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A New Entrant
Page 76
Page 77
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to the
Coach Market
First Published Details of the Gloster Gardner Chassis Speci ally Designed for a Com pression-Ignition Power Unit
p&RTIOULAR interest attaches to the new Gloster Gardner oilengined coach chassis, which has just been produced by the Gloucester Railway Carriage and Wagon Co., Ltd., of Gloucester, not only because it is an entirely new model from the works of a maker -which has not hitherto entered this market (although having a great amount of transport experience in other directions), but because it is designed throughout to meet the special requirements and characteristics of the com,pression-ignition engine, which, as is now well known, gives an excellent torque at low speeds.
Perhaps the most important point about the design is, therefore, the overtop gear, which constitutes the fifth for. ward speed, the actual ratios being: overtop, .742 to 1; fourth (direct), 1 to 1, third, 1.69 to 1; second, 3.35 to 1; first, 6.41 to 1; reverse, 8.20 to 1. The result is that, although the power unit is governed to 1,700 r.p.m., in the overtop drive, the corresponding vehicle speed is 53 m.p.h., the other forward ratios giving 39.1 m.p.h., 23 m.p.h., 11.5 m.p.h., and 6.1 m.p.h., respectively. The axle ratio is 4.8 to 1, the tyres being 9.00 by 20. The overall gear ratio in the overtop is 3.56 to 1. Control of the gear changes is through a single shaft from the central lever.
The overtop gears are straight spurs, but are extraordinarily quiet, as we proved to our satisfaction during a short test run at Blackpool, when we were greatly impressed by the general performance of the vehicle, the almost complete lack of vibration and the mancevrability in some narrow streets, whilst the Dewandre servo-brake equipment, with the front.ovheel servos mounted over the kingpins, showed itself to be highly efficient.
One of the reasons for the absence of vibration is that the gearbox is a separate unit; this not only assists in preventing noise, but renders maintenance cheaper than with the unit form of construction, whilst extreme care has been paid to engine suspension, which is by Silentbloc bushes.
It was last Friday that we were on the chassis, and it was only on the previous Sunday that the assembly was finished. Such was the confidence in the chassis, however, that it was driven first to Chepstow, where it was examined by the directors of Red and White Services, Ltd., which cempany collaborated in the design, and then direct to Blackpool, and no adjustments had to be made. During the run, a loose bolt had been accidentally left upon a flat surface with nothing to prevent it working off, but it was still in position when the chassis reached Blackpool.
We had no opportunity, at that time, of testing the petrol consumption, but we are assured that, despite it being new, the chassis with a 3-ton test load is running 20 miles to the gallon of oil fuel, a remarkable figure which shows how extremely economical and efficient the oil engine can be when it is utilized in a proper Manner.
The. Gardner engine is the 61AW, of 41-in. bore and 6-in, stroke, giving a swept volume of 8.4 litres. It develops 66 b.h.p. at 1,000 r.p.m. and 102 b.h.p. at 1,700 r.p.m. The maximum torque is 4,200 in.-lb. at 1,000 r.p.m. As an example of its strength, the crankshaft is of nickel-alloy steel and has main journals 31 ins. diameter. The forgedsteel connecting rods have central duets carrying oil under pressure to the gudgeon pins, which are of the floating type and unusually large.
To provide a vacuum for the brake servo, a Williams and James 24-in. by 2-in. exhauster motor is fitted on an extension of the front timing case and driven by a Resold roller chain, whilst fuel is fed to the engine through an Autovac tank of unusually large capacity, the main tank, which holds 40 gallons, being slung at the near side on frame outriggers, the filler cap being 4 ins, in diameter. Every care is taken in the fuel-supply system to prevent leakage and creeping at the pipe joints and at the fuel sprayers where oil emitted is led back to the tank.
Power from the engine is conveyed through a 14-in. diameter Borg and Beck clutch with an efficient stop. The cross-shaft carrying the operating fork is mounted on self-aligning ball bearings and adjustments can easily be carried out at the pedal end.
