A NEW CHASSIS FOR LIGHT 'BUSES.
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First Published Details of the Latest Type Graham-Dodge Brothers Product for Bodies Holding 16 or 20 Passengers According to Wheelbase.
MARKED attention is being paid by manufacturers, not only in this country, but throughout the world, to the production of chassis suitable for buses of small capacity running on pneumatic tyres and capable of maintaining comparatively high average speeds. Such a chassis has been produced by Graham Brothers in conjunction with Dodge Brothers (Britain), Ltd., and is marketed in two wheelbases—the long, known as the L.B. model of 13 ft. 2 ins., and the short, the F.B., of 11 ft. 8 ins.
As is usual with the Graham Brothers chassis, the standard power unit utilized oh all Dodge Brothers' vehicles is embodied. Several important improvements have been made in the new chassis as compared with previous inodels. The frame of the L.B., for instance, is 2 ins. lower ; this may not appear to be much, but it is surprising what a difference it makes when actually viewing the vehicle. It is attained by employing smaller wheels carrying 32-in. by 6-in. straight-sided pneumatic tyres in place of the 36-in. by 6-in. tyres previously employed.
The frame, also, is different. Whilst being flat on the upper flange, the lower flange is slightly upswept over the rear axle and a thick rubber cushion bolted under each side-member, so that, in the event of exceptionally bad roads being encountered, resulting in the axle touching the frame, the shock is greatly reduced. Incidentally, the frame is tapered to front and rear, and given a long but slight insweep to the front, where the side-members end in a stout channel-steel fender instead of in the usual dumb-irons, whilst brackets under the side-members carry the front ends of rbe springs.
Important differences are also to be found in the braking gear. The external-brake bands employed on previous 30-ewt. models are no longer fitted, both brakes now consisting of internalexpanding bands situated side by side in wide brake drums and possessing the feature of being totally enclosed.
It is obvious that the braking has received much attention, and it appears to be highly efficient. Each band is fulcrumed at the rear _end and expanded by a cam at the front end ; but the rear mounting is slidable, and the slide is held against the action of a compression spring so that, as the band is expanded, the pressure on the drum is not concentrated over the front portion, but over the whole area. The bands are also held by a spring-loaded bracket so that no side thrust is exerted On the cams.
One brake cam is operated by a tube, whilst the other is on a rod passing through this tube, and the levers are secured by miniature splines or serrations on the tubes and shafts. Thumbnut adjusters are provided for each brake, and major adjustments are effected by removing the levers and fitting them in a different position on the serrations, where they are locked by cotter bolts. Miniature whipple-tree compensators form another addition to former design.
Following the most modern practice, lubrication throughout is by grease-gun, the system being the latest Tecalemit, previously known as the Allyne-Zerk. This system gives an extremely high pressure and obviates clogging of the ducts.
It is rather unusual in a chassis of this size to find that cast-steel-spoked wheels are employed, and we must say that these .give the vehicle a satisfactory air of solidity and add considerably to its general appearance. They are equipped with Firestone demountable rims, and the brake drums are bolted on, whilst the spare rim and tyre are carried on a special frame under the rear of the frame proper.
Dealing with the power unit, this, as has already been stated, is the wellknown Dodge Brothers engine with an R.A.C. rating of 23.8 h.p. and a b.h.p. of from 30 to 35. The four cylinders are east en bloc with the upper half of the crankcase, and are equipped with a detachable head.
Carburation t is attended to by a Steward instrument, and ignition by Watford magneto situated on the off side and driven through the centrifugal water pump, a special Watford enclosed rubber coupling being utilized. A. combined North-East unit is employed for starting and providing the electric current, and a four-bladed fan is mounted, for adjustment purposes, on a swinging bracket and driven by a flat, rubberized
fabric endless belt. The North-East unit is driven, or drives when starting, through a silent chain. The bore and stroke are 31 ins. and 4-i ins, respectively, and the valves are all at the off side, the cylinders being L-headed. Three bearings are employed for the crankshaft, and the oiling system is combined pump and splash, the pump being of the eccentric type driven by spiral gears from the crankshaft. Quietness of the timing gears is ensured by using helical teeth.
Cooling is effected by a radiator of the vertical tubular-core type, with horizontal gills the whole width of the block. The capacity of the system is approximately 21 gallons. • The fuel supply is on the Autevac principle, the tank in the chassis we examined being of oval shape, holding 15 gallons, and mounted under the driver's seat ; but it is a very simple matter to change this to any other position to conform with licensing regulations.
Engine, clutch and gearbox form a unit, which is three-point mounted in the chassis.
The clutch has seven discs and runs dry. It is enclosed in a pressed-steel housing, and the driving discs are faced with a moulded asbestos friction material. Three speeds forward and a reverse are provided by the neat but strongly constructed gearbox, which is of the selective sliding type, and possesses the important and somewhat unusual feature that the layshaft is idle when the direct drive is employed, a feature which reduces wear and makes for silent running. Incorporated in the gearbox is a drive for the speedometer.
Behind the transmission ease is a ball and-socket casing enclosing a ring-type
universal joint. A point in the construction of the ball-and-socket joint is that, when first assembled, the proper clearance between the ball and socket is effected by the use of a number of steel shims .01 in. thick, and these can be removed as required to take up any slight wear which occurs.
The propeller shaft is in two sections, with a self-aligning centre bearing and a special type of ball-bearing universal joint behind this, whilst another of this type is mounted in front of the axle. In this joint a spindle with a ball at the end is welded into the tubular propeller shaft, and a trunnion pin pressed through the ball end on which two hardened and ground balls are free to rotate, and at the same time to-ran in ground cylindrical ball races in the housing, whilst the main ball fits closely into the large cylindrical section of the housing.
Final drive is effected through spiral gearing, and the axle shafts are splined and slightly tapered for the wheels, the shafts being semi-floating.
In the case of the Elliott-type front axle a further improvement is the Pro
vision of ball-thrust bearings in the steering pivots, thus making the steering.much easier than in former models in which plain bearings were employed.
In the L.B. model the frame height from the ground of the complete vehicle
with load is 2 ft. n ins., the road clearance Si ins, and the turning radius 29 ft. 6 ins. The road speed is between 25 m.p.h. and 30 m.p.h.
The price of the L.B. model is £410 and that of the F.B. £390.