Braking down in Arundel
Page 8
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• Hersham Valves of Arundel, West Sussex has developed an engine retarder based on its variable pressure slide (VPS) exhaust brake. It uses a patented pressure plate and pushrod assembly to modulate the exhaust pressure.
While manifold pressure varies according to engine speed, the Retro VPS device maintains it at between 4.3 and 4.5 bar (62 and 65psi) from 700 to 2,400rpm. The pressure is sensed via a hole in the slide and a spring-loaded plate lifts off when it exceeds a pre-set limit.
VPS retarders become available next month; they are available in two sizes, for 75 and 100mm diameter mountings.
They can be fitted (within 4-6 hours) into the downpipe or clamped directly to the turbocharger on all popular makes of engine. Price is expected to be about E700 excluding fitting, which will be carried out by Hersham Frontier Truck Care of Wigan or by agents yet to be appointed.
The device is being tested at MIRA to ensure that it complies with APR retarder regulations, and several prototypes are being evaluated in service.
One is on an F,RF E14 38tonne tractive unit belonging to Hepworth Minerals and Chemicals; another has been fitted to a Perkins Tx375-powered Foden 8x4 belonging to Ken Longthorne of Hebden, North Yorks.
Longthorne says: The Retro can hold the laden 30-tonner at 30km/h on a 1-in-6 gradient in fifth gear without having to use the service brake."