The Pierce-Arrow Chassis.
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The Rolls-44oyce of American-built Commercial Vehicles Described.
Admittedly the finest example of commercial vehicle construction turned out by any American factory, although at the same time it should be pointed out that the design is British, the Pierce-Arrow on inspection would certainly appear to justify the boast of its makers that it is the Rolls-Royce of American "trucks." The two models manufactured are nominally two and five-ton machines, and the gross loads which the chassis are designed to carry are 5000 lb. and
12;500 lb. respectively. The specifications of the two models are very similar, and we shall confine ourselves for the time being to a description of the five-tonner.
40 h.p. Engine : Automatic Lubrication.
This is equipped with a power unit of 4 ins, by 6 ins, bore and stroke, four-cylindar, with T-head Cylinders cast in _pairs. Pump-circulated water ; IT.T. Bosch dual ignition ; automatic, governor-controlled carburetter, with all governor connections enclosed and sealed ; and adjustable valve tapPets are all features which one naturally looks for, and usually finds, on an up-to-date power-unit. They are all to be discovered on the Pierce-Arrow.
One or two others, just as normal to modern design, such as valve gear covers, forced lubrication to main bearings, neatness in exterior, are wanting. The lubrication system is peculiar : a gear-type pump, carried low down on the off-side of the engine, and driven by skew gear from the camshaft, lifts oil from the sump to a sheet-metal container carried under the bonnet, and situ
ated above the level of the cylinder. Four feed pipes convey the oil thence to the timing case and three main engine bearings respectively. (On the two-ton chassis the engine lubrication is forced.) The depth of oil available in the tank is indicated to the driver by means of a gauge glass on the dash.
An interesting feature of the engine, as showing to some extent the thoroughness of the design and construction, is the provision of greasers for each end of the spindle of the water pump, and also the arrangement whereby the carburetter may be heated by drawing the incoming air from the region of the exhaust pipe, or, in the alternative, by allowing a portion of the circulating water to run through a jacket surrounding it. The method of tensioning the fan belt is interesting. It is modelled on the popular bicycle chain adjuater. The engine itself is three-point suspended from a pair of strong forged-steel cross members bolted to the main frame. A little criticism may be directed to the arrangement of the exhaust manifold. One outlet only is provided for each pair of cylinders. This has long ago been proved to result in a considerable amount of baffling of the exhaust gases and consequent loss of power. An outlet should be provided for each cylinder.
Large Radiator, of Pleasing Appearance.
The radiator is well on the safe side as regards capacity for cooling; no less than seven well filled rows of vertical gilled tubes being provided. These open at either end into cast-aluminium headers, the top one being provided with radiator fins, so as further to increase the efficiency of the unit. The headers are spaced by cast distance pieces, with which the journals for support of the components are integral. The latter are carried in bearings bolted to the frame side members. The provision of a large six-bladed fan, behind the radiator, materially assists in the effective cooling of the circulating water.
Cone Clutch, Three speed Gearbox.
The transmission from engine is via a leather-lined cone clutch, , in the design of which is incorporated a very neat form of clutch stop and a double-jointed shaft, to a three-speed-and-reverse gearbox, with gears of the sliding type. The box is fitted throughout with ball-bearings, and is three-point suspended. The fashion of this suspension is quite unusual, as regards the .front end of the box, which is carried on a ball-pin similar to those provided for the radius and torque rods, and which is carried from a link supported on a cross-shaft, carried in bearings and carefully. provided with means for adequate lubrication,
• Foot Brake.
Behind the gearbox is a very deep pressed-steel cross member. This, as may be seen from our illustration, is lightened by having holes cut in it, and serves to carry the rear end of the gearbox and also to take the whole of the load which is consequent on the application of the foot-brake. This is a very substantial component. The shoes are carried as is usual in locomotive practice and the application is by means of a special cam motion.
Propeller Shaft and Rear Axle.
Inside the brake drum is an enclosed universal joint and from this a short shaft about 15 ins, long runs to a second universal joint. The rear end of the short shaft is carried in a ball bearing attached to a cross member of the frame. From the second of these universal joints the usual type of propeller shaft runs to the overtype wormdriven full-floating rear axle. The load-carrying portion of this component is a inassive well-ribbed steel casting. Journals are formed thereon for the reception of bearings for the rear springs and also bosses which serve to take the rear ends of radius and torque rods. The radius rods are attached to horizontally disposed ball-pins of special design carried in the bosses referred to, and at their front ends they are carried by simi lar pins in substantial brackets riveted to the 'frame. -These brackets serve the dual purpose of carrying the radius rods and also supporting the tubular cross member of the frame. At its centre this particular cross member carries a link, to the lower end of which is attached the front of the torque rod. This at its rear end is carried by a vertical pin in the brackets on the rear-axle casing.
Short Springs. Well-made. Road Wheels. Screw and Nut Steering. Control.
The semi-elliptic springs fitted both in front and rear, we should say, are decidedly on the short side as compared with current practice.
They appear, however, to be quite strong enough, and those at the rear are carried by substantial shackles on spring-carrying cross members of the frame. The brackets for these spring carriers again give evidence of the careful thought which has been expended on the design of this chassis.
The wheels are of the artillery type, well designed and constructed, with oval spokes, those on the front being for 36 in. by 5 in. single tires and those on the rear 40 in. by 6 in. twins.
The steering gear is of the screwand-nut type, with provision for taking up wear. The control of the engine is by means of ignition and throttle levers beneath the steering wheel, and by the accelerator penal. The usual brake and clutch pedals are provided ; the changespeed gate and the side brake lever are on the right-hand side of the driver.
• From end to end of the chassis there is little that calls for criticism. We have already referred to the questionable design of the exhaust manifold and also to the springing. It seems rather unfortunate that, in a machine like the one ender review, -where generosity seems to have been the keynote, quite small bearings are lubrica.ted by large-size grease cups, the two universal joints on the short shaft between the clutch and gearbox should appear to lack any satisfactory way of applying lubricant. So far as can be seen, all that is available are small oil holes. The foot brake we have already mentioned. The rear braking is by internal-expanding shoes in large drums on the road wheels.
in order to avoid any risk of thoughtless drilling of the frame by inexperienced bodymakers, wood sills are clipped to the chassis arid included as part of the equipment.
One of the Finest.
We can only conclude this article as we have begun by remarking that, notwithstanding the criticisms which we have levelled at this machine, it is really one of the finest examples we have had the privilege of examining for some time past.
The London agent is De Silva and Wallace, Ltd., of 3, Northumberland Avenue, Charing Cross, W. C.
The machines which we examined were on the premises of Heath's Garage Ltd., 56-70, John Bright Street, Birmingham.