Although the planetaries are smaller and travel faster how does
the number of them play into the equation ?

John

John,
Good question!
More planets provide for a greater contact area, and Paul will tell you he
dislikes spur gear because of the small contact area, where all the load is
concentrated in such a small area. Unlike the spur gear the planets in a
planetary float to a degree, centralizing the planet housing ( between the
sung and ring gears) and sharing the loads equally between all planet gears.
The weak link is the planet gear as it is smaller, spins faster and requires
bearings, greater numbers reduce the loads each one has placed upon it, but
the speeds are still the same.

Numbers of planets are restricted by the area available for them, but from
what I gather 6 is a good number both from the loads perspective and
available space. I guess more would be even better but the planet cage has
to held rigidly between each planet gear, this takes up any remaining space.
The Ford is quite limited on space and Bell planets seem the same - can't
quite visualize the Mistral, but would assume the same with that large sun
gear.

I suppose you could try for more planet gears with a smaller diameter with
the bigger sun gear ( reduced ratio) - but the speeds would then be the
killer.
Hope that helps!?
George (down under)

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