TechArchive

Original article date: October 1999

Some of the most interesting news in power transmission this month has been software related. STUART NIVEN reports

Two gear suppliers are busy using computer systems to help with gear design this month. Holroyd is playing a leading role in developing a radical new method for predicting contact patterns and other details vital to the successful design and manufacture of worm gears.

It means that highly accurate data can now be provided by computer, putting important aspects of production on a much more scientific basis and giving a number of advantages over existing procedures, which are heavily reliant on costly empirical trials.

The development is the result of a study into work gear transmission carried out by Michael Fish (no, not that one), a research assistant at Huddersfield University’s mechanical engineering department. With the backing of five British gear manufacturers, the consortium had the support of the DTI and the British Gear Association (BGA).

Holroyd has now appointed Fish as a full-time research engineer, where he will continue the work and where the system is now being used as a practical design and development tool.

The software quickly generates accurate representations of the final off-load contact conditions that will be achieved using the given parameters. An exact contact-marking pattern illustrating this information can be generated up-front.

The close correlation of the synthesised and recorded marking pattern confirm the accuracy of the new method. The software can calculate – to an accuracy as good as 2-3Em – the transmission error for any gear design, including simulated error courses anticipated by the operator in contact conditions.

So the new system enables the required contact conditions to be achieved more quickly that with existing iterative processes which involve cutting then marking the worm and wheel set, followed by inspection and assessment.

Meanwhile, at a less fundamental level, ZF is releasing a user-friendly CD-Rom to assist machine manufacturers who are considering using the company’s Servoplan range gearboxes, which are of a compact planetary type and feature very high torsional rigidity and low torsional backlash.

Although the range has been designed to be user-friendly, with whole number integer ratios and coaxial input and output, ZF still believes there is merit in going one stage further with helping the designer in the selection process. The program automatically selects the ideal gearbox from input data including output torque. The size of the search range is then selected, to offer as few or as many possibilities as the user requires. Alternatively, a more direct method of selection can be used, by simply choosing the relevant size category and ratio.

Other functions include a menu which lists general information about the range, including efficiency, installation details, mounting positions, degree of protection and so on. An innovative feature is that any information the user finds relevant can be placed on a special clipboard.

• ZF
• Holroyd

October 1999