What brushless motor

[RobsParticipant @robs46138]

Hi, is there any formula or way of deciding which size of brushless motor is suitable for a model boat? Cheers, Rob

[RobsParticipant @robs46138]

[ashley needhamParticipant @ashleyneedham69188]

Robs. I am sure there is NO formula for this. As a forum we cannot decide on ordinary motor combinations !! everyone has their own preference.

 

However. This is to some degree assisted by your intended battery, as the brushless motors are specified by rev/volt, as well as overall power.

 

I may have said this before, but you need to decide on prop size, likely revolutions and what sort of battery/voltage you will be using and make some calculations.

 

THEN look at the power developed by the motor from its specs and decide how much power you need, or can afford from the battery.

 

Good luck. As it happens I am thinking of putting a brushless in the next project and am struggling with the very same variables…

 

Ashley

 

OR decide what sort of brushed motor you would go for and match the specs to a brushless….?

 

 

[Colin BishopModerator @colinbishop34627]

I think a lot of people are jumping on the ‘brushless bandwagon’ because it is fashionable.

 

Unless you need ultimate speed and performance, brushed motors are perfectly adequate for most scale boat applications and run perfectly happily on SLA or NiMH batteries without the need fot LiPos. They don’t need special speed controllers or chargers either.

 

Colin

Edited By Colin Bishop, Website Editor on 14/02/2012 21:28:32

[RobsParticipant @robs46138]

Thanks guys, cheers, Rob

[TelstarParticipant @telstar]

Colin reading your post (above) you seem to indicate that a brushless motor requires LiPo batteries. This is not so. I have been 'playing' with brushless motors in boats not for all out speed but just to see what it's all about..

In an old waverider (vernon kit I think) I refitted with both MFA brushed motor and a geared and ungeared brushless motor running on Nicads. Props were selected to give very similar speeds. The only noticable difference was the higher efficency brushless motor drained about 15% less from the battery, but bench tests showed less electrical 'noise' with no brushes hence less chance of interferance

 

Tom

Edited By Telstar on 17/02/2012 22:44:26

[shipwrightParticipant @shipwright]

I thought that I'd use this older thread rather than start a new one. So far I have only used brushed motors with brushed ESCs. With the brushed motor the performance is well specified if you have just a few parameters (Mark Beard provided an excellent discussion on this topic see – "Method for Choosing the Right Prop and Motor" **LINK**). I am now thinking about replacing the brushed motors in one of my boats with brushless. But I am puzzled by the high values quoted for no load current Io – in a good quality brushed motor this is often a small current of a few hundred milliamps. However I have seen no load currents quoted in order of 2 amps or more for brushless. Does this imply that you must use a brushless motor at close to its maximum current rating if you want good efficiency ? If that is the case you won't get long duration sailings (with my brushed motors I often do a couple of high speed runs and then just "amble along" at low speed – I can keep going at low speed for quite a long time before the battery volts start to drop as the current will be only slightly higher than the no load current). Can anyone clarify this for me please.

Ian

[hobbiesruzParticipant @hobbiesruz]

Hi shipwright… Answer to your question… You don’t need to run brushless motors to its maximum amperage to get best efficiency… I have been testing a big range of brushless Inrunners & outrunners for my local club and most motors run at a 1/4 of its efficiency but give plenty of power for a boat… The only thing I’ve found is outrunners tend to try and torque roll at start up.. Gary

[ashley needhamParticipant @ashleyneedham69188]

Several chaps on the pond have come along and are swearing by brushless. They have fast boats (and even the ones that are not fast , are) and they do mostly make a funny noise when being motored. There are large outrunners "G32`s" ?? or something or other, Turnigy or whatever (cant remember)

I had the Seahawk out the other week (MFA850) and it was noticeably quiet compared to the others.

Ashley

[hobbiesruzParticipant @hobbiesruz]

That’s the only difference the Noise.. But it is a nice elegant wine (on mine it is as its a twin).. All my boats are aprox 2-3 ft long with 150watts of power and all get on there plane not like when they had brushed motors…

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