(ET) field weakening on E15 and moving dirt

[agp@???]

I have been doing more investigation on the capabilities of my new ET.  One
unfortunate thing about the control modifications made by Mark Hanson:  No
field weakening, therefore top speed is only 4 mph.  :(    

I have examined the circuit that GE used for field weakening and it appears
simple enough.  But I think it would be better to use some kind of
semiconductor switch for my 48V system.  Do any of you Trakkers know how
golf cars have their field weakening set up?  

I'm thinking of using a FET (in series with the field) that will be in the
linear region until the motor gets very close to full speed.  Then initiate
a change in the input to the FET so that it will transition to a state
where it is dropping 36 or 40 Volts at a reasonable current level (between
1/4 and 1/2 Amp).  The transition should take place in an amount of time
not so short that the acceleration would cause undue force on the driver.
But quick enough that the wait time for the speed change is not noticable.
Maybe between 1/2 to 2 sec would be good.  I think of it as a sort of
"overdrive" where the result (in gear "D2") would be infinitely variable
control of speeds between 0 and 4 mph, and then a jump to the 8 or 9 mph
"warp speed".  (I might consider a variable speed control for the "warp
drive" if someone points me in the right direction.)

One other note.  The Club Car controller that is being used has an input
for a Tachometer.  The tach was apparently functional at one time.  But the
"studs" that were glued on to the pulley of the motor have fallen off.  I
thought of having a machine shop just use some small bolts as the studs.  I
believe the output of the tach would then be a pulsed waveform with
rectangular shaped pulses of magnitude no greater than 5V.

On the positive side:  I was able to push some dirt today!  I had been
digging a trench in the back yard to put in an electrical cable out to the
water pump down by the creek.  When I was done digging I laid the cable and
then used the Elec-Trak to move the dirt back into the ditch.  The only bad
thing that happened was that the strap on the front lift broke twice.  (And
was repaired twice.)  I think I'll just buy one from Bill Gunn with the
order I'm placing on Monday.  Does he accept VISA?  (Prior emails in the
archive said he only takes checks or COD.)

That's all for now,
Andy Poush
Andrew Poush