Sweetening the discharge
Page 29
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by Trevor Longcroft REDUCED NOISE, increased payload, and greater discharge efficiency. These are features of the new 24.4-tonne (24-ton) six-wheel bulk tipper/ pneumatic tankers now replacing similarly plated eight wheelers currently in service with Tate & Lyle Transport Ltd.
Broad design parameters for the new vehicles were set out by Tate & Lyle, the resulting specification is the fruit of close liaison between this company and the vehicle, gearbox, blower and tank manufacturers. Design strategy covered six points including : O the vehicle should be mare environmentally acceptable, especially in terms of noise ; O the design be based on a proven 24.4-tonne (24-ton) gross six-wheel chassis ; O Payload capacity should be increased by at least 760kg (15owt) to 15.5 tonnes (15 tons); O the existing 12-14-year-old tank shells must be reworked and remounted on the new chassis.
blower and discharge equipment has been achieved by reworking the pipe runs and generally tidying up •the pto drive-line to the blower.
The blower, by Peabody Holmes Ltd, is directly driven from a single combined pto unit and hydraulic pump, and the pto ratio has been in creased from 1.11 to 1.5 to 1 to reduce the engine revs during discharge and so reduce engine wear.
Acoustic shields are fixed around the blower, and the in let and outlet silencers have been purp-ose-built, with a reactive silencer at the inlet and an absorptive one at the outlet. At full blowing conditions, 35.6 tonnes (35 tons) per hour against a pressure of at least 69kN/sqin (10psi) lowest noise levels of $2dBH have been recorded.
The existing bodies on the Foden eight-wheeler are reworked by Metalair Ltd, and lengthened by about 229mm (9in) to achieve the extra volume for the payload increase. The original cladding from the body is not refitted, the cylindrical tank being finished in Tate & Lyle livery. The underbody rams are replaced by a single front-end ram and the bodies are remounted on new sub-frames to enable the tank to pick up on the front tipping gear.
The reworked tank is also fitted with an improved design discharge valve made from stainless steel. The air is blown over the feed-pipe outlet from a ring around it, and the cargo feed rate is controlled from a butterfly valve in the feed pipe. This arrangement has increased the optimum discharge rate by about 50 per cent.
The first vehicles to enter service are based on the Mercedes-Benz LPK 2419 6x4 tipper though bodies have been fitted to Leyland Bison chassis.
The exhaust stack on the Mercedes is remounted vertically instead of horizontally to direct gases away from passing pedestrians.
Tate & Lyle also specified that the new vehicles must achieve specific stability levels and tests completed at the MVEE at Chobham indicate that •the Mercedes-Benz vehicles are, during static tests, more stable than the vehicles they supersede.
However, Tate & Lyle are considering the fitment of antiroll bars on extra springs to improve stability for high C of G payloads, mainly because at the point of the vehicle tipping over there is a 10deg relative difference between axles and body angle. The original eightwheeler vehicles produce just a 4deg relative difference.
One of the reasons for the significant difference between the vehicles is obviously the softer suspension of the Mercedes-Benz.