Page:Aerial Flight - Volume 1 - Aerodynamics - Frederick Lanchester - 1906.djvu/410

§ 246 is formed by the face in presentation, being the normal plane the pressure on which constitutes a measure of the reaction on



the friction plane. The area of the normal plane can be extended at will by cementing a mica plate to its face, the edges of which are clipped until exact balance is obtained.



The opposite arm of the beam carries the friction plane E (Fig. 159); this is carefully formed of cedar of 6 mm. maximum thickness, the grain being well filled and served with a thin coat of varnish, or otherwise finished as may be required. The friction plane is carried on a holder formed by two pen steel