mounting brushless motors

[Johneames]

Hi there,

Is there some reason a brushless motor can't be mounted on a metal motor mount (aluminum or steel)? I bought 2 Surpass 2216 motors and bench tested them attached to a wooden motor mount (piece of 2x4). I ran both of them successfully several times logging voltage, amps, rpm and time. Tests mimicked a flight with 1 minute of full power followed by reduced power (calculated cruise power) logging each minute. Tests lasted more than 15 min. after which I went to full power and recorded volts and amps. I was satisfied with the results, so I installed one in my plane mounting it to an aluminum extension that I had machined (this motor is much shorter than the DC motor I am replacing). The nose was a little light so I made some steel shim-like weights and sandwiched them between the motor and aluminum mount.

After watching some electric aircraft whiteboard animation videos ,When I ground tested the plane for the first time, in 2 or 3 minutes the motor quit with a puff of smoke, never to run again. I concluded the cowling reduced air flow and caused overheating so I installed the second motor and left the cowling off so the motor was fully exposed. The second motor also quit in a puff of smoke in a couple of minutes. After much head scratching, the only difference I could see was that I bench tested the motors mounted to wood but in the plane they were mounted against steel shims and screwed to aluminum. I am really at a loss and hope that someone can help me shine a light on this problem. Those motors were very inexpensive but I feel I must get to the bottom of this before spending serious money.

Thanks

 

[Hai-Lee]

You did not state if the metal mount you were using for the test was made of steel or Aluminium.

Both metals may develop eddy currents because of the rotating motor magnets and therefore drain energy from the setup BUT steel mount too close to the rotating magnets will severely alter the magnet field around the motor and might be causing a loss of magnet coupling and possibly a reduction in the back EMF generated through the rotation of the magnets around the motor coils. without the back EMF the coil current could rise to the maximum current available and smoke it all up!

You may even get the same result from using steel support plates for spinners.

Just a thought!

Have fun!

 

[Bricks]

I do not believe the steel motor mount is the cause as Hanger 9 sells steel adjustable motor mounts for electrics. Unless your shims prevented and air flow thru the motor but still does not seem likely that would cause this...interesting?????