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Author Topic: Help please, best way to run 2 small brushless motors in an E Boat  (Read 550 times)

driver2008

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Using  Lockdown time, I've nearly completed my 34'' long, 5 '' beam, German S Boot ( E boat), by Vic Smeed, Nexus Plans service, purchased about 20 years ago.
Being an aeromodeller, I'm trying to use up the following items I've bought at Swapmeets.
2 off EMax CF2822 , 11.1V, brushless motors.
7.2v NiMh buggy battery pack with Tamiya connector.
Unmarked, believe 40A, heat shrink covered, aircraft  brushless speed controller.
Hobby King HK-60A ESC, no BEC, Timing 1/7/15/30 (programmable), PWM8/16K, brushless speed controller.
I've bought Chinese Left/right 35mm dia., dog drive plastic props, with very sharp tips removed, making them about 30mm, and looking more vintage.

 
I connected both motors in parallel, to the output of the 45Amp controller, but only 1 motor would run, The other was trying, but just chattering. I have not yet tried the other controller.
I've also realised I won't have any reverse.

 
Could anyone advise me how I can get it all to work, with reverse, and if I have to buy new controllers, which ones please?
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JimG

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Re: Help please, best way to run 2 small brushless motors in an E Boat
« Reply #1 on: July 22, 2020, 08:53:15 PM »

You need two esc to run two brushless motors, each motor needs its own esc. The brushless esc needs feedback from the motor to allow it to set the correct output, two motors will confuse the esc and one of the motors will get out of sync so not run properly. Aircraft esc generally do not have reverse and do not allow for it in programming (there are some Hobbyking aircraft esc that will give reverse but these generally use a second control input to provide this.) You will therefore need to look for an esc for either a boat or a car, car esc tend to have a brake as default and would need programming to remove this.
Jim
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driver2008

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Re: Help please, best way to run 2 small brushless motors in an E Boat
« Reply #2 on: July 23, 2020, 09:20:11 AM »

Thanks Jim.
I will try both my ESC's, I guess with a Y lead, is that correct?
You mention another control input with some Hobby Kings. Where does this come from? I only have a 2 ch 27MHZ


If I purchase 2 new controllers with reverse, will the neutral zones of both line up, or is there an adjustable dead band?


Anyone any thoughts on types of cheapy reversible controllers. Space, and funds are limited
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malcolmfrary

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Re: Help please, best way to run 2 small brushless motors in an E Boat
« Reply #3 on: August 11, 2020, 09:22:56 AM »

Using 2 ESCs opens the possibility of introducing a mixer to enhance manoevering.  Hardware mixers are available that plug between the 2 radio outputs and the ESCs and steering servo to gain more control fro 2 channels.
Running 2 motors off one ESC has been done, it needs a sensorless ESC capable of handling the required power and very careful matching of the motors.  I have yet to see a diagram of a brushless ESC with any feedback circuit that didn't have a position sense lead.  Mostly they just offer power to the wires in the right order and the motor responds.  With well matched and equally loaded motors, they respond equally.  Any mismatch gives problems.
A sensored ESC would obviously get very confused with two lots of sensors to deal with, so definitely one ESC per motor.
With sensorless, life is much simple with one ESC per motor.  If they are auto setup ESCs, there is an element of hope and luck for both to respond identically, if there is a "training" facility, it comes down to your dexterity setting them up.
Boat power bits need a more pessimistic outlook over plane bits,which usually get a lot of cooling airflow.  Much less cooling inside a boat, and a fast boats motor is always in a state of hard accellerating.
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barriew

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gra2

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Re: Help please, best way to run 2 small brushless motors in an E Boat
« Reply #5 on: August 12, 2020, 07:23:55 AM »

Hi I did build this model many years ago I think two brushless motors would have to much power for this model.
I would suggest two small brushed motors and you will only need one brushed esc to power both motors.

When I built my model I used one 540 motor and that was more than enough power.

Hope this helps.

Graham
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malcolmfrary

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Re: Help please, best way to run 2 small brushless motors in an E Boat
« Reply #6 on: August 12, 2020, 08:09:51 AM »

Hi I did build this model many years ago I think two brushless motors would have to much power for this model.
I would suggest two small brushed motors and you will only need one brushed esc to power both motors.

When I built my model I used one 540 motor and that was more than enough power.

Hope this helps.

Graham
That depends on the size and rating of the motors.  Lots of different ones available.  Picking the right one(s) and matching props is the problem area.
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driver2008

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Re: Help please, best way to run 2 small brushless motors in an E Boat
« Reply #7 on: September 08, 2020, 03:26:19 PM »

Thanks guys, I did buy some of the esc's mentioned, and motors rotate, 1 cw, 1 acw, forward and reverse, as intended, from 1 battery, using a Y lead and 1 central input wire removed from 1 esc.
Just finishing off topsides. Tried 1 mm hard stainless wire silver soldered to  2.5 mm x  30 mm stainless pan head screws, {heads below gun mounting, V notch in top of screws] for gun guard railings. Whilst not accurate, and reflective, looks OK, and very stiff. Would be great for a modern yacht.
Be careful not to overheat, use a narrow flame, as stainless can heat discolour, although wet and dry, or fine grindstone brings shine back up
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