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A FREAK HILL CLIMBED BY A COACH CHASSIS.

3rd August 1926, Page 12
3rd August 1926
Page 12
Page 13
Page 12, 3rd August 1926 — A FREAK HILL CLIMBED BY A COACH CHASSIS.
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A Remarkable Performance by a Standard 2-2k-ton Laffly Chassis which Achieved 54 m.p.h. on the Level and Climbed Easily a Hill of l in 4.

nktlt first acquaintance with the kl2-21-ton Laffiy chassis, which is a particularly interesting model, designed especially for passenger service or fast goods transport, dates from the Commercial Vehicle Exhibition of last November. At that time we were very impressed with the. many practicable points embodied in this chassis and the general cleanliness of the design. Since that time detailed improvements have been made, and the chassis as it now stands represents one of the most modern examples of Continental design, which includes a high-efficiency power unit with overhead valves; a multipledisc clutch with Ferodo friction surfaces, ball-and-socket centring devices for the propeller-shaft flexible joints, an unusual pot type of rear axle, in which the opening faces to the front, and most efficient four-wheel brakes. These are merely general features, and we will deal later with further details of the

chassis. • •

What we were desirous of ascertaining was the performance of this chassis on the road and its hill-climbing abilities. We therefore asked the concessionnaires, the Laffiy (England) Co., Ltd., 20-26, Lansdale Road, Kilburn, London, N.W.6, to afford us an opportunity for making such a test. So confident were they of the capabilities of this new model that they suggested an attempt to climb Alms Hill, near Henley, and just off the Oxford road.

Very Dangerous 1 in 4.

This hill may be alluded to as a freak one, and is well known to motorcyclists and car owners with sporting proclivities. The A.A. sign at the top reads: "Alms Hill, Maximum Gradient 1 in 4. Very Dangerous." The surface is chalky and scored by deep channels, down which water rushes in wet weather, although on the occasion of the test the surface was dry. Upon our arrival at the Kilburn depot of the corn

pony we found that the Laffiy was carrying a test body containing approxi mately 2 tons of iron, etc. It was mounted on 855 mm. by 155 mm. pneumatic tyres, singles at the front and twins at the rear, these being of Michelin make on Michelin disc wheels.

On the outward run we followed a devious route, which gave us a good impression of the manoeuvrability of the vehicle and its general ease of control, until we reached the Great West Road. Along this we proceeded steadily at between 30 m.p.h. and 40 m.p.h., and we were afforded ample opportunity for noting the remarkably smooth running of the engine and the general steadiness of the whole chassis, whilst the propeller shaft ran perfectly true and caused no vibration. As we were sitting immediately over the exposed front universal joint, we were glad to observe that no oil or grease was escaping.

Upon reaching Alms Hill a trial ascent was first made in a powerful car.

and this not without a certain amount of difficulty through wheelspin. We descended the hill and again boarded the Laffly, and a standing start was made from the bottom, naturally on first gear. The ascent was made at a speed which we computed never to fall lower than 6 m.p.h. to '8 m.p.h., and without the slightest hesitation, although at one point dead leaves caused a small amount of wheelspin, which, however, did not seem to cheek the ascent. A turn was made at the top and the Laffly driven

flown the hill, when it was found that it could be held easily by the hand brake alone. This, however, haused locking of the rear wheels, whereas with the four-wheel brakes in operation the vehicle was brought to a standstill on the steepest portion without any sign of wheel lock. A second climb followed, and the vehicle was purposely arrested on the steepest part, a restart being made without running back an inch and without any of that " bucking " which occurs with some vehicles.

At the conclusion of these climbs we Proceeded to Marlow, and the long hill, with its several bends leading from this well. known riverside town, was ascended at a speed of something like 35 m.p.h. Later, along a fairly level stretch of road, the driver was asked to put on sPeed, and a maximum of 54 m.p.h. was reached, and even at this speed the vehicle held the road in a really 'remarkable manner._ Although the load carried was a dead one, springing was so good that riding proved almost as comfortable as on a private car ; in fact, we have known many 'cars in which we would not have been so comfortable at equivalent speeds.

We will now give a résumé of the chassis details. Commencing with the frame, this is of exceptional width, actually nearly half as wide again as certain other foreign vehicles of the same capacity which we have examined. At the front this frame is inswept to give a large lock, and is rendered immensely strong by a wide plate carried over each side-member, whilst the crossmembers are also strongly gusseted. In the engine the overhead valves are mounted in a detachable head, being operated by tappet rods from a single camshaft. The contact between the rocker arms and tappets is by ball and cup, in which the oil forms a noisereducing cushion. Internally, the samo cleanliness of finish is to be found as

shown externally ; for instance, the connecting rods are machined all Over. in the cover plate over the valves is a large combined oil filler aud breather, so that the valves and tappets .are thoroughly soaked with fresh oil at each filling operation. . :The gearbox, clutch housing and engine form a three-point-suspended

unit. Four speeds are provided, the operation being by a centrally disposed lever. Cooling is effected by a gilledtube radiator carried in trunnion bear ings, the circulation being maintained by a centrifugal pump. Cooling is assisted by a four-bladed cast-aluminium fan, running on ball bearings.

The rear axle, to the casing of which we have already alluded, is of the fully floating type with spiral-bevel gear. In the rear-brake drums are Duplex brakes, each shoe covering approximately a quarter of the braking area. The foot brake operates shoes in the front-wheel drums simultaneously with one set of shoes in the drums on the rear wheels.

It is of interest to note that the propeller shaft is so well balanced that it can be run at 5,000 r.p.m. without whip occurring.

At the off side of the gearbox is a plate which can be detached for fitting a hydraulic. pump or air compressor, whilst the speedometer drive is taken from the top of the gearbox just in front of the change-speed lever. Accessibility is a pronounced feature, and one of our illustrations show how the water pump, magneto, dynamo and starter are all grouped together.

The main dimensions, etc., of the chassis are as follow :—Load, up to 50 cwt., including a body allowance of 10 cwt. It is designed for 20-seater passenger bodies. Engine, four cylin dots of 90 mm. bore and 130 nom. stroke.

R.A.C. rating, 20.1, h.p. At normal engine speeds the road speeds are, on first gear, 10 m.p.h.; second, 171 m.p.h.; third, 28 m.p.h.; and tourth, 45 m.p.h. Back-axle ratio, 6i to 1. Weight, 1 ton 18 cwt. Wheelbase, 12 ft. Si ins. ; track, front 5 ft., rear 5 ft. 9 ins.; ground clearance, Si ins.; body space, 14 ft. 31 ins.; width -of frame, 3 ft. 6i ins.; overall length, 18 ft. 6i ins.; overall

width, -6 ft. 10+ ins. Chassis price, £475, including duty.

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