear up and even it goes even slower and runs even colder .

Oh well I'll gear down to 27/84 combo and see if it picks up some speed.

Thanks for your help dudes

Cheers
Stephen
Stephen, Brushless combo's can be a fickle beast. I bought all new batteries to go with my brushless system so i could take them out of the equation when it comes to performance.

As I said, I use the equivalent of 84/28 with new Intellect 3800's and the temps are good. But I would not go any lower as you would start to lose the efficiency in the motor.

Ben
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Old 09-10-2008, 02:55 AM   #8
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Stephen,

Another option to look at is the size of your spur gear, Particularly as 17.5 will be the Brushless stock equivalent Challenge Cup next year.
A lot of drivers are running smaller spur gears with smaller pinions to arrive at the same FDR.
It's something you'll have to play with for a while.
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