A smooth piece on the side reduces drag
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Sideguards supporting flush fitting outer panels could improve aerodynamics and boost mpg, says H. W. F. Davidson, AIRTE, AlnstTA, AffIMI
IOUT WISHING to detract the sterling efforts eyed by heavy vehicle dews, I feel certain that even engineering artists would a that the criterion for truck In is as much influenced by lation as by a designer's dorn of expression. The term acceptance of this tion can lead to an air of )lacency if the needs and Irements of a progressive port industry are not conIly monitored.
t another distraction has rey been added to the cornties of Government legison, and that is the duction of mandatory rear side-guard protection on Ific trailers.
lite retaining the right to iree with particular areas of legislation, it is apparent the overriding British desire compromise is adversely ting the ability of design s to exploit all the possible cations. Fit this form of proan we must, but at the same , it is the brief of designers ilise guardrail structures, if at all possible, to facilitate an advance in vehicle technology It is not difficult to see that guardrails have a potential of their own. With the increasing research being undertaken, in the field of aerodynamics, air resistance figures are slowly being reduced, with the consequential returns of lower fuel consumption as the reward. Frontal areas are the first to receive attention and thus the first to submit to the assault, surrendering valuable fuel consumption rates, in the wake of roof deflectors and the like.
As if to illustrate these advantages, the Ford Cargo range has received considerable acclaim for its aerodynamic qualities, using in addition, under-bumper air dams and flush-fitting ancillaries. The radiusing of cab corners has produced a measure of success and the precedent has been carried over into trailer design.
Trailers now have radiused leading body corners, to encourage airflow to spill around the front panels, and curved panels fitted to the leading sides, to assist their movement through the atmosphere. Indeed, the level of success has prompted a definite market for the retrospective fitting of curved frontal panels.
With all but prototype exceptions, little extra is offered in the field of trailers. No practical equipment is currently available to suitably smooth airflow along the length of a trailer's body. Rear-axle assemblies, in particular, are afforded no aerodynamicâ– protection, yet twin and tri-axle bogie fittings have considerable bulk.
Depending on which published figures you choose to be
lieve, somewhere between 10 and 15 per cent of a vehicle's total drag rating is created by the trailer, so any reduction is likely to be of significant benefit to operators.
Smooth side panels have, by Bedford in particular, been demonstrated to offer better, more efficient aerodynamic qualities, but the advantages of this type of research are being withheld from the consumer. There can be no doubt that one reason has been that the structure required to mount and install any such panel is susceptible to unacceptable risks of damage.
A more substantial mounting frame would have increased the unladen weight.
These problems can now be justifiably and realistically reviewed. The side guards fitted to trailers can be used as the support for flush-fitting outer panels. The framing is itself substantial, leaving designers with the simpler task of material selection.
Clearly the material must be light, to be attractive to operators carrying near maximum loads, while at the same time strong enough to resist minor impact damage. To facilitate ease of maintenance, the panels should be hinge mounted under the trailer bed, allowing each panel to be swung up out of the way for access. There may also be a case for a second hinge, part way up the panel to permit the panel to fold in the centre.
In this case the area occupied in a workshop, when the panels are open for access, is reduced, removing the lack of space argument. The mounting for the hinges and the eventual weight may predetermine the choice of material.
Simple catch fittings, to secure the panel to the side-guard frame present less of a limitation. With the support already available the panels could easily be of light alloy or even Keylar (special ultra-strong grp) construction.
As a form of spin-off from the achieved stabilisation of the airflow, the constant problem of wheel spray from trailers may be reduced or more strictly directed, enabling a feasible solution to this as well.
It is no secret that the Government, when it has succeeded in quantifying spray levels, will pass legislation to reduce spray to specific limits. By introducing a more effective form of trailer aerodynamics, a reduction in fuel consumption is made available from the outset, as well as a pre-emption of impending legislation.
The argument may be carried further, by the careful and thoughtful design of vehicle and trailer chassis. This could accentuate any financial saving, although rear guards appear to offer little hope by way of drag reduction. It may be possible, however, to use this device as the mounting for a reverse spoiler, to deflect air from under the body, into the low pressure area created behind the upper structure of a vehicle in motion. Roof-mounted spoilers could help in this department on van trailers, but this situation is limited by the overall height dimensions recently imposed.
The result of these measures would be an overall fuel saving, with very little increase in unladen weight. In the modern economic climate this must be the goal of all designers. So far as heavy vehicles are concerned, it is early days in streamlining, but it should be recognised that the science is of prime importance for a continued economic future. Perhaps it can be argued that trailer streamlining is too radical for most customers at this time. There may be some truth in this statement, but this implies a very conservative attitude is adopted by the transport industry.
With modern trends in both design and operation, the comment is demonstrated to be unreasonable. Short local delivery work may require simple, uncluttered vehicles, but with transit distances increasing, as the result of transport expansion throughout Europe, many operators are looking for better fuel consumption, particularly when road speeds are high on long motorway routes.
As drag factors increase by the square rule, aerodynamics are vitally important in this typr working environment. If the dustry is to be severely tricted by legislation, this is area where clever design car ploit Government requireme The technology of design i no means the only way in w the industry can help itself. I cation of those employees ponsible for vehicle loading fundamental importanc( loads are not to inhib vehicle's potential.
The sight of badly loa trucks is all to common, eve' high-speed roads. Loads r high, well above cab height one part of the load bed, vs the remaining load area is empty, constitute poor loac which merely increases I drag and fuel use. With the ti towards pre-loaded vehic this education needs to directed at those whose task to load both vehicles trailers. All to frequently tl people receive little or training although their skills reflect in an operator's run costs.
One last point to ponder possible increase in road-sr limits. Now is the time to a, ensure that when the limit crease, fuel costs do not r prices above the economic that customers can afford. A dynamics is an important fi today, but the foreseeable ft will make the subject param to all operators.
Bigger more powerful eng may offer a short-term solu but what will the cost be in t( of fuel usage? This is an which, everybody must ac needs an urgent reductio costs are to protect an opera trading ability.