V,
Hey kids, what time is it?
"Howdy Doody time!"
No, actually, it's ball-bearing motor time again. The old motor was
disassembled and remade into a more nimble form. The spacing between the
bearings was halved, thus reducing resistance. Also, the wobbly allthread shaft
was replaced with a much more balanced smooth steel shaft, with a copper spacer
to keep the bearings separated and give a bit less unit resistance. The pulley
was mounted this time with an allen setscrew, which again made things run truer.
Turns on the transformer secondary were doubled. Now the whole set of jumper
cables is being used! Open circuit secondary voltage is now 7.26VAC.
With this connected across the motor, giving it a gently spin with my hand now
causes it to rapidly accelerate. It ends up going at what I would estimate is
at least 1000 rpm. I've had that running for a few minutes at a time, and there
was no evidence of the bearings trying to seize; it doesn't begin to slow at
all. The only limit I can see is how long the insulation on the wires can stand
the heat generated. The advantage to the transformer over the battery is pretty
clear to me, at least: no killing of an expensive battery, no (effective) limit
on run time, relatively steady current, no risk of hydrogen explosion/acid
shower. The only disadvantage is that we are out of the DC realm. Still, this
can be alleviated to a degree by using a bridge rectifier made with high
current diodes. I might have enough diodes of high current capability to do
this. Have to look.
Note: these are with the bearings still packed with the original grease;
removing that, cleaning everything carefully, and perfoming Horace's graphite
powder treatment (do have graphite powder) would be interesting to see.
Horace: I will go back over your first response to this thread and see what I
can do for some measurements.
--Kyle
