Page 262 - Tribology in Machine Design
P. 262

Friction, lubrication and wear in higher kinematic pairs  247

                                 following equation




                                                                            n
                                 where n is the cam shaft speed [r.p.m.], 5 = (^ 0 alO ) lubricant parameter
                                 and b — 2r^ — l , where / is the distance from the nose tip to the shaft axis,
                                 and r l is the nose radius.

      Figure 6.7


                                 where r is the follower radius and <j = ^]a\ +a\ is the composite roughness;
                                 where 0*1,2 is the root mean square (r.m.s.) surface roughness of surfaces 1
                                 and 2 in /im. If the arithmetic average K a (also known as c.l.a.) is available,
                                 multiply by 1.3 to convert to r.m.s.
                                   In general, the value of A in cam systems is well below one. In this regime,
                                 elastohydrodynamic lubrication is not very effective and we must rely
                                 heavily on surface film or boundary lubrication to protect the surfaces
                                 against scuffing and excessive wear.


      References to Chapter 6    1. F. F. Ling. Surface Mechanics. New York: Wiley, 1973.
                                 2. A. W. Crook. The lubrication of rollers, I. Phil. Trans., A250 (1958), 18-34.
                                 3. A. W. Crook. The lubrication of rollers, II and III. Phil. Trans., A254 (1961),
                                   141-50.
                                 4. A. W. Crook. The lubrication of rollers, IV. Phil. Trans., A255 (1963), 261-9.
                                 5. B. Jacobson. On the lubrication of heavily loaded cylindrical surfaces consider-
                                   ing surface deformations and solidification of the lubricant. Trans. ASME, J.
                                   Lub. Technoi, 95 (1973), 176-84.
                                 6. D. Dowson and G. R. Higginson. Elastohydrodynamic Lubrication. New York:
                                   Pergamon Press, 1966.
   257   258   259   260   261   262   263   264   265   266   267