Rotalink, the UK manufacturer of miniature power transmission systems and controls, has combined spur and planetary gear stages in a standard ovoid gearbox to achieve a potential increase in output torque of at least 400%. The boxes, available in three sizes, will allow higher-torque or smaller gearboxes to be used in existing applications, and offer other benefits including high power-to-weight ratios, compact dimensions and quiet operation.

Typical ratios are from 24:1 to 3200:1 with top output speeds from 300–400 rpm. The gearboxes are available with various gear materials, including polymers, and a choice of bearings. They have zinc-plated, pressed-steel cases and covers with four-point mounting.

The spur gears run on fixed steel spindles leading to the final planetary output stage with precision ball bearings supporting the stainless-steel output shaft.

The 330 series is a form-fit replacement for standard industrial ovoid boxes with a 13Nm peak holding torque. The larger 360 series offers 28Nm of peak torque in a case measuring 95 x 60 x 31.5mm.

The 310 series is Rotalink`s smallest ovoid gearbox, providing 2.6Nm of holding torque in a 45 x 29 x 20mm envelope. It is also available in spur-gear-only versions and with a choice of plain or ball bearings.

The gearboxes interface easily with Rotalink’s DC, AC and stepping motors, and single- and dual-channel encoders that fit between the motor and gearbox assemblies. This allows the use of off-the-shelf single-output-shaft motors and helps to reduce product costs and development timescales.