What's the Advantage of a Sun-and Planet Gear Setup over a Traditional Setup?

1. Nov 12, 2011

Sorry about the less-than articulate title, but I was defeated by the thread-title character limit. The title of this three was to have been: "What's the Advantage of a Sun-and Planet Gear Setup over an Eccentric Rod and Driver Wheel Setup?"

The eccentric rod-driver wheel setup seems to minimize the mechanical backlash inherent in the sun-and-panet setup, while maximizing torque with the more eccentric placement of the joint, which, in turn, allows for the efficient functioning of the counterweight opposite the joint.

2. Nov 12, 2011

256bits

3. Nov 12, 2011

Got it. But how is concentricity an advantage when an eccentric rod/driving wheel converts reciprocal hertz into rotational torque, when I want torsional power?

4. Nov 13, 2011

xxChrisxx

It's a bit of an odd question, and I don't think I understand what you are getting at.
Could you clarify?

The way the question is worded at the moment, one is a gearbox the other is a crank slider. So comparing them just seems odd.

5. Nov 13, 2011

Here's a sun and planet gear:

http://www.mekanizmalar.com/sunandplanet.html

And here's a traditional connecting rod:

Last edited by a moderator: Nov 13, 2011
6. Nov 13, 2011

DaveC426913

I can barely make it out. Can you send a larger picture?

7. Nov 13, 2011

Staff: Mentor

8. Nov 14, 2011

pantaz

For one thing, a crank & rod design is typically used for converting linear motion to rotary motion. The only rotary-to-rotary configuration that comes to my mind is in the case of old locomotives, where a link connects successive wheels, and that is at 1:1. It also has an efficiency problem -- power is transferred over limited degrees of rotation, and at a constantly varying ratio.

The crank & rod design also relies on momentum to function. From a stopped position, if the rod as at top-dead-center or bottom-dead-center, no motion can occur until the crank is rotated by an external force.

9. Nov 14, 2011

xxChrisxx

They seem to have totally diffent applications, the sun and planet gear has several ratios depending if you lock off the sun, carrier or everything. The input and output shafts are on the same axis.

I'm not seeing the reason for the comparison.

10. Nov 14, 2011

Thanks. I don't know how to resize a photo. Next time that happens I'll just link to the image, rather than inserting it.

11. Nov 16, 2011