Rolf Pfeiffer wrote:

Halloo Paul and Group,

It is puzzling to have the same planetary gear box with reduction ratios
not being different by 1, when used differently and the input is the sun
gear in both cases. Likely (presumably) the sun gear is of different
size as follows.

I trust it is like this.

PSRU 2.85:1. Stationary ring gear. Input is sun gear. Output is planet
carrier. Same direction of input and output.
Ring gear: 78 teeth, sun gear 42 teeth, planetary gears (78 - 42) /2 =
18 teeth.
Ratio: 1 + 78 / 42 = 2.85.

PSRU 2.17:1. Stationary planet carrier. Input is sun gear. Output is
ring gear. Opposite direction of input and output.
Ring gear: 78 teeth, sun gear 36 teeth, planetary gears (78 - 36) /2 =
21 teeth.
Ratio: 78 / -36 = - 2.17.

This assumes the same diameter ring gear of 78 teeth and using the 2.17
ratio.

In your message of 06/01/2003 11:35 AM, "Be thankful for our blessings",
the scale is close to 1:1 on my 19 ? screen.
Looking at the gear pictured in your hand, it appears to be about 1.5
inches pitch diameter, and presumably it is the sun gear of the 2.17
unit of 36 teeth. This would point to a diametrical pitch DP of 24 (36
teeth / 1.5"). If DP of 24 is right, then the ring gear pitch dia is 78
/ 24 = 3.25". (If DP is 20, then the ring gear PD is 3.9" (78 / 20)).
Which DP (diametrical pitch) is it? Also, are above assumptions correct?

Regards
Rolf Pfeiffer

The 2.17 set uses a 33 tooth sun gear.
The 2.85 set uses a 42 tooth sun gear.
The ring gears are about the same pitch diameter but they do NOT interchange.
They have a different number of teeth.

Paul Lamar

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