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Old 07-02-2009, 09:57 PM   #1
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Default How to calculate FDR

Hi guys,

I'm sorry if this question has been asked thousands of times before, but how do you calculate the FDR for a 1/10th EP touring car?

I have just purchased an early production shaft drive tourer with no details as yet of the internal ratio.

Also, I will be trying this car out with both a 10.5t brushless and a 17.5t brushless, so what are the idea ratios as a starting point for both these winds? (I have run a 17.5t in another car at about 3.6:1 which seemed about right).

Thanks in advance,

Steve
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Old 07-02-2009, 10:08 PM   #2
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Originally Posted by stephenianjames View Post
Hi guys,

I'm sorry if this question has been asked thousands of times before, but how do you calculate the FDR for a 1/10th EP touring car?

I have just purchased an early production shaft drive tourer with no details as yet of the internal ratio.

Also, I will be trying this car out with both a 10.5t brushless and a 17.5t brushless, so what are the idea ratios as a starting point for both these winds? (I have run a 17.5t in another car at about 3.6:1 which seemed about right).

Thanks in advance,

Steve
spur/pinion X internal gear ratio.
how large is the track you're running on. i was at a 3.5fdr for my 17.5 but tried a 4.0fdr and i was just as fast but the motor was cooler and i had more low end speed.

for the 10.5 i believe it/s 5.6fdr and up, just guessing.
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Old 07-02-2009, 10:14 PM   #3
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thanks for the quick reply, but is the internal gear ratio the the diff gear divded by the crown gear or the other way around?
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Old 07-02-2009, 10:14 PM   #4
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which car do you get ?
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Old 07-02-2009, 10:26 PM   #5
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The car is called a Hyro, not a known brand but a good design in my opinion.
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Old 07-02-2009, 11:17 PM   #6
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Yes its the number of teeth on the crown gear divided by the number of teeth on the pinion gear (on the shaft )
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Old 07-02-2009, 11:34 PM   #7
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Thanks mate, I appreciate your help.

Cheers,

Steve
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Old 07-03-2009, 02:36 AM   #8
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[QUOTE=Timmie;6018214]Yes its the number of teeth on the crown gear divided by the number of teeth on the pinion gear (on the shaft ) [/QUOTE

yup

spur gear / pinon gear x ( diff gear / ring gear) = fdr
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Old 07-03-2009, 02:44 AM   #9
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Thanks guys,

The internal ratio works out to be 3.09 so it's going to be tough I think to gear it for stock.
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