D. Stewart and Company (1902), Limited.
Page 20
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Exhibit:—A Standard Stearn Wagon for 5-ton Loads.
This maker, D. Stewart and Company (1902), Limited, of the London Road Works, Glasgow, has, for the past few years, been the sole British maker of steam wagons built to the well-known designs of Sir John I. Thornycroft, and it has done good business with these vehicles among the brewers, collieries, county surveyors, and borough corporations of Scotland, and also of this country. The vehicle which it is exhibiting has been built to the order of the Corporation of Smethwick, near Birmingham.
With the exception of the locomotive type of boiler which, during recent years, has been fitted, there has been no radical change in the designs of this make of vehicle since it was so successful in the trials promoted by the Liverpool Self-Propelled Traffic Association in 1899 and 1901. The locomotive type of boiler, which is now fitted, is a very good steamer, and is thoroughly stayed at every point. The fuel is fed to the fire through a vertical steel tube, about nine inches in diameter, and which connects the fire-box crown plate with the saddle plate, bracing the two plates together, and acting as a most effective stay to these flat surfaces. The boiler is fixed in the frame by means of two lugs (one on each side) from the outer 'shell of the fire box, and the forward end of the barrel rests on the front transverse member of the main frame. The compound engine is fitted4with flat valves, over which cast-iron sOitigloaded saddles are fitted. The object of these saddles is two-fold firstly, they relieve the steam pressure from the back of the flat valve, and thus save wear on the valve faces ; and, secondly, they act as safety valves in the event of either of the cylinder's becoming water logged. When a cylinder gets into this undesirable stale, there is a great risk of the knocking out of one of the cylinder covers, but, with the spring-loaded valve saddles, the water can escape by its lifting up the saddle off its seating. The squared shaft, on which the change-speed pinions are mounted, is in line with, and is connected to, the crankshaft, and the power is transmitted from it to the second-motion shaft. It is this latter shaft, and the manner in which it is used to convey the power to the back axle, which forms the most distinctive feature in the Thornycroft design. The second-motion shaft is articulated, and on one end of it a double-helical pinion is mounted; this pinion meshes with a corresponding wheel, which is mounted on the live axle, and the two gears are kept at the correct meshing distance by means of a triangular bracket : one corner of this bracket is occupied by the back axle; another by the floating end of the second-motion shaft ; and from the other corner a radius rod anchors the bracket to the main frame. By the use of a suitable combination of radius rods, the back axle practically moves along the arc of a circle, the centre of which coincides with the centre of the secondmotion shaft.
Both the driving wheels are mounted freely on the axle, and they are driven, through the differential gear, by laminated plate springs which transmit the drive close up to the felloe, thus relieving the spokes of all driving strains. This vehicle is fitted with a wooden, end-tipping body, suitable for municipal use, which is interchangeable with a water tank, for street watering.