As has been stated,
one rail in each track is used for signal purposes and the other is
utilized as a part of the negative return of the power system.
Adjacent rails to be used for the latter purpose are bonded with two
copper bonds having an aggregate section of 400,000 c. m. These bonds
are firmly riveted into the web of the rail by screw bonding presses.
They are covered by splice bars, designed to leave sufficient
clearance for the bond.
The return rails are cross-sectioned at frequent intervals for the
purpose of equalizing currents which traverse them.
[Sidenote: _Contact Rail
Guard and
Collector Shoe_]
The Interborough Company has provided a guard in the form of a plank
8-1/2 inches wide and 1-1/2 inches thick, which is supported in a
horizontal position directly above the rail, as shown in the
illustration on page 113. This guard is carried by the contact
rail to which it is secured by supports, the construction of which is
sufficiently shown in the illustration. This type of guard has been in
successful use upon the Wilkesbarre and Hazleton Railway for nearly
two years. It practically eliminates the danger from the third rail,
even should passengers leave the trains and walk through a section of
the tunnel while the rails are charged.
Its adoption necessitates the use of a collecting shoe differing
radically from that used upon the Manhattan division and upon the
elevated railways employing the third rail system in Chicago, Boston,
Brooklyn, and elsewhere.
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