Wood Howe Truss bridge (Idaho Springs)

[snapped_bolt]

   Hi folks

     I have been considering building one, maybe two of these. Now, Harry Brunk spurred us on to model the C&S like no other I am aware of- but I am having issues resolving the Gazette drawings with the few photos I have found online.
    I never stood on this bridge, nor ever got near it- but something tells me that the railroad would not have ordered an unusual beam 18" high for the lower chord stringers. I would think they would have been 16" high. like the stringers in the other bridges.  
    One small image I found is near plan view, but it is tough to take dimensions from; but the best I can reckon from it would be no higher that 12" by comparing the lower to upper chord. The width of the upper chord beam assembly should also be the same width as the lower chord beam.
    The distant cousin known as the Hermosa Creek Bridge seems to have upper and lower chords of the same height, what ever that may be. However, we are talking about different railroads...

   I would appreciate some input, please! Photos could be VERY helpful.

   Harry did mention that one should refer to photos of the actual bridge should they wish to build one "more specific".....

       Thanks!!!

            Stan

   

[Chris Walker]

Stan,

I presume you are meaning the Truss at Stanley Mills, Br#16  originally Bridge 716.

Two more pictures appear in the Colorado Central RRail Road book by Abbott, McCoy, McLeod on pg 324, the two pictures I have on this other than the Gazette article by Harry Brunk were in here http://c-sng-discussion-forum.41377.n7.nabble.com/Stanley-Mills-Part-Two-Salisbury-Mill-and-Donna-Juanita-Mine-td3483.html.

The trestle-type deck was set on top of the truss cross timbers giving it a strange look.

If you want I could dig out these and post them here tomorrow.

[snapped_bolt]

  Hi, Chris

   That IS the bridge...

     It seems to have been known by other numbers....I can understand the change from Colorado Central....but why 7xx? I thought that series was for the main line.
     So.... apparently this bridge had been rebuilt/replaced more than once, more than likely a result of it's being placed so close to Clear Creek.
     The overall construction seems a little odd in that the rails of the narrow gauge could have been carried without the "additional" stringers and ties. I am thinking this bridge probably was picked out of Clear Creek more than once after a flood, and perhaps the "odd" construction reflects this.
     I imagine that once the railroad investors got rails laid to their goal, they probably found the territory in which the rails were perched were wildly unpredictable, unlike any other location described in any Railway Gazette article. Spring thaws and flash flooding should have been a real eye opener as rocky hillsides rapidly returned the water to the streams.
     The bridge has peculiarities that beg (at least me) to model.
     More pictures would certainly help, I would hope. I am still at no more than 12" lower chord height.

         Cheers!

           Stan

[snapped_bolt]

     Morning

      One of the items I am trying to resolve is the angled post blocks. It isn't clear from the photos whether they are white oak, treated white oak, or a casting. It will certainly determine the finish on the blocks!
      I know that more modern versions of Howe truss bridges used castings, but being that this is narrow gauge, and possibly original construction, they could have been wood. The main difference in the model of course will be the final finish of the blocks.

      Any thoughts? Any pictures from the sides?

       Thanks

           Stan

[Chris Walker]

Stan,

Colorado Central Rail Road book by Abbott, McCoy, McLeod states that "The original 54-foot Colorado Central span was replaced by the Union Pacific in 1885, and again by the C&S in 1901, which renewed it in 1918"

There is one of the two mentioned photos in that book that shows an outside corner of the block you mention, it appears to be shallow and ribbed opposite the Timber suggesting Cast Iron.

A close up of the R.B.Jackson photo courtesy of Mal Ferrell, shows a distinct difference of colouration also suggesting C.I.




Courtesy of Mal Ferrell, R.B.Jackson photo from C&Sng: Colorado & Southern Narrow Gauge.

[snapped_bolt]

  Thanks, Chris!

     I was reading along in a document regarding the construction of the Howe Truss bridges....apparently they did start with wood for the angle blocks, but went on to iron castings, more so as the Howe design came of age with keys and pins to help maintain structural integrity.
     I'll bet I now know what color those angle blocks are...they would be the color of weathered cast iron blocks after about 7 years of service ( modeling around 1925). The repair dates you provided were quite helpful!

     Cheers!

        Stan