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Dec 03, 2019, 08:21 PM
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Question

help me understand


so, local track races 13.5 turn and 17.5 turn motors in 1/10 scale classes. the question of how to set motor timing was raised... now, i'll be honest, when it comes to timing im not too sure, but i have a fairly good grasp of motor mechanics. but when i asked some questions, these were the responses- and im having a very hard time understanding- maybe im not on his level, maybe some of you are and can help me out.

Just a heads up, on todays motors it's not about AMP draw anymore. It's about motor noise. Each sensor board and rotor combo has their own sweet spot (that's why you'll see many boards off the mark from can to actual timing).
By ear or by analyzer, set it to the lowest noise because todays rotors are less stressed to heat as they were in the past. So you would try to keep the motor around 6 ish amp draw regardless of noise (motor rotational friction) due to heat and delamination.
These motors now are leap years ahead of their former variations. Rotor heat stress is deflected greatly, timing has been increased, coil strength increased as well as rotor gauss strength.

Mid timing with low noise will make a much more efficient motor.

As for the efficiency question, electric motors have what is called "stall speed settings" they are at each end of the current draw that is increased and decreased by can timing adjustment.
Each "stall" is a point past electric draw efficiency.
Each motor has what is called low end noise and high end noise. Low end can lead to stall at a much faster rate, electricity doesn't flow 100% all of the time it has gaps, these gaps cause "noise" and this translates as electrical motor friction. This friction has two paths both leading to stall. Again low end stall, high end stall.
In racing friction plays two roles, good friction is with traction (to a point) and bad friction is in rotational mass.
Sufficient amp draw with low motor noise = an efficient motor setting do to less motor friction without stall.


FYI, stall speed may also mean the torque load that causes the output rotational speed of the motor to become zero.


i cant even get started with this, and naturally the topic turned into me trolling him..... but can anyone give me some insight onto what this means?
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Dec 03, 2019, 11:02 PM
If it flies, I can crash it.
rocketsled666's Avatar
I'm not afraid to say I have no idea what any of this means. I've never heard of "Stall Speed Settings". Neither has the Internet, at least that I could see. The only thing I could find that related to electric motors was specific to model railroading and how to get a model train to start moving slowly, in a scale like way, and if I understood correctly it's a function of the control power supply, not the motor in the train.

I have to say that the text you quoted reads like someone who doesn't really understand what they're talking about is trying to sound like they know what they're talking about.

The motor's stall speed is always zero RPM, that's the definition of "Stall". And when an electric motor is stalled, the current flow is continual and governed only by the winding resistance and applied voltage, the motor timing doesn't matter because the motor isn't commutating when stalled, and timing is adjusting the commutation "phase", when the winding is energized relative to where it is in relation to the magnet. The motor always produces its maximum torque when stalled. So there is a term called "Stall Torque". But it's measured when the motor is not turning at all. If it's still turning, even just a little, it's not stalled.
Dec 04, 2019, 02:05 AM
Registered User
Maybe he’s talking about timing. Not talked about much related to power output and wonder why
http://site.petitrc.com/Tech/RCCA_MotorTimingExplained/
Dec 04, 2019, 07:30 AM
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Thread OP
he is talking about timing, but setting the sweet spot based on "Noise"? isn't the noise we hear from the motor just a by-product of the switching frequency of the esc? if that is the case, i'm not sure changing the motor can timing would do anything other than change the KV- that still wont change the switching frequency, and thats the audible sound you hear.
Dec 04, 2019, 08:15 PM
If it flies, I can crash it.
rocketsled666's Avatar
Contact arcing is going to be effected by timing. But suggesting the timing is optimal when the arcing is minimized isn't correct. What's optimal depends on how exactly you're using the motor (otherwise, why would motors have adjustable timing? They'd all just be manufactured exactly the same with the timing already set to "optimal").
Dec 07, 2019, 12:31 AM
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vollrathd's Avatar

Brush type motors?


Are these brush type motors? If so, I did a lot of timing tests on my old collection of Astroflight brush type motors in the 1980's to 1990's. And, found that the maximum efficiency at full load (With a propeller load) occurred when the brush arcing was at a minimum. As for maximum power, advancing the brush timing resulted in a very steep increase in the current pulled by the motor while under load.

On those brush type Astro motors, just reversing the motor wires for reverse rotation REQUIRED retiming the motor brushes. If that retiming was not done, the much higher current pulled by the motor, even with no load could burn it up.
Dec 09, 2019, 09:52 AM
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wparsons's Avatar
Quote:
Originally Posted by jkrych
he is talking about timing, but setting the sweet spot based on "Noise"? isn't the noise we hear from the motor just a by-product of the switching frequency of the esc? if that is the case, i'm not sure changing the motor can timing would do anything other than change the KV- that still wont change the switching frequency, and thats the audible sound you hear.
It doesn't really change the kv, but it can effect power and rpm output. The timing alters how far ahead, or behind, the switching happens in relation to the rotor position. Switch too soon and it'll stall the rotation slightly, too late and it never really accelerates the rotor as much as it should.

I would suspect the "noise" is electric feedback more than audible noise, but not sure.

Quote:
Originally Posted by rocketsled666
Contact arcing is going to be effected by timing. But suggesting the timing is optimal when the arcing is minimized isn't correct. What's optimal depends on how exactly you're using the motor (otherwise, why would motors have adjustable timing? They'd all just be manufactured exactly the same with the timing already set to "optimal").
No contact arcing on brushless motors

Quote:
Originally Posted by vollrathd
Are these brush type motors? If so, I did a lot of timing tests on my old collection of Astroflight brush type motors in the 1980's to 1990's. And, found that the maximum efficiency at full load (With a propeller load) occurred when the brush arcing was at a minimum. As for maximum power, advancing the brush timing resulted in a very steep increase in the current pulled by the motor while under load.

On those brush type Astro motors, just reversing the motor wires for reverse rotation REQUIRED retiming the motor brushes. If that retiming was not done, the much higher current pulled by the motor, even with no load could burn it up.
Brushless for sure, it mentions sensor boards which don't exist for brushed motors.
Dec 09, 2019, 09:30 PM
If it flies, I can crash it.
rocketsled666's Avatar
Quote:
No contact arcing on brushless motors
We were talking about brushed I thought. That's what I was talking about, anyway.
Dec 15, 2019, 04:02 PM
Registered User
If the question is about 13.5 and 17.5 wind motors, those are brushless.
Brushed motors in that low wind count are insane.


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