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Date: Tue, 14 Jun 2005 23:24:50 -0400
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: planetary gear ratios
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I ran across some information in one of the scientific newsgroups on how 
to calculate the gear ratio of a planetary gear set.

ratio = 1 + r / s

where: r = number of ring gear teeth
           s = number of sun gear teeth.

I haven't replace my 3-pinion gear set with a 6-pinion set, because I've 
not been able to positively identify it to where I could call out a part 
number.  Order strange gearset from the internet is not what I consider 
an efficient way to spend money.  So I went out and counted.  74 teeth 
on the ring and 34 on the sun.

1+74/34 = 3.176

That is not the 2.17 OR the 2.85 from the Ford gear sets.  Is it 
possible that the one isn't added in standard practice, so that what I 
actually have is the 2.17 gear set?

-- 
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."