Electric motors

[mark69Participant @mark69]

Hi I'm looking for some info for my next build !! it will have two electric motors but ….which ones are best ? Brushless ,brushed ,or can motor all I have used in my planes but not in a boat ! could anyone please explain what the advantages and disadvantages of these types thanks ….mark

My model will be 35" and about 2.5 to 3kg ish ??

[mark69Participant @mark69]

[Kev.WParticipant @kev-w]

"My model will be 35" and about 2.5 to 3kg ish ??"

But is it a fishing boat, a torpedo boat Or is it a paddle steamer ?

The more info the better for those who can help.

[mark69Participant @mark69]

Hi Kip No its none of those its a twin moter " fast launch" so a bit of scale speed is what I'm after the plans do show a heavy construction using 1/8 ply bulkheads ,I will be useing lite ply plus the hull is a single skin so no double planking as I'm glass skinning the hull which will give double the strength for half weight !!……..mark

[harry smith 1Participant @harrysmith1]

Hi Mark69

If you use 37mm 3blade props, 3639-750kv brushless on 3S Lipo's.

If you use 30mm 2blade props B28-57-17L or B28-57-15L brushless on 3S Lipo's.

[Eric HoareParticipant @erichoare71058]

Hi Mark. My model is 2 metres long with twin engines, I tried those brushless motors and found that I could stop the props turning with one finger and the counter rotating prop hardly made any headway in the water whatsoever. I have now decided to buy two 12 volt brushed electric drill motors which have the same torque in either direction. I think I would have to reverse the polarity in one engine to make it spin anticlockwise but they should have the power and torque as the motors run at 24500 revs at 12 volts in either direction.Will keep you posted on the results..

regards Eric

Edited By Eric Hoare on 04/04/2016 14:39:45

[Dodgy Geezer 1Participant @dodgygeezer1]

Posted by Eric Hoare on 04/04/2016 14:35:42:

Hi Mark. My model is 2 metres long with twin engines, I tried those brushless motors and found that I could stop the props turning with one finger and the counter rotating prop hardly made any headway in the water whatsoever. …

That is surprising. Could you tell us what brushless motors you used? The size of motor I would use for a 6 ft boat would be capable of cutting a finger off…

[mark69Participant @mark69]

Hi Eric sorry but what made you think that was a good idea ,not something I would recommend ,no I'm asking which moter would suit my needs and after reading Dave M s threads I'm starting to look at brushed motors ,we had a bloke who put his hand in a prop ,not very pretty !!!!!!!! ……..mark

[Malcolm FraryParticipant @malcolmfrary95515]

Posted by Eric Hoare on 04/04/2016 14:35:42:

Hi Mark. My model is 2 metres long with twin engines, I tried those brushless motors and found that I could stop the props turning with one finger and the counter rotating prop hardly made any headway in the water whatsoever. I have now decided to buy two 12 volt brushed electric drill motors which have the same torque in either direction. I think I would have to reverse the polarity in one engine to make it spin anticlockwise but they should have the power and torque as the motors run at 24500 revs at 12 volts in either direction.Will keep you posted on the results..

regards Eric

Edited By Eric Hoare on 04/04/2016 14:39:45

You only get one set of fingers, using them as a torque meter with a prop is not a good idea.

Reversing the connections of a DC motor is the accepted way of getting them to turn the opposite way, as opposed to brushless where the order in which pulses of current is applied to the coils is changed. Is the 24500RPM loaded or unloaded? How much current do they take loaded? Many drill motors, used away from a drill, are only good for seeing how fast a battery can be drained.

[mark69Participant @mark69]

Hi I'm not sure if this motor I have would be suitable for my boat but it's been robbed from one of my planes

Himax C3516/1130 with a multiplex bl54 ESC if this is any good then I've saved myself a few quid!! "Which is nice "

…….mark

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