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Archive
chris@highpowermedia.com
/ Categories: Archive, test-equipment

Dynamometer Testing Facility

Jag XK At JLR - FrontRET was recently invited to Jaguar Land Rover’s PCC – Product Compliance Centre – at their Solihull plant to witness the CO2 emissions testing of the 2009 BTCC race cars. Whilst there we had the opportunity to see what goes into a truly world-class vehicle testing facility.The PCC consists of two, four-wheel drive rolling road dynamometers, Cell 1 and Cell 2. Hatton Systems Ltd are responsible for the dynamometer equipment and control systems and Horiba for the gas analyzing technology.

The original specification for the Cell 1 dynamometer was firmly focused on building a world class facility to meet the future needs of the vehicle testing market. This started with creating a 4WD facility for the emission testing of petrol and diesel vehicles to EPA standards. One key element of this is having a dynamometer with full road load simulation.Vehicle testing using a chassis dynamometer with 48” rollers and centre-mounted AC motors is the recognized ‘gold standard’ for emission testing to EPA requirements. That determined the basic format of the machine. From there the specification took on what would be needed to carry out emissions tests for cars of the future with increasingly low emissions.JLR were also keen to push the boundaries of the dynamometer’s specification to a position well ahead of contemporary visions. This extended the scope of the project to enable the new facility to carry out power testing and vehicle development on a wide range of products.The AC motor specification was increased from a typical 125 kW to a continuous rating of 255 kW per axle. Up to 1MW can be absorbed for short periods of time. The physical range of the machine was increased; wheelbases between 2,300 and 4,000 mm can be accommodated as can axle loads of up to 3 tons.

Several automated features were included in the specification. The wheels are automatically centred to consistently position the vehicle on the crown of the rollers. Automated roller covers allow the unused part of the roller to be covered for increased operator safety.A unique automated dead-weight calibration facility was also added. This runs through an EPA calibration sequence handling the 670 kg of calibration weights all by remote control from above ground. This avoids the health and safety issue of handling many large weights and a calibration beam. The individual calibration weights go up to 280 kg and are certified to with 250 mg to National Physics Laboratory traceable standards.Cell 1 also features a bespoke vehicle restraint system. Retaining a vehicle on a dynamometer to the required standards is complicated. The vehicle must remain within ± 25 mm of the crown of the roller, which is not a stable position. The restraint system cannot contact the wheels during the test and no vertical forces can be applied to the vehicle. A multitude of different attachment points and towing eyes must be accommodated. No paint damage is allowed during fitting and removing of the restraint system. The restraint system must withstand the considerable forces that can be applied during power testing – over 4 tons – and the restraint must not block the flow of vital cooling air during the test. Finally the restraint must not cause a health and safety issue by introducing tripping hazards into the test cell.Achieving this goal is made even more complicated as many current cars use air spring suspension which can change their ride height at fixed speeds. Simple restraining straps are simply not feasible in a world class facility like the PCC; particularly as they will stretch, allowing the vehicle to move.JLR designed a solid vehicle restraint specifically for Cell 1; a unique and much admired solution. Having such a stiff restraint gives the drivers enormous confidence and allows them to concentrate on the difficult job of driving the vehicle to the required standard.Next month: Future development plans for Cell 1 and a look at Horiba’s latest gas analysing technology.

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