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One of the Newest Upgrades that Can be Added to an RTR or Kit is the Brushless Motor.

 

Brushless motor and electronic speed control  (ESC) offer the benefit of a more consistent power and the performance needed to go from one run to the next with very little or no maintenance at all.  Other than the fact that they cost a little more, there is no reason that the brushless system should be overlooked.

 

Speed Ratings with Brushless Motors

Unlike when using brushed motors the person using the brushless motor no longer has to consider brushes or springs.  However, there is a large variety of brushless motors, just like with the brushed variety, that are available in several different KV ratings or turns.

There is not one standard by which to measure the speed produced by a brushless motor.  Reedy and LRP use the turns to measure the speed while others choose to use the KV rating.  These terms help the user to select a motor with the best speed.

Numbers such as “10.5T” indicate the motor speed when measured in turns.  Larger number of turns on the brushless mean a slower spin of the armature or acceleration.  If the number is followed by the KV then the manufacturer rates the speed in KV.  Higher KV ratings mean a faster acceleration.   For comparison sakes, the 10.5T motor is equivalent to a 4000KV motor, within a couple of hundred KV and depending on the specifications of the manufacturer.

Hobbyists that choose to play alone rather than race may decide that they need the speed.  For a faster motor, select one with the lowest number of turns or the highest rating of KV.  This additional speed can make the driving of the vehicle more difficult and is not recommended for one’s first motor.  Those new to the RC hobby might want to consider a motor that has a lower rating as it is easier to drive and more fun initially.  Once the skills are up to it, consider getting a faster motor.

Those who choose to race may find that the motor size decision has already been made for them.  The classes of the competition normally specify the motor that can be used in the vehicle.  Off road racing running stock requires a 17.5 motor.  However, the pro-stock requires a 13.5 motor.  Modified allows motors that are 10.5 or lower.

Motors do not work on their own, however.  The hobbyist also must choose a speed control to handle the motor which is our next subject.

 

Brushless  Electronic Speed Controls (ESC)

In order to operate a brushless motor, you must have a brushless speed control.  Brushed speed controls do not work with these motors.  In addition, it is important to select the speed control (ESC) that is designed to handle the motors falling into the correct range.  The LRP SXX control is designed for motors from 5 turns and up, however the LRP controller is designed for motors that are 12.5 turns and up.  The controllers that are able to operate a larger range are also more expensive.  Using a controller that is out of the motor range can cause damage to both the motor and the controller, so be sure that you carefully select the speed control (ESC) that will work with the selected motor.

 

Speed Control Specifications

The ESC specifies the number of RPMs at which the motor operates and the vehicle speed.  This is accomplished with the throttle position on the radio transmitter.  The ESC regulates power flow from the batteries going to the motor.

The ESC is what determines if the car will go in reverse.  This is not determined by either the kit or the motor, so if reverse capability is important select an ESC that provides it.

If you plan to race, remember that most rules prohibit use of ESC that has reverse.  Some offer the capability of turning the reverse mode off.  For serious competition, choose the ESC that is designed for such use.  While these ESCs cannot perform in reverse they are able to supply more power.

Once the user gains a better understanding of ESCs, he or she should be able to make choices based on the ESCs individual features.  This includes selecting ESCs that offer low on-resistance numbers and high amp numbers.

 

Sensorless or Sensored

With the sensored system, motors include a sensor that transfers exact info to the ESC.  This provides greater precision for the speed control.  The sensored system allows the user to have the feel of a vehicle that makes an accurate response to even slight changes in speed.  Most racers prize these motors more highly, especially when looking for an edge in competition.

Sensorless speed controls and the motors they control only provide an estimate in the rotors position.  If the rotor is pictured like a clock face with a 12 o’clock position and a six o’clock position.  Without the sensor, the ESC does not know where the rotor is currently located.  On an odd occasion, pulling the transmitter trigger the speed control can mix up the signals and make the motor travel in reverse.  To correct the condition, the driver must release the trigger, let the car come to a stop and then start once again.  Generally this will result in the car moving in the direction you want.

 

Advantages of Brushless Motors and Controls

  • Better acceleration and performance
  • Maximum RPM
  • More power
  • Longer runtime
  • Higher efficiency

 

Maintenance of Brushless Motor

Since there is little or no maintenance to these motors, users simply need to blow them out on occasion using canned or compressed air.  Add some lightweight machine oil to the bearings for lubrication and the motor is ready to go.

With brushed motors, complete servicing is needed every 7 to 10 runs.  When racing, more frequent maintenance is needed in order to maintain a like new performance.  Complete service of a brushed motor requires dis-assembly of the motor, cleaning the armature and can, lubrication of both bearings located in the hood and can, recutting the commutator and deburring it.  Finally, the motor is reassembled with new springs and brushes and the brushes are broken in.

Costs

Plan to spend more initially on the brushless speed control and motor, but know that the long-term investment provides a consistent and increased performance and the maintenance costs will be less in the long term.

 

Select the Pinion Gear

The pinion gear from the motor drives the spur gear that interfaces to the transmission for turning of the tires.  Once again, the owner will find several choices.  These gears differ in the pitch and number of teeth they include.
The pinion gear determines the top speed as well as acceleration.  There is sometimes an advantage to selecting a pinion gear with more or less teeth than indicated in the manual.  To increase top end speed (for use in tracks that have large straight-aways) a pinion gear that contains a couple of extra teeth.  If you want faster acceleration for use on small tracks or those with many twists and turns, select a gear that has fewer teeth than listed in the chart.

It is important to remember that gains at the top end will be lost in acceleration and gains in acceleration are lost in top end speed.  There is no way to have both the fastest speed and acceleration.  The racer will want to juggle these options in order to design the kit with the best possible performance for his or her situation.  Choose the options that are most important to conquer the surface of the track, size and layout as well as your own style of driving.

brushless motor pinion gear selection

Most drivers choose to use the spur gear that was supplied with their RTR.  Should you wish to change this you really should know what final drive ratio you are looking for and what you hope to achieve.

Changing the spur gear has the opposite effect of changing the pinion gear. Put a spur gear on with less teeth and you get more top speed. Replace the spur with one of more teeth and you get better acceleration.

 

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