[Illustration: PL. 41 FIG. 1. FIG. 2. FIG. 3. AERODROME ON LAUNCHING-CAR] [Illustration: PL. 42 ‹Aerodrome “A”› ‹Details of Clutch Post for Launching Car›. ‹Scale 1/3 Full Size› DETAILS OF CLUTCH POST FOR LAUNCHING-CAR] [Illustration: PL. 43 FRONT END OF TRACK JUST PREPARATORY TO LAUNCHING AERODROME] On the large launching car the arrangement of the struts against which the bearing points of the frame were tightly drawn by the clutch was similar in all respects to that used on the model car, there being only slight differences in details. The details of the uprights on which the bearing points of the aerodrome frame rested are clearly shown in Figs. 6, 7, 8, and 9 of Plate 40. From the photographs (Plate 41, Figs. 1, 2, and 3) which show the large frame mounted on the launching car, the general arrangement of the struts and the clutch-hook can be readily seen; and from Plate 42, Figs. 1, 2, and 3, which show in detail most of the important features of the clutch-post and its clutch, a very good idea of the size of the different parts may be had by observing that the distance from the fulcrum of each half of the hook to the pin by which it was connected through the universal joint to the vertical rods is five inches. As previously stated, this clutch-hook gripped the lower pyramid and pulled the bearing points of the frame firmly against the forward and rear struts of the launching car, and in launching the aerodrome the triggers arranged on the bottom of the car, which at the proper time pull on the vertical rods and thereby force the two halves of the clutch-hook apart, are so arranged that they strike a cross-beam at the front end of the track one inch before the triggers, which keep the struts from being pulled down by their springs, which tend to fold them up and force them down against the car. The triggers, which prevent the struts from being folded down, strike a cross-beam in the track one foot before the buffer pistons on the end of the car begin to enter the buffer cylinders at the end of the track, and, consequently, one foot before the folding prop, which supports the front end of the track, is knocked out by the car striking a special trigger which allows this folding prop to swing forward when the front end of the track folds down to insure that the aerodrome will not become entangled with the car, even though the aerodrome be not quite up to soaring speed at the moment of launching. The manner in which this front end of the track folds down can be very readily seen by comparing Plate 43 with Plate 95 of Chapter XII, the former showing the front end of the track in horizontal position, with [p161] the aerodrome at the extreme rear end just preparatory to launching, and the latter showing the front end of the track folded down with the hinged prop standing outward in its downward path and the aerodrome just launched. These photographs will be more particularly referred to later, but attention