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Discussion Starter · #1 ·
Hi all,

I have a Gizmo EV ( which has a 48V
pack and a 6.7" D&D Separately Excited Motor. I have
run it for a year but the hill climbing I have to do
has started to burn up the motor. Jim H has it right
now to rebuild/repair. We had been considering
installing a 7.5" motor to see if it would handle the
workout I give it a little better.

I decided to do some calculations to see what rpm the
motor was spinning and here is what I found:

Speed : tire rpm : motor rpm
10 : 171 : 514
20 : 343 : 1029
30 : 514 : 1543
40 : 686 : 2057
50 : 857 : 2572

What I am wondering is if I can change the gearing to
get a better than a 3:1 ratio maybe a 6:1 ratio will I
still have the same top speed? Right now my top speed
on the level is about 44mph. Jim, and I think he said
Tim, thought that maybe the existing motor would
handle my needs if the motor spun at a much higher

My next question is, does any one have any suggestion
as to where I might find some replacement
gear/pulleys? This is a belt driven vehicle which has
the "teeth" in a V shape like this:


including the gap in the middle. The belt is a
GoodYear Eagle W-1280. I also need to know what the
smallest drive gear I can safely use. The current one
is 30 teeth. The one on the drive wheel is 90 Teeth.

I have attached 3 pictures. (I hope this doesn't
violate list rules.) It appears that there are two
sets of bolts which bolt the gear/pulley on the wheel.
One set bolts to the wheel hub, then there is an
aluminum adapter which then bolts to the gear it self.
There isn't much room to go larger with the wheel's
gear since the belt would interfere with a support. I
think I could go to a 115 tooth at the wheel so if I
could go as small as a 20 tooth drive it would be at a
5.75:1 ratio.

David D. Nelson
[email protected]

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