. Machine design. rs unevenly, usually as-suming a concave shape as seen in profile. 55. Schieles Pivot. By experimenting with apivot and bearing made of some friable material, it wasshown that the outline tended to become curved asshown in Fig. 49. This led to a mathematical investi-gation which showed that the curve would be a trac-trix under certain conditions. This curve may be traced me-,5 C^\ chanically as shown in Fig. 48. W Let the weight W be free to move on a plane. Let the stringSW be kept taut and the end Smoved along the straight line will a pencil attached to the TO AO ce
. Machine design. rs unevenly, usually as-suming a concave shape as seen in profile. 55. Schieles Pivot. By experimenting with apivot and bearing made of some friable material, it wasshown that the outline tended to become curved asshown in Fig. 49. This led to a mathematical investi-gation which showed that the curve would be a trac-trix under certain conditions. This curve may be traced me-,5 C^\ chanically as shown in Fig. 48. W Let the weight W be free to move on a plane. Let the stringSW be kept taut and the end Smoved along the straight line will a pencil attached to the TO AO center of W trace on the plane a Fig. 48; . r tractrix whose axis is SL, SCHIELES PIVOT. 115 In Fig. 49 let SW=lengthof string =r\ and let P be anypoint in the curve. Then it isevident that the tangent PQ tothe curve is a constant and =?\ Also Let a pivot be generated byrevolving the curve around itsaxis SL. As in the case of theconical pivot it can be provedthat the normal pressure onan element of convex surface is. Fig. 49. dP = SWrdr (a) (dl—d$)sind Let the normal wear of the pivot be assumed to beproportional to this normal pressure and to the velocityof the rubbing surfaces, i. e. normal wear proportionalto pr, then is the vertical wear proportional to prsinB But is a constant, therefore the vertical sind wear will be the same at all points. This is thecharacteristic feature and advantage of this form ofpivot. As shown in equation (a)SW^dr Cli — CL% dP rjrp di d\ and T _%Wfr1 r\-r\ Wfdx1 ~ dl-dl 2 ~~ 2 .(72) T is thus shown to be independent of d, or of the*length of pivot used, 116 MACHINE DESIGN. This pivot is sometimes wrongly called will be seen by comparing equations (68) and (72)the moment of friction is fifty per cent, greater thanthat of the common flat pivot. The distinct advantage of the Schiele pivot is in thefact that it maintains its shape as it wears and is self-adjusting. It is an expensive bearing to manufactureand is seldom used
Size: 1405px × 1778px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyo, bookyear1906
