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The 3 wire problem


PeteMitchell
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PeteMitchell

I have sometimes been asked how I deal with the 3 power wires which exit from the side of most out- runner motors. Because even if the fuselage is wide enough to mount the motor, it can be difficult to stop these 3 wires touching the rotating can part of the motor. I have tried most of the usual fixes, like gluing them to inside of the fus, or fitting a sleeve between the motor and wires, or even cutting the fus so that the wires pass outside the fus.

The model I am putting together now needs a gearbox motor, but the fus is very restricted and motor wires touching the motor can is still a real risk.

I have attached a few pics which I hope shows the method I use,  and one I have copied from the Reisenuer website.

As can be seen, I make a thin piano wire support, the ends of which are located into the front fixed part of the motor and the power wires are secured to the wire frame with heatshrink. The wire frame is effectively a spring which keeps the motor wires away from the revolving motor can, and presses them against the fus wall.

Very simple and works very well.

3.jpg

2.jpg

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I like it. I might be tempted to put a length of silicon tube over the piano wire where it pushes on the three wires, just to spread any stress on the motor wires over a larger diameter. Not necessary, obviously, just more elegant and possibly preventing failure in a few years time. 

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PeteMitchell

It depends how much space there is between the motor and the fus wall if you feel adding silicone tube would improve things. In one installation I have done which was a very tight fit, the gap between the motor can and the fus wall was  just over 2mm. In this case I removed the silicone insulation on the motor wires and replaced  with heatshrink. The spring worked very well in this case..

There is usually plenty of space in side the fixed end of the motor and between the case and the internal windings. The spring wire can be sharp and it  needs care not to scratch or dig into the enamelled winding wires when fitting. Once inside the case it 'springs open' and never touches the windings.

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