--- In BRHSlist@y..., Ralph Brown <cbq682@g...> wrote:
> What is a cantilever? Is it a "half" signal bridge?
> Here in Galesburg just south of the current depot, there is a
structure...
As Ed DeRouin indicated, this forum would not be the best place to
share all of the Q Signal Bridge information, because it is such a
large amount of information (there were signal bridges at over 400
different locations). However, I do want to answer your question
about the bridge at Galesburg, Ralph, and also ask the list a
question about this style of bridge.
A cantilever signal bridge is exactly what you are looking at in
Galesburg. A cantilever bridge is one in which the main beam or
truss is supported at one end only. In order to avoid using left-
hand signals, cantilever bridges were employed where multiple tracks
did not allow supports on both sides. Because this placed the
majority of the load out away from the support, the tower was subject
to "overturning". That is why the supports are wide, typically 4',
and contain multiple legs, and large concrete foundations.
The cantilever at Galesburg, MP 162.45, is one of the first of this
style of bridge, being constructed in 1930. This is the most
prevelant style of cantilever, and was built in "one" and "two" track
variations. Br. 162.45 was of the two-track design. There was even
a "T" cantilever bridge built to this plan for 3 tracks at Western
Ave. in 1964, with the two track "cant" on the north, and the single
track "cant" on the south.
The plan for this style of bridge is Drawing 51371 (technically
51371B since it has two modifications), originally dated 1922. The
earliest installation I can find, however, is 1929, where the plan
was used at Br. 441.87 Red Oak, IA., and 471.16, Hastings, IA.
And that brings me to my question. This style of bridge, I assume,
was used somewhere in 1922, but where. The only cantilever that I
have identified as existing, but have no date or details for, is Br.
427.82 at Daytons Bluff. Is it possible that this bridge is the
original one fabricated to plan 51371? If anyone remembers seeing
this bridge, and can identify it, I would appreciate knowing.
Glen Haug
|