Comparing brushless / brushed motors

At last, the big question. Well, it's time to choose your side: either laugh or cry since it is almost impossible to compare these two motor technologies and sort them in a table. Several reasons to this:

Time: just like it happened with brushed motors, brushless motors performance (and controllers) gets better as technology evolves. As an example with brushed motors, the famous pink Acto-Power of the Dyna Storm is rated 14T as of 1992: a 23T SuperStock released 10 years later has about the same performance. The same applies to brushless systems, even accelerated since evolutions in electronic/computer technologies are much faster.

Quality and motor/controller setup: an excellent 23T brushed motor can outperform 19T or even 17T brushed motors of lower quality. This is due to the level of quality of the different motor elements and the timing. With brushless motors (and controllers), many aspects also influence the final motor performance (timing, number of poles, winding etc).

Operating mode: at "equivalent" performance, a brushless motor provides (much) more torque than a brushed motor, whatever revs are high or low. As a consequence, you can run higher geared (more teeth on the motor pinion) when going from a brushed motor to an "equivalently" powerful brushless motor (it is even recommended). The result is the model gets both the same torque amount at low revs (at least: generally, it gets more) and a greater top speed.

There are other aspects in the way to compromise any performance comparison between brushed and brushless motors. Some examples:

• M-03 chassis: performance is the same running either a Sport Tuned motor or an Hobbywing EZ-Run 13T combo (20T motor pinion).
• DT-02 chassis: very close performance between an Hobbywing EZ-Run 13T and the SuperStock BZ motor, whereas the Sport Tuned motor performance is significantly lower (17T motor pinion for all motors).
• DF-02 chassis: very close performance between an Hobbywing EZ-Run 9T and a SuperStock BZ motor.

So, depending on the chassis type, an Hobbywing EZ-Run 13T is the "equivalent" of a Sport Tuned (27T with timing) or directly compares to the SuperStock BZ (23T with timing). When you know that the performance difference between a Sport Tuned and a SuperStock can be seen from the first millimeters of the throttle trigger course...

Another example with Tamiya 54132 TBLM-01 12T instruction manual:

"Equal to 23T brushed motors", that is a SuperStock motor. Strange, the 3160rpm/V (Kv) of this motor are lower than the 3300rpm/V (Kv) claimed by the Hobbywing EZ-Run 13T motor. Here, the difference may come from the motor rotor size: the Hobbywing has a 380 sized rotor wrapped into a 540 sized cage, so performances are potentially lower, even though I do not know Tamiya motor rotor size. Anyway, figures don't say it all and you'd better consider there are no "equivalence" between brushed and brushless motors.

Anyway, there has to be some sort of "equivalence" to be set, especially for official racing. However, better than "equivalences", they should be considered for what they truly are: the replacement of the ancient brushed categories with new brushless ones. Some people consider there is a possible direct comparison between brushed motors and sensored without timing brushless motors: the T value is to be multiplied by a factor of 2 to get the brushed T equivalent. For example, a 5.5T brushless motor would be the equivalent to an 11T brushed motor. Well, this is theory and purely informative: during the last 10 years, I highly doubt any manufacturer spent a dime to improve brushed motors performance. So, at best, the comparison is between a modern motor and an "old fart" from year 2000.

In short, here is what would be such an equivalence (if there is such a thing):

More about categories:

Standard: 27T brushed motor without timing with closed endbell (example: Mabuchi 540). The Standard category is typically for beginners. At the time, there was a difference between "standard" and "modified" motors like the Sport Tuned (27T with timing closed endbell) or any other 27T motor with timing (closed endbell or rebuildable).

Stock: 23T brushed motor with or without timing, rebuildable or closed endbell (example: SuperStock BZ, RZ, TZ). This category replaced the "modified": it is often raced at club level.

Open: free, no motor limit (well, there are rules to avoid Saturn V reactors). Motors can go as low as 4.5T ("equivalent" of a 9T brushed motor).

Sensored brushless motor limits per category are somewhat confusing because they are different from one federation to another. The 17.5T is meant to be the standard category but it is also called "Stock", and you sometimes can find the 13.5T too. Anyway, if you race, you know, if you don't there's no problem then .

Conclusion

Many technical aspects of motors and controllers were not covered, or basically covered sometimes: this is a deliberate choice to keep this article both complete and easy to understand.

The brushed / brushless comparison table is purely informative: don't consider it as an absolute reference because the motor technologies are way too different for any true direct match. As for the "categories", motor limits are dictated by federations: they are not meant to represent any kind of "equivalence".

One more question that wasn't answered yet: what motor for my chassis?

The best answer would be this one: the one the driver's fingers can deal with. Other important aspects to consider: what the chassis can handle, the usable power the track layout allows, etc... The most important is always to have fun without ruining your model because of an exaggerated power plant for the chassis/driver's skills. On the opposite, never forget a TT-01 or M-Chassis race can provide tons of fun with just the box silver can and ball bearings on a winding track.

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