An inside look at ball-speed reducers

Fixing disc A, and moving disc B through an eccentric path of amplitude E, a ball will roll on both discs with a circular path of diameter E. Note that disc B does not rotate on axis B but merely oscillates on an eccentric path relative to A.

Fixing disc A, and moving disc B through an eccentric path of amplitude E, a ball will roll on both discs with a circular path of diameter E. Note that disc B does not rotate on axis B but merely oscillates on an eccentric path relative to A.

If a rotational motion is introduced to disc B on axis B while it follows the eccentric path, the ball will move between the discs as shown. The action of rotation and eccentricity generates a series of epicycloidal lobes on disc A and hypocycloidal lobes on disc B.

If a rotational motion is introduced to disc B on axis B while it follows the eccentric path, the ball will move between the discs as shown. The action of rotation and eccentricity generates a series of epicycloidal lobes on disc A and hypocycloidal lobes on disc B.

Typical disposition of the lobes on the discs. Around the same pitch cycle, the number of epicycloidal lobes is always two less than hypocycloidal lobes.

Typical disposition of the lobes on the discs. Around the same pitch cycle, the number of epicycloidal lobes is always two less than hypocycloidal lobes.

Grooves are machined in two discs and loaded with the appropriate number of balls. When an eccentric motion is applied to disc B by a rotating input, the balls are forced around the path formed by the grooves and this action results in a speed reduction and torque transmission from disc B to disc A.

Grooves are machined in two discs and loaded with the appropriate number of balls. When an eccentric motion is applied to disc B by a rotating input, the balls are forced around the path formed by the grooves and this action results in a speed reduction and torque transmission from disc B to disc A.


Lansea Systems offers a line of ball-speed reducers that use eccentricity to generate reductions. Kamo Seiko's Q-Ten reducers eliminate backlash and ensure 100% mesh throughout the drive by preloading the balls. Because torque transmits only through steel balls, efficiency is high and noise level is low. The reducers are supplied with input and output shafts, but a hollow input shaft can be substituted to accept step or servomotors. They are available in ratios from 5:1 to 1,600:1 and have a torque range from 35 lb-in. to 1,500 lb-in.

This information provided by Lansea Systems Incorporated, Quincy, Mass.