Spetz

Hey guys,

I know that the less turns, the less power but more rpm, and the more winds, the higher in the revrange the power will be.

My question is, a 13 turn single motor with 40,000 max rpm Vs a 27 turn single motor with 20,000 max rpm, is most of their torque going to be at the same rpm?
ie, will most of the torque on both engines be around 5000rpm?
Or is it like a ratio thing, where the 13 turn will have peak torque at 10K rpm (25% of max rpm) and the 27 turn at 5K rpm (at 25% it's maximum rpm)

All numbers are made up for arguements sake.

Any help is appreciated

Access

You can't think of electric in the same way as an ICE, with 'rev ranges' or such, the torque always starts out high and then drops as RPMs increase. By the time you hit max RPM, the torque is close to zero.

If the motors are the same size, same family, etc. The 27-turn will have more starting torque than the 13-turn. But at some point the torque of the two will cross, since torque at maximum RPM is near zero. Now if motors are different sizes or different qualities, its hard to say anything at all about torque, ie. try comparing an old traxxas stinger 20-turn to a reedy quad mag 19-turn. The quad mag has a great deal more torque, despite the similar number of turns. This is just b'cos the quad mag is superior quality.

gpm-parts.com

All electric motor have the max torque at startup. And the torque will drop when the RPM increase. For motor with the same turn a single will have the higest torque (best for eg. touring and 4wd buggy), a quard will have less torque (better of eg. 1/12). Hope this answer your questions.

Spetz

But the more winds, the higher up the peak torque will be? Or is peak torque still going to be low in the revrange?

magnat

What sort of Course were you going to be running on ???

Different motors suite different applications..

Take the Tamiya RZ and TZ motors.. Both are 23T Both offer around 500Grams of Torque...
The difference is in the delivery of the Torque and the Max RPM of each motor..

The TZ is designed for short courses with lots of corners allowing the Midrange Torque to be spread over a larger rev range..
The RZ is for courses with longer straights.. offering you alot more Torque in the Higher end giving you a higher top speed...

Access

Always, lower RPMs will have more torque. Theoretical peak torque is always going to be at 0rpm, from a locked rotor position. There is never a case where you have more torque at a higher RPM than a lower RPM, that only happens with a ICE.

But, torque in reality is rarely a limiting factor, most modern setups can get to maximum speed in 2 seconds or less, at most maybe 3 for a setup with weaker batteries. Traction (for off-road), power, and in the long term, heat - those are the limiting factors.

http://www.rctech.net/forum/electric...al-thread.html

If you read through the above thread, you'll find lots of dyno curves (which plot RPM vs. torque), but he is gearing based on peak power, not peak torque. You want your motor to be providing peak power as you accelerate out of the corner.

Now with brushed motors you do have a timing advance you can adjust, this can shift your power band up farther.

Spetz

Actually the reason I am asking is I have an FF01 and I would like a motor where low end torque is low so it doesn't wheelspin, and once it has good traction at higher speeds for the power to come in
It's a shame to hear that an engine like this can't exist

Access

For brushed you got to depend on throttle control, though lots of brushless controllers have a programmable 'punch control' feature that can be enabled to varying degrees, and then there are motors specifically designed to deliver less torque like the Novak 'L' series.

Spetz

Less torque at the expense of rpm?
I think ideally I need something with high revs and fairly low torque

Access

No, RPM is not changed with a 'L' motor or with punch control.

http://www.teamnovak.com/products/br...hts/index.html

Spetz

They are brushless though
And I think even this Light series brushless probably make decent power compared to brushed motors?

rc rock

you don't want brushless???

SAVAGEBANE

[/quote]
Now with brushed motors you do have a timing advance you can adjust, this can shift your power band up farther.
[/quote]

can anyone elaborate on this for me. i am a nitro guy but i love to play with my old rustler. My Epic intense motor has timing degrees on it from (+40)-0-(-40). the problem is, I cant tell which side is advancing the timing..... and which is retarding the timing.
What does advancing do you the performance?
Which gives more battery runtime?

Spetz

From what I gather, if you advance the timing, you get less torque, more peak rpm, less runtime and more heat

The same is true for an opposite scenario

Access

Rotate the endbell the way the motor normally spins to make the car go forward. This will advance the timing. Rotate it back to the midpoint to make it 0. You never want negative timing.

Fixed timing advance is never optimal across the entire RPM band. It will be optimal only for a narrow range of RPMand then less optimal as you go out. You will have increased torque and power in that one range at the cost of the rest of the band. The more advance, the higher the range and the more extreme the dropoff is.

ie. if you spend most of your time in the lower RPMs, set it at 0 or 10 degrees. If you want some mid-range power, 15 to 25 degrees. If you want high range power, in the 30-40 range. But generally, try to stay below 24 degrees. A lot of it is just trial and error.

0 degrees is the most efficient state of the motor, if you want best runtimes leave it there.

SAVAGEBANE

cool, thanks guys for the info. I understand now.

Spetz

Where are engines set at standard?
In particular, a Tamiya Type S motor?