Oil-Engined Models In the Guy Range

Some of the outstanding features of an interesting range of medium-sized and large-capacity vehicles

The article is from The Commercial Motor, October 27th, 1931

During the past decade Guy Motors, Ltd., of Wolverhampton, has gained world renown for large-capacity vehicles of both the freight and passenger types. Many six-wheeled machines have been supplied to various Governments and there are a number of bogie-axled buses operating in Great Britain, besides fleets of goods vehicles of all sizes, ranging from 30 cwt. capacity to 11 tons. The programme for a new season of such a concern is, therefore, regarded with interest.

Of outstanding importance to large operators is the fact that various chassis, at present being manufactured by the Guy Company, can now be obtained with compression-ignition engines in place of the usual petrol type. These particular models are the Goliath 11 tonner, the Warrior 6 tonner, and the Conquest and Invincible 32 seater and 51seater passenger chassis.

In each case the power units are interchangeable (i.e. oil or petrol types) and it is possible for an existing petrol engined chassis to be equipped with a compression-ignition engine without involving a great deal of alteration to such items as controls, and without making any structural modification to the general build of the chassis.

The Guy 11 ton six-wheeled lorry equipped with a heavy-oil engine.

Before describing the oil engine, which is the new type Gardner six-cylindered unit, we will enumerate a few of the salient points in the design of the 1932 chassis.

Several alterations have been made in the latest type. To start with the four models already mentioned, the 6 tonner and 11 tonner, and the 32 seater and 51 seater passenger vehicles have new front axles which incorporate directly operating Dewandre vacuum cylinders attached to the brake drum and shoe assembly. The use of such a system has entailed redesigning the brake rods generally and we are assured that the new layout provides a fine, well-balanced retarding action.

A normal Dewandre servo motor is  attached to the off side of the frame and is coupled in the ordinary way to the pedal; a rod runs rearwards to the rear brake cross-shaft, whilst two pipes lead from the master valve of the main servo to the auxiliary cylinders attached to the front-axle assembly.

The frame of the 11 tonner is slightly shorter than in previous models but it retains its exceedingly strong section of 12 in. depth with flanges made from seven sixteenths of an inch steel. The cross bracings are deep and although extremely strong, are of relatively small weight. The tyre size is 40 in. by 8 in., with twins at the rear.

Another point of interest concerns the engine, clutch, and gearbox mounting, which, as in previous models is effected by means of a sub-frame, this last named component if rigidly mounted in the frame, compensates for relative movement if the vehicle is used over uneven ground. The gearbox has been moved further back than in the 1931 types and fabric joints have been incorporated in the clutch shaft; furthermore, the box itself is three-point mounted to the sub-frame.

A new pattern of radiator is used throughout the larger machine, the outstanding feature being a stone guard which protects the more delicate parts from damage. In the petrol engined version, power units have been improved by redesigning the cooling system. The water pump has been slowed down somewhat and the water spaces in the cylinder heads altered to allow a better flow of water around the exhaust pockets.

A near-side view of the new Gardner six-cylindered oil engine used in certain Guy models, showing fuel pump and the controls which permit starting by hand.
We can now deal with the Gardner power unit. The model chosen for use in the Guy vehicles is the six-cylindered model which, at 1,650 r.p.m. gives a maximum b.h.p. of rather more than 100. As is usual in compression-ignition engines, an exceedingly good torque figure is attained at low and medium crankshaft speeds; actually this Gardner unit develops approximately 350 lb.-ft. at 1,000 r.p.m., thereby giving the vehicle a most creditable top gear performance.

The front axle assembly of the Guy 11 tonner showing flexible connections to the Dewandre vacuum servo cylinders operating the brakes.

It will be recalled that the latest engine of this make has received careful attention at the hands of the designers in regard to the vexed question of weight. The unit, with the flywheel, oil and water, scales 1,480 lb. Electrical apparatus is not included in this weight, because it is considered to be a non-essential part of the general equipment, although a comprehensive layout has been included in the Guy oil-engined vehicles.

With bore and stroke dimensions of 4ΒΌ ins. and 6 ins. respectively, the R.A.C. rating works out at 43.5 hp., which is a usual figure for six-cylindered petrol units as fitted to the large chassis produced by the Guy concern. The compression ratio is 13 to 1, the fuel-injection pressure at maximum being in the order of 2,000 lb. per sq. in.

A gear-type oil pump forces lubricant to all the working parts, with a special filtering device incorporated in the system to ensure freedom from trouble over long periods of operation.

A view from the rear of the bogie of the 11 ton six-wheeler showing chief constructional features, including double inverted semi-elliptic springs.

In this latest Gardner engine, many improvements over the earlier types have been incorporated. For instance, modifications have been made to the valve diameters and the timing, port and passage contours, etc., whilst the special design of inlet valve with tangential location to ensure good turbulence is symmetrical with the exhaust valves.

Injection is, of course, direct, and the differential injectors which are centrally located in the combustion spaces are of exactly the same type as are used in all kinds of Gardner engine.

Due to the excellent torque figure at medium speeds, the axle ratios of the chassis having the compression-ignition engines have been raised somewhat; the ratios are now 8.25 to 1.

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