ends thereof although for clarity of illustration only one hand wheel 66 is shown it will be appreciated that the teeth 44 of the rolls 40 and 42 need not be equal in size and their profile need not be standard involute gears however are easily cut and readily available and their contours can be modified with little difficulty particularly the addenda various tooth shapes are depicted in fig1 18 the wavelength of the corrugation is strongly dependent on gear pitch but it is also influenced by the load on the leaf spring 60 which is the dominant factor in determining the amplitude of the undulations of the backing the amplitude and to a lesser extent the wavelength are also influenced by the yield strength and flexural rigidity of the foil finally the local curvature of the deformed foil will be strongly influenced by the tooth profile as well as by the yield strength and flexural rigidity of the foil the deformation process is illustrated schematically in fig1 the simultaneous transport and indentation is shown in that drawing while the effect of tooth profile is depicted qualitatively in fig1 17 and 18 since the outer foil fibers of the foil 52 deform plastically while the inner fibers do not exceed the elastic limit considerable 34 spring back 34 occurs from the fully deformed shape assumed by the foil between gear teeth two sharp corners of the addendum will produce finite curvatures in corresponding regions of the corrugation on the other.