Figure 11-13.—Differential gear hookups.will be equal to half the difference between therevolutions of the two inputs. A change in the gearratio to the output shaft can then give us anyproportional answer we wish.We have been describing a hookup wherein thetwo sides are inputs and the spider shaft is theoutput. As long as you recognize that the spiderfollows the end gears for half the sum, ordifference, of their revolutions, you don’t need touse this type of hookup. You may use the spidershaft as one input and either of the sides as theother. The other side will then become the output.Therefore, you may use three different hookupsfor any given differential, depending on which isthe most convenient mechanically, as shown infigure 11-13.In chapter 13 of this book, we will describe theuse of the differential gear in the automobile.Although this differential is similar in principle,you will see that it is somewhat different in itsmechanical makeup.LINKAGESA linkage may consist of either one or acombination of the following basic parts:1. Rod, shaft, or plunger2. Lever3. Rocker arm4. Bell crankThese parts combined will transmit limitedrotary or linear motion. To change the direction ofa motion, we use cams with the linkage.Lever-type linkages (fig. 11-14) are used inequipment that you open and close; for instance,valves in electric-hydraulic systems, gatesclutches, and clutch-solenoid interlocks. Rockerarms are merely a variation, or special use, oflevers.Bell cranks primarily transmit motion froma link traveling in one direction toanother link moving in a different direction.The bell crank mounts on a fixedFigure 11-14.—Linkages.11-9
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