[Healeys] Fw: [TR] 'A' type overdrive question

Ed Woods fogbro1 at comcast.net
Tue Apr 20 09:54:27 MDT 2010


Dave and List,

Of course everyone's entitled to his own opinion, but I feel the need to 
quote Wikipedia on this subject:

"Some designs use "compound planets" which have two differently-sized gears 
on either end of a common casting. The large end engages the sun, while the 
small end engages the annulus. This may be necessary to achieve smaller step 
changes in gear ratio when the overall package size is limited. Compound 
planets have "timing marks" and must be assembled in the correct initial 
orientation relative to each other, or their teeth will not simultaneously 
engage the sun and annulus at opposite ends of the planet, leading to very 
rough running and short life."

So, the alignment or "timing" marks serve a much greater purpose than simply 
"ease of installation".

Ed Woods 


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