Posted by: Edmund Glueck | May 7, 2013

Advantages and Disadvantages of Planetary Gearmotors

planetary gearhead assembly We design all our standard parallel shaft (helical or helical/spur) and right angle (worm or helical/worm) gearboxes in-house, and all gearheads are manufactured and assembled in our main factory in Iowa. Occasionally, we’ll receive a request to mate one of our standard AC, DC or BLDC motors to a planetary gearhead. To identify the best gearmotor option for our customer’s application, we review all critical performance requirements and parameters and then propose the most competitive solution.

If gearmotor cost, gearhead noise, and overall gearmotor length are critical factors, we find that design engineers often drop the requirement for a planetary gearhead and instead select a more compact right-angle or inline (helical) gearhead solution. However, there are certain applications where the benefits of a planetary gearhead outweigh its disadvantages. Below is a brief review of advantages and disadvantages of small planetary gearheads used with fractional horsepower small motors (FHP = <746 Watts) .

Advantages of planetary gearheads:

  • Compact size and low weight – as much as 50% reduction with same torque output.
  • High power density – several planets share the load rather than one gear, the more planets the more sharing.
  • Longer gear life at similar loads.
  • Gearing can be very accurate with virtually no backlash.
  • High efficiency – 95% per stage is common.
  • Typical ratio per stage is 9:1, 4 stages 9000:1
  • Coaxial arrangement – no offset output shaft
  • Modular, most planetary stages can be stacked.

Disadvantages of planetary gearheads:

  • Noisier Operation – some planetary gearheads are noisy.
  • Gearing must be accurate to assure load sharing
  • High bearing loads can lead to early wear in dead stud or sleeve bearing construction
  • Generally grease lubricated (oil bath is the better).
  • High ratio of length to diameter when using multiple stages (gearhead gets very long).
  • High cost if low backlash and long life are required


Custom Gearmotors: Bodine type 22B4FEBL-60P, 24 VDC brushless DC gearmotor (also available with 130 VDC winding). This example shows a 2-stage, 30:1, 76 lb-in, 60 mm diameter gearmotor developed for an OEM application. The gearhead has a continuous duty rating of up to 226 lb-in (26 Nm), with available gear ratios from 4:1 – 162:1. Gearing efficiency varies with the number of gear stages. Minimum annual order quantities apply for custom designs. AC inverter-duty options with our 30R motor are also available for OEM designs.

To view our stock selection of planetary type 24A4-60P PMDC gearmotors, click here. 12, 24 and 90/130VDC models available.

Copyright Bodine Electric Company © 09/2017. All rights reserved.

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