Page:Aerial Flight - Volume 1 - Aerodynamics - Frederick Lanchester - 1906.djvu/380

§ 234 given in Fig. 147, in which a light stiff beam, built on the lattice principle, is mounted on knife-edge gimbals on a frame which is in turn free to rotate about a vertical axis. This beam, which is functionally comparable to the beam of a balance, carries at its outer end (i.e., the end remote from the axis of the whirling table) the “wind plane,” attached by a tubular arm to the divided circle $$G ,$$ by which it may be set to any desired angle. The inner and outer limbs of the beam are symmetrical, and the whole is enclosed in a box or case to afford shelter from the wind. A dummy end is allowed to project at the inner end to balance (as to wind pressure) the attachment arm at the outer extremity.

A pencil arm (indicated as such in the figure) is provided, attached to the gimbal frame, to record direct on the chronograph drum. This pencil arm also serves to attach the spring by which the horizontal component is measured. Friction wheels $$R$$ are fitted at both ends of the beam to limit the vertical movement.

The delicacy of suspension was found to be greater than could be employed under outdoor conditions, and a brush $$H$$ was added to develop a certain regulated amount of friction.

The chief work accomplished with the component pressure recorder was the following:—

(1) The determinations for planes of different proportions, of the velocity of “soaring” corresponding to different values of angle and load. Incidentally, the existence of an angle of reversal, already mentioned in connection with the plane dropper, was clearly brought out, the previous result being confirmed.

(2) The determination of the values of $$P_\beta / P_{90}$$ for planes of different aspect ratio.

(3) The determination by direct measurement of the horizontal component of the reaction on planes at different angles and soaring speeds supporting a known weight.

Fig. 148 gives, plotted to a reduced scale, one of the soaring speed diagrams taken from the Memoir. The “reversal” is well