University Invests in Gear Research

The Gear Research Group (GRG) at the University of Huddersfield has been involved in nine major research projects worth about £800,000 over the past 15 years.

The Gear Research Group (GRG) at the University of Huddersfield has been involved in nine major research projects worth about £800,000 over the past 15 years.

The GRG is part of the Precision Engineering Centre (PEC) within the School of Engineering at Huddersfield University.

In the last 15 years Huddersfield has become one of the most active universities in gear research in the country and it is an academic member of the British Gear Association (BGA), based in Burton on Trent.

The BGA (www.bga.org.uk) was founded to improve the competitive position of the industry, to develop the industry's technology to improve the UK's share of world markets, to encourage collaboration between industry and higher education establishments and to disseminate existing research data and to identify new, common research needs within the Mechanical Power Transmission industry in the United Kingdom.

There are various BGA committees covering issues of Technical, Marketing Educational and Training interests.

These committees collectively set policies and future strategies for the forthcoming year.

The Research Committee is open to Full and Research members.

The affairs of the committtee are directed by a Management Team that comprises industrialists, representatives from the Ministry of Defence (MoD), the Department of Trade and Industry (DTI), the Engineering and Physical Sciences Research Council (EPSRC) and Universities.

The Research Committee works to develop collaborative research programmes and to promote research at universities to benefit the industry.

These projects have been a tremendous benefit to the collaborators in assisting companies to embark on further commercial and research initiatives and in bringing together other groups of individuals to work to a common goal.

Huddersfield's specialist gear measuring and test equipment, valued at £400,000, is among the best in UK universities and industry has access to all research undertaken by the GRG.

The university's interest in the subject stems from the fact that gear manufacture is an important activity in the surrounding area of northern England and also because of the backgrounds of the research team leaders, Professor Bob Munro and Dr Lena Morrish.

Their approach is to first develop a clear understanding of the fundamentals of a particular research topic and to take into account the vast amount of practical data for industry.

The GRG, who are able to undertake consultancy work, are strong advocates of experimental validation and the university is well equipped with gear test rigs and metrology equipment.

The GRG aim to produce guidelines for gear design which will improve gear performance in terms of accuracy, efficiency, vibration and noise.

By developing improved metrology methods the aim is to help the identification of error sources in manufacture and to predict performance in operation.

The work in this area is internationally recognised for investigation into vibration, noise and transmission performance of gears.

Gear research is in collaboration with Holroyd, Eaton, Gleason, David Brown, Renold Transmissions, Highfield Gears, Express Lifts and Case UK.

The research approach seeks: A deeper understanding of the fundamentals of gear kinematics and dynamics; Experimental verification with test rigs, in addition to computer simulation; Close collaboration with industry to take account of best practice; and The publication and dissemination of improved design rules, for higher performance and more efficient production.

The university has recently completed gear metrology research projects on screw compressor rotors and involute profile measurement.

The screw compressor rotors research was supported by the EPSRC and Holroyd Ltd.

Although not strictly gears, the kinematics of screw compressor rotors have a similar but more complex three-dimensional geometry.

The relationship between a pair of rotors has been analysed and a unique optical method was developed to measure the gap.

The method has been patented and measuring machines based on this method are now being made by the collaborating company Holroyd, winning several national awards.

Research into involute profile measurement was supported by Gleason Company, USA.

Many involute error measuring machines are based upon the simple principle of a base circle disc to generate the correct stylus motion.

This method is very good for long production runs, but inconvenient when the disc has to be changed for a different gear.

This problem has been overcome by using large displacement transducers (optical gratings) which permit a disc of the wrong but known size to be used and a microprocessor corrects for the fact that the disc is not equal to the base diameter.

The measuring system is now being marketed by Precision Services Ltd.

Current research work involves gear kinematics projects on spur and helical gears and worm gears.

The study of kinematics of loaded spur gears has resulted in a precise design method for tip and root relief, whereby the transmission characteristics of a gear pair can be tuned to a specified torque range for minimum transmission error.

