that opening is of a depth and length sufficient to have the projecting end 52 of the finger 48 pass through the opening 51 when the two are in register such as shown in fig4 in that aligned or registered position the shifter 38 can move the clutch element 19 to the left and right as desired that provides for engagement of the lugs 22 and 24 only when the openings 23 and 26 are respectively ready to receive those lugs that is when they are in aligned position and thus there can be a smooth shifting motion with a minimum of wear and tear on the elements and with immediate response to the clutching that means that the gate itself that is the clutch elements 48 and 49 are arranged to be synchronous with the engagement of the clutch element 19 with its driving pinions 13 and 18 as mentioned fig6 depicts the ultimate in the synchronization achieved and mentioned for each two revolutions of the pinion 13 the pinion 18 makes a complete cycle or one revolution clockwise and one revolution counter clockwise since the pinion 18 is driven by a crank action its speed varies from zero to a maximum which is considerably in excess of the speed of the rotating pinion 13 to insure a smooth and precise shift from rotation to reciprocation and vice versa the shift must be made at the instant the pinions are rotating at the same speed and in the same direction fig6 shows a sine wave type of line 53 plotting the reciprocating pinion rpm from zero and starting upward and the figure also shows the straight line 54 plotting the speed of the rotating pinion 13 and.