. The steam-engine and other heat-motors. mination of the table and the figure shows that theheights of the cones become very small and impractical at speedsmuch exceeding 80 revolutions per minute. This becomes moreapparent when we remember that it is the difference in the heightof the cones that affords the motion of the mechanism for closingthe throttle. Thus, in changing from 80 to 85 revolutions a REVOLUTION CONTROL. 333 minute, the difference in height of the cones is 1 inch; at 200 revo-lutions the cone height is only .88 inch, and the speed would haveto reach 300 revolutions per minute
. The steam-engine and other heat-motors. mination of the table and the figure shows that theheights of the cones become very small and impractical at speedsmuch exceeding 80 revolutions per minute. This becomes moreapparent when we remember that it is the difference in the heightof the cones that affords the motion of the mechanism for closingthe throttle. Thus, in changing from 80 to 85 revolutions a REVOLUTION CONTROL. 333 minute, the difference in height of the cones is 1 inch; at 200 revo-lutions the cone height is only .88 inch, and the speed would haveto reach 300 revolutions per minute to change the height .88 —.39 = .48 inch. These dimensions are entirely too small for anypractical mechanism. Referring to our fundamental formula, page 331, let k = will be the case when the upper and lower arms are of equallength. Then (w+L)r = wV2h w(in2N2)h gr 60V or m( 1 + w )- N2h. 2936 1 + w N2h. The relation between this formula and that for the simple pendu-lum is at once apparent. For simplicity, let the heavy central. Fig. 171. weight be nine times that of one of the balls, then the height ofthe cone will be ten times that of the simple pendulum. Thismakes this form of governor available in cases of governor revolu-tions ranging from 200 to 240 revolutions or higher. Sensitiveness.—If iV\ is the highest and N2 the lowest numberof revolutions permitted by the governor, the sensitiveness is 334 THE STEAM-ENGINE AND OTHER HEAT-MOTORS. N1-N2expressed by ^ ^ = the range of speed divided by the mean 2 speed. The smaller this fraction the more sensitive the Ni—N2 becomes 0, the governor ceases to act properly fromsii per sensi ti veness. K)- For convenience let 2936 = CX2 and 11 +— ) = C22 C CThen for the loaded governor -^—?=JVi, Vhi Vh2 Subtracting, Adding, ^-?^,- Vhx. Vh2/ CiC2(4= + -7-- )=N1+N2. Whx \/h2/ Ni- N 1 Nj +N2 V^x V/i We would obtain the same expression for the sensitiveness of anunloaded governor. It is therefore evident that the
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