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Spur gear and pinion combo

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Spur gear and pinion combo

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Old 07-12-2019, 01:46 AM
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Default Spur gear and pinion combo

What is the difference between having a 72 spur with a 26 pinion with Internal Gear Ratio of 2.6 COMPARED to having a 78 spur with 28 pinion and the same internal Gear ratio

72/26X2.6 = 7.20
78/28X2.6 = 7.24

which combo would give more acceleration/torque?
which combo would have a cooler motor?
which combo is faster in the straight?
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Old 07-12-2019, 02:21 AM
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These two are so close together that you will probably not feel any difference at all. For example, if you only changed the pinion of the first combination by 1T, you'd already end up with around 7.5 - which would be 0.30 of change instead of 0.04. Changing only the spur by 1T, you'd end up with 7.3 - a change of 0.10 instead of 0.04. That's why, if you want to make changes to your FDR, it usually doesn't make much sense to change both, pinion and spur, in the same direction (i.e. making both bigger or both smaller, as these changes then counteract each other).

Generally, the higher the number of the FDR, the higher the accelaration and the slower the top speed will be.

An FDR change of 0.04 should not really effect your temperatures, as again, it's too small a difference,
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Old 07-12-2019, 02:43 AM
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The larger gears would make the motor position (and thus weight balance) slightly further forward than the smaller gears. That's about the only thing I can think of that would be affected. The only time I changed linearly like that was because the motor couldn't be positioned where needed to get a proper mesh.

Is that what you're running at HRH? If so, I might be using way too large of a pinion.
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Old 07-12-2019, 07:41 AM
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Originally Posted by BugleBoy10 View Post
The larger gears would make the motor position (and thus weight balance) slightly further forward than the smaller gears. That's about the only thing I can think of that would be affected. The only time I bchanged linearly like that was because the motor couldn't be positioned where needed to get a proper mesh.

Is that what you're running at HRH? If so, I might be using way too large of a pinion.
I run 72/26 at hrh.
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