Inside Electric Motors Motor Tuning Advice from a Pro
Words: Gary Katzer
Electric motor technology is one of those things that is constantly changing. Just when you feel like you have things figured out, someone goes and releases a new motor, brush compound, or endbell design. It can be difficult to understand your motor, how to maintain it, and how exactly to tune your motor. Troy Schroeder, owner of Fantom Racing, has provided the horsepower for many national champions in on-road, off-road, and oval classes. He recently provided his input on motor tuning, cleaning, and how to get the most out of your power plant.
Motor technology has changed quite a bit over just the last few years. As a motor builder and tuner, the challenge to stay on top of things and stay ahead of the curve must be a challenge. You have an advantage in being able to use Epic, TOP, or Yokomo-based motors. When you begin to tune a motor, what is the process you go through in deciding what brush and spring to use and, in the case of modified motors, what sort of timing to run?
Brush size and shape has changed over the number of years. From left to right, here's an example of a TOP V2 Cylindrical brush, a laydown brush, and a standup brush. Below is an example of the new Octagon long-wear brush.
Motor brush technology has really gone in a number of different directions. The Slot Machine 2 introduced the world to "laydown" brushes for stock motors; the P-94 motor introduced oversized brushes; the TOP V2 motors introduced cylindrical and angled brushes; now the Shock motors have octagon-shaped brushes. How do you determine which variation of brush is best for a particular application?
Is the cogging issue the reason laydown brushes work so very well in a stock and 19T motor but Stand-Up brushes still dominate the modified classes?
I go way back to some pretty old-school brushes. I remember things like the H-cut, diamond cut, timed brushes, and more. In more recent years, however, it seems like fewer people are actually playing with brush shapes, relying instead simply on the full face of the brush and the brush compound to create power. Is this perception true or are just as many people experimenting with brush cuts?
If you've never taken a motor apart, here's what one looks like. The different parts are the endbell (top left), can (top right), brushes (soldered to the endbell), motor springs, and the armature.
Some were initially against "rebuildable" stock motors. Some feared that cheating would increase because of how much easier it would be to get inside the motor to tinker with things. As time has gone on though, that hasn't materialized and motors are lasting longer than ever now because maintenance is so much easier. Racers can now cut their commutator on a lathe whenever it's needed. On stock motors, you can often find greater excessive wear around the slots in the commutator than what a modified motor may have. It sounds like this is directly related to the arching and the overlap you've mentioned. Would using a timed brush or shaving material off the trailing edge help to prevent this issue? And just as important, what would that do to the performance of the motor?
Some people believe that you should break in a motor with new brushes until the serrations are gone. Others believe that once the serrations are gone, the brushes should be replaced. What's a good rule of thumb to follow on this? How would you recommend someone prepare their motor before running it for the first time?
Comm drops can enhance the performance of your motor. Applying just a little on each brush can improve amp draw, RPM, and torque.
How and why would you use Comm Drops on a motor?
One of the most confusing concepts for newcomers to grasp is that when you install a "hotter" motor, you actually gear it with a smaller pinion. What are some of the other mistakes that you see people make?
When replacing the brushes, it's well known that it is more efficient to solder the brush lead to the hoods than to use the screw-on terminals. Is it better to solder the lead onto the motor's tab where the ESC wires get soldered, or to solder it onto the hood itself?
Some manufacturers have come out with motor zappers to increase the strength of the magnetic field. Does this actually make a difference on the track or is it a gimmick?
The Stock and 19-Turn classes are still extremely popular around the USA. In some parts of Japan and Asia, they have gone to a 23-turn Spec motor and 8-minute long races for sedans. Do you foresee this as a viable option that could eventually takeoff here in the USA?
The JMRCA (the governing body in Japan, similar to ROAR here in the USA) recently announced a rule change for their upcoming 2006 racing season. All sedan classes will now have the number of cells allowed in the car reduced from 6 to 4. This seemed to help out the 1/12 scale division along with oval racing here in the USA. Do you see this coming to the USA and what are your feelings on it?
What advice would you offer the person who is just starting to tinker with their motors in an effort to improve performance and extend the life of their motors?
The motor on the right has been run a number of times, while the motor on the left is brand new. The brush on the right is slightly discolored, which indicates possible over-gearing.
Maintain your motor's performance by cutting the commutator on a motor lathe. A motor lathe uses a carbide or diamond bit to skim the surface of the commutator, providing a clean and smooth surface for the brushes to ride on.
Keeping ahead of the learning curve can be challenging, but taking some time and not being afraid to experiment can pay huge dividends. Keeping your motor properly cleaned and maintained can make the difference between winning and not making the A-Main. We'd like to thank Troy Schroeder from Fantom Racing for taking time to answer our questions.
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