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Drive Design Can Be Based On Torque Required

14 March 2013

In the past rack and pinion drives were generally developed from a planetary gearbox with a pinion fitted to the output shaft and the matching gear rack, but the radial moment load on the gearbox from the rack and pinion is typically the factor that actually determines the size of the gearbox required.

The actual utilisation of the gearbox output torque can be in the region of 40-60%.

Stober wanted to change this philosophy and developed a new concept for a super compact and highly efficient rack and pinion drive systems jointly with gear rack manufacturer Atlanta.

The integral output bearing housing on the new HighForce ZTRS rack and pinion drive is a stiff supporting assembly for the pinion which relieves the moment load on the gearbox output bearings. Reduced tilting moment from this construction makes it possible to base the drive design on the torque actually required for the machine operation.

As a rule this means that the gear unit can be a size smaller than normally used in the past. Due to the comparatively small pinions, a higher output speed is required
which means that the gear ratio can also be lower and in many cases a single-stage planetary gear unit can be used instead of a two-stage. The new mounting system makes it possible to use rack pinions with a very small number of pinion teeth, which can increase linear stiffness by up to 100% and reduce linear backlash by approximately 40%