BREMS-MOBEEL PART 2: BREMS FIRE

Cambridge-town was recently blessed with more than 2 feet of snow.

I attached the front ski and wrapped a length of chain around the rear tire.  I deflated the tire to wrap it and reinflated it after securing the chain.  That made a good snug fit.  I closed the chain with a cable clamp.

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At MITERS, a fleet of snow vehicles were in various states of repair.  Pictured here are BREMS-CHOPPER, ben's All Terrain Scooter, and dane's dane-ger scooter.

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Well we had some good fun.  I arrived at MITERS just in time to catch the inaugural test of a strange fan contraption.  Later, I filmed ben BREMS-CHOPPING it up.  The ski and chain worked great.

I got on after the motor had been pre-heated and gave it a good whanging on.  On about the second pass through the unplowed section of street, the motor finally gave out.  BayleyW just happened to be taking 60FPS video at the time of failure:

Disappointment or triumph?  Definitely triumph.  We've pushed This Moter to its limits.  120 volts at ??? amps.  The failure wasn't without adequate warning.  I could really feel the power drop off as the winding resistance increased with temperature.  The burning insulation stench was stronger than ever for those last few minutes.  I heard reports from others that it could be smelled more than a block away.  I believe the motor got particularly roasty in such a short time for two reasons: elevated load (takes a lot of energy to plow through that snow) and snow-blocked ventilation holes.  In spite of the temperature being -7 C, snow is a really good insulator.  It took a good ten minutes post mortem for the motor to melt all of the snow which had caked it.

After letting the whole thing air out for a good half hour (that sickly sweet insulation smell is quite unpleasant and headache-inducing), I opened up the motor and pulled the rotor for diagnosis.  Looks like a couple of slots got particularly toasty.  The commutator was more scarred than last time and had a couple of globs of copper welded between segments.  The solidified globs had taken chunks out of the brushes.  Everything was coated in a sticky carbon goo, and the brushes were jammed by the goo.  I am not sure if stuck brushes were a component of the failure.

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The future is uncertain.  brushless brems?  maybe.  For now, we've got to get this motor spinning and have some more fun in the snow.  Chances of it being revivable…?  we'll see.