# Epicyclic gearing: 3 free axes

## Homework Statement

The teacher said it is possible to use an epicyclic gearing with no axis fixed but nobody use the gearing like that. I watched this video:

at time 42s it's possible to watch it. I have 2 questions:

1) Is it possible to used the epicycloidal train with no axis fixed ?

2) If yes, what is the ratio of reduction ? is it dependant of the torque ?

Maybe if you have a link ?

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## The Attempt at a Solution

I'm looking for this case, but each time the epicyclic gearing is used with one fixed axis.

Last edited:

mfb
Mentor
1) Is it possible to used the epicycloidal train with no axis fixed ?
I don't see an argument against it.

2) If yes, what is the ratio of reduction ? is it dependant of the torque ?
You have to consider all three rotations at the same time. Things like a ratio of reduction that consider only two do not make sense any more. That's probably the reason they are not used in that mode.

Things like a ratio of reduction that consider only two do not make sense any more.
I can set the input to the sun gear and the output to the ring gear (planets are free to turn like they want) ? Why there is no a ratio ?

In this case, it's possible to reduce a rotational velocity without give a torque on the support ?

mfb
Mentor
(planets are free to turn like they want) ?
Then your output will not get any torque (neglecting friction). The free axis will rotate with the right speed to give zero output power.