GILFOR.D MODELS FOR 1932
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FROM its inauguration the Gifford Motor Co., Ltd., has been a pioneer in the development of passenger chassis, and it was responsible tor the first really successful lbw-level coach. It is meet, therefore, that it should again show striking originality in its latest products, of which the most interesting, as exemplifying much advanced design, are the new front-wheel-drive passenger
vehicles which are being constructed as single and doubledeck buses.
In these vehicles frame and body are built as a unit with main members of steel of box section, which, together with pressed-steel wheel-arches, form lattice girders, as employed in the building of a bridge. The whole construction is so rigid that, in a recent test, with the body supported on four trestles, the lifting of one corner to a height of in., by jacking, sufficed to lift the other end of the body, at the same side, clear of its support. This experiment was carried out at the ends of the length between the wheel-arches.
Concentrating drive and transmission at the front end has enabled the floor to be kept perfectly flat, and its laden height is 1 ft. 14 in. from ground level and there is no running gear whatever under the floorboards. In the case of the double-decker, the interior height of the lower saloon is 5 ft. 11 ins. The upper saloon floor is also flat and requires no portions to be sunk., although if this were to be done the roof height, which is at present as low as any other double-decker on the market, could be still further reduced.
The upper floor is supported on special light-alloy brackets bolted to the steal main pillars, and access to it is obtained by an extra-wide seven-step staircase, from an entrance platform 4 ft. 3 ins, in width. The interior height is 5 ft. 8 ins, and the overall height (laden) 12 ft. 11 ins.
B38 The upper saloon is designed to carry 31 people and the lower 25, in an overall length of 25 ft. 6 ins. Emergency doors are provided for both decks, the upper one being only 5 ft. 5 ins, from the ground.
Now we come to the remarkably interesting drive unit, which consists of a six-cylindered Junkers two-stroke-cycle oil engine of 70 rum bore and 210 min. stroke. This is mounted to the rear of the unit. Next in order come a plate clutch, a box containing the final-drive worm gear and differential and, forward of this, the gearbox. Much space is saved by the ingenious system of taking the drive from the clutch via a shaft passing through the hollow worm and worm shaft to the gearbox, the drive then being returned by sliding dogs to the forward splined end of the shaft of the overhead worm' universally jointed driving shafts conveying the power to the front wheels.
The gearbox gives four forward speeds and reverse, and is of the constant-mesh type, operated by a change-speed lever mounted on the main drive casing. There are only three sets of gears instead of the usual four, and the longest shaft in the box is 7 ins.
One of_ the essentials in front-wheel drive is to utilize satisfactory universal joints, and those employed in the Gilford are of the constant-velocity pattern, each joint utilizing six 11-in. steel balls, so arranged that they give this desirable feature, as well as an extremely large bearing area. The driving shafts and these joints are totally enclosed, so that they can be thoroughly lubricated and kept free born dirt. The drive unit may be said to be mounted between the wheel-arches at the front, and it would be an easy matter to Withdraw the whole unit from the front of the vehicle. Ample space is given for a seat at each side of the engine. ' Another remarkable feature of this extraordinary vehicle is that the four wheels are Independently sprung by a unique method, about which we are not yet permitted to give particulars. The front wheels are controlled by a Marks steering gear.
The foot brake operates on all four wheels through a servo-assisted hydraulic system, whilst the hand brake acts on the rear wheels only. Single tyres of 11.25-in. by 20-in. dimensions are employed on all wheels. The track is 6 ft. 3i ins, at the front and rear, and the wheelbase 15 ft. 8 ins.
In the case of the single-deck bus with front-wheel drive, the roof is so low that a man of ordinary height could place his hand over it and suitcases can be lifted on to the roof with ease. Despite this fact, there is more headroom than is proVided in the ordinary coach.
Another new product is the Gifford M.O.T. chassis for bodies seating up to 32 persons. As its name implies, it is a type which has been designed particularly to meet the M. of T. regulations. Notable features in this connection are the arrangement of the brakes and the protection of the petrol tank by expanded metal.
The engine is of a new overhead-valve type not hitherto employed on Gifford chassis. It has six cylinders of 110 mm, bore and 140 mm. stroke, giving a capacity of 7,983 e.e. and an R.A.C. rating of 45. It develops 63 b.h.p. at 1,000 r.p.m. and 117 b.h.p. at 2,200 r.p.m. The torque is 325 ft.-lb. at 1,000 r.p.m. and 290 ft.-lb. at 2,000 r.p.m.
The camshaft is operated by a silent roller chain, adjustable for tension. This also drives the 22-in.-diameter fan through the medium of a friction clutch. Seven bearings of 3-in, diameter are utilized for the crankshaft, whilst the creak pins are 21 ins, in diameter ; four bolts are used for each big-end. An ordinary type of centrifugal water pump is driven from the dynamo shaft, whilst the magneto is a Scintilla with automatic advance. A submerged gear-type oil pump feeds the erankshaft, camshaft and big-ends.
The engine, clutch and gearbox form a unit which, at the front, is supported in a radial. bearing carried by a crossmember. From this member project: doivnwards two steel stampings which carry the radiator. They are adjastable, so that the radiator can be properly setIt is also held by a stay at the top and can be removed with the greatest of ease. Still tubes give efficient cooling.. The two other supports for the engine-gearbox unit are afforded by a pressed-steel banjo member riveted in position and insulated from the unit by rubber blocks. The banjo is sufficiently large to permit the unit to be vaithdrawn through it from the front.
Thought is shown in the design of the bonnet, as there is a permanent serni-scuttle portion, arranged So that lifting of the bonnet cannot scratch the paintwork. •The copper petrol pipes are covered with stout rubber tubing to prevent chafing. The new gearbox gives four speeds of the foll,owing ratios :—Top, direct ; third, 1.62 to 1; second, 2.72 to 1; first, 4.41 to 1; reverse, 5.51 to 1.
The rear end of the first portion of the propeller shaft is carried in a radial bearing supported in a cross-member, and three Spicer joints are used. Final drive is by underneath worm, the gearing being carried in an axle casing of the forged-pot pattern, with long underslung springs ; the ratio is 5A, to 1. Luvax shock absorbers are mounted inside the channels of the frame members, so that the springing should prove comfortable.
The foot-brake hook-up is entirely separate from that of the hand brake, and a worm-and-wheel master adjustment is provided close to the Dewandre vacuum servo. There is a " stop " light operated from the brake pedal. The adjustment of the hand brake is effected by rotating a knob at the top of the driver's lever. All brake shafts and the brake camshafts in the shoe carriers are mounted in roller bearings, which obviate the risk of binding, even if lubrication be neglected, although there is no excuse for this, as batteries of Tecalernit nipples are mounted on the side members, which, incidentally, are of f-in, material and 8.f deep. They are up-swept at the front and over the rear axle. More space is given to the driver by offsetting the engine to the near side to the extent of 2 ins.
Grass air springs, carried by the dutnbirons, relieve the front of the vehicle from road shocks not absorbed by the semi-elliptic springs. The front axle has a stronger beam than in previous models. As an example of care to detail, the silencer swings on shackles, thus allowing for expansion. Low-pressure tyres, 38 ins. by 8.25 ins., are mounted on detachable wheels, singles at the front and twins at the rear.