This is my second brushless motor. This one is larger and is based on a 18.4mm stator from a 340 meg Viper laptop hard drive. The stator is very thin so I used 5x2.5x2mm N45 magnets oriented lengthwise to match the thin stator. Winding is Star pattern with 30 turns of #32 wire.

This motor is really a collaboration with Gail Graham. He machined the flux ring as I didn't have any stock larger enough, and that would have tortured my small lathe anyway. He also CNC machined some flat aluminum plate for the front bell, which is then turned round on a stub mandrel after choping off the corners. He also gave me lots and lots of machining advice along the way. The number of emails each way as this motor was built has been huge.

The motor weighs 9.34 grams complete with motor mount and the screws to use with it. My next motor of this size will hopefully use two of the stators in "double whopper" configuration. I hope this will result in a reasonable increase in torque.

And finally, this motor was a good learning experience on my way to a smaller outrunner motor. The pictures above are a sort of "wordless workshop" version of the construction of a micro outrunner motor.

Tests of the initial winding of 30 turns of #32 wire proved the motor to be an amp hog, pulling 3.07 amps. A second stator has been wound with 50 turns of #32 and the amp draw has dropped to 1.4 amps. Now the motor can also be run at 10.5 volts, equivalent to a 3-cell LiPoly pack, without getting hot. More winding and testing is required to continue optimizing this motor for the max amp draw of ET-250 cells.

This was my first attempt at a micro outrunner. The air gap is too large (I knew that when I made it). The outrunner does wobble a bit since the bearings are way up front. Mostly it was a proof of concept. The stator in the picture is the 6.9mm diameter M20 stator. The flux ring part of the outrunner is made from 4130 cromemoly steel tubing (because I had it) machined on the inside and outside to the correct diameters. Front bell is one piece aluminum. The "snout" has a flange on the front so a CF prop can be bored out the correct diameter and glued directly on the flange and turn with the outrunner. Bearings are 1mm id brass bearings. Estimated weight for this particular size brushless outrunner with the 14 rare earth magnets is about 3.5g.