Tyre pressure monitoring system
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• A new system for monitoring tyre pressures on heavy vehicles while the vehicle is in motion has been developed by Redman Heenan Froude Ltd, of Worcester, and will shortly go into production.
The system uses radio to link the wheel-sensing unit direct to the cab which overcomes the difficulties experienced with many earlier systems using electrical, mechanical or pressure connection between the rotating wheel and axle.
Each unit comprises a sensitive pressure transducer, a radio transmitter and a battery mounted on a ring which fits international standard eightor 10-stud wheels. The pressure transducer is connected by a hose to the normal tyre valve and detects any change in pressure above or below the original setting. Twin transducers are used for twin-wheel hubs.
The transducer allows sufficient variation to account for normal operating change of pressure, but if these limits are exceeded a radio signal is transmitted to a receiver mounted in the driver's cab and an audible warning sounds inside the cab.
To save battery drain the equipment is designed so that normally it only operates when the vehicle is moving, but by positioning a magnet on the outside of the equipment case the units can be operated while stationary to check the pressure in each tyre without disturbing the units in any way. This provides a much quicker check on tyre pressures than can be obtained with a pressure gauge, especially with twin wheel units when the inner valve is inaccessible.
Standard tyre valves are mounted on the transducer to permit tyre inflation or use of a pressure gauge. The magnet can also be used to trigger the transmitter to check the radio link.
The wheel unit is designed to remain unaffected by road grit, salt or steam washing. There are no modifications to the hub, and wheel changing involves no extra difficulty. The only maintenance the unit requires is a once-yearly replacement of batteries.
The receiver, which runs from the vehicle batteries, can be fastened to the cab and operates automatically with any trailer fitted with wheel units.
The new system is called ASPA (automatic systems pressure alarm) and it is intended that it will be marketed by a new company, called Heenan ASPA Ltd, at Worcester.
The units are already being manufactured in pre-production quantities and it is understood that the DoE has shown an interest in the device and has asked that it be sent to the RRL for evaluation.
• The Wincanton Group Engineering Division, the Sherborne-based subsidiary of Unigate, is to produce 48 2000gal milk collection tankers, worth L150,000—most of which will be for service within Unigate. The tanks, both singleand double-compartment type, will be mounted on Bedford 16-ton chassis supplied by another Unigate subsidiary, Wincanton Garages Ltd.