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Author Topic: Two Emax BL4030's  (Read 1098 times)


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Two Emax BL4030's
« on: November 23, 2015, 08:21:30 AM »

I am about to build a 1/12 Severn Lifeboat and I will run it on two Emax BL 4030 motors.
I am sure this is a well used set up and I have several questions that occur to me.

1.   Does anyone know a link to a wiring diagram?

2.  I was thinking I might use one big speed controller to control both motors. Is this an ok idea or is it better to use one controller for each motor? It seems desirable to me that both motors are running on exactly the same "pulses".

3.  I don't know what fuses will be required but what type of fuses are used? On my other boat I can get away with using automotive fuses but they get hard to find over 40 amps. When higher fuse ratings should be used what do people generally use?

Thanks in advance


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Re: Two Emax BL4030's
« Reply #1 on: November 23, 2015, 09:18:54 AM »

It has been reported that some bloke somewhere has managed to get two brushless motors running from the same ESC. I would venture that this is very lucky, as normally the ESC is almost an integral part of the motor i.e. you need one for each motor. It certainly wouldn't work with a sensor-equipped motor.
Personally I've never been inclined to fit more than one motor to one speed controller in that you effectively lose full control of both. The idea of saving a significant amount of money on a 1/12 Severn build by omitting one ESC is almost laughable, too!
For two ESCs it's easy to connect up if you think of it as two separate models. This involves the usual chain from battery to fuse to ESC to motor - times two. You can then either connect both ESCs to the same throttle output on the receiver via a Y-lead or use the two Up/Down sticks on your Tx for "tank steering". You might even fit a motor mixer like the ACTion P40E. Whatever you do, remember that brushless ESCs have battery-eliminator circuitry so you must disconnect the red wire from one of the ESC's Rx connection.
As regards fuses, start with a 30A fuse for each motor and see if you get nuisance tripping. Those enormous continuous current values often quoted are highly suspect; most would just melt the cabling!


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Re: Two Emax BL4030's
« Reply #2 on: November 23, 2015, 12:21:42 PM »

I suspect that the luck that was experienced by the guy who did the single ESC to two motors came via a good deal of experience and thinking, but given that the motors are well capable of turning their props, and the ESC is capable of handling the combined load and the battery is up to the job of starting the things, then the motors must stay perfectly synced with each other.
A fuse would need to be heavy enough to handle the startup current, but can only be between battery and ESC - no point in trying to fuse the individual phases of the motors.  With more than one ESC, obviously, one fuse per ESC makes sense. 
With sensible loading, in all probability, fusing can be reliable at much lower values than the motor spec suggests, and if it needs to be that high, a) can the battery supply it anyway for more than a few seconds,  b) just how big a fuse mount can be carried?
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Re: Two Emax BL4030's
« Reply #3 on: November 23, 2015, 10:05:35 PM »

Two motors and one esc has been tried a lot in flying with little success. There was one combination of motors and esc that did work well (I think it was e-flight) but little success with others. It needs both motors to start up at exactly the same time and the same direction. The esc relies on back emf from the motor for timing so two motors will confuse it. In some cases the motors had to spun by hand to start them both in the right direction, not really practical in a boat.
Best to stick to one motor per esc, the extra cost is not that much compared to the cost of the boat.

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