— 76 — 
Tim. 
rin Bearing. 
Chonl racking &c. 
Evpamioii rollern. 
Turn-bncklei au<l 
Sleeve-nut^. 
Nu レ . 
In loop eyes the distance of the inner point of the loop from 
the centre of the pin must be not less than three times the diameter 
of the piu. 
The loop raus t fit closely to the pin throughout its semi- 
circumference. 
Pin holes iu eye bars shall be bored to an exact size and dis- 
tance, and to a true perpendicular to the line of stress; no error iu 
tbe length of bar exceeding ouo sixty fourth ( み ） of an inch will be 
allowed, nor any variation of more than one sixty-fourth ( 占 ） of an 
inch between the centre of the eyo and the centre line of the bar. 
Pius are to be proportioned lo resist the bending produceil in 
them by the bars or struts which tliey connect. Steel pins are also 
lo be proportioned for shear. 
No pin is to have a iliameter less than eight tenths ( T ö ö ) of tlie 
depth of the deepest bar coupled thereon, nor shall it vary from 
that of the eyes of tlie bars coupled thereto by more than one fiftieth 
( 万 ’ 0 ) of au inch. 
Tlie least allowable diameters for pins are two (2) inches for 
those belouging wholly to the Intend systems or sway bracing, and 
two and a half (2 士 ） inches for all other pins. 
All pin holes shall bo reinforced by additional material, so as 
not to exceed the permissible pressure on the bearings. 
Where a pin bears against a reinforced channel bar, the web 
of the lattei’ is not to l)e assumed to take up auy bearing stress, 
unless the reinforcing plate or plates bo rivetted to it before the pin 
hole be bored. 
The lower chords are to be packet! as closely as possible and 
in such a manner as to produce the least bending moments upon 
the pins. The various members attached to any pin must be packed 
as closely as possible, and all iuterior vacant spaces must be filled 
with wrought iron fillers. 
Expansion rollers aro to be proportioned by the formula 
P == 0.25 \J^ d } where p is the working load in tons per lineal 
inch of roller, and d ia the diameter of the roller in inches. 
The least allowable diameter for rollers is two (2) inches. 
The spaces between rollers must never exceed one half (.J) of 
tlieir diameter. 
All tarn-bucklcs and sleeve-nuts must be made so strong that 
they would be able to with. stand Avitlioufc ruptiu-e the ultimate pull 
of tlie rods "which they connect. U nuts are not to be used in any 
part of a bridge. 
Tlio dimensions of all square and liexagonal nuts for the various 
diameters of rods are to be taken from Chapter XIX. 
Thoac for the ends of pins, when not subjected to calculable 
