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First Authentic Details of
Page 92
Page 93
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THE A.E.C.
type Bus
CHASSIS
Details of an Unorthodox Model Now Revealed after an Experi mental Try-out of the Chassis Under Service Conditions. An Unusual Layout for which Definite
Advantages are Claimed
IN our issue dated September 9 of last year we were able to disclose certain of the features of the experimental A.E.C. single-deck bus with the enginegearbox unit mounted at the side of the chassis frame, which was being tried out by the London General Omnibus Co., Ltd. At that time we were permitted to deal with the new model in a. general way, and enumerated the different advantages resulting from the unorthodox mounting of the principal components. Although the chassis was originally introduced for single-deck service, it has subsequently been used as the basis of a double-decker.
It is only now that authentic details of the chassis design have become available, for information has been withheld until the experience gained from the initial operation of the vehicle has enabled some definite form of standardization to be reached.
The new model is known as the Qtype chassis, and the engine and gearbox are mounted o ut s i de the chassis frame behind the off-side front wheel. This unusual layout has meant designing a special frame, narrow in the forepart and widening considerably towards the rear.
The engine cylinders are mounted at a slight angle from the vertical, in order . to keep the overhead seat level as low as possible and to facilitate the removal of the cylinder head. A metal casing separates the engine (which is mounted on rubber) from the main part of the body, and assists in preventing heat from entering the passenger section.
Ease of access to all engine auxiliaries Las been achieved by moving the valve gear, carburetter, magneto, starter and other important components from the near side to the off side, where they can readily be reached by the removal of a panel fitting flush with the body side. The transmission is carried obliquely to an offset differential.
It should be mentioned that this design, and alternative designs of frame, engine mounting and method of carrying the transmission, are protected by patents.
From the operator's point of view the Q bus has a number of outstanding features. First and foremost comes increased seating capacity. .Secondly, the position of the driver, inside the pas
senger compartment and immediately opposite the front entrance, has advantages. The driver has improved visibility and does not suffer discomfort from the heat of the engine.
The overhang of 6 ft. at the front enables a lifeguard, similar in some respects to the tramcar type, to be used, and this has been successfully tested and approved by the Ministry of Transport.
Another important point is that weight is equally distributed on each Of the four wheels, which provides better riding and greater stability, The ridingqualities are also improved by the fitting of larger tyres. Furthermore, only single tyres are used at the rear, which enables the springs to be placed much wider apart. The wider frame also gives a better body mounting.
Equipped with a fluid dutch and fourspeed epicyclic gearbox, the change speed has been still further improved on this model by the incorporation of a vacuumservo clutch pedal.
The six-cylindered engine has a bore of 110 mm. and a stroke of 130 mm., and it develops 62 b.h.p. at 1,000 r.p.m. and 120 b.h.p. at 2,400 r.p.m. Features of the power unit •are an overhead camshaft a detachable aluminium cylinder head, magneto ignition, Soles carburetter, water pimp circulation controlled by thermostat, and pressure-feed oil lubrication to main and big-end bearings.
The radiator is of the gilled-tube type and is placed in front of the engine ; it is mounted on rubber blocks,
The fonr-speed gearbox provides the following ratios :—First, 4.15 to 1; second, 2.36 to 1 ; third, 1.56 to 1,
fourth being direct : the reverse ratio is 6 to 1. The front and rear cardan shafts have Spicer couplings.
The rear axle is of the worm-driven, fully floating type, with 8-in, worm centres, and has a standard ratio of 6.2 to 1 for the double-deck chassis and 5.4 to 1 for the single-decker. The axle is a one-piece banjo-type forging, with aluminium worm easing and cover. A good maintenance feature is that the brake drums can be removed without disturbing the wheel hubs. The steering is of the worm-and-nut type, as on other A.E.C. passenger models.
Servo hydraulic brakes are employed, the foot brake taking effect on all four wheels, whilst the hand brake actuates shoes in the rear-wheel drums.
The frame is of 11-in. by 3-in, pressed channel section, and the front end of the near-side member is down-swept to facilitate low loading ; the cross-members are tubular. The 45-gallon petrol tank is carried outside the frame on the near side, between the front and rear wheels, and fuel is fed to the carburetter by a positively driven diaphragmtype pump.
The dimensions of the tyres for the double-decker are 11 _25 ins. by 20 ins. and for the single-decker 10.5 ins. by 20 ins. ; detachable disc wheels are fitted.
The following are the main chassis dimensions for the two models :—
Double-decker: Wheelbase, 15 ft. 10 ins.; front track, 6 ft. 41 ins.; rear track, 6 ft. 6 ins.; overall length, 25 ft. 84 ins.; overall width, 7 ft. 54 ins.; frame height (laden), 1 ft. 10 ins.; turning circle, 60 ft Single-decker : Wheelbase, 18 ft. 6 ins.; front track, 6 ft. 4a ins.. ' rear track, 6 ft. 6 ins. ; overall length, 27 ft. 2,k ins. ; overall width, 7 ft. 54 ins.; frame height (laden), 1 ft. 115 ins.; turning circle, 66 ft.
The body, which is of registered design, is streamlined and has no cavities or projections in front. In the single-deck model the entrance is behind the near-side front wheel and faces a longitudinal seat for six persons over the engine housing. In front of this is the glass-partitioned driver's compartment, and, on the left, facing the nearside front window, two transverse seats. Between these and the doorway is a longitudinal seat for two persons. The rest of the seating is on orthodox lines.
In the double-decker the entrance is ahead of the near-side front wheel and opposite the driver's compartment. Behind this the stairs ascend to the upper deck, the longitudinal seat over the engine housing accommodating _three people. Opposite, on the near side. is a longitudinal seat for two people.