Overspeed device protects gearboxes
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MERSEYSIDE PTE has successfully fitted part of its fleet of Bristol VRT double buses with gear-change overspeed protecdon devices.
Its VRTs which date from [970/1 and 1974, have suffered -epeatedly from drive-line and .ransmission problems, partiularly accentuated on 10rietre (33-foot) doubleleckers.
The buses were originally to lave been converted from ;emi-automatic to fully iutomatic control, but tutomatic gear controls tested were unreliable. Drivers also isually prefer semi-automatic :ontrols to fully automatic. Fidus overspeed devices, made by Fidis Control Ltd of South Shields, were fitted to a small batch of vehicles. The results were so encouraging the entire VRT fleet has now been so equipped and the Leyland Atlanteans may also get the device.
The unit consists of an electronic device that senses road speed, the direction of travel and the gear engaged. Speed and direction are sensed by a probe mounted to view the prop-shaft universal joint near the rear axle. The gear is sensed via the driver's gearchange switch.
Only if the driver changes gear incorrectly, at too high a speed for example, does it operate. It either holds the previous gear or puts the gearbox into neutral until another gear is selected.
As well as geing generally more popular with bus crews than fully automatic controls, the device is considerably cheaper than a fully automatic control system.