The method has been verified on a back to back rig at the university and used successfully in industry.

The analysis and design methods are now being extended to the more complex three-dimensional case of helical gears and the test rig is being modified accordingly.

The research is supported by the EPSRC and companies Eaton Ltd (UK and USA) and Case UK.

GRG's research project on worm gears is supported by the EPSRC, DTI and BGA and companies Holroyd Ltd, David Brown Radicon Ltd, Renold Transmissions Ltd, Highfield Gears Ltd and Express Lifts Ltd.

The traditional way to devise the correct mismatch between cutter and worm wheel is by trial and error machining and this has been replaced by computer simulation of the cutting process.

Marking patterns, entry and exit gaps, tip and root clearances, and transmission errors are plotted to allow the designer to make cutter and setting modifications in seconds.

The computer predictions have been confirmed by marking tests and by an industrial single flank gear tester using a range of gear designs.

The highly successful programme has been developed to allow for elastic deformations of the teeth, shafts and bearings in conjunction with experimental results obtained on a rig in PEC designed to transmit typical industrial torques.

The effects of the mismatch on tooth wear and friction losses is now being studied as part of a three-year follow up project.

Research into a gear vibration and noise project on spur and helical gears is being supported by the EPSRC and companies Eaton Ltd (UK and USA) and Case UK.

A mathematical model of the PEC's back to back test rig gives predictions of dynamic transmission error.

These compare well with measurements on the rig, which has specially developed instrumentation to measure dynamic transmission errors over the complete torque and speed ranges.

Sound pressure levels are also measured within an acoustic hood.

The GRG's design method for tip and root relief has been confirmed by tests which give a remarkable correlation between quasi-static and dynamic transmission error for the transmitted tooth load and the corresponding sound pressure levels.

A similar analysis and test programme are now planned for helical gears where few research results have been published.

Sponsorship is being sought for gear vibration and noise projects on gear rattle in machine tool drives.

Machine tool spindles are becoming more lightly damped because of the trend towards lighter lubricating oils and lower friction oil seals in an effort to reduce energy losses and heat generation.

This is resulting in an increase in the incidence of gear rattle, especially at light loads, where it produces an irritating noise.

The vibrations are complex and mathematically non-linear.

An analytical and experimental project is now being drawn up.

Gear metrology projects seeking sponsorship involve combined profile and transmission error measurement and gear quality control.

The measurement of the elemental errors of involute, lead and pitch are normally performed on one type of machine and the measurement of transmission error on another type of machine.

The Gear Group are developing software to combine these functions on one machine, a Frenco type SH450, in the metrology laboratory.

This combination not only saves space and set up time, but also allows a gear mesh to be simulated from details of a mating gear on file, without physically meshing them.

The process can be taken further by predicting the transmission error under load, hence assessing the likely vibration and noise in operation.

The gear quality control project will involve the development of software to make more use of the comprehensive measuring data obtained on modern CNC gear measuring machines.

Currently, analysis is limited to assessing whether the parameters fall within tolerance limits, but it is feasible to develop analytical techniques and expert systems which pinpoint deviations in the manufacturing process.

The likely effects of these deviations can then be assessed by the mesh simulation software developed by the Gear Group and the appropriate quality control action can then be taken.

Background information The Precision Engineering Centre, within the university's School of Engineering, focuses on three areas of expertise: engineering control and machine performance; gear/transmission performance and associated metrology; and surface characterisation or engineering surfaces.

Projects to the value of £9m have been accumulated by the PEC's three groups independently over the past five years.

Plans are now in hand to upgrade it to an Ultra Precision Engineering Centre, featuring Europe's first working nanotechnology laboratory.

Significant funding from industry and other sources is expected to support the centre.

There is a broad range of experience in the team comprising six permanent academic staff, five post-doctoral researchers, 11 post-graduate researchers and one research technician, all with many years of industrial experience.

The centre has £1m of metrology equipment and facilities at its disposal with plans for a further £4m investment in new facilities.

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