Outboard Mountings.—In the English service the camera was first attached to the plane outside the fuselage by a rigid frame, to which the camera was strapped or bolted (Fig. [81]). Obvious objections exist to placing the camera in this position, such as the resistance of the wind and the difficulty of changing magazines. However, in the earlier English planes with their fuselages of small cross section no other accessible place for the camera was to be found. Vibrational disturbances with the rigid outboard mounting are quite serious, as is so clearly indicated by the trace shown in Fig. [78]. Extremely short exposures are alone possible, and a very large proportion of the pictures are apt to be indistinct.
Floor Mountings.—A step in advance of the outboard mounting is to support the camera snout in a padded conical frame on the floor of the plane (Fig. [82]). This mounting avoids the objection on the ground of wind resistance that holds with the outboard, and has possibilities of being worked out as an entirely satisfactory support. Yet to be satisfactory, the point of support must lie in the plane of the center of gravity of the camera, and the camera must be of a type that preserves its center of gravity unchanged in position as the plates are exposed. Unless these conditions are fully met the floor mounting gives results little better than does the outboard.
Cradles or Trays.—Floor space in the cockpit being unavailable in the battle-plane, due to duplicate controls, bomb sights, etc., the English service was driven to the practice of carrying the camera in the compartment or bay behind the observer. Here it was attached either to the structural uprights or longerons, or to special uprights and cross-pieces built into the plane to serve photographic ends. As an intermediary between the camera and the supporting cross-pieces there was introduced the camera tray or cradle. This is essentially a frame carrying sponge rubber pads into which the camera is more or less deeply bedded. Figs. [83] and [84] show an American L camera cradle based on the design of the English L camera tray. Thick sponge rubber pads support the two ends of the camera top plate, and additional pads are provided to hold the nose of the camera. Careful tests show this cradle to be superior to the outboard mounting, but still leave much to be desired. Its performance is better with the nose of the camera left free.
Fig. 82.—“L” camera in floor mounting.
Fig. 83.—“L” camera and cradle mount in skeleton DeHaviland 4 fuselage, side view.
Tennis-ball Mounting.—A very simple mount used by the French consists of a frame enclosing the nose of the camera, and carrying four tennis balls, on which the whole weight rests (Fig. [40]). If the center of support is in the plane of the center of gravity and if the four balls are of uniform age and elasticity, this form of support is good. As provided by the camera manufacturer, the tennis ball frame fits much too far down on the camera. Another application of the tennis ball idea was frequently made in the French service, in which the balls were close up under the shutter housing (Fig. [85]). Additional support was, however, given to the camera nose by flexible rubber bands, the success of the whole being largely a matter of the adjustment of the tension on the bands.
Fig. 84.—“L” camera and cradle mount in skeleton DeHaviland 4 fuselage, front view.