LONDON'S NEW
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SIX-WHEELED
BUS
Details of an Experimental Type Embodying the A.E.C. Renown Six-cylindered Engine and Providing Greater Speed and Comfort for Passengers.
SINCE the early days of development of the six-wheeled chassis for passenger and goods transport the London General Omnibus Co., Ltd., has closely studied six-wheeler design. In 1927 the first six-wheeled double-saloon bus, known as the LS type, was placed in service on the London streets and sine then the company's engineers have been engaged in evolving six-wheeled vehicles still mere suitable to the special requirements of London service.
On Tuesday last, August 6th, a new type of double-deck bus, accommodating 54 passengers and known as the "LT1," was put into use on the 16a service which operates between Victoria Station and Cricklewood Broadway. This motorbus is the first of three experimental vehicles that are to be built, and after a study of the comparative merits of them the company will determine its specification before commencing upon an extensive building programme. The new chassis is the thirty-seventh type which the company has produced during the past two decades. It is not a large-capacity vehicle, since it accommodates 30 passengers in the upper saloon and 24 in the lower saloon, but it will be appreciated that, having a six-cylindered engine capable of developing 95 h.p. when rotating at 2,000 r.p.m., and six road wheels, four of which are driven, the new vehicle will be capable of high average speeds and quicker stopping and starting, and will afford liberal comfort 524 to the passengers carried The chassis has been designed with special regard for speed, braking, smoothness and silence. The engine is of the A.E.C. Renown type and has a bore of 100 mm. and a stroke of 130 mm. It develops 48 b.h.p. at the slow speed of 1,000 r.p.m. Inverted valves are operated by an overhead camshaft, the cylinder head being detachable. Water circulation is by pump and pressure lubrication is provided to all main and
big-end bearings. The crankshaft is particularly heavy, ensuring a vibrationless power unit, and its seven bearings are 21 ins, in diameter. With the object of obtaining accessibility the dynamo, magneto, carburetter, water pump, sparking plugs and oil filler are located on the near side of the engine and, as the front cross-member of the chassis is detachable, the engine can be easily removed from the chassis.
The engine and gearbox are constructed as a unit which is suspended at three points in the chassis frame. The use of driving belts has been eliminated, fan and dynamo being driven by the timing chain. Each chassis is equipped with an electric starter. The sliding gears provide four forward ratios as well as a reverse. Very wide gearwheels and shafts of large diameter are used, all gears and shafts being ground all over. The gear lever is spherically mounted on the left of the driver. The two rear axles are constructed with shafts 3 ins, in diameter mounted on adjustable tapered roller bearings. Worm drive is employed, the worm gearing and differential being quickly detachable from the axle casing, and a third differential is mounted on ball and roller bearings in the forward axle at the rear end of the worm shaft. Both axle casings have exceptionally large oil capacity. Torque is borne by a blade of chrome-vanadium spring steel carried in robust cast brackets mounted at the centre of each of the axle casings; this blade has cylindrical ends, the forward end being free to oscillate and slide in its bearing whilst the rear end is capable of sliding only.
The rear bogie is suspended by two springs of ample length which are carried in the centres by heavy spring chairs swinging in the bogie brackets. The brackets are riveted to the frame and are stiffened by a 4-in, tubular crossmember. As regards braking, both hand lever and pedal operate on all four driving wheels, each actuating an independent set of internal expanding shoes. The foot-operated brakes are assisted by Dewandre servo vacuum mechanism.
The orthodox springing of the front axle is improved by hydraulic shock absorbers, and the steering gear is of the Manes type. The frame is upswept over front and rear axles and has a maximum depth of ill ins. All the cross-members are of tubular section. Two 25-gallon petrol tanks are carried at the sides of the frame, the supply being by an Autovac which has a 3-gallon reserve. A mechanically operated tyre pump is mounted on the gearbox and positively driven by a layshaft.
The chassis weighs 4 tons 3 cwt. 2 qrs., the front axle bearing 1 ton 17 cwt. 1 qr. and each rear axle carrying 1 ton 3 cwt. 14 lb. The turning circle is
59 ft. and the clearance under the rear axles Is 61 ins. All wheels are equipped with 36-in. by 8-in. pneumatic tyres.
As regards the body, an entirely new design of seat is employed which gives more room for the two passengers side by side than in any previous model of L.G.O.O. bus. There is also ample knee room. An improvement has been ,effeeted in the lighting arrangement. No lighting fitments are visible in either saloon but in sections of the ceiling translucent panels have been fitted which conform to the curve of the roof. These give a diffused glow throughout the bus sufficiently bright for reading purposes without being in the least glaring. The vehicle is well ventilated, the upper deck having 14 half-drop windows and the 'lower deck eight half-drop windows. Each saloon has three front ventilators. The waist rail is unusually wide and strong, the object being to provide greater security.
An innovation so far as London buses are concerned is the cab provided for the driver. It is not completely enclosed but affords ample weather protection and has a more businesslike appearance than the experimental types of half-cab which Londoners have seen on one or two buses recently. The cab is so arranged that the driver has good visibility in all directions and he is able to signal his intentions to other road users, In conclusion it should be stated that although the new vehicle is being tried out on a heavily trafficked route, it is designed rather for suburban services where higher speeds are possible. The second and third experimental buses will be somewhat larger than, the LT1 and more suited to the busier town routes.
A provisional order has already been placed by the London General Omnibus Co., Ltd., for 270 new • vehicles, of which 200 will be double-deckers and 70 will be single-deckers, and it is expected that in the spring 41930 further orders will be placed. The final specification of the 270 buses which are on order will be the result of experience gained with the three experimental types of -which the .LT1 is the first to be put into service in the Metropolis.