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RC Cars -> RC Tips -> RC Electric Motor Guide

Making Your R/C Electric Motor Faster

Update 2009: List of brushless motors approved by IFMAR.

Here are tips to help get the most speed out of your brushed stock or modified motors. Let us start of with getting the most speed out of the stock Mabuchi 540 RS motor.

Entry level kits usually come with the Mabuchi 540 RS or the Johnson motor. These are the "stock" and "closed end bell" type design. You cannot adjust the timing nor change the brushes to gain more speed.  
The best way to gain power from these motors is to properly break-in the motor brushes and the bronze bushings. One quick method to break-in the brushes is by using the "water dipping" method. Simply dip the motor in a jar of water, then attached a 3 volt battery supply to run the submerged motor.
You can make a 3-volt battery pack by putting two 1.5-volt batteries in series. DO NOT use a battery charger or electronic speed control (ESC) as a power source for the submerged motor. You might damage your charger or ESC.

This "water dipping" method will also break-in the bronze bushings, which will make the armature rotation smoother, giving you more rpms and power. Let the motor dry out, and put 1 or 2 drops of lightweight oil on the bushings. Now your motor should be 20% better than before.

Hot Tip: Serious racers in the stock motor class usually break-in several of these stock motors. They then test for power by using a dynamometer. The best motors are then used for racing. This is the reason why some stock motors seem to be faster than others.

Modified Motors

It is easier to get more speed out of modified motors, primarily because you can change the brushes and advance the timing.

With modified motors, you can disassemble the entire motor. You can "true" the commutator to make it as round as possible and remove the carbon deposits left by arcing and the motor brush.

The washers are used to align the armature properly with the magnets and magnetic field inside the motor can. Washers prevent the armature from moving back and forth inside the can, which robs the motor of power. With the proper use of washer, you can gain power and speed advantage over your competition.

Brushes play an important role in providing maximum power. The composition (e.g. silver, copper content) and the brush "cut" vary. Also there are "hard" and "soft" brushes.

Hard brush - More power, more commutator wear.
Soft brush - Less power, less commutator wear.

Full brush - More power, more torque, less rpms.
Cut brush - Less power, less torque, more rpms.

Springs are used in tandem with the correct motor brush. In general:

Hard springs - More tension, more amp draw, more torque, less rpm. For off-road and 4wd touring cars.
Soft springs - Less tension, less amp draw, less torque, more rpm. For 1/12 on-road pan cars.

Warning: Using springs that are too soft will cause the brush to bounce around, causing excessive arcing, and premature commutator wear.

Adjusting the motor timing will have a significant impact on performance. In general:

More timing - More rpms, less torque.
Less timing - Less rpms, more torque.

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