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Accent on Service in P.S.V.s 1/ , 1 his paper, " The

9th May 1947, Page 35
9th May 1947
Page 35
Page 36
Page 35, 9th May 1947 — Accent on Service in P.S.V.s 1/ , 1 his paper, " The
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Which of the following most accurately describes the problem?

Future Develop' merit of the Public Service Vehicle," Mr. D. M. Sinclair M.I.A.E., M.Inst.T., general manager Birmingham and Midland Motor Omnibus Co., Ltd., said that the name "public service vehicle" should always serve as a reminder that the aim must be to build and equip buses that would really serve in a manner which the public had a right to expect.

First to be decided, in design, were arrangements needed for passengers and crew. After that the engineer should accommodate those needs, then provide a bus that was economical to operate.

For the benefit of the passenger, them should be complete ease of entrance and exit. Regulations. should, perhaps, be amended to permit folding doors opening outwards.

One of the defects of the doubledecker was that the regulations did not permit adequate headroom, upstairs or in the lower saloon.

Heating Needed A serious effort must be made to provide adequate heating in both singleand double-deckers. 'this could be done by forcing heated air through suitable ducting. Good draughtless ventilation was also essential.

Closer attention should be given to windows, interior lighting, and flooring. Every bus should have adequate destination-indicating equipment.

As to the driver, he should be given every comfort. On the average, a bus driver covered 100-120 miles per day. Cab entrances should be made easy and cab planning as a whole given great attention. More elbow room was badly needed. Seats should be adjustable, and should have comfortable cushions and squabs. Controls should be carefully positioned.

The conductor was in many ways better off than the driver, but there were oertain special requirements. Signal-bell pushes should be easily accessible and destination gear simple to operate. There should be a personal locker. A tip-up seat was desirable.

Before going on to consider the construction of a suitable bus, it was necessary, first, to determine what sort of general performance was required.

"Present maximum speeds were satis factory, but not acceleration or hill climbing. More power was required and a general increase in engine sizes was predicted. The engine in the bus of the future would be of at least 10 litres capacity.

There would have to be a big improvement in suspension. Soft riding, with an absence of pitch or roll, was the ideal. Brakes, which must be smooth in operation, would have to keep pace in design with the improved per formance visualized. Suppression of noise must be improved.

Legal Handicaps When the stage had been reached at which the specification could be handed over to the engineer, he would find himself at once up against a serious difficulty in the restrictions imposed by the existing Construction and Use Regulations and Conditions of Fitness. He would be especially handicapped by restriction of width to 7 ft. 6 ins., and length on two axles to 27 ft. 6 ins, for single-deckers and 26 ft. for doubledeckers.

The logic which decreed different lengths for singleand double-deckers was beyond understanding. The proposed 36 ft. maximum should he permissible on both types.

• Permission could now be obtained to operate 8-ft.-wide vehicles, but we

should not deceive ourselves. The Ministry of Transport had so tied up this permission with conditions, that it was a difficult and laborious matter to obtain it. Answers were slow in corning, and, meanwhile, no one knew whether to build 8-ft. buses or the old unsatisfactory ones of 7-ft. 6-in. width.

It was not only in these respects that the regulations required amending. In fact in the interests of progress, the only sensible thing to do was to scrap the lot and start again. The redrafting should be done by a committee of practical men, including, if desired, a driver and a conductor. The regulations should be drafted in simple language. Legally minded people would be better kept out of this job, said lMr._ Sinclair.

Returning to design he remarked that much could, and must, be done in the development of the crankcase assembly. He did not, however, believe that the cast-iron crankcase was a cure for broken crankshafts in oil engines. Use of it was a retrograde step.

Crankshaft FailurPs

He suggested that the chief cause of crankshaft failures in compression-ignition engines was faulty design of the crankshaft itself, coupled with the excessive running clearances allowed with lead-bronze bearings. Manufacturers should try to develop a bearing material which would stand up to oil-engine pressures and at the same time permit of running clearances comparable with those required for white-metal bearings.

In the comparatively near future it was thought that crankcases would again be in light alloy integral with the cylinder block, with hand-fitted hardened cylinder liners. Cast-iron crankshafts might, in due course, replace the steel shafts.

Tappets would be of the automatically adjusting type, probably hydraulic. The oil filter would be of a really efficient pattern and would make it possible to discontinue the practice of changing the oil except at major docks. Air filtra tion would also be improved. The industry would then have gone far towards achieving the ideal engine—one which could be boxed up and forgotten.

Mr. Sinclair-suggested that the makers of fuel-injection equipment should consider producing a pump with the plunger elements mounted in a circle and

operated by a single cam. The earn could be similar to that used in radial engines for valve operation and the whole assembly would be rather like an oversize ignition distributor, It was thought, he said, that the forward-mounted engine would have lost much of its popularity and that engines would be mounted amidships, under the floor. There were many arguments in favour of this position, and few against it.

As regards transmission, there was ample room for both the hydraulic type and the normal gearbox and clutch. The time was fast approaching when the worm-driven rear axle might be superseded by the bevel-driven type, probably with hypoid gears.

There was little, Mr. Sinclair said, in favour of retaining the leaf spring. Several other suspension systems were available, and all had been employed with marked success on cars. The use of independent front wheel suspension was probable. Tyre manufacturers had a big part to play, by offering tyres which could be run at lower pressures than was the case to-day.

Chassisless Construction

He felt no hesitation in recommending the use of chassisless construction. In such a design the whole of the body was treated as a stressed member, and was sufficiently strong to carry all the load normally imposed on a chassis frame and separate body. Such a structure would be entirely metal. Nevertheless, he advised caution in the wholesale use of light alloys.

In conclusion, Mr. Sinclair said that he would gladly see the end of the double-decker bus. In most respects, it was• a thoroughy unsatisfactory type. Conditions demanded however, that it continue to be used for a long time in this country.

He said he had tried to present a picture of how the public service vehicle was likely to develop in the next 10 years. Beyond that period it was diffi

cult to make prophecies. The atomic age might have arrived and we might even be having atomic power cuts?

One could, however, visualize the advance of the supercharged two-stroke engine, possibly with air-cooling and, perhaps, of the opposed-piston type.

It seemed doubtful whether the gas turbine would be useable on public service vehicles, mainly because of the question of fuel economy. There was also to be thought of the possibility of electrical power units picking up current by means of radio. This might seem fantastic, but stranger things had happened.

The universal adoption of chassisless construction was more than likely, as was that of fully automatic transmission systems. A hydraulic pump, driving hydraulic motors connected directly to each driving wheel was an arransement which might be worth considering. The leaf spring would have disappeared, and probably all wheels would be independently sprung.


Organisations: Ministry of Transport
People: Sinclair

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