Weight Saving May be
Page 45
If you've noticed an error in this article please click here to report it so we can fix it.
Costly—Major F. J. Chapple
Whilst Weight Saving was Desirable, it Should not be Achieved at the Expense of the Present Standards of• Reliability : Need for Co-operation Between Operator and ,Vehicle Maker
IvEIGHT saving in vehicles is the present general , demand, primarily to obtain fuel nomy, but it is not an object in itself. ight saving at any price may prove be an expensive operation.
4ajor F. J. Chapple, D.S.O., 0.B.E., irman of The Bristol Tramways and Tiage Co., Ltd., made this comment ). paper dealing with public service icle design, which he read yesterat the annual conference of the ttish Road Passenger Transport ociation at Pitlochry, Perthshire. Iter dealing with the development the modern bus, Major Chapple ted to the chassisless vehicle. It was cult to agree, he said, that the ;sisless type of construction had a Lt deal to do with weight saving, :cially as the body was usually also light construction and had a imum of items that were usually ient in connection with seating, ring, windows and so on.
he disadvantage of the use of an erfloor engine in such a design was, said, that a comparatively heavy TIC had to be supported more or less way between the axles, and the )orting structure had more to do i was the case with a forward
toted engine. ,
High Floor Level arther, this design necessitated a . floor and four wheel-arches had to circumvented. Consequently, the 7 had, in most cases, to be further id. The main objection was that ss appeared to he more difficult with a forward-engine design. the case of a coach, the high floor essed some advantage, inasmuch as we passengers a better view of the
itryside. . see 'seemed to he good reason for uring integral construction. The simply meant that the vehicle was tiled as a whole and, as far as ible. full use was Made of the igth available in both the body and underframe. Close collaboration needed between the engineer and bodybuilder, but it did not necesit mean that the whole vehicle I be provided by only one maker. ie obvious course in weight saving carefully to examine established ice and to determine which parts I be usefully retained and which I be modified. In the case of ;is units, a detailed examination the saving of a pound here and were normally required.
The engine was the principal item of weight, and the standard oil engine was heavy. The simple course might be to reduce the size and regain the power lost by increasing the speed. The 'present large mileage between overhauls yielded great economy, and high engine speed was liable seriously to affect it.
If, however, a smaller high-speed engine could be accepted as satisfactory, the reduction of torque would enable a lighter transmission to be employed, subject to proper gear arrangement, including a considerable gear reduction in the axle.
If it were felt that a normal oil engine was still the most satisfactory type in economy and maintenance, some weight could be saved by careful attention to detail in design.. It might be, said Major Chapple, that the more extensive adoption of belt drives could offer some saving and enable higher-speed dynamos, water pumps and so on, to be used to cut weight.
Big Engine Justified
In the case of London Transport, the use of the larger engine could be argued on the ground that the routes operated were congested, and entailed many stops. Here the bus must be able to keep its place with other traffic, and must attain the average speed in a minimum of time.
Some increase in average speed was the only form of economy that would affect the high wage costs, but it must not be accompanied by a higher maximum speed. A faiiPly easy country route did not, of course, present the same problem.
The user should, however, in fairness to the vehicle maker, declare whether he was going to turn a 45-seat, bus into one carrying 73 passengers on occasions. Engine capacity of about 0.8 to 0.9 litre per ton for laden single-deckers had been generally accepted for some years. With smaller engines, the output demanded meant that more horse power per litre must be found, either from higher b.m.e.p. or higher speed, or both.
Single tyres for rear wheels would save weight, but operators would have to satisfy themselves that the use of the vehicle was satisfactory. Major Chapple had recollections of reduced adhesion with singles at the rear, especially as they had to be of the highpressure type.. Riding comfort was also affected.
On the use of light alloys, Major Chapple said that whilst they had a part to play, it was not quite of the extent that many people suggested. Cost, too, was of some importance.
It seemed that the greatest weight saving could be achieved in the body, always provided that the requirements of the operator were modified. The author gave a table in which was shown the increases in weight of a low-height double-decker between 1939 and 1949.
Sliding window units with patent glazing and 32-oz, glass, instead of 26oz glass, and half-drop lights, raised the weight by 144 lb.; interior roof lining including domes by 106 lb.; larger and more robust seats by 143 lb.; 19 s.w.g. upper saloon panels by 28 lb. There were numerous other items all adding a few pounds to make a total of 8 cwt.
Refinements Must Go
Major Chapple thought that weight saving must involve the sacrifice of many refinements, and that the bodybuilder could not do so effectively without some modification of the general specification.
A second table gave weight details of a 45-seat body for an underfloor-engined chassis, the overall dimensions being 30 ft. by 8 ft. The total figure was 2i tons.
The bodybuilder who filled light-alloy sections with timber would have to desist and would probably have to produce lighter sections and adopt riveting on a more extended scale than now. The manager, who did not spend much of his time on a bus, was not always the best judge of what the passenger regarded as essential.
Major Chapple concluded his paper with some remarks on suspension. No doubt many people were experimenting with various forms of suspension as an alternative to the leaf spring, he said. He had always had in mind that the body and underframe should form a rigid box, and if this were supported by independently sprung wheels this box need not possess the same strength and solidity as was necessary with the usual method of suspension.