FEATURES OF LONDON'S SIX-WHEELED BUSES.
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The Arguments in Favour of Three Differentials. Pneumatic Tyres, Four Forward Speeds and a Body Seating 68 Passengers.
LONDOX has always been prepared to accept improvereents in its passenger transport facilities with scarcely more than a mild flutter of the eyelids, and it will absorb the six-wheeled 68-seater covered top saloon bus with as little, remark as it expended upon the low platform covered top N.S. bus, which attitude, however, is not to be regarded as exhibiting any lack of appreciation ; rather, it is the simple recognition of the fact that it looks to the London General Omnibus Co., Ltd., its directors and its engineering staff, to keep up-to-date in it vehicles and their equipment, and to the Public Carriage Department of Scotland Yard to be receptive of new ideas. At one time, innovations were strongly disapproved by the police, but of later years that attitude has changed and larger capacity buses have been folloWed by top deck protection and the approval must logically follow of a further increase in seating capacity rendered possible by the adoption of the four-wheel bogie and the pneumatic tyre, both of which have long ago passed the experimental stage.
The ability to carry just twice the number of passengers of the old B-type bus justifies the heavier expenditure in construction and maintenance entailed by the latest type, and the use of pneumatic tyres removes all cause for objection on the part of local authorities and property owners on the bus routes on the score of vibration.
That the pneumatic-tyred six-wheeled bus has already been adopted in some of the more advanced of the provincial cities and towns and before the London General Omnibus Co. has put a similar vehicle on the road is not a matter for surprise, for with so much' more at stake the London company must perforce move more warily in its changes, for it is useless to make any experiment in London with fewer than about a hundred buses of a typo. The best way to experiment is found to be the equipment of an entire garage with the new type, so that the data on revenue and cost of running and maintenance and the experience in actual Operation can all be learned at once and without possibility of confusion and error.
The six-wheeler proposition has, to our knowledge, been closely studied by Mr. G. J. Shave, the Operating Manager and Chief Engineer, and his technical staff, for some years, for we have discussed six-wheelers with Mr. Shave from the earliest days when information concerning the experimental work carried out at Akron, U.S.A., was in our hands. The outcome of the work of the designing department of the Associated Daimler Co. Ltd., follows accepted practice in most respects, but in the transmission of the power to the driving wheels there is a distinct departure, and as we have had the advantage of listening to the arguments of the designers in support of their plans, we feel that many will be in accord with them.
From the front axle to the centre of the two rear axles the wheelbase, so we are told, will not exceed 18 ft. C28
6 ins., and the overall length of the vehicle will be within the projected maximum allowance of 30 ft. On these,dimensions, a 68-passenger body is possible with a loaded overall height not exceeding 14 ft. 3 ins, and with full headroom to both upper and lower saloons. The practice introduced with the N.S. type of employing one step -only to the platform with a 9-in. step to the interior will, no doubt, be followed.
The power unit will be the Daimler sleeve-valve sixcylindered engine of 97 mm. in the bore and with a piston stroke of 130 mm., developing 50 h.p. at 1,000 r.p.rn. and 100 h.p. at 2,000 r.p.m. The cylinders are cast in blocks of three. There is thermostat control of the cooling water temperature, pump lubrication to all bearings and timing gear chain, an air cleaner to the air intake and a special filter in the oil-circulating system.
Through a single-plate dry clutch and a four-speed gearbox of the spur type the power is transmitted to all four rear wheels by means of central underslung worm gears. There is a differential to each axle and the departure from general practice referred, to lies in the provision of a simple form of differential gear between the drives for the two axles. Thus each axle must always carry its fair share of the drive, although any wheel is capable of spinning when it loses contact with the ground. In exchange for this small loss, which sacrifices a possible saving in tyre wear, the possibility, when a pair of tyres is worn or not inflated to the same pressure as the others, for the whole of the transmitted torque being passed through one axle only with the other axle overrunning the first and therefore taking no part in driving the vehicle is obviated.
The final drive to each road wheel is through the rack and pinion system devised for the N.S. chassis. The wheels will be equipped with 36-in. by 8-in, pneumatic tyres, and they are of the detachable-disc type.
Brake drums of the largest possible diameter that can be accommodated inside the standard disc wheels are employed. Braking has had special attention. The driver's brake pedal acts through Westinghouse mechanism and -applies brakes on all four rear wheels. The pedal is also mechanically connected so that it will actuate the brakes should the air system fail.
Such is a brief sketch of the new six-wheeled chassis as we foreshadow it. The body is well up to the L.G,O.C. standard for appearance, comfort and lightness and conforms to the company's recent practice, except that, so we understand, sliding lights are to be fitted in both saloons, whereas so far they have only been employed for the upper saloons of the covered top buses.
When the first bus is built and completed it must be submitted to the Public Carriage Department for approval and after that will come the consideration of manufacture and placing the type in service.