Between the clutch and the gearbox is a short shaft with two Hardy disc couplings. The gearbox itself is compact and is carried on a sub-frame slung between two tubular cross-members. The front end is supported by a ring mounting around the main-shaft bearing-housing spigot, whilst a plate at the rear of the box is secured by Silentbloc bushes.
Kayser Ellison KE805 steel, oilhardened and tempered, is utilized for the gears ; they are of the spur type, having involute teeth of 20 degrees pressure angle, full depth, with such addendum correction as will give the maximum strength and durability. Provision is made for a power take-off, the facing complies with the S.M.M.T. standard. A speedometer drive is provided. The complete gearbox can be dropped from the chassis by removing four bolts.
The forward portion of the large diameter propeller shaft has a Spicer joint, and its rear end is carried in a spherically mounted bearing ; two more Spicer joints are incorporated in that part of the shaft communicating with the rear axle. An oscillation damper is provided behind the centre bearing.
The final drive is by underslung worm with 7-in, gear centres, and the axle is fully floating. A one-piece, nickelsteel forging is utilized for the casing, whilst the axle shafts are of nickelchrome steel of 1f-in. diameter. The brake drums have an inside diameter of 17 ins. They are of .5 per cent. carbon steel, oil-hardened, toughened and ground, and the shoes are 6 ins, wide with Hu. linings. The aluminium casing which carries the worm has an oil capacity of 2i gallons, and the differential is of the four-bevel-pinion pattern.
All spring bangers are of cast steel, and the shackle stampings of nickelchrome steel. They are all interchangeable and easily detachable, whilst provision is made for adjustment sideways to take up wear. The front springs are 3 ft. 10 Ins, long and those at the rear are 5 ft. Tapered roller bearings carry the thrust at the top of the kingpins; similar bearings are used for the forgedsteel hubs. To keep the springs under the frame side members, the spring centres are 3 ft. apart at the axle centre line, but they taper towards the front at an angle of 30 degrees 30 minutes.
To facilitate steering, a cam-type gear is provided, the lock being 40 degrees.
Three per cent, nickel steel is used for the frame side members, which have a maximum depth of 11 ins., a width of 3 ins, and a thickness of 7-32 in. These members are reinforced by flitch plates 5-32 in. thick where they sweep down from the front axle to between the front-spring rear hangers and the gearbox front cross-member. Channelsection cross-members are situated at the extreme front and rear of the frame, and five others evenly down the length of the frame.
A handsome appearance is afforded by the radiator, which is of cast aluminium with detachable top and bottom tanks. It is supported at three points by spherical rubber mountings and is relieved of all distortion due to relative movement between the frame and cab. Shutters of a new type are fitted. These are manually operated, in accordance with the sight gauge, or thermometer, mounted in the radiator filler cap. The shutter pivots are of stainless steel, and the shutters them selves are of chromium-plated soliddrawn tube, substantial enough to enable a stoneguard to be dispensed with.
The accelerator pedal is connected to the speed-control lever on the engine, and a stopping switch is mounted on the instrument panel. A small, quickrelease gauge on the left side of the starting handle is coupled to the decompression devices, so that the engine can be started manually from cold.
The lighting dynamo can be either of C.A.V.-Bosch MYR type with an output of 650 watts, or a Simms type 7D. This is driven through a flexible coupling. Exide Ironclad accumulators are employed.
The general dimensions of the chassis are: wheelbase, 17 ft. 6 ins.; track, (front), 6 ft. 31 ins.; rear, 5 ft. 9i ins. ; turning circle, 58 ft.; maximum frame width, 3 ft. 10i ins..; height laden, 1 ft.
tt ; chassis weight, including oil, fuel and water, 80 cwt. As a coach the seating capacity will be 30. The distance from dashboard to centre of rear axle is 15 ft., and from this point to the end of the frame 7 ft. 1 in. ; the overall length of chassisis is 27 ft. 2 ins. and the overall width 7 ft. 51 ins.
Reference to the drawings which ,we reproduce will indicate the leading characteristics and general layout. The performance will be given in detail in an article which will be published after we have given the chassis a full road test.
The vehicle was inspected by many delegates attending the.Municipal Tramways and Transport Association Conference at Blackpool, and at once created an excellent impression.