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Author Topic: Advise on Brushless Electric Setup please.  (Read 1174 times)

Bugsy

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Advise on Brushless Electric Setup please.
« on: November 16, 2010, 02:03:43 PM »

As someone who has only ever sailed RC yachts I have very little knowledge on electrics. (as in nil) %)

I am scratch-building a 39" semi-scale model of a French Customs vessel with a hull very similar to a Perkasa.
I am aiming for scale speed (plus a bit) and planning to power it with two brushless outrunners through a single ESC.
Spec is as follows,

Two Keda outrunners 2837/18 with 830kv
Seaking 60A forward and reverse ESC
M4 shafts driving 40mm brass props

On a 7.2v NimH battery that theoretically gives me 5976 rpm - is that enough as a starting point ?
8.4 = 6972
9.6 = 7968
12  = 9960

The ESC is fan-cooled by a 5v, 7.2v max fan. If I go bigger than 7.2v I will need to separate the fan power supply to a separate 6v battery and it would seem logical, if I do this, to disarm the BEC and use a separate 6v battery to power both the receiver and the fan unit.

Is that sensible ?

Its mainly that I have to buy the batteries and would like to end up correct first time.

Thanks for any advice you can give.

Gary.


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dodgy geezer

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Re: Advise on Brushless Electric Setup please.
« Reply #1 on: January 07, 2012, 12:28:21 AM »



I am scratch-building a 39" semi-scale model of a French Customs vessel with a hull very similar to a Perkasa.
I am aiming for scale speed (plus a bit) and planning to power it with two brushless outrunners through a single ESC.



The first point to make is that you cannot power multiple brushless motors through a single (brushless) esc. Each motor MUST have its own esc.

The reason is that for a brushless motor the esc provides the switching between the coils at the correct time to make the motor turn. It is an integral part of the motor, unlike a brushed motor where the commutator provides this timing. Without its ESC a brushless motor will not operate.

If you connect two motors to one esc, each motor will have slightly different timings and need slightly different signals - but it won't get them from a single esc. What would probably happen is that one (or both) motors would not turn, and they might burn out.
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dodgy geezer

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Re: Advise on Brushless Electric Setup please.
« Reply #2 on: January 07, 2012, 12:36:54 AM »

I'm a little confused by your 'SeaKing' spec.  This one: http://www.giantcod.co.uk/hobbywing-seaking-reverse-program-brushless-p-403647.html

shows it as watercooled (and with a BEC capable of 24v). Is your version intended for a car?
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Subculture

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Re: Advise on Brushless Electric Setup please.
« Reply #3 on: January 07, 2012, 11:04:00 AM »

Assuming the batteries are up to it, that combo should be good for about 7-8 knots, assuming 1.4 pitch props.

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