TWO NEW A.E.C. MODELS.
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Provincial Bus Chassis for 52-seater Double-deck and 36-seater Single-deck Bodies Respectively. Simplicity, Accessibility and Interchangeability of Units the Leading Features.
111 ONG EXPERIENCE in the design of chassis for passengers and goods has enabled the Associated EquipMent Ca-, Ltd., to produce two. new chassis of exceptional interest, in which the main trend of design has been towards standardization of the units employed, combined with a commendable simplification of all details, a general cleaning up and the promotion of accessibility.
Of the two, perhaps the more interesting is the new provincial bus chassis designed to carry double-decked, coveredtop bodies having 52 seats, and coming within the gross weight of 9 tons.
Despite the many improvements incorporated in this chassis as compared with its provincial prototype, better methods of assembly, etc., have enabled a considerable reduction Pt price to be effected, so that from the point of view of value for money the improvement is
even more than appears on the surface.
The power unit employed on this and the other chassis is the 5-type engine with a bore of 120 mm. and a stroke of 150 mm., giving 45 b.h.p. at 1,000 r.p.m. This unit is highly efficient, and has proved itself in actual service to be )st reliable. The valves are all at the near side, and there is a three-point adjustable chain drive for the camshaft an the magneto, the combined pump and fan being driven by a 1-in. V belt. Lubrication is on the pressure 'and trough system, with a level adjustment for tli troughs. The cylinders themselves are cast in pairs, and the pistons are of aluminium alloy, the gudgeon pins being clamped in stamped-steel rods and working direct in the pistons. Four rings are employed, the fourth being at the lower end to act as an oil scraper.
Carburation is effected by a Zenith instrument, and above the carburetter
is a butterfly valve operated by a centrifugal governor, ,
The method of suspending the engine on the new chassis differs considerably fn.:wa that employed in previous models. The front of the engine is hung on a had in the centre of a frame cross-bearer, whilst the hack is carried by two spherically seated bolts which are continued through their frame brackets and provide . with springs; each giving a pressure of 700 /b, In this way the engine is, normally, secured almost rigidly, but if exceptional frame torsion occurs one or otner side of the rear bearer can lift slightly against the compression springs. This is an interesting feature as it is not always fully realized that even the ordinary three-point suspension does not relieve the crankcase of all torsional stresses if the two rear points be rigidly secured.
It is of interest to note that a thermostat is concealed in the water outlet from the engine to the radiator top tank.
From the engine the drive is taken through an internal cone clutch, the clutch spring adjustment being inside and rendered completely accessible by the provision of large hand holes in the clutch cone. The clutch stop iS of the fabric-disc type and actually of 10 ins.
diameter. The clutch iS faced with Ferodo.
Behind the clutch a split:led shaft, with a flexible coupling at its rear end, takes the drive to a four-speed gearbox, the forward end of which is mounted in a trrinnion bracket suspended from a cross-member. Spicer joints of large size are provided for the tubular propellet shaft, which has ar diameter of
8k. ins. A solid, stamped banjo axle casing is carried at a few degrees tram the horizontal, and beneath this is the worm gear.
Bon brakes act direct on the rear wheels. They are adjusted by means of huge wing-nuts on the back rods, these bei.ig accessible through the body trap for the rear axle.
A feature of the bus chassis is a dropped cross-member at the rear, which permits the provision of a low gangway entrance. There are also dropped frame extensions bolted on to carry the rear platform.
Taper roller bearings are provided for all the wheels, and the weight of the chassis is 3 tons 10 cwt.
So far as the frame is concerned, it is or rressed-steel channel tapered slightly to the ends and having a maximum depth f 9 ins. It will be remembered that in the former model the frame was of flitch-plate construction.
One of the innovations in this chassis lies in the change-speed control sear. It has the great advantage that whether applied to the forward-drive model or that in which the driver is in the ordinary position, the only modification required is an alteration in the length of one rod.
On the rocking lever of the change.
speed is a ball joint operating a combined sliding and rocking shaft which, in turn, operates a rocking and sliding shaft passing from the side of the frame to the selector forks of the gearbox. A leather muff is provided for the second ball joint-.
In some cases trouble has developed through the loosening of bolts in the rearspring front brackets because these have to take the driving and braking stresses. To cure this, the brackets are now bolted to the frame and each has a vertical tongue dropped between two pressedsteel channels bolted together and to the frame side members, being also well g-usseted.
To avoid binding, the brake crossshafts are all carried in spherical bearings. Wherever possible, brackets, etc., have been combined to serve two purposes; for instance, the engine rear brackets also carry the shackle pins for the front springs.
Rubber springs are provided to take a part of the load.
Steering is effected through a casehardened worm and complete wheel with a square-ended shaft which permits the wheel to be turned to fresh wearing positions. The wheel is carried on taper roller bearings.
A feature of the petrol tank construe
tion is that the tank itself is-carried in a special casing and it can be slid out by removing part of this casing.
This chassis can be obtained with 38-in. by 7-11. pneumatic tyre equipment if desired.
All the above-mentioned details apply to the 5-ton lorry chassis, except that in this case the driver is in the ordinary position and the axle is reversed with the worm abote, giving a straight-line drive.
The 6-ton chassis resembles the Ramillies chassis, and the drive is in the forward position, thus putting more weight on the front axle, which is designed accordingly, without adding more than a trifle to that on the back axle.
it is of interest to note that the Renown chassis can now be obtained with front-wheel brakes of the Rubury type, the selling agents for which are Clayton Wagons, Ltd., of Lincoln. Where this type of brake is employed it is connected to the pedal operatingone set of brakes on the rear wheels, the four wheels being braked together.
The Grenville provincial bus chassis for single-deckers or coaches holding 86 people has the standard position for the driver, overhead worm drive, and the same engine as in the Ramillies.