Introduction

 

Many areas of the brushless technology are misunderstood and rumours and false information are pretty common when it comes to this issue, we’d like to shed some light into this and explain a few things about brushless technology which will possibly help you to make the right decisions in order to make this great hobby grow.


 

Situation of brushed motors today:

 

Most drivers are pretty much fed up how much maintenance is required to be competitive in electric racing. Cutting commutators and replace brushes has unfortunately become a must in competitive racing. It is not something the clubracer or novice likes to do and his wallet doesn’t like it either when motors and brushes wear out quickly! Spending in the range of €30 just for brushes for a race-weekend and continuously rebuild the motors is expensive and troublesome for racers at all levels. Additionally it keeps new customers away from entering the hobby.

 

Ever since low-turn motors are used, due to the continuous improvements in battery technology, there has been a new problem occurring. Armatures get out of balance or solder-joints become unsoldered at the commutator, due to the high rpms and the high current draw. An expensive 100€ modified motor can become “trash” within a few runs if this happens. The racer has no other choice then to buy a replacement armature or complete new motor!
 

There have been some improvements on this problem due to endbell design (V2 technology) and new brush compounds lately (LRP P-brush, etc.). These improvements reduce the maintenance of the motors, but to be competitive, there´s still the need of skimming the commutator and changing brushes regularly.

 

As stated before, one of the main reasons why all these issues have become more and more of a problem during the last 2 years are the latest developments in battery technology. Modern cells have such a low internal resistance and high capacity that average currents of over 35A are common. Spike currents in excess of 120A during acceleration are common! This just kills the brushed motors, which are fundamentally based on old-style technology and in some way are “outdated”.
 

Brushless Technology - Facts & Fictions...

Is brushless a new technology?

No, it isn’t! It was introduced in the early 90’s in airplanes/boats and is widely used there with no problems.
 

Actually the brushless technology made the electric classes grow over the nitro-classes in planes/boats in the last years.
 

The electric car market is the exact opposite, electric is shrinking and gas is growing.
 

So far, the brushless technology wasn’t promoted by the present electric car motor manufacturers and therefore wasn’t introduced to competition rc-car racing.

 

Is brushless much more expensive then brushed?

No! Initially the costs for a brushless system are only about 10-20% higher then a brushed system.
 

In the long run, the brushless system will be much cheaper since no replacement brushes, replacement armatures or comm-lathe are required by the racers!

 

Can brushed and brushless systems compete with each other?

Yes, of course! Power output and RPM are similar between the two systems.
 

In Off-Road, both systems will be equally competitive (power & runtime are no issue there due to lack of traction of the tyres!) with most likely an advantage for the brushed system due to the familiar feel and driveability for the driver.
 

In On-Road, there might be an advantage for the brushless system in efficiency and torque.

 

Will brushless motors & speed-controls be interchangeable between manufacturers?

Yes, this will be possible in a similar way as with current brushed motors, as long as the proposed rule by ROAR to IFMAR (see EFRA proposal below) will be adopted. The only exception will be, that sensored speed-controls will only be able to work with sensored motors. Sensorless speed-controls on the other hand, will work with sensored- and sensorless motors.

 

How does a brushless system work?

Simply speaking, the brushless motor is an “inside out” brushed motor with no commutator or brushes. The commutation (what is done by the commutator and the brushes in the brushed motor) is done electronically inside the speed-control. As there is no brush and no commutator, there is no wear.

 

Do brushless systems work reliable?

Yes. As seen in plane/boat applications, they’re probably even more reliable then brushed systems. Also the stuttering at low speeds, which 1st generation brushless systems had, are a thing of the past with modern brushless systems. New sensored brushless systems offer almost identical driveability as known brushed systems.

 

Do brushless motors fit into existing models?

Yes, of course! The systems, especially designed for cars by known “car system manufacturers” (like Novak or LRP) do perfectly fit into existing models. Pinions, spurs, etc. are exactly the same and can be used with brushless and brushed systems.

 

Do brushless motors wear out?

No, as there is no commutator and brush.
 

The only mechanically loaded parts in a brushless motor are the ball bearings. They need to be changed as in brushed motors.

 

Do brushless systems work with 4- to 6-cells?

Yes, they work as good as brushed systems with 4- to 6-cells.

 

Overview of several interesting facts/features of brushed and brushless systems:

* if regular competition motor is used.
** one run if armatures gets out of balance or solder becomes soft