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FDR

Old 12-09-2017, 11:24 PM
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Can any one tell me, if wanted a FDR of 7.93 what is the better way to get it. A spur of 61t and piņon of 20 or spur of 58 and pinion of 19. They both will do a FDR of 7.93 is one way better than the other.
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Old 12-09-2017, 11:35 PM
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No difference in speed but there will be a slight shift of weight form the motor depending on what you choose.
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Old 12-10-2017, 02:28 AM
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True. Only difference will be motor position - and therefore weight distribution. But we are talking about small differences here - in this case here, assuming we're talking about 48dp, the motor would move ~1.1mm.

The maximum change I can reach in motor positions, while staying with the about the same gearing on my T4'17, is ~3.5mm (calculated for a target FDR of 5.0, or closest possible, without ever going any lower (so no 4.999s), the combinations with the max. distance in 64dp are 37/98 and 42/111, with actual FDR varying from 5.021 to 5.032, between those extremes, while the in-between 38/100 will hit a perfect 5.000 spot on).
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Old 03-20-2018, 08:59 AM
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Fdr is fdr, use the best combination for your particular car
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Old 03-20-2018, 03:56 PM
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You may get slightly better wear using the larger pinion.

Cheers,
Jim
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Old 03-20-2018, 04:31 PM
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Originally Posted by DirkW
True. Only difference will be motor position - .
Do not forget the gyroscopic effect of a larger spurgear....
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