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CENTR ENGI1
0 NE of the novelties of the Commercial Motor Show will be the latest Seddon 32-seater bus with a vertical engine carried below floor level between
the axles. As this model will be exhibited complete with a body having a level floor, it might be passed by as a conventional underfloor-engined bus with a horizontal power unit.
This unorthodox chassis has been designed mainly to promote accessibility of the engine, without need for a pit when changing components or the complete unit; to make working conditions for the maintenance staff more comfortable, and to embody all the virtues of the underfloor-engined model, such as a short transmission line, clear floor and improved distribution of load between the axles.
A batch of the new passenger chassis has been sent to Bermuda, but the radiator header tank mounted above the power unit caused a bulge in the engine cover which was concealed by a seat frame. The latest example, which will be shown at Earls Court with a body built for the West Riding Automobile Co., Ltd., has the header tank mounted remotely from the engine. The body will have a full-length central gangway and 16 double seats facing forward.
High Frame The Seddon is necessarily a high-frame chassis, the front being 2 ft. 11 ins, from the ground when fully laden. Modifications have been made to the manifolds, air cleaner and sump of the Perkins engine before installation, so that it stands proud of the chassis by 4 ins, at the top, yet leaves 11 ins, ground clearance at the base when the springs are fully deflected. The body floor is 3 ft. 5 ins, above ground when laden.
There are many interesting developments in the chassis, including its construction for rightor left-hand drive, a wide frame devoid of outriggers, fans for the radiator and engine to improve airflow, and interchangeable spring brackets. The Show Model has a 13-ft. 11-in. wheelbase for a body 25 ft. 9 ins, long, having a front overhang of 5 ft. 2 ins, to afford space for an entrance
118 that can be controlled by either the driver or conductor. Another central-engined bus of 16-ft. 6-in. wheelbase. has also been developed incorporating an alternative power unit with an output of 110 b.h.p.
The frame is 3 ft. 64 ins, wide at the rear, but tapers to 2 ft. 9 ins, in the region of the engine and is reduced in depth at the front to provide a lower entrance. The springs are carried below the side members and specially designed standard brackets and dumbirons with parallel faces are employed so that outriggers can be attached if required. This will save the need for drilling holes in the side members.
A feature in the Seddon, which is now becoming more common, is that the first cross-member (of pressed-steel section). is set back from the front of the frame, with the steering column attached to the forward edge. The gear lever is bolted to this member and linked by a two-piece shaft having Hardy Spicer couplings to the side of the gearbox. All linkages between the driving controls and operating units have been arranged for rightor left-hand drive.
A Clayton Dewandre servo, with a hydraulic cylinder attached, and a vacuum reservoir are located between the frame members at the front, and a cast-aluminium radiator having an integral cowl supporting the fan bearing is mounted below frame level immediately behind the axle. A six-bladed fan, of normalpressed-steel pattern and size, is employed and driven through a relay of belts, pulleys and a jackshaft from the crankshaft. There are integral adjusters for the belts on the front of the timing case and at the radiator spider. The standard Perkins P6 six-cylindered engine, with a new flat intake manifold and sump which is devoid of a well, is retained on normal mountings at the front and rear, a bracket being built into the frame to fit under the bed of the timing case and form an additional cross-member. The wide frame has enabled ample space to be provided on both sides of the engine and there are trap doors in the body so that the fitter can stand on the ground when working on the power unit. The floor is at a convenient height to be used as a workbench.
At its rear, the engine is suspended in the frame as a unit with the clutch and five-speed direct-drive-top gearbox, the mounting brackets with Metalastik bushes being outrigged from the clutch housing. To assist in preserving correct weight distribution--a third on the front axle and two-thirds on the rear—the battery is
housed in a crate at the centre of the frame and slightly ahead of the rear axle, and the 30-gallon fuel tank is within the wheelbase.
Because the engine and gearbox are central in the chassis, the transmission line to the hypoid-d riven axle is almost in direct line and the propeller-shaft joints have practically neutral angles under normal load. NewtonBennett direct-acting hydraulic absorbers are fitted to both axles and 9.00-20-in, low-pressure tyres are standard. The braking system employs Girling wedge operation for the leading-shoe units, the front drums being 16 ins. in diameter and 3 ins. Wide. At the rear the drums are 15:1, ins, in diameter and the 'shoes are 4+ ins, wide.
An all-metal full-fronted body is mad,: for this chassis by Seddon Motors, Ltd., in the Woodstock Factory at Oldham. it has electrically operated sliding doors at the entrance, a wide door amidships and an emergency exit at the rear. The central door enables the engine to be removed with the aid of a normal garage swanneck hoist.. in the latest version there are three risers at the entrance and a waist-high rail separating the driver's cab from the gangway. This partition is arranged to give unobstructed visiort to the driver.
The Show model will have a 1-ft. 7-in.-wide clear central gangway. The engine trap doors can be lifted without disturbing the seating. The cverall width is 7 ft. 4 ins., length 25 ft. 9 ins, and headroom above the gangway 6 ft. 2 ins, The chassis has a track of 5 ft. 11+ ins. at the front and 5 ft. 7I ins, at the rear.
The power unit in the ,Show model is a. Perkins sixcylindered oil engine of high rating, developing 79 b.h.p. at 2,400 r.p.m. and 203 lb.-ft. torque at 1,500 r.p.rn. To assist in reducing the height, the oil-bath air cleaner has been removed from the normal position and placed
above the gearbox.