Vehicles in the Trials.
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The "Thames" 10-Cwt.1 20-Cwt., and 60-Cwt. Vehicles.
If one were asked the question " which of all the vehicles in the trials is the most striking from the advertising point of view " it is pretty certain that the answer would be" The Palmer tire van, No. Mr." It has far and away the smartest and most unique body, and the performance of this van throughout the trials has been most satisfactory. The chassis on which the " tire-body" is mounted is one of the standard 15-2o cwt. type manufactured by the Thames Engineering and Shipbuilding Co., Ltd., of Greenwich, S.E., for which company W. T. Clifford-Earp, Ltd., of 74, Mortimer Street, London, W., is sole selling agent. Another of the vehicles in the trials (No. A5) by the same maker has a chassis which is precisely similar to the first mentioned, but it is fitted with a tilt-van body of ample capacity for dealing with the bulkiest of goods up to Tocwt. in weight. This particular vehicle has not done so well as the sister chassis in class B, but none the less its performance cannot be termed unsatisfactory. A vehicle only gives out the best results if it is worked up to its designed load and speed. To underload and over-run—as is the case with this vehicle—is to invite trouble. To the excellent workmanship which is put into the " Thames " vehicles must be attributed the absence of serious breakages while driving A5 hard over the granite setts of Lancashire and parts of Yorkshire. The two-cylinder engine is rated as of 8/h.p., at L000 revolutions per minute, but we believe that it is capable of giving more than that power, and to-t 2 h-P• at 1,200r.p.m. would be nearer the mark. The cylinder diameter is 3i inches and the pistons have a stroke of 41 inches. The cylinders are water-cooled and the circulation of water is maintained by a gear-driven pump. A honeycomb radiator, with a belt-driven fan, is fitted. The engine depends principally on the splash system of lubrication, but that is supplemented by a drip-feed arrangement which is fitted to the dashboard. The commutator is placed in a most accessible position : it is mounted above the cylinders on a vertical shaft which is driven through skew gearing, and it is used in combination with an accumulator and coil.
The clutch is of the metal-to-metal type, enclosed, and running in oil. From the clutch to the gear-box, the drive is transmitted through a short universal shaft. The gear-box, as may be seen in our illustration of the arrangement of this chassis, is .integral with the differential conntersimft casing. There are three changes of gear ratiofor forward running and these give speeds of 4, 7,1, and 15m.p.h. with the engine running at its normal speed. A reverse gear is also fitted. On top gear, thete is a direct-drive through the gear-box to the bevel-ring on the
differential shafts. It will also be noticed that the outer ends of the differential shafts form parts of positive clutches. Between these parts and
similar parts on the short, chainsprocket shafts, a floating ring of the Oldham coupling type is inserted. The final transmission to the rear wheels is through roller chains.
The larger " Thames " chassis (E44) is fitted with an open-sided lorry body and, carries a load of 3 tons throughout the trials. At first sight, one would think that this machine had an enormous engine beneath its unusually large bonnet. That, however, is by no means the case. There are no less than six vehicles in the trials (by other makers) whose engines are larger than that of the "Thames " " 3-tonner." This machine has several rather good points about it, not the least of which is the accessibility of all the component parts of the engine. There is nothing cramped under a bonnet too small to allow of reasonable disposition. A large bonnet certainly gives one the impression of great weight, but that is more apparent than real, as this particular vehicle, in running order, but unladen, weighs 3 tons 4 cwt. against the 4 tons 5 cwt. of another maker's vehicle in the same class. The engine has four cylinders each 41 inches in diameter ; they are cast in pairs, and Have mechanically operated valves. The pistons have a stroke of inches. At its normal speed of Sso revolutions per minute, the engine develops from 35 to 4ob.h.p. ; it is fitted With a multiple-jet carburetter which is designed to give the correct mixture at all speeds. The lubrication of their engines has been the subject of much experiment by many motor designers during the past year or two, and there is no doubt that real improve_ rnent and a reduction in the amount of smoke emitted, has been the result of their labour. The makers of the Thames wagon claim to have entirely overcome the smoke trouble, and, at the same time, to have ensured thorough lubrication of all parts of the engine. The almost entire absence of smoke emission on this vehicle, which we have kept under observation throughout the trials, would indicate that the claim is not without some justification. The oil is pumped from a sump into a special fitting on the dashboard, so that the driver can observe the flow of the oil. A constant level of oil is maintained in the crankcase. The engine is controlled by a single lever, placed on the top of the steering-wheel ; it does not, however, rotate with the latter (see section of steering pillar reproduced on page 135). A cone clutch of large diameter, and faced with leather, transmits the engine
power to the gear-box through a cardan shaft the couplings of which are of un_ usual size. A low intensity of pressure on the joints is thus secured and lubrication is more easily effected, as there is not the same tendency to force out the grease. As may be seen in our illustrations of the gear-box, the change-speed gear and differential-countershaft are all enclosed in one casing as is the case on the smaller vehicle. All the changewheels have teeth i inches wide, and they are of hardened steel. Loose keys or square shafts are avoided, and the sliding members are mounted on castellated, or fluted, shafts. The four, forward gears give speeds of 31, 6, to, and 54 miles per hour and a reverse speed of 3 miles an hour is also provided. The box is suspended from three points, and the changes of gear ratio are effected by means of three levers placed centrally on the footboard and operated by the driver's left hand.
The final drive from the countershaft to the road wheels is by means of roller chains, and a good point about the final drive as fitted to this wagon, is the large size of its chain sprockets. It is owing to the ample dimensions of the sprockets that the chain links are thus not called upon to oscillate through an excessive angle.
The steering-gear is a sound job, and is a combination of the screw and nut with the rack and quadrant : absolute irreversibility is obtained. The arrangement of this important component is clearly shown in our sectional illustration on page n.
This general design of vehicle is quite up to the standard one would expect from such an old-established engineering concern as the one in question.