Pitch is the linear distance traveled per shaft revolution.

There are two Amacoil/Uhing rolling ring linear drive models. Model RG linear actuators offer variable pitch control. Model RS linear actuators are a fixed pitch design.

In the Model RG, the angle of the rolling ring bearing assembly relative to the shaft is adjustable. Adjusting the angle changes the drive's pitch.

Increasing the angle of the rolling ring bearing assembly on the shaft increases pitch. This makes the drive move faster per shaft revolution which means the drive travels a greater linear distance per shaft revolution.

Conversely, when the angle of the rolling ring bearing assembly on the shaft is decreased, pitch is reduced. The drive then moves slower -- therefore a shorter linear distance, per shaft revolution.

With the Model RG rolling ring linear drive, you can make these changes in linear speed and linear distance traveled by the nut without any adjustments to the motor speed or shaft rotation direction. This means a variable speed system may be free of clutches, cams, gears and so forth. In most cases, it permits the use of a relatively inexpensive, single-speed, unidirectional motor.

Adjusting the pitch setting affects the linear travel speed of the drive relative to each revolution of the linear drive shaft -- even if the drive motor speed remains unchanged.

If the rolling ring bearing assembly is pivoted so that it is perfectly perpendicular to the shaft, the pitch is essentially zero. In this case, although shaft-ring contact is still perfectly intact (zero backlash), the rolling ring bearings turn on the shaft without causing linear movement.

When the ring assembly is angled relative to the shaft, pitch is either increased or decreased, depending on how acute the angle is.


Amacoil/Uhing RS linear drives do not offer pitch control. Pitch in an RS rolling ring linear drive is fixed. The RS comes standard with a pitch setting of 0.5 times the shaft diameter. Each RS drive is also available with four other optional pitch settings: 0.1, 0.2, 0.3 and 0.4 times the shaft diameter. Pitch is determined by pitch wedges installed at the factory.