valves are arranged as in figs. 31, 32, and 33, is fitted with a bent crank, and balanced by means of weights placed between the arms of the flywheels near the boss. Figs. 37 and 38 are The crosshead pin and brasses, however, by this arrangement are easy to get at for adjustment. The 85 B.H.P. (fig. 36) has a cylinder 18 inches diameter and 24 inches stroke, in which the FIGS. 37, 38.-400 B.H.P. STOCKPORT TANDEM ENGINE an elevation and plan of a tandem engine, having cylinders 25 inches diameter and 36 inches stroke, which, when running at 120 revolutions per minute and working with coal gas of 16 candle-power, it is stated, will develop 400 B.H.P., and 330 B.H.P. when working with producer gas. It is, however, impossible to give any reliable data as to its B.H.P. or the gas consumed, as there are several other engines working from the same producer plant. The cycle of operations in this engine is that shown in fig. 1 at B, and also in fig. 3—that is, an impulse every revolution when working at full power. The two pistons are connected by side rods supported at their ends by slide blocks, the connecting rod being common to both. The blow from the explosion of the charge delivered by the connecting rod at centre of cross-piece gives the latter severe bending, whilst the action at its ends on the slide blocks is calculated to add greatly t the friction and resistance. Unlike their usual practice, the air and exhaust valves are placed on the end of the combus tion chamber, one side shaft actuating the whole of the valves and the gas inlet of both cylinders is under the control of one centrifugal governor. The self-starter used by this firm is very simple and efficient. Fielding & Platt, Gloucester Messrs. Fielding & Platt's experiments in gas motors date back to 1879, from which year to 1890 they were engaged, like many other firms, in comparing other types with the now universal Otto.' The evolution of their present form of valves has been very interesting. However, a description of these is outside the scope of this treatise. It is difficult to understand why, when designing an engine to combine the many advantages of the girder frame, engineers should nullify those advantages by arranging the bearings so that the force of the 3 explosion has to be taken up by the cap bolts, when it is as easy to arrange that the main casting shall be utilised for the purpose. Fig. 39 shows that this firm, like others, have fallen into this error, as in the 100 B.H.P. engine this defect is very pronounced. The girders and main bearings are in one casting, to which the cylinder is bolted, the bolts for which are, however, covered over with a loose ring. Although this gives the engine a very neat appearance, it does not admit of easy access to the bolts. The air and exhaust valves are carried in one box, forming part of the combustion chamber, the air valve being arranged at the top and the exhaust valve at the bottom. The governor and gear are of the ordinary dead-weight centrifugal pattern. An illustration of the development of large power in gas engines is shown in figs. 40 and 41, wherein 180 B.H.P. is arranged to drive direct an air compressor at the high speed of 150 revolutions per minute. The distinctive feature is that the crank shaft, arranged between the back end of one cylinder and the front end of the other, is placed above the centre |