# Thread: Need help with a Planetary Gear Arrangement

1. ## Need help with a Planetary Gear Arrangement

Hi all,

I need help with a Gear Train described below. A rough sketch is attached.

I have a Round Plate above which there is a 88 Tooth Gear (Gear A). Both have their own drive and the ratio is 1:4. For every 1 turn of the plate, the Gear A rotates 4 times. They both rotate in the same clockwise direction.

On the plate is fixed a Gear B which meshes with the 88 Tooth Gear A.

I want it such that for every 1 rotation of the Plate, the Gear B rotates 18 times.

I am unable to figure out the no. of Teeth for Gear B, and would be grateful for any help with the formula/calculation.
If required, I can change the ratio between the Plate and the Gear A and/or the No. of Teeth on Gear A.

2. Isn't it 22? 88/22 Give a 4:1 ratio

3. Originally Posted by mike_willard
Isn't it 22? 88/22 Give a 4:1 ratio
Hi,
With 88/22 I get a ratio of 2.5:1 using the following formula:

(R+S) x Ty = Ts x S

R= Ring Gear Teeth (Calculated to be 132 [R=2 x P + S])
S= Sun Teeth (88)
P=Planet Teeth (22)
Ty=Turns of Planetary Gear Carrier (1)
Ts=Turn of Sun Gear (2.5)

Does this seem correct?

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