NTM Prop Drive 750kv + Turnigy AquaProp 43mm

[njs552]

Here is the thruster design for my ROV. I plan on running them open in the water, but all wires and the connections between the wires and the motor winding will be sealedwith epoxy.

I am using:
Motor: http://hobbyking.com/hobbyking/store/__ ... _140w.html
Prop Adapter: http://hobbyking.com/hobbyking/store/__ ... _Pack.html
Prop: http://hobbyking.com/hobbyking/store/__ ... x9mm_.html

Here is a video of an in water test with this thruster to measure the current draw. The wires between the motor and ESC are about ~18in long(45.7cm). I saw it mentioned somewhere that the wires should not be longer than 50cm or the ESC timing could be off. Can anyone confirm this?



I am not sure what the motor pulled at full throttle because the test tank was too small and at over 40% throttle the motor started pulling air into the prop. I guess I need a bigger test tank next time...

At 40% throttle the motor pulled 2A at 12v. Next I am going to use a force gauge to measure the thrust, and I will post an update with those numbers.

Thanks,
njs552

[bikerbones1968]

I doubt the short lenght of control cable your talking about will have any effect on the ESC timing. For comparison I drive a PPM signal, (and thats what the ESC sees, a PPM signal) over 1000 feet of 30 guage twisted pair, running 4 ESC's to control 4 brusless thrusters. It performs exactly the same on that 1000 feet of cable as it does on only 10 cm long cables. There may be a limit where it would be noticeable but I havent found it yet. I would say your safe with your setup. Even if you want to add a few feet more wire your not going to see any difference. It may be measurable on a scope but its not going to be noticable.

[njs552]

Hi, thanks for the reply!

I think I mixed up my terms a little! I meant motor timing, not ESC timing:)

I am worried about the three wires from the ESC to the brushless motor.

The actual PPM signal from (in my case) an Arduino only goes a few inches to the ESC, so it should be fine.

I am worried that the actual power pulses to power up each motor winding will be off if the three power wires are too long.

Thanks,
njs552

[bikerbones1968]

Ok I understand where your coming from now. I wouldn't be concerned . I would suggest using identical ESC's and motors i.e. two horizontal thruster. Just make sure that all the wires are the same length for both. So if your port motor has 4 feet between it and the ESC make all three conductors the same length for it and for the starboard motor do the same.

[Rover]

Yes, I agree, when we test our thrusters we have 4 to 5 feet of wire between the brushless motor and ESC motor connections without any problems.

Rover

[ScottishTom]

njs552,

Have you waterproofed the motors at all, for instance with epoxy?

Or are they just standard outrunner brushless motors?


Many Thanks

Tom