GU-S57 Helical-Worm Gear Unit

A helical primary stage ahead of the worm set. That first reduction drops the worm sliding speed and lifts efficiency roughly ten points over a plain single-stage worm box of the same ratio.

How this frame is rated

The GU-S57 carries 250 Nm of rated output torque, calculated on tooth flank and root capacity to international gear rating standards at a service factor of 1.0. Ratios run from i 10.3 to i 244.6, which at 1450 rpm input puts the output shaft between 5.9 and 140.8 rpm. Motors from 0.12 to 3 kW bolt to the input.

With the largest listed motor the frame reaches its mechanical torque limit at about i 15.1. Below that ratio the motor governs and output torque still climbs with the reduction; above it the frame governs, and extra ratio buys you speed reduction only. That is the knee you can see on the characteristic chart further down this page.

What usually decides the selection

Thermal capacity is 4.2 kW of continuous throughput without auxiliary cooling at 20 °C ambient. Permissible radial force at the shaft mid-point is 5,200 N; move the load towards the shaft end and that figure falls quickly, so tell us where the pulley actually sits. Housing is Die-cast aluminium, protection IP65, and the unit weighs 32 kg dry.