Gearbox drops in to upgrade test rig

Edited by the Engineeringtalk editorial team Oct 14, 2005

ZF Industrial has supplied a custom Graessner gearbox for testing apparatus used to simulate airflow through new engine components to the Aeronautical Research Unit at Loughborough University.

ZF Industrial has supplied a custom Graessner gearbox for testing apparatus used to simulate airflow through new engine components to the Rolls Royce sponsored Aeronautical Research Unit at Loughborough University.

In order to drive the test rig compressor system and provide the correct results, the replacement gearbox needed to produce output speeds of 5000rev/min.

As the original gearbox was no longer manufactured, ZF supplied a PowerGear unit with a custom lubrication system as a drop-in replacement, which offered high performance operation and extended wear life.

In continued efforts to reduce emissions and fuel consumption from modern aeroplanes, Rolls Royce Aerospace sponsors the Aeronautical Research Unit at Loughborough University.

To improve the performance of the combustor units in gas turbine engines, Bill Rasmussen and his team operate a test rig which simulates airflow over and through new component designs.

By artificially recreating engine conditions, cooling, quality of airflow, the efficiency of air/fuel mixing can be monitored and the results used to develop higher performance engines.

The test rig itself consists of compressor disk assembly driven by 81kW motor and 4:1 ratio gearbox operating through 90 degrees.

To test engine hardware such as fuel injectors and diffusers, the rig requires input speeds of 5000rev/min to the compressor system in order to create an accurate simulation of airflow through a jet engine.

"We were previously relying on a bevel gearbox from another manufacturer for the application, which had begun to run hot due to oil starvation", explains Rasmussen.

"When we made initial enquires, we were informed that the unit had been discontinued, we then had difficulty finding a suitable replacement until we contacted ZF, whose range of gearboxes promised the high levels performance required as well as direct compatibility".

David Morgan, the ZF Sales Engineer in charge of the project, recommended a P240H Graessner PowerGear unit fitted with a bespoke oil feed system as the optimum solution.

"The Graessner unit acted as a drop-in replacement and provided the high speeds and levels of accuracy required to drive the compressor blades and produce the precise airflow needed for accurate results".

"The forced through oil lubrication system keeps the gearbox cool despite the high output speeds while contributing to a longer wear life".

"Originally designed for compact machine tool applications, the PowerGear unit occupied minimal space in the small cellar room where the test rig drive assembly is situated, allowing for simple fitting and easier maintenance".

"The housing and flanges of the PowerGear units are made of spheroidal graphite iron for maximum rigidity and the use of high quality taper roller bearings allows a high axial and radial load capacity, making them ideal for the test rig applications".

Options available include two-, three- and four-way shaft configurations and gear ratios ranging from 1:1 to 5:1.

With Gleason bevel gearing providing high levels of efficiency (98%), and a parameter optimised gear tooth contact pattern that promotes uniform load distribution, the units are able to offer high levels of torque (up to 7800Nm) compared with their diminutive size.