Table 149. 



FRICTION. 



The following table of coefficients of friction / and its reciprocal \//, together with the angle of friction or angle of 

 repose <>, is quoted from Rankine's "Applied Mechanics.'" It was compiled by Rankine from the results of 

 General Morin and other authorities, and is sufficient for all ordinary purposes. 



Material. 



Wood on wood, dry 



" " " soapy 

 Metals on oak, dry 

 " " wet 

 " " " soapy 

 " " elm, dry 

 Hemp on oak, dry 

 " " " wet 

 Leather on oak 



" " metals, dry 

 " " " wet 

 " " " greasy 

 " " " oily 

 Metals on metals, dry . 

 " " wet . 

 Smooth surfaces, occasionally greased 

 " " continually greased 



" " best results 



Steel on agate, dry * . . . 



" " " oiled* . 

 Iron on stone .... 

 Wood on stone .... 

 Masonry and brick work, dry 



" '• " " damp mortar 



" on dry clay 

 " " moist clay . 

 Earth on earth 



" " " dry sand, clay, and mixed earth 

 damp clay . 

 wet clay 

 shingle and gravel 





« 



.25-.5O 



.20 

 .50-.60 

 .24-26 



.20 

 .2O-.25 



•53 



■33 



•27--38 



.56 



•36 



•23 



•15 

 .15-. 20 



•3 

 .07-.08 



.05 

 •03-.036 



.20 



.107 



•30-70 



About .40 



.60-.70 



•74 



•51 



•33 

 .25-1.00 



•38-75 

 1. 00 



.81-1. II 



1// 



• Quoted from a paper by Jenkin and Ewing, " Phil. Trans. R. S." vol. 167. In this paper it is shown that in 

 cases where " static friction " exceeds " kinetic friction " there is a gradual increase of the coefficient of friction as the 

 speed is reduced towards zero. 



Smithsonian Tables. 



