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The big news in the industry may be weights going up but one manufacturer predicts only 25-30% of operators could usefully use an increase to 44 tonnes. For many operators the smartest move may be going the other way—downplating. And that doesn't only include those moving fresh air with arks. There are two types of downplatingthose done (and type approved by) the manufacturer and those carried out by converters or individuals as a notifiable alteration.
In the past many operators uprated vehicles but as manufacturers design more weight out of the chassis, scope has become limited. Another problem with uprating is that you are left with a powertrain which may not really be up to the job.
The first reason for downplating is usually a saving in the road fund licence— taking an eight-legger from 32 tonnes to 31 saves 11,000 per year. But there are other reasons too: taking a vehicle below the 75tonne limit will allow use by non-LGV drivers, shortening the wheelbase on a multi-wheeler will increase manoeuvrability The incentive to downplate is based on lighter axles causing less road wear. But there are limits beyond which you cannot go: 26-tonner six-wheelers can be taken down to about 20 tonnes, and 17-tonners to 12. Tractive units can come down to 20 tonnes while the most movement on eight-leggers is to lose one tonne off the GVW.
Physical changes
Many within the industry would prefer to have downrating by licensing only rather than any physical changes to the vehicle. "If we engineer a vehicle to gross 32 tonnes, we don't want to change it to gross 31," says Iveco Ford's Ron Armstrong. However, the Department of Transport does not agree so physical changes are needed although some are, at best, cosmetic.
For most downplating jobs there are several ways of affecting the change required by the DOT, some are easily and cheaply reversible, others are not. While this might not be a concern when considering downplating the vehicle, it will be a feature when it comes to selling it. Restoring a vehicle's full carrying potential before resale also restores the residuals and can even boost them as potential buyers perceive the truck to have had an easy first life.
If you need to downplate, the manufacturers offer a wide range of options which can be ordered off-the-shelf. Where no off-the-peg option exists (or the method used is not suitable) downplating can be carried out by dealers or specialist companies and registered without type approval. Perhaps the easiest and one of the most common downplating exercise is with tractive units. These are almost universally done (by the dealer) via the fifth wheel. By varying the number, diameter and quality of the bolts holding the fifth wheel frame to the chassis a single fifth wheel can be rated between 20 and 44 tonnes in one tonne increments.
Attractive method
Another attractive method of downrating rigids is by changing the tyres. With this method, the GVW of the vehicles is derived from adding the carrying capacity of the tyres together. However, in doing this the latitude for loading becomes zero and axle overload becomes almost an inevitability when running at the new GVW Changes on the load sensing valve is another option for mechanically suspended vehicles. This involves resetting the valve to give full pressure braking at the new GVW (but in doing so it begs the question was the braking adequate before and if so why change it?).
Favourite among the converters is one of the simplest modifications, packing the suspension bump stop. For example, if a vehicle is able to carry six tonnes but you want to restrict this to say four. The springs deflect by some 60mm when a 6.0-tonne load is put on, Restricting this to 40rnin by packing out the bump stops will effect the restriction. Until recently the DOT wouldn't allow this method of load restriction on multi. wheelers because of concerns about restricting the articulation.
When a vehicle comes up for resale, the packers can be removed: fill out a VTG10, pay the £13.50, have the vehicle inspected, get the necessary road fund licence and the full carrying potential is restored.
Vehicles with air suspension can have their carrying capacity restricted to the ministry's satisfaction by having a pressure restricter fitted in the line. This reduces the pressure in the air bags and so limits the capacity. Again this is reversible when the vehicle is sold or the contract comes to an end.
Other methods include downrating the spring brake actuators, This doesn't affect the foundation brakes but will restrict the performance of the park brake and thus the GVW. With Leyland Daf's latest 65, 75 and 85 Series rigids, downplating can be achieved by drilling a hole in the top shock absorber mounting on the front axle(s). These holes vary in diameter from 2mm to 32mm depending on the vehicle and degree of weight reduction required. Having done so, the vehicle can be homologated at the new weight using a reference from the manufacturer.
Operational flexibility
One such conversion allows BOG to run its 85 Series cylinder carriers at 23 tonnes hut to retain a full 38-tonne GCW for drawbar operations. Following a six-month evaluation of the weights of its cylinder carriers, BOC concluded that it could limit the weight to 23 tonnes without losing operational flexibility Depending on the mixture of gases being carried, the difference between the weight of the vehicle going out with full cylinders and returning with empty ones is a maximum of three tonnes.
Douglas Concrete runs its six-legger
Fodens at 25 tonnes, If they run at 26 tonnes the 7m3 barrel has to be set a long way back from the cab to get the axle loadings right. At the lower weight the vehicle carries only 6m3 but on a shorter wheelbase with the barrel set closer to the back of the cab. Savings are not large (see table). As Douglas's Clive Price points out, the consequently over-engineered chassis and reduced wheelbase makes the resulting vehicle rugged and manoeuvrable. To use this to the full Douglas specifies a 335hp 12litre Perkins engine, twin plate clutch and Eaton 11609 gearbox. The resulting vehicle will be kept on site work for up to eight years.
Taking a look at your operation, weighbridge tickets and the duty tables could show that there are potential savings to be made.
If these are real, go for it but take two things into account. First, the vehicle's resale value is reduced with the weight, so make sure any changes are reversible. Second, these rates of VED can be changed at the drop of a Chancellor's hat.
El by Colin Sowman