Waste Heat & Bearings
So . . . have you ever wondered what happens to
your motor when you get to your destination in your fuel efficient
electric vehicle? Im not just talking about ComutaCars here, but all
electric/hybrid cars. Havent thought much about it? Maybe you
should. The motor is baking in the waste heat that was being controlled
by the cooling fan. The one that is not working with the ignition
switch turned off.
Baking the enameled wire on the armature and in the
stators is no big deal, it is designed for the heat. Tolerances have
even been designed in to account for the metal expansion. So what is
the big deal? Bearings. The tighter tolerances means less room for
heat expansion and the need for a lubricant. If you have had a bearing
fail, you know what Im talking about. The supposed grease is a hard
cake in the open spaces around the outside of the bearing housing. What
is left of the bearings themselves shouldnt be discussed in mixed
company.
So what can be done to alleviate the cause of
premature bearing failure? Changing the grease on a regular basis is a
start for open bearings. Changing the sealed bearings on some schedule
is an expensive option. Or one might just set in the vehicle after
completing each trip and allow the cooling fan to run for a minute or
two to remove the heat. I have better things to do with my time. Lets
see, three hours to pull the motor, change the bearings, re-assemble the
motor, re-connect the batteries and test. With two minutes of cooling
time after each trip, thats ninety trips. My car makes far more trips
than that each year, so, even with expenses not a bad trade off.
An alternative. While working on a diesel truck
with a supercharger, I heard this tickity-Tick noise after the engine
was turned off. Upon investigation, I learn that superchargers turn at
a Bah-zillion RPMs; changing bearings in them cost many thousands of
U.S. dollars and that the tickity-tick noise was an oil pump used cool
bearings. The owner showed me a little box called a Cooler Man that
kept that little electric pump going for about two minutes after the
engine was turned off. It was not a little light that went on in my
head! Here was a solution to cool my EV motor without me wasting time
or even thinking about it.
Installation was easy enough, two screws to hold
the little box in place, cut the wire feeding the fan. Connected the
two ends to the box, added a ground wire and ran a new wire from an
always on fuse to the box. Hopped in the car and everything worked
like normal for a trip around the block. Got back home, shut off the
ignition and lo-n-behold, the fan stayed on! One-minute and 56
seconds later it shut off. The instructions say it will run two minutes
plus/minus 20 seconds and handle 8 amp continuously. For big
superchargers or little 6-Hp electrics, this is a pretty cool little
gadget. |
