slowrotor,
Wow. Not an easy question.
This is the list of books. __________________________
'Machinery's Handbook' is an obvious one, which you probably have.
'Helicopter Theory' by Wayne Johnson has over 1,000 pages of mathematics and it is very economically priced.
A Preview of an Analytical Guide to Helicopter Transmission Design ~ 56 page paper by Kaman,1972 ~ was available on the Internet.
'Mechanical Design and Description ~ Rotary Wing Aircraft Handbooks and History '~ Vol, 8 ~ Dated 1954 from the United States Department of Commerce - Office of Technical Services ~ is a good simple book but is possibly not available.
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I found that the greatest problem was trying to determine what the life and safety factors should be for rotorcraft. When working on the SynchroLite, I even partially reverse-engineered the transmissions of the Mini-500 and the Ultrasport.
The little SynchroLite was taken to the point of building the craft. You should be able to dig a reasonable amount of information out of
its web pages, but remember that they are my, unqualifed, calculations.
Dave