Looking for mech. engr.

[davidallen]

does anyone have any experience with designing planetary gear systems?

in particular, I want to drive the sun and ring gears with 2 different sources and take the power off of the planet mounting plate. I need to calculate the resultant torque.

I think I can do it for the case of either the ring or sun held static, but when both turn (either in the same or opposite directions) is it simply the sum of the mechanical levers or is it dependent on the ratio of the velocities?

tia

da

[gerald_d]

"The sum of the mechanical levers" and the "ratio of the velocities" should be the same value - ie. give the same answer.

Take source A and multiply speed x torque to give PA

Take source B and multiply speed x torque to give PB

Add PA to PB to give PTOTAL

Divide PTOTAL by the output speed to give the output torque.

This approach assumes no power loss (heat) inside the gearbox. And it assumes that I havn't made a mistake, which I may have....

[davidallen]

so, if A and B are turning at the same speed and in opposite directions, the output speed will be zero.

does that mean that the 'holding torque' will be infinite?

[gerald_d]

Theoretically yes, up to the strength of the construction where something breaks.

[davidallen]

kewl, that's what I was hoping.

why doesn't it back drive one of the motors though?

da

[gerald_d]

If the drive motors can't handle the torque, they will change speed and your whole equation changes. "Something breaking" in this case is a breakdown of the motor.