×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

# Epicyclic for torque balancing?

## Epicyclic for torque balancing?

(OP)
I am having a hard time getting my head around this concept and if it would even work and was hoping a sharper mind could help. I have seen it work by driving the sun but can it work by driving the ring. In this example (see attachment) the drive is in yellow. A propeller is attached to the Carrier and another propeller having reverse pitch is attached to the sun. The torque from the Carrier prop turns the planets driving the Sun prop in the opposite direction. We will assume both props require the same torque to turn at the same speed opposite of one another. Ideally if one prop did consume more than the other the mechanism would compensate by balancing the loads by speeding up the other. This mechanism would use friction elements as opposed to gears so we need not be concerned about the correct number of teeth. The question is 1) will it work? and 2)with a ring diameter of 100, what would be the diameter of the sun and planets and what would their individual reductions be?

### RE: Epicyclic for torque balancing?

Yes it will work but the two output torques will never be the same magnitude (dark blue - green = light blue in your diagram) and therefore the prop torques do not cancel. Also the power to each prop will be unequal (by an even greater ratio than the torques).

je suis charlie

### RE: Epicyclic for torque balancing?

(OP)
Thanks you for your response gg. It appears that driving the sun and attaching the props to the carrier and ring work as there are some examples of this out there. If I went that route is there a relationship between the ring and carrier I should look for to produce an equilibrium?

Edit- I was able to find a few photos (use link to my dropbox)of the example I was referencing. I would like to create a scaled down version of this unit. the gearing is s=16, p=32, and ring with 80

https://www.dropbox.com/sh/gtbu5m8sxbqxev1/AACEzHc...

### RE: Epicyclic for torque balancing?

Carrier locked.-> Sun/Ring = 5/1 so Ring torque = Sun torque x 5
Ring locked.-> Sun/Carrier = -4/1 so Carrier torque = Sun torque x -4

Regardless of the ratios you choose you always get Carrier torque = -(Ring torque - 1) so the torques can never be equal. You could put a larger/coarser prop on the ring if you wanted to equalize the power split.

je suis charlie

### RE: Epicyclic for torque balancing?

As noted, due to difference in friction losses between the single input and each of the two outputs, and/or the difference in load produced at each of the two fixed pitch props, it will be hard to get an even torque split.

### RE: Epicyclic for torque balancing?

"As noted, due to difference in friction losses between the single input and each of the two outputs, and/or the difference in load produced at each of the two fixed pitch props, it will be hard to get an even torque split."
More than "hard". It is actually impossible to get an equal torque split since the output torques will always be in the ratio dictated by the gearbox ie 5:-4 in the example given and never 1:-1 for a simple planetary box.

je suis charlie

### RE: Epicyclic for torque balancing?

(OP)
I have been working other differentials (and realizing they dont work). I am wondering what if we were no longer bound to having all the elements in one plane? What if we canted the planets? Could we achieve torque balancing of the outputs? See the dropbox link below for cutaway, side view, examples of what I am thinking and also some fails

https://www.dropbox.com/sh/hoxc4cxl9x0y3da/AACTjqr...

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!