. American engineer and railroad journal . eral, but those a^. \ Jfl-- \ --«r- .— —- jj .„, i -*-*■ i** « s* kv s. s ^ y rl ^ r aooo Shp /ft •nefn a .04 .or oa .a* ./#■ from tapered holes rise more rapidly and are thus more rigid. During the progress of these experiments a form seemedwanted, to put the rolled metal under an initial stress in the di-rection of the axis of the tube, thus reinforcing the frictionalresistance to the first slip. A tapered hole in the sheet was there-fore given a reverse taper also, so that its smallest diameter wa«A in. from the tube side of the sheet This amounted
. American engineer and railroad journal . eral, but those a^. \ Jfl-- \ --«r- .— —- jj .„, i -*-*■ i** « s* kv s. s ^ y rl ^ r aooo Shp /ft •nefn a .04 .or oa .a* ./#■ from tapered holes rise more rapidly and are thus more rigid. During the progress of these experiments a form seemedwanted, to put the rolled metal under an initial stress in the di-rection of the axis of the tube, thus reinforcing the frictionalresistance to the first slip. A tapered hole in the sheet was there-fore given a reverse taper also, so that its smallest diameter wa«A in. from the tube side of the sheet This amounted to a slight chamfering of the inner side of thetube sheet. Rolling the tube against the two tapers would developsuch stresses along the tube as should help to resist Figure 4 numbers 36, 44, 26, 25, 38 and 37 had double ; ompared with the straight holes the general effect was to lowerthe slipping point somewhat but increase the rigidity. A study of the several t<--ts made shows that in the usual ma-. 47 48 33 40 46 43 41 41 43 tSerrafee/ Ho/ej 33 36 44 £6 iS 6 38 3r FIG. 4. ir 33 n 3414 31 chined joint the resistance to the first slipping comes from fric-tion only. The friction is dependent on the normal pressure ofthe expanded tube against the sheet and this will be a maximumwhen the rolled metal of the tube is stressed to its elastic limitThe rolling of the metal elevates the elastic limit, but it takes asmall amount of rolling to reach this maximum value. Furtherrolling reduces the thickness of the metal in play as fast as theelastic limit is exalted. Assuming the elastic limit of the rolled metal at from 30,000 tr>40,000 lbs., the observed slipping point shows that the coefficientof friction must have been 35 to 26 per cent. The total frictionper square inch of tube bearing area seems to be about 750 tube plates % and 1 inch thick. It was observed that in straightand tapered holes wherever a high final strength was attained
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
