38 tonnes can the operator really benefit?
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GOVERNMENT arid others still to prove their arguts that road damage is ed by heavy lorries. This the theme in the environtal discussions which surded the 38-tonne debate. I wear is caused by heavy axles, but if our roads were billiard tables, then lorries, liard balls, would not need ension.
ad springs are designed to a dynamic response to ament which, in-most cases used by the undulations in urface of the road. Bad road ices do not figure in envinentalists' statistics that Id not help their argument Yfore neither does suspenmovement and the resulvibrations this causes.
ere have been suggestions weight presses to a fourth er ie, 104 {10 tonnes x 10 es x 10 tonnes x 10 tonnes)
• eby causing structural age to roads. In fact, what happens is that the weight of an hgv bounces and vibrates as it moves. It does not press heavily.
The Government, having based its decisions on dubious calculations, has generated substantial revenue through vehicle excise duty based on gross vehicle weight. This has now been made worse when one considers the potentially frightening consequences of physically weakening a vehicle by altering it to have it downplated. The requirements now have had to go beyond helper springs or lowering the tyre ply rating.
These features have added an edge to the discussion that was not originally foreseen. Add to that the need in many cases to move the load away from the headboard to reduce the possiblity of overloading the drive axle of a 2x3 combination and safety becomes almost secondary to an odd desire to enforce an al
most impossible weight distribution situation.
Consequently, operators, ved costs have increased sharply if they continue to operate at 32 tonnes, as the table shows.
Now take a look at the insurance costs at 38 tonnes. Most goods-in-transit policies will increase slightly. Vehicle accident damage will increase vehicle cover premium and third party claims. A marginal increase perhaps, but still an added cost.
On the question of depreciation, there will be an initial cost penalty which will level out. If 1968 is used as a comparison, when 32 tonnes was introduced it was found that, initially because of market forces, the vehicle and trailer value appreciated slightly until the number of larger vehicles increased. Then it stabilised and eventually fell away.
Drivers quite naturally wanted more money for the greater productivity 38 tonnes afforded the operator.
The trade unions have pushed hard and successfully for the extra payment; this will filter through as the year pogresses.
The driver plays a key role in economic operation. Early indications are that fuel consumption does not necessarily in crease at 38-tonne operation.
This is a cost which is dependent on the driver. If he is anti 38-tonne, the vehicle will be driven aggressively and fast. Fuel consumption will therefore suffer accordingly.
At £1.30 per gallon, 8mpg represents 16.25ppm. At 6mpg, it represents 21.7ppm — 5ppm extra. Covering 1,000 miles per week represents E50 per week or £2,500 per annum. This is happening at 32 tonnes.
At 38 tonnes the loss is at least compensated by the extra payload but at no real benefit to the operator.
One of the arguments raging over 38 tonnes is that with the extra axles, tyre scrub will be excessive. There is substance to this argument and the two main aspects to be considered are: 1 Correct and accurate alignment of the axles (either new or converted). Even a 1/4in misalignment can scrub tyres. Added to this is the constant problem of overbraking.
2 If on a conversion, two type 24in brake chambers are fitted on the extra axle, the trailer they are fitted to will be overbraked. This is not a bad thing at 6 0 mph with 38 tonnes, but the brakes on an unladen trailer will lock up very quickly and will cause unnecessary tyre wear.
The driver must treat his brakes with great care (just "breathing" on them in a sensitive professional way). Reversing a tri-axle trailer in a tight manoeuvre will also cause costly tyre damage.
Lift axles are an obvious answer, but again drivers must be taught to lift the axle at the ap
prop rate time. Experience shows that twin tyres will give better traction than super singles when fitted to tippers.
However, in the main, the answer is based on driver training. This might be more appropriately described as driver conversion to 38 tonnes.
The maintenance staff also have a major role. The extra weights, because of bad roads, will cause damage to suspension and bracketry, particularly bushes, on equalisers and radius arms.
This would be reduced more if the suspension was of a more dynamic type, such as rubber or air. This is proven without a doubt, and there is far less damage to the vehicle and the load.
But what does it all mean to the operator? Is there more money in it for him? The answer is yes, if he converts his drivers and updates his maintenance schedules.
An extra five tonnes payload is possible with the right combination. There are a number of considerations. Guard against lightweight trailers unless they are aluminium. The most important factor is that the trailer, whether new or converted, is strong enough to carry the increased weight.
Proper stress calculations must be carried out. The extra revenue is short lived if the trailer finishes up in two pieces!
Another major factor is that a bending moments calculation has been done effectively so that the trailer bogie is positioned correctly. If not, there is a possiblity of either the kingpin or the bogie being overloaded.
36 tonnes is feasible on six axles, giving four tonnes extra payload with the right combination of light tractor and trailer fitted with 3x6 tonne single tyres, ie 1,200x20s on the trailer, giving 18 tonnes on the bogie.
Although operators have had to fight hard for an increase on the rate, an extra five tonnesdoes mean, on a large contract, that for every four trips, one vehicle has been saved.
With a saving on vehicle excise duty alone, one trailer conversion is paid for. There are particular types of operation where 38 tonnes is beneficial beyond doubt. Steel is obvious; in .particular coil carriers. This is probably the closest possible operation to a uniformly distributed load.
Transport of heavy chemicals in liquid form in tank trailers, particularly milk, again benefits because of light running. A lift axle will make for economic operations for this traffic.
In the bulk tippers field it has been realised very quickly that there is potential saving at 38 tonnes. Large numbers of tipper operators have already converted to tri-axle trailers.
The maximum gross weights for ISO standard containers of 20ft, 30ft and 40ft length are 20.32 tonnes, 25.40 tonnes and 30.48 tonne respectively. This means that only the 20ft container can be carried fully loaded on roads in the UK. Heavier maritime containers either have to be loaded or unloaded at the dockside or carried light for the whole journey.
There would therefore be financial benefits to freighting companies or shipping lines in reduced handling of goods and possibly in more efficent use of container ships if more containers were carried fully loaded.
Container transport is often charged at a "box-rate". That is a charge per container which is related to its size but not its weight. More efficent use c tainers would eventually lected in the charge anc benefit the shipping comp; National port statistics that about a quarter of ti' containers passing throul ports would be too he carry by road at 32 tonnes.
The higher gvw limit wi enable a greater number containers loaded to les maximum weight to be car
A survey at a container nal has shown that abot third of 20ft containers at ried in pairs; if this prop could be increased there be significant transport savings.
Roll on/roll off vehicles • ling between Britain and European countries with I vehicle weight limits wil benefit in being able to ma whole journey with a g payload.
A part of this gain will lected in transport cost s• in Britain, but a proportic be external and hence is ar tional saving. It has not possible to estimate the magnitude of these savir There will be benefits tional to the transport savings to some compar receiving larger consign of certain types of good: cost of vehicle receptior load recording will be red& there are fewer vehicles. example, processes usinc coil will suffer fewer stops ger coils are used.
This first look at 38. operation has been mair attempt to set the scene. A it, judicious planning is es: and far from every traffic i able for 38 tonne operation Much has to be done ; traffic desk, the workshop i the driver's cab before thel cal side of the operation sidered.