Re: [Amc-list] ELECTRO-RAMBLER =revisited=

[adh@xxxxxxxxxxxxxxxxx (Sandwich Maker)]

" From: Wrambler242@xxxxxxxxxxx
" 
" I'm not going to try and argue the point.,well, maybe a little.
" It's beyond my knowledge base and I'm not about to pretend otherwise.
" All I know is if you take a tablesaw and run green wood thru it the
" thing slows down and the motor gets hot. Shortening it's life and since
" I don't have an AMP meter on my tablesaw I don't know what the useage
" of electrical amps does, but if extra heat is generated, then I assume
" elctricity is being wasted. 

an incomplete assumption.  loading it up asks for more power; as it
slows down it draws more power -- less back emf.  even with constant
efficiency, more power means more heat.  and the fan is turning slower
since it's coupled to the motor, so it has less cooling!

and the motor iron is sized for the running power level and is
inadequate for higher demands.  that's a short way to generate lots of
heat.  a controller would reduce voltage as current draw increases to
keep total power constant, but your saw runs on constant voltage.

also, if the motor is an ac type, it'll lose torque rapidly as it
falls off line frequency.  ac variable-speed controllers such as for a
car would use a tach input from the motor to determine what frequency
to generate.

for a traction application i'd want a separate blower motor with its
own thermostatically governed controller.  this would really pay off
in stop-and-go, where the drive motor alternates between high power
demands - either accel or regen - and no motion at all.  but if it's
still [over]hot from a recent blast, it still needs cooling -
especially in anticipation of another blast.

" Leading me to believe that even if energy usage was the same, less heat
" generated would lead to longer life of components. On the flip side if
" you get the motor to run 3,000 rpm freely it would be better then
" spinning the motor at 5,000 rpm freely. Or would it???

little or no difference.  trivial increase in air and bearing drag.
decrease in brush life, if it's a dc motor.

" I did see the XJ's Motor is rated for 5,000 rpm and he is looking at
" installing 4:56 gears!
" He also said he does not use 4&5 gears in the manual trans. It would
" be interesting to see if he accomplishes anything by instaling 4:56
" gears!  Since he now runs in third at speed what difference would 4:56
" gears really do?

probably show him he didn't need as big a motor as he got.  150 lbs!

" I would expect he will simply switch the gears commonly used in the
" transmission!

yup.

" The high pinion in the rear of an American body sounds interesting, But
" is it really needed? You could build any one of a number of high pinion
" axles for this purpose. Reverse cut gears could even put the motor
" facing rearward 

that's what i had in mind, and yes you could simply turn the low
pinion axle around, but then you're pulling on the ring gear to move
the car instead of pushing and the setup isn't designed for that.

maybe by studying the reverse-cut d35 housing you could see how they
keep it lubed, then just flip the rambler axle over.  a gas engine
cares which direction it turns for 'forward' but an electric motor
doesn't!

" and then the battery packs could be placed in the rear
" floor area and under the hood till everything balanced out neutral.

i was imagining batts under the hood until they equaled the gas
powertrain and cooling system [10-12], then more in the trunk until
they equaled a full load [5-6] - even with hd wagon springs, probably
half the underhood count.  then the car would handle like a loaded
sedan.

" I expect that a single geared electric car would not have the
" versatility of a multi geared transmission equipped vehicle. 

i don't think you'd give up much though, and you'd gain simplicity.
the most you'd gain is a smaller motor for starting from a dead stop;
once you're into the constant-hp area of the motor performance curve
gears don't get you anything.  if the threshold - i'm guessing here -
is 10-15 mph, then all you need is one gear.  and you don't even need
a lower gear for starting if you're willing to be slow, except maybe
for hill starts.

" Which leads into the next thought. Larger motor, with a hunt or switch
" reducing voltage at a set point or speed to increase range? They
" routinely run the motors in on as little as 12volts by installing a bus
" across to posts on the motor. Could this same type thing be done with a
" controller or say steering wheel mounted switch or paddle?

the controller does this routinely; that's its point.  that's how you
'throttle' the motor in an ev.
________________________________________________________________________
Andrew Hay                                  the genius nature
internet rambler                            is to see what all have seen
adh@xxxxxxxxxxxxxxxxx                       and think what none thought
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