Brushless Electric Motors

Brushless electric motors are quickly becoming the hottest thing in speed RC boats. Their superior efficiency and lack or brushes makes them an attractive option to brushed permanent magnet motors.

Brushless electric motors are an excellent option if you are looking for a powerful and efficient motor for your speed RC model boats.

A brushless motor is technically a synchronous electric motor – a type of AC motor. The ESC (electronic speed control) not only controls the amount of juice going to the motor, but is also a DC-AC converter.

A typical Brushless Electric Motor with water cooling jacket.
brushless electric motor with cooling jacket

The DC-AC converter, when being part of the motor is known as commutator. In a conventional DC permanent magnet motor it is in the commutator where the brushes rub on the rotor, causing friction, sparks and poor connection. By the brushless design, this design flaw has been eliminated.

Benefits of brushless motors compared to brush permanent magnet motors:

  • High efficiency
  • Run cooler for the same output
  • Less noise
  • Moving parts are in rolling contact – they’re all ball bearing
  • Little wear
  • Long life
  • Less EMI (Electro-Magnetic Interference)
  • The relation between rotational speed, input voltage and torque is linear

There are a few drawbacks of brushless motors. The most important is their relatively high price compared with traditional DC motors. The cost is sure to come down over the next few years.

Remember to shop around, read reviews and ask people. You'll find the best prices on ebay or Amazon, but are they any good? I don't know. However, I think all brushless motors for hobby use are made in China these days, I don't think there necessarily is much difference between a brand name and the low-cost competition.

A Graupner first: Outboard Brushless Motors
brushless electric outboard motor

Another option is the brushless outboard motors from Graupner. The benefit with an outboard motor is that there is a lot less drilling in the hull than modifying a hull for a standard propeller shaft.

Since the DC-AC conversion takes place in the ESC you need a special speed controller for brushless motors. So forget using your old ESC.

Not all model boats would benefit from a brushless motor. Remember speed boats – hydroplanes, deep vee and tunnel hull are all good for brushless motors.

For any models that are not planing types, I see limited benefit in using brushless motors. The price advantage is still with a regular brushed motor and ESC - especially if you 'scrounge' or shop in the surplus bin. Chances are, as long as you're not chasing grams you'll be fine.

For just about all electric scale model boats, brushed motors still makes sense. If you have a PT boat, motor torpedo boat or planing launch, and you’re itching to try a brushless – then by all means, go for it.

As far as brushless and scale models, a new venue is opening up, much as it did for planes and helicopters. It is now possible to build much smaller RC boats than what used to be possible largely thanks to new technology in high-efficiency brushless motors, condensed battery sizes through LiPo-technology and new compact RC gear. Converting plastic kits to RC has also become wide-spread for the same reason.

Choosing a brushless motor

Much simplified, aim for similar wattage as a recommended brushed motor for the same type and size model you have. The wattage is measured as the rate at which energy is gobbled up by the motor on the supply side.

Comparing a brushless motor with a brush permanent magnet motor with the same wattage and load, the brushless will run faster and last longer on the same battery charge.

You may have to play with different size and pitch props to optimize performance going from a brushed to a brushless.

Most brushless electric motors on the market are designed for airplanes, helicopters, cars and trucks. These motors are all air cooled. For model boats, watch for motors with an integrated cooling jacket. Some manufacturers make you buy it separate. When you shop around, make sure you consider this extra cost.

Brushless Motor Options

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