© 1949 by Oxford University Press
THEORY OF A LOOP REVOLVING IN AIR, WITH OBSERVATIONS ON THE SKIN-FRICTION
( University of London Observatory Mill Hill Park, N.W.7 )
An investigation is made of the dynamics of a flexible loop, driven by a small pulley at a constant speed, for the case when the speed is sufficient to cause the loop to become air-borne. It does this when the air-friction is greater than the weight of the loop. The shape and position of the loop may be calculated for values of the ratio, 2
, of air-friction to weight and the angle, ø*, that the tangent to the ascending portion of the loop at the pulley makes with the horizontal. This angle may be controlled by means of a second pulley so arranged as to press the loop against the driven pulley. If
= 1, theory predicts a point of the loop at which its radius of curvature becomes zero. For values of
between
and 1 the motion is stable, and the precise value of
may be found from the photographed shape of the loop. As the result of some trials, values of
have been obtained which have given a value of the air-friction drag coefficient of the right order of magnitude.