South Hills Tunnel

[Fred Schneider]

I remembered to bring the cross-sectional drawing of the South Hills Tunnel
to work with me this morning.  

Tunnel width was 24'-0".  Height from top of railhead was 20'-0".  Walls
were perpendicular to a height of 8'-0" above the railhead and for perhaps
18" below the railhead, however the lower portion of the wall was obscured
with ballast up to top of ties.  Ceiling curvature was 12'-0" radius.
Inside was faced with five courses of brick with hid the original timber
supports and facing.  Whether or not the brick facing was added to add
strength to older timber facing is unclear albeit possible because the
drawing dates to March 16, 1925, some 21 years after the tunnel was built.  

Original drawing or the print or both has ( have ) shrunk, so I cannot take
precise measurements off the drawing.  The span wire strain insulators were
mounted about 18' above the railhead making the wire somewhere around 17' -
6" above the railhead.  The drawing actually shows a perfectly taut span
wire but we know better, don't we...  

The gauge line of the inner rails was 5'-0".  Because we are converting to
standard gauge for models, we should work from center line to center line,
which would be 30" plus 31 1/4" or a total of 61 1/4 inches from center of
tunnel to center line of track or 122 1/2 inches from track center to track
center.  This left a rather abundant devil strip of about 26" depending on
car width (certainly more than we can expect with two buses pasing in the
bore today).  The west side of the bore had an encased conduit box, 5' high
above the tunnel invert or about 3 1/2 feet high above the rail head, and 9
inches wide.  This apparently ran the lengtyh of the bore.  On both sides of
the tunnel were three parallel 3" feeder cables on a blank centered centered
about nine inches above the rail head.  The east side had four 2" cables on
a plank support centered about 2'-6" above the railhead.  Fire extinguishers
were mounted on both sides of the tunnel between the two sets of cables on
the east side and between the counduit and cabling on the west side.  

The brick walls also had anchor bolts that stuck out about 3" from the brick
at 12 different locations which I cannot describe but which are
insiginifcant in an HO model.