BRIDGES IN THE MOUNTAINS

A signature element of the climb up into the Cascades are several steel trestles and other bridges.  All three of the major steel trestles on the line are represented on my layout:  Salt Creek, Noisy Creek and Shady Creek.  These were among the final roadbed construction on my mountain grade as I built toward mainline completion and the Golden Spike. http://espeecascades.blogspot.com/2015/04/golden-spike.html  I needed to at least prepare for the trestles and bridges even with temporary construction. 

First up was a pair of bridges in the midst of Cruzatte that span Cascade Creek.  These are deck girder bridges and employ the basic construction method I use for most such girders.  I create a central spine that continues the subroadbed through the bridge.  This is sheathed with Central Valley girders.  I used this technique previously for the mainline bridge over Salmon Creek on the RR-West end of Oakridge. http://espeecascades.blogspot.com/2014/04/salmon-creek-mainline-bridge-1.html   http://espeecascades.blogspot.com/2014/06/salmon-creek-mainline-bridge-2.html That bridge has a deck.  The pair spanning Cascade Creek at Cruzatte needed to represent open deck construction. 

Though the actual bridges are “open,” one does not see much down through the ties or up from the bottom.  I chose to cut out the plywood subroadbed at Cruzatte to create a ½ inch wide spine for each bridge.  I then painted these spines a dull black.  The actual bridges at Cascade Creek are still painted black, just as my models are, so a dull black interior works well. 

Spines for Cascade Creek bridges cut out of plywood subroadbed for Cruzatte.

The Central Valley girders were shortened from the 72 foot through plate girder kit.  Separate girders are packaged as Central Valley 1903-1.  I added “angle iron” to the bridge ends and decal rivets to the visible side of those angles.  Top and bottom plates were added.  The two girders were then joined by three short sections of 0.125x0.156 styrene.  All of this was painted black and then weathered.  These bridges sections fit neatly over the plywood spines.  Bridge track was laid on top and joined to the regular flex track on either side of the bridge.

Cascade Creek bridge girders.  Correct side is up for the one on the left.

Cascade Creek bridges installed.  Abutments will come later.

I will use a variation on this theme for the three large steel trestles.  All are built on curves, so they are composed of many sections of straight bridge girders.  I previously noted the use of aluminum strap as the spine for these trestles. http://espeecascades.blogspot.com/2015/03/connecting-ends.html   I will use the same technique of sheathing this spine with Central Valley bridges girders.  I needed to temporarily install the track over these spans, though.  Even basic girder bridge construction takes a bit of time for me.  These trestles will take longer with their need for the tower construction.  Meanwhile, I need to get this railroad into operation for the fast-approaching NMRA National Convention in Portland this August! 

I found that the hardboard spline material I used for much of the mountain grade made a perfect pattern and substitute for the eventual Central Valley bridge girders.  That happy discovery was made as I built and installed the Cascade Creek girders.  I cut sections of hardboard to the individual girder lengths making up the trestle.  These varied between 30 scale feet for the sections over the towers up to 70 scale feet long for sections of Salt Creek Trestle.  I then trimmed the ends of the non-tower sections to an angle to fit the curve each trestle is aligned on.  I found it easy to make an initial guess as to the angle—after all, these are “temporary—and found those guesses to be very good.  Most are 7 or 8 degrees at each end.  I then affixed the temporary bridge girder patterns to the top of the aluminum spines using Dap 230 adhesive caulk, following up with a level for cross-ways alignment.  Once the caulk set, I could lay the bridge track on