ROAD TEST RESULTS
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Unbiased Reports Which Help the Operator in Vehicle Selection, and the Maker with Valuable Performance Data for Comparison
IN response to requests from operators and other readers of " The Commercial Motor," a summary of road tests of post-war vehicles, which have been conducted by this journal, is produced on the following page. These tests are generally recognized as being unbiased reports on vehicle performance and are used by operators as a guide in their selection when purchasing a model in any particular iange.
Manufacturers regard these tests as a standard by which to judge their own particular product, and they are enabled to draw comparisons of results with their own tests.
Our road tests are made with standard machines in the condition in which they would normally be supplied to users. To observe a closz check on fuel during the consumption test, a small calibrated tank is fitted in place of the main fuel supply. Thus, although only a small mileage may be covered, the results are as accurate as would be obtained on an extended test on a full tank of fuel, which is normally the operator's method of checking consumption. From a comparison with operational figures, our results show that the course chosen, and the conditions of the test, are perhaps more stringent than would normally be encountered, and the consumption is usually slightly heavier.
This is only to be expected because a full load is carried all the time, whereas the same machine, under operational conditions, would presumably be running light for periods throughout its day's work Some operators have claimed up to 25 per cent better fuel consumption than those obtained in our tests, but these claims have invariably been made where the vehicle is fully laden on the outward journey and running light on the return, or where a bulk load is carried which is considerably below the maximum weight capacity of the particular chassis With the high pePformance demanded of modern commercial vehicles, the braking system plays an important role. It is known !hat some models which have an effective braking system are troublesome because of the need for frequent adjustment at the shoes if efficient and constant retardation is to be achieved. This may be regarded as a factor brought about by incorrect selection of brake drums and facing materials, or by employing a size of shoe and facing which has insufficient surface area for its particular loading.
The frictional area and load, per sq. in. facing area are given in the data panel of each test report, but the selection of materials, except for tests of brake fade under overheated conditions, cannot be judged during a one-day test. Even so, our tests have revealed weaknesses in certain designs, and these have been brought to the notice of manufacturers. Within the past 12 months two vehicles have been subjected to major modifications in design following the results of our tests.
Lubricating-oil temperatures are closely observed by the vehicle manufacturer and oil concerns The vehicle manufacturer looks for overheating under adverse conditions, whilst the oil companies regard these tests as a basis for operational requirements and form their recommendations for certain grades of lubricants from the results.
With the, return of normal conditions and the announcement of more new models from the manufacturers, every effort is made to keep up-to-date with
road tests. Wherever possible, the manufacturers co-operate, and when it can be arranged we road-test the vehicle before the announcement is made. However, this does not mean that prototypes are accepted for test.
Thus, we are able to supply our readers with a full road test, in addition to the description of the vehicle, upon its announcement. The reader is not left with the impression—here is the vehicle, now surmise its performance Our readersthus have a record of what a particular vehicle can do arid may judge its relative merits against those of.other makes of chassis or earlier models of a similar type.
Some passenger-vehicle operators have asked for tests to be made on complete buses or coaches. Whilst we would like to co-operate, body builders are not readily forthcoming who would be willing to risk a body, possibly costing several thousands of pounds, to the rigours of our tests It would be necessary to load the machine with ballast in the form of sandbags or weights; unfortunately, these have a habit of breaking loose on emergency brake applications, possibly causing heavy structural damage. Loading, unloading and repairing would involve many man-hours of work With the present shortage of labour, materials and
vehicles, the makers cannot readily grant this favour. •
In the table of results given, the salient features of .
construction and performance have been detailed. Certain performance results may require qualification, such as comparatively poor braking figures which may have been obtained under adverse conditions, or fuelconsumption tests where specific conditions may have been employed representing operational requirements. Before drawing a strict comparison from the results of the table, reference should be made to the conditions outlined in the actual tests, the serial number of which is given in the second column.
Because of the restriction of space, the performance results of many of the battery-electric vehicles have been omitted, as to accommodate these results it would be necessary to use additional columns. However, we are willing to supply further pal ticulars of any of these tests, battery-electric o otherwise, on request.
• To draw a strict comparison of performance between vehicles, it would perhaps be better if they could all be tested over the same course. With the present shortage of vehicles and the time they are available to us for test, it would not, however, be possible to follow this procedure. At present, the fuel-consumption course is mapped out to give as near comparative tests as the local territory will permit, and the acceleration and braking tests are
made, wherever possible, on a concrete-surfaced road. Of course, tests are always made with runs in opposite directions and the results arranged to compensate for any slight variation in gradient or wind. The accuracy of the data published has, on numerous occasions, been the subject of favourable comment by operators