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Old 11-29-2011, 09:04 PM   #1
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Default Brushless Motor Torque Effect

Got bored. Tested the torque effect of brushless motors. There is significant torque effect (though I've read many who say there is negligible torque effect from brushless motors).

+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.


13.5T motor
Sakura Zero - +75grams
Tamiya TA05 - +60grams

I guess even more (I hear 150grams) with modified motors.

Just food for thought.
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Old 11-29-2011, 09:10 PM   #2
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Could you try that test without the wheels ?

More power could be causing more gyro effect on wheel speed ?

Just curious.
Nice idea.

edit:
Might be more accurate without a pinion attached, to remove all driveline speed difference.
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Last edited by RedBullFiXX; 11-29-2011 at 09:17 PM. Reason: pinion
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Old 11-29-2011, 09:25 PM   #3
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I'm afraid the motor might explode without a pinion

Great idea on removing the wheels. I removed it. Less effect now, maybe 10grms. But when holding in my hands, balanced in middle, it will noticeably dip to the rear upon acceleration even without tires.

Can someone test side to side torque effect with a shaft drive like a TB03? Curious why my friends tell me a shaft drive does not handle well taking a left (or is it right) corner due to torque effect.

Thanks.
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Last edited by rccartips; 11-29-2011 at 09:37 PM.
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Old 11-29-2011, 09:35 PM   #4
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Uhm, yeah, like RedBull said; please disconnect the driveline.
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Old 11-29-2011, 09:39 PM   #5
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Should also try same tests with a brushed motor...
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Old 11-29-2011, 09:41 PM   #6
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Quote:
Originally Posted by TryHard View Post
Should also try same tests with a brushed motor...
LOL
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Old 11-29-2011, 09:50 PM   #7
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I Googled and found this:

http://www.welltall.com/ymc/discovery/car/wt_xfer.html
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Old 11-29-2011, 09:52 PM   #8
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Hi, why would we want to disconnect the drivetrain?

My understanding is the motor shaft (however light it is versus a brushed armature), will meet a strong resistance from pinion/spur/drivetrain/tire/road. And that resistance will create an opposite torque effect on the motor can (connected to the motor mount/chassis/suspension/tire/road).

I would expect a brushed motor to have a less effect (given brushless are more powerful). But too lazy to test that.
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Old 11-29-2011, 09:56 PM   #9
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Quote:
Originally Posted by rccartips View Post
I'm afraid the motor might explode without a pinion

Great idea on removing the wheels. I removed it. Less effect now, maybe 10grms. But when holding in my hands, balanced in middle, it will noticeably dip to the rear upon acceleration even without tires.

Can someone test side to side torque effect with a shaft drive like a TB03? Curious why my friends tell me a shaft drive does not handle well taking a left (or is it right) corner due to torque effect.

Thanks.
Would be more comparable with a 21.5, 13.5 spins much faster than a silvercan.
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Old 11-29-2011, 09:58 PM   #10
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Most of that torque effect is from tyres and driveline as others have said.

I am still racing a FT TC4 and it suffers no torque effects which can be seen on track with brushless motors.

There is a torque produced by the motor but the shaft is spining in the opposite direction and also produces an apposing torque and the on track effect is not noticeable. In theory with certain gearing this could be cancled to zero. With brushed motors there was a slight torque effect with this car that was noticeable on track.

The torque effect from a belt drive car drive line can improve rear traction slightly out of corners by aiding wait transfer but again this difference is very small and barely noticeable and the less resistance shaft drive drive line more than makes up for this.
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Old 11-29-2011, 10:21 PM   #11
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Thanks for the ideas guys.

I think I need to get 4 scales, put each suspension arm on a scale. Then see the effect of throttle acceleration on a belt vs shaft drive on each corner of the car's suspension.

I have the scales, but no shaft. Can someone with a shaft drive do the test and post results? Hehe.
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Old 11-30-2011, 12:14 AM   #12
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Quote:
Originally Posted by rccartips View Post
Thanks for the ideas guys.

I think I need to get 4 scales, put each suspension arm on a scale. Then see the effect of throttle acceleration on a belt vs shaft drive on each corner of the car's suspension.

I have the scales, but no shaft. Can someone with a shaft drive do the test and post results? Hehe.
Great idea on checking the torque effect. Lets do it sunday, will bring my Evo5 with a BL 13.5 motor so bring your scales too.
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Old 11-30-2011, 03:26 AM   #13
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I think they say you get less torque effect with brushless as the rotating part of the motor is a lot smaller in comparison with the old brushed motors.

You say that the weight has a bias towards the rear upon acceleration, but the motor can is actually trying to rotate the other way.
So the weight transfer your seeing is what you expect to see for any vehicle under acceleration. If anything, the motor torque is actually reducing the rearward weight transfer.

Shaft drive might show completely different results.

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Old 11-30-2011, 10:45 AM   #14
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Quote:
Originally Posted by Skiddins View Post
If anything, the motor torque is actually reducing the rearward weight transfer.
Skiddins
Absolutely. Mid-motor 2wd buggies run an extra idler gear in the transmission to flip the motor over to get more weight transfer to the rear under acceleration.

What you're seeing in the video is mostly from the wheels and tyres.

With the wheels removed, its from the drivetrain, with some of it cancelled out by the rotor.

An interesting experiment (once the wheels are off), as it shows that even though the drivetrain is going a lot slower than the rotor (due to the gear ratio), the fact its heavier and that the diffs have a large diameter mean the drivetrain creates a bigger force than the rotor does.
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Old 11-30-2011, 10:55 AM   #15
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Quote:
Originally Posted by Skiddins View Post
If anything, the motor torque is actually reducing the rearward weight transfer.
+1

it's mostly from the tires, and to a lesser extent the spool and diffs.
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