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Old 06-26-2004, 06:12 PM   #1
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Unhappy hpi sprint gearing help

I've got an HPI Sprint, which is not the best electric to race with in the first place. I stuck a 17 turn motor in it and put a 64 pitch 122 tooth spur and a 31 tooth pinion. I got plenty of run time and a killer take-off, but no top speed! How should I gear it to reduce the take-off and increase the top speed? How can I keep up with the big guys without getting another motor?

Thanks for the help
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Old 06-27-2004, 01:41 AM   #2
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If the faster people are running lower wind motors (10, 11, 12 turn) it will honestly be tough for you to keep up with them using a 17.

Otherwise, you can always try gearing up a couple of teeth on the pinion, but don't overgear it. Try not to go below an 8.0-8.5 final drive ratio. You can calculate the ratio like this:

(teeth in spur / teeth in pinion) x internal drive ratio

Not sure what the internal ratio is on an HPI Sprint, you may have to check www.hpiracing.com for that information.

If you need a cheap, lower-wind motor to keep up, you might try one of Trinity's machine-wound Speed Gems motors. They are in the $35-or-so range and should get you a bit closer on top speed.
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