Tech Tip: Planetary Gearboxes

Video Transcript

Hello!  This is Paul with a Groschopp Tech Tip.  Today we will be discussing planetary reducers – how they work, advantages, and disadvantages.

We’ll begin with the planetary’s layout.  Simple planetary gears are arranged with a centrally-located, externally-toothed sun gear that meshes with one or more externally-toothed planet gears.  As the name implies, the “planet gears” rotate around the “sun gear.”  The planet gears also mesh with an internally-toothed ring gear—which encompasses the entire gear set.

The construction of the planetary reducer lends itself to many advantages, for example:

  • Planetary reducers give you high torque in a compact package; sharing the load between several planet gears allows the reducer to handle the same torque that larger parallel axis gear sets handle.  
  • They are highly efficient with a single stage typically 95% efficient.
  • These reducers provide for ratios as high as 11:1 to be achieved in a single stage, whereas, it is difficult to achieve much higher than 5:1 in a single parallel axis stage.
  • Since the sun gear contacts multiple planet gears, resistance to elastic deformation, is higher in a planetary gear set than parallel axis gear set, giving the planetary reducer high torsional stiffness.
  • They allow for coaxial alignment, meaning no offset output shaft in relation to the motor shaft.
  • The output shaft on Planetary reducers rotates in the same direction as the motor without needing an idler gear, as in a parallel axis gear set.  
  • Planetary reducers are ideal for intermittent duty applications but also can be used in continuous duty applications.
  • Finally, Groschopp planetary’s have an integrated housing, meaning the ring gear is integrated into the outer housing for the gearbox, adding to the robusticity.
  • Compared to the advantages of the planetary reducers, the disadvantages are minimal for most applications for example:
  • High ratio of length to diameter when using multiple stages (gearhead can get very long).
  • Potentially high cost if low backlash, high precision gearing is required.
  • Specific numbers of gear teeth are required equally spaced planets (ease of assembly) and noise mitigation.
  • The gear ratio determines how many planet gears may be used.

You should consider planetary reducers when designing for applications requiring high torques in a small package with an output shaft needs to be co-axially aligned with the motor.

This has been a Groschopp Tech Tip.  For more information about any of our products or to view other Tech Tips please visit us online at www.groschopp.com

How to use the Motor Search Tool

Narrow your search by selecting motor type, gearbox, voltage, and phase options for your desired motor.

Select a dominant variable: choose one of the three parameters to narrow your search. The selected variable determines which slider bar you will be able to manually move.

Use the slider corresponding to your dominant variable to further narrow your motor selection. The other sliders will automatically move to show available ranges based on the range of your selected variable.

Results will upload as your search criteria changes. If you have any questions regarding your results or how to use the search tool, you can chat with us using the green tab on the left-hand side of your screen.

Note: Groschopp Universal motors are custom built to fit your application so no additional options are available to narrow the search. Selecting the Universal motor type will prompt a message taking you to the Universal product page.

Not sure what you need?

One of our team members would be happy to help. Contact us at 800-829-4135 or by email at sales@groschopp.com. You can also chat with us using the green tab on the left side of your screen.

send us an email

Universal Motors

Groschopp Universal motors are custom built to fit your application so no additional options are available to narrow the search. Standard frame sizes and motor features can be found on the Universal page.

go to Universal page