Farmer breaks the hush-kit silence
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by Jack Semple THE FIRST operator to have .a lorry fitted with a ban-beating "hush-kit" spoke exclusively,to Commercial Motor last week about his experience as a Greater London Council guinea pig.
His story makes alarming reading for anyone thinking of fitting hush kits, although the designers say their programme has been a success with other operators.
David Saltmarsh is a Newmarket farmer, and a member of the National Farmers Union's fresh fruit and vegetable committee for Cambridgeshire. He runs a tidy 1975 Guy Big J6 sixwheeler, which he uses partly to deliver produce into London markets.
Farmers were worried last summer that the GLC's proposed ban would affect their ability to take produce into .London, and Mr Saltmarsh volunteered to let Sound Research Laboratories, the Sulfolk arm which has a contract to develop hush-kits, work on the Guy.
• SRL took the lorry into its test centre at Sudbury for one week in August last year. The test centre has a sound chant
ber and sophisticated electronic measuring equipment.
In September, the lorry was returned to have a hush-kit fitted. This comprised three bits of high grade cladding. One went on the back of the cab (see picture), and one piece went on either side of the engine area, running from almost the front bumper to behind the front axle.
Mr Saltmarsh ran the lorry through the winter arid spring without any problems, and access to parts was not significantly affected.
The installation came unstuck, however, when Mr Saltrnarsh's lorry went to Royston test 'centre for its annual test. The two side panels were found to be fouling the air brake pipes and steering track rods. There were chafe marks.
The test centre thought that the installation was unsafe arid insisted that the side cladding be removed.
Mr Saltmarsh said he believed that the noise from the engine had been reduced Considerably: But his Big. J makes a lot of rear axle noise, and that was not tackled at all.
The experiment points to the fact that noise reduction is something that has got to be done at the point of manufacture, he said.
"I can sympathise with what they [the GLC] are trying to do. It is a vote-catching measure." But he remains unconvinced about hush-kits.
The GLC agreed to pay for any damage caused. to Mr Saltmarsh's lorry as a result of the experiment. But other operators who are compelled to fit hush kits when and if the ban conies into force may not have such protection.
SRL rejects any claims that its installation amounts to a "Heath Robinson" device. The firm is part of Europe's biggest independent sound research group, and provides high-techno]ogy cladding on, for example, a variety of plant equipment.
The acoustic quilting it uses comprises glass fibre, with a thin lead barrier in the middle. As well as being a good sound insulator, it does not burn.
SRL says it has now fitted eight different models with hush-kits, and has had no problem — including overheating — with any other lorry.