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New A.C.V. Passenger Range
Page 154
Page 157
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Three New Models Designated Regent V, One a Lightweight Chassis with 103 b.h.p. Engine : Monocontrol Transmission Eliminates Gear-change Pedal: New Power Steering System
THREE new passenger models have been produced by the A.C.V. group and an example of one of them will be shown, as reported in last week's issue of The Commercial Motor, on the stand of Crossley Motors, Ltd., at Earls Court.
A new semi-automatic gearbox known as the Monocontrol transmission system and a new power steering gear have also been introduced.
The latest range is designated the Regent V, and the three models are known as D3RV, D2RA and MD3RV. All have a wheelbase of 16 ft. 4 in., with alternative widths of 8 ft. and 7 ft. 6 in., and are two-axle, right-handdrive chassis.
Designed for double-deck bodies, the new chassis have full-width bonnets and flush-fitting head and fog lamps. A conventional bonnet and exposed radiator are ,offered as alternative equipment
Lightweight Chassis
The D2RA chassis is fitted with the Monocontrol transmission. The ivID3RV is a lightweight chassis with a smaller engine and is designed for a gross vehicle weight of 7 tons.
Model D3RV weighs 4 tons 171 cwt, and is powered by an A.E.C. 9.6-litre oil engine. This unit has been used successfully for many years in the Regent III chassis and develops 125 b.h.p. at 1,800 r.p.m., with a maximum torque of 430 lb.-ft, at 1,000 r.p.m. It has dry cylinder-liners and, twin interchangeable cylinder heads and is rubber mounted, in conjunction with the gearbox, at three points.
. The single-dry-plate clutch has a solid centre plate of 151-in. diameter and clutch withdrawal is mechanical. The gearbox is a new unit with four forward speeds, each with inertia-lock synchromesh engagement. Straightspur gears are pressure lubricated from a layshaft-driven gear oil pump. The gearcase is a two-piece light-alloy casting split horizontally on the plane of the mainshaft and layshaft centre lines.
Standard Ratios
Standard gear ratios are 4.68, 2.62, 1.57 and 1 to 1, with a reverse ratio of 4.17 to I. The selector forks and shafts are housed in the upper half of the box, and are linked to the gear lever by a universally jointed shaft.
Hardy Spicer 1,600-series joints are fitted to the two-piece propeller shaft and transfer the drive to the offset underslung-worm drive of the rear axle. The axle casing is an alloy-steel drop forging and bellows packless-gland oil seals are used in the axle wherever possible.
Worm-and-nut steering gear is used. This has a ratio of 33 to 1, giving 5N ' turns from lock 'to lock. • Reversedcamber semi-elliptic springs are fitted without dampers, although these may be c60 specified for the front axle if required. The frame is built up of i-in.-thick channel-section pressed steel, the maximum depth of the side members being 11 in., with a constant flange width of 3 in. Fitted bolts may be used in the assembly instead of rivets, but extra cost is involved.
Triple-vacuum-servo braking is fitted, t and the Clayton Dewandre rotary-vane exhauster is driven in tandem with the fuel pump. All brake drums have an internal diameter of 151 in. The front shoes are 41 in. wide, whilst those at the rear are 71 in. wide. The total frictional area is 746 sq. in.
Insulated-return 24v. electrical equipment is standard, and dynamos of either 1,320-watt or 1,390-watt output are specified. The total battery capacity is 185 amp.-hr. Automatic chassis lubrication can he supplied. The weldedsteel fuel tank has a capacity of 35 gallons.
Semi-automatic Gears Model D2RA differs from the D3RV in that semi-automatic transmission is fitted. The electro-pneumatically operated epicyclic gearbox may be used in conjunction with either a-iluid coupling or a centrifugal clutch. The fluid coupling, which is the standard equipment, has a bellows-gland selfadjusting oil seal.
The single-dry-plate centrifugal clutch is similar to that. employed in the D3RV chassis, but it is automatic in operation. Steel balls running in semicircular radial grooves between the pressure plate and driving member are forced outwards under the action of centrifugal force and the pressure plate is brought into contact with the friction, plate. The speed at which the driveis engaged is controlled by the strength of springs which hold the pressure plate in the disengaged position.
