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Old Mar 09, 2010, 10:23 PM
Bone Breaker
Lammergier's Avatar
Dallas , Texas, United States
Joined Oct 2002
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Question
Using sensored brushless motors

A friend of mine race rc cars. He uses sensored brushless inrunner motors. He claims that he can push the timing way high and that it produces alot more power.
He is using an inrunner unlike the outrunners that plane guys use. Why not make an outrunner motor do the same thing?
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Old Jun 15, 2010, 12:19 PM
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USA, AZ, Tucson
Joined Aug 2008
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Come across you post while searching for something else.

The main reason is that most rc car racing uses a class/size of motor. Even the brushless classes are limited in diameter, weight, etc.

Another reason is that nobody makes sensored outrunner motors. Why sensored? You can race cars with sensorless, but at low speeds and high torque (startup and accelleration) sensored motors win every time. Sensored motors know where the rotor is relative to the windings so the controller knows which winding to turn on. With sensorless, the motors act like jackhammers while trying to figure out which winding to turn on.

Advancing timing does not increase power. Increasing timing for sensored motors has the controller turn on a motor phase earlier to compensate for the inductive switching delay in the windings. The higher the rpm the higher the advance needed. Sensorless controllers already compensate by sensing the windings for when to switch. So generally the sensorless motors/controllers are more efficient over a wider range (hence more power) but have poor starting torque.
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Old Jun 15, 2010, 12:48 PM
jrb
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Edina, MN, USA
Joined Oct 1999
11,430 Posts
FYI -- the following speaks to Sensored motor timing:

Setting the Timing:
All motors are factory timed for normal rotation, unless requested otherwise. All geared motors are timed for proper rotation at the prop shaft, so if you buy a spur and pinion geared motor, all you need to do is reverse the direction at the controller. There is no need to retime the motor.

All measurements must be done unloaded and without gearboxes on 6 cells or a powersupply at 7V with all controllers, execpt for HV and H60 controllers should be done with 16 cells or 18 V. This it to keep the no load rpm low, and prevent the severe overheating that would occur at high rpm’s. Running the motor for more than 10-15 seconds unloaded can damage the motor from overheating.

To run properly, Aveox Brushless Electric motors must be advanced from the neutral position. Failure to advance the motor can damage the controller. All motors are advanced to typical settings at then factory, but it is always a good idea to check. To advance the motor’s timing, turn the rear end bell in the opposite direction that the motor shaft is running. This is the same as in a brushed motor. First, loosen all 3 set screws in the rearend bell, and turn to find the lowest no load current for the direction the motor is running. you must set the controller for the desired direction before adjusting the timing. (old motors have 4 screws, and the 1114 motor rearend bell is captured with an e-ring on the shaft, and is fixed in position with the label. Typically, advance the motor from 1.2 to 1.5 times the lowest no load current value. 1.25 typical for motors that run at partial throttle or run at very low rpm’s, or currents. 1.5 for high rpm/current competition motors

Failing to operate in the advanced position can destroy the controller. Do not make any adjustments with gearboxes or props attached to the motor. Be sure that you have not retarded the motor to the recommended no load current, but have advanced it. If the motor, controller, or large capacator get hot after a few second of running the motor unloaded, the timing may be incorrect. More power can be had (at lower efficiency) the more advanced the motor operates. Do not run the motor with retarded timing, as poor efficiency will result, and the controller and motor can be damaged due to overheating. Tighten the set screws after adjusting.
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Old Jun 15, 2010, 03:06 PM
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Canada, ON, Rockland
Joined Aug 2008
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And another reason why most are sensorLESS is that is one less component that can malfunction. As him if he ever had a motor sensor fail on him.

Brushless ESC will operate both sensored and sensorless but in sensorless mode anyways.

Sensored ESC can ONLY work with sensored motor.
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Old Jun 15, 2010, 03:10 PM
jrb
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Edina, MN, USA
Joined Oct 1999
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Sensorred will always start and run lower rpm more reliably!
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