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LOAD CELLS
Page 46
Page 47
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A spring deflection system is not the only type of weigher that can be installed. Load cells can be fitted, instead.
These are more accurate normally to within 0.5% or around 50kg but do not usually give individual axle weights, although there have been a number of attempts to develop packages that will do so.
Furthermore, they are awkward to retrofit.
They have to be mounted between the chassis and the body, and require a separate sub-frame. According to one prominent supplier, it can take two days to fit load cells to an eight-wheel tipper.
This adds to the size of the final invoice. "Retrofit four load cells to an 18-tonner and it will cost you from £2,003 to £2,500 in total," says Paul Makings, joint managing director of Solutions Onboard, along with business partner Mark Bassindale.
"On the other hand, they are probably more durable than a spring deflection set-up and don't require recalibrating so frequently," says Phil Bridge, sales office manager at Red Forge.
The company offers a wide range of different onboard weighers that make use of either spring deflection or load cells.
Designed with tipper applications in mind, Omniweigh from Red Forge employs the latter. An in-cab display snows the gross vehicle weight and the payload, and a sleep mode can be used to stop it sho ing deceptive readings while the vehicle is braking accelerattng. "Uttle input is required from the driver," ge remarks.
can be used with a telematics system and allows the operator to capture data by plugging in a USB memory stic if that option is specified. It can then be taken back to the if ice and the information it holds can be downloaded ont a PC for analysis. A printer is offered as an option.
Load cells are comparatively heavy. A four-cell package for a four-wheeler will tip the scales at 35kg to 40kg, says Bridge, compared with no more than 10kg to 15kg for a spring-deflection system.
Another possibility is to install sensors that measure the amount of pressure imposed on an air suspension's airbags. On a tipper, the change in pressure inside the tipping ram can be monitored too.
e've fitted them to trailers carrying scrap and they've tur ed out to be accurate to within a:Mg,' Makings says. 'Thy weigh less than 10kg and give you an approximation of how much weight you've got on board rather thai a precise figure. They won't give you individual axle weights, but will tell you if the rear bogie on a trailer is overloaded. An air-weigh system for a four-wheeler will set you back about 21,700 and we can fit it in no more an Bri It than four hours, including calibration,' he says.
"It is maintenance-free and easy to switch from one truck to another, and you can use it to monitor the airbags on a tractor as well as those on a trailer."
Light commercials are at just as much risk of being overloaded as heavy trucks and trailers, and Hack is receiving more and more enquiries from firms running 3.5-tonners.
"Obviously, you don't require an 0-licence to operate them," he says. "However, if you happen to be an 0-licence holder because you also run heavies and you're caught overloading your lighter vehicles, then that will affect your 0-licence [OCRS] score."
"I would say 3.5-tonners represent our main market now," says Bridge. "It's because people are trying to make them do the job of a 7.5-tonner and overloading them as a result."
For vehicles grossing at up to 6.9 tonnes, it offers Limitlite, with Lirnitlite Plus suitable for up to 8.2 tonnes. The former comes with an LED in-cab display, the latter with an LCD display. Red Forge says both systems are accurate to within 5%, and both are capable of warning of axle overloads and can provide a feed to a telematics system.