The Monocontrol transinission, which will be installed in a Regal IV schassis to be exhibited on the Crossley stand; is a development of the air-operated epicyclic gearbox which has been fitted to A.E.C. passenger vehicles for many years, but has simplified control, •
A new system of selection and engagement which uses electrical and
air-pressure operation is now incorporated in it, and has dispensed with the need for a gear-change pedal and ensures a smooth and positive change
of ratio at all times. The gear i pre-selective, but reduces drive fati The Monocontrol transmission sists basically of four compo These are a four-speed epicyclic box with air-pressure application brake bands and top-gear c an electro-pneumatic selector assembly which is mounted oi gearbox, an electric gear-change which can be mounted on eithc instrument panel or the sti column, and a hydraulic coupli centrifugal clutch.
Although essentially similar tc of the earlier type of box, the ru gear of the new unit has strengthened to transmit the full of an A.E.C. 11.3-litre oil e which is 505 lb.-ft. at 1,100 r.p.m. gear is a direct drive and is ob through a multi-plate clutch. 'I engaged by a small air cylinder acts through a mechanical linka to the thrust bearing
Air Operation
The intermediate-ratio pan brought into effect by the appli of conventional dual brake banc these are operated by similar air ders. The cylinders are contaii a one-piece aluminium block whi steel liners and they vary in size a jog to the different holding 1 required,
A smooth change-over, with tinuous drive between gear chan afforded by automatically cont the rate of admission and release from each cylinder. When E change is made the control actuates, a solenoid on the g valve block, which causes' airadmitted to the appropriate cylin the same time allowing air to from the cylinder of the gear pre. used.
A metering valve in the air each cylinder ensures, that air from one cylinder faster thar admitted to the other, and beet this regulated time-lag there shock-loading on the gears. quently, the life of the ba increased.
. Electric Control tfse Of ifehric control : 'air valves allows greater choice Position of the control switch a -penses with the need for long a or mechanical linkage g from th box to the driving seat.
The new gear, Which has be jected to prolongedtesting, is factured entirely by A.E.C., Lk offered with ratios of 4.28, 2.z and 1 to 1, and a 5.98 to 1 revel.:
Air braking equipment of Westinghouse or Clayton Dc manufacture is fitted to this cha twin-cylindered compressor also ing power to operate the g Drum sizes are the same. MD3RV is a lightweight and has the A.E.C. AV470 oil as fitted to the Mercury goods This unit develops 112 bhp. y, but is governed down to give .p. at 1,800 r.p.m. for economy. dition to using a lighter engine, • r saving in weight is effected by smaller clutch, lighter gearbox tiler fuel tank. The bare chassis S 4 tons 41cwt, w form of power steering has ;veloped and will be seen fitted ammoth Major III six-wheeled hassis on the A.E.C. stand at the rcial Motor Show and to a IV passenger chassis on the stand. The system, which ■ n the continuous-flow hydraulic e, may be fitted in any A.C.V. and.would be .a particular asset 'avy gorids vehicle: The steering gear is the normal A.E.C. worm-and-nut type, but attached to it is a small spring-loaded control valve. When the steering wheel is turned, the valve is actuated by the raising or lowering of the steering wormshaft caused by a slight axial clearance in its bearing housing.
Spring loading -in the valve keeps the wormshaft thrust .bearing central in its housing until a pressure at the wheel greater than 20 lb. is exerted. The valve then moves to.allow fluid to pass to the appropriate side. of the Clayton
Dewandre double-acting pOwer cylinder. This in turn acts on the steering drop arm either directly or through a relay linkage, depending upon the type of chassis to which it is fitted.
• Hydraulic power is supplied by a Plessey gear pump. This may have a
capacity of 4.3 gallons per minute at 1,000 r.p.m., and be driven from the engine crankshaft, or have a capacity of 94 gallons per minute at 1,000 r.p.m., and be driven in tandem with the fuel-injection pump.
A vehicle which will be seen for the first time at Earls Court is the 0860 forward-control 6 x 6 heavy-duty tractor. This is basically a six-wheeled version of the well-known Matador chassis and is powered by an A.E.C. 11.3-litre 150 b.h.p. oil engine, it has a fully articulated rear bogie and double-reduction driving axles. A constant-mesh five-speed gearbox, air braking and a winch are also specified. The chassis, which has an overall length of 23 ft.. 10 in., weighs 7 tons 16 cwt, and is suitable for a gross train weight of 32.tons,.or 40,fons where legislation perm i CS.