668 ME. C. "W. SIEMENS ON TNIFOKM EOTATION. 



and would have to be got rid of by the application of cooling agents, if the natural dis- 

 persion of heat by radiation would no longer suffice to keep down the temperature. 

 This would, however, be a wasteful proceeding, and it becomes necessary to operate, not 

 upon the power produced, but rather upon the source of power, by rendering it always 

 equal to the accidental resistance or load in order to maintain uniform velocity. The 

 arrangement adapted for this purpose is represented by Plate XXIX. figs. 2, 3, 4, 5 & 6. 



S is the main shaft of the engine, which imparts motion to the upright spindle H 

 carrying an inverted wheel E. The axis A of the regulating cup, being concentric with 

 the spindle H, carries a pinion F, and both the wheel and the pinion gear into two 

 intermediate or planet-wheels G and G', which latter are loose upon studs and are 

 suspended from a rocking-frame I, the latter being free to turn upon its central support. 

 The rbcking-frame I is connected by a rod R to a bell-crank lever O, which is fastened 

 upon the spindle of the steam-regulating or throttle-valve V ; but the horizontal arm 

 of the lever O cames a weight P which, being acted upon by gravity, tends to open the 

 valve and at the same time to force the rocking-frame I, with its planet-wheels G and 

 G', round the vertical axis. This pressure is resisted, on the one hand, by the teeth of 

 the pinion F, which can only yield in the ratio imposed by the rotating cup C, and on 

 the other hand, by the teeth of the inverted wheel E, which latter, being driven round 

 by the engine in the direction contrary to the effort produced by the weight P, causes 

 the latter to be continually raised. If the engine should succeed in raising the weight 

 P, say 100 millims., while the regulating cup yields also to the extent of 100 millims., 

 then the lever O, and with it the regulating valve V, will retain their relative position ; 

 but if the engine should raise it, say 95 or 105 millims., while the cup yields 100 

 millims., then the valve will be either opened or closed by 6 millims., and the engine 

 will be urged or checked, as the case may be, to such an extent as to make its revo- 

 lutions coincide again absolutely with those of the regulating cup. 



The driving-power of the cup is limited by the weight P, and may be considered as a 

 constant regulated quantity (although it is derived indirectly from the engine) ; but when- 

 ever the valve has to be opened or closed, a resistance arises which goes either in dimi- 

 nution of or in addition to the weight P, and the power of the cup must be such that its 

 speed remains sufficiently uniform under the influence of these occasional variations. 



By means of the automatic dip arrangement it would not be difficult to obtain per- 

 fect uniformity, notwithstanding these irregularities in the driving-power ; but in the case 

 of steam-engine governors this arrangement is dispensed with for the sake of a more 

 immediate action upon the valve at the moment when a differential velocity arises. 

 Supposing that the greatest amount of occasional variation of speed is to be 1 per cent., 

 and that the dimensions of the cup are as follows. 



Diameter at upper rim =200 mUlims. 



Diameter of rim above the liquid =200 millims. 



Diameter of orifice at bottom of cup =90 millims. 



we find the available power of the instrument in the following manner : — 



