The best known of the spring form of governor is that used by Messrs. Robey & Co., of the 'Richardson' type, which consists of a spring and revolving weights having great lifting and thrusting power, the sleeve being raised from the lowest to the highest position with a slight variation of speed. Figs. 85 and 86 are sectional end and transverse elevations of a governor suitable for a 24 B.H.P. engine, and clearly show its construction and action. The following formula were used in its design, and as it would involve too much calculation to obtain strict accuracy, a margin of per cent. is close enough for all practical purposes. It was assumed in making the following calculations that the governor arm was hanging vertically, and the short arm resting upon the pad, formed a right angle with it. In a well-designed governor disturbing action may be neglected, since its object should be to signal to a separate part of the engine to perform the work, such performance being carried out without interfering with the governing proper. Weight of governor head, two arms, balls, spring, and two pins = 7.25 lbs. = 3.25 lbs. Proportion of arm leverage = 5 to 3. Revolutions of driving shaft = 90. Centrifugal force formula. 00034 × weight x radii in ft. x revolutions." Force acting on pad due to centrifugal force on pad - weight of governor head, balls, arms, springs, pins, &c. = required spring resistance. In governing a large engine the conditions are somewhat different from those which obtain in small engines; for though FIG. 87.-ROBEY GOVERNING GEAR wwwwww the ordinary gas roller works well on small and medium sizes— even when arranged for 'close' governing-when applied to large ones it is a source of trouble, owing to the small amount of surface contact under heavy lifting pressure. In fig. 87, which is the governing arrangement used on a large-size Robey engine, it will be seen that so long as the governor is in its mid-position, the gas valve is lifted by the lever A, the connecting levers from the governor being so designed that no disturbing action takes place; but immediately the load is released, the striking pecker is pulled out of action and a cut-out effected. Graduated notches are, however, arranged on the end of the gas valve spindle when the engine is used for electric lighting. The lifting pecker, as well as the end of the gas valve spindle, is made of tool steel, case-hardened, and has very broad striking edges. If, through any cause, the normal speed of the engine be considerably increased, so that the governor assumes a position midway between its normal and the highest, the pecker is moved out of action to such a point that it acts as a strut, and holds the governor in that position until the engine stops. This feature enables a communication to be made by a wire with any part of the building or offices, so that in case of accident the engine may be readily brought to a standstill. Crossley's Centrifugal Governor Messrs. Crossley's dead-weight governor (as shown at fig. 88) was introduced by them in the early days of gas engines, and has retained its form to this day. The sleeve is not in contact with the counterpoise until the engine has attained a certain speed, it is until that time an unloaded governor; but for all practical purposes may be treated as a loaded one, and by varying the weight of the poise the speed of the engine may be altered. Crossley's Inertia Governor (Patented in 1881) Fig. 89 is an elevation and fig. 90 a plan of an inertia governor arranged on a vertical engine. |