Torque sensor used in high-speed motor test rig

TorqSense torque transducers from Sensor Technology are playing an important role in new product development at Gloucestershire-based Lister Shearing, which is described as the oldest and one of the most successful suppliers of animal shearing and clipping equipment in the world. The sensors, which are based on SAW (surface acoustic wave) technology, are being used by the company as an aid to evaluating the performance of miniature electric motors.

Lister Shearing invests heavily in product development. As part of the development process, it sends engineers to work with leading grooms and shearers around the world to learn about common problems and to devise innovative solutions. These are translated into practical products at the company's development facility at its Gloucestershire headquarters.

An issue commonly encountered with powered hand tools, which form a significant part of the Lister Shearing product range, is sourcing motors that will combine high efficiency and high torque output with smooth operation and long life. This situation is complicated still further by the high operating speed required from the motors - up to 20,000rpm in some applications.

Motor test rig

To address these motor selection issues and, in particular, to assist in the development of a new type of handheld sheep shear, Lister Shearing decided to build a motor test rig that would allow the performance of motors from various suppliers to be compared quickly and easily.

A key requirement for this rig was that it should be able to accurately determine the torque produced by each motor and its speed under a wide range of operating conditions. Initially, it seemed that this requirement would be hard to satisfy, as most available torque sensors were either unable to cope with the high motor speeds involved, or required wired connections that would have been inconvenient or impossible to provide in this application.

Fortunately, one of the development engineers at Lister Shearing saw mentioned in a magazine the novel TorqSense torque sensors produced by Sensor Technology. These are available in versions that can be used at shaft speeds well in excess of 20,000rpm and, therefore, easily met Lister Shearing's requirements in this area. In addition, they have a high overload margin, they operate equally well clockwise and anticlockwise, and they feature integral temperature monitoring. Also, in addition to measuring torque, the sensors provide accurate data about speed and power. Taken together, these features meant that a TorqSense sensor offered a convenient and cost-effective all-in-one device for the Lister Shearing motor test rig.

Data acquisition and analysis

In this application, the sensor was complemented by Sensor Technology's TorqView software package that runs on a PC, combining data acquisition with a real-time display of torque, motor shaft speed, power and temperature. TorqView also stores the data it captures, and offers powerful tools for its subsequent analysis.

Robin Howell, Chief Development Engineer at Lister Shearing, comments: "The team from Sensor Technology provided really excellent support in helping us to choose the right sensor and set it up so that it would provide the best results. As a result, we were able to acquire useful data right from the outset. The data is interesting and even, in some cases, rather surprising.

"After using the rig for some time, I have no doubt at all that it will help us to produce equipment that will set new standards for performance in sheep shearing. Thanks at least in part to Sensor Technology, sheep around the world will soon be shorn more swiftly!"

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