Exercise 71: Engine Cross-head.—The cross-head shown in fig. 69 is for an inverted cylinder marine engine. A is the piston rod, and B B are pins, forged in one piece with C, to which the forked end of the connecting rod is attached. Draw the upper view with the central part in section as shown. Make the right-hand half of the lower view a plan without any section, and make the left-hand half a horizontal section through the axis of the pins B B. Scale 4 inches to a foot.
Exercise 72: Ratchet Lever.—The lever shown in fig. 70 is used for turning the horizontal screw of a traversing screw jack. Draw the two views shown, and from one of them project a plan. Scale full size.
Exercise 73: Steam Whistle.—Draw, full size, the elevation and section of the steam whistle shown in fig. 71. Draw also horizontal sections at A B, C D, and E F.
Fig. 75.
Exercise 74: Screw Coupling for Railway Carriages.—Draw the three views of the screw coupling shown in fig. 72. Scale 6 inches to a foot.
If the link A is fixed, through what distance will the link B move for two turns of the lever?
Exercise 75: Loose Headstock for a 6-inch Lathe.—Two views of this headstock are shown in fig. 73. On one of these views a few of the chief dimensions are marked. The details, fully dimensioned, are shown separately in figs. 74, 75, and 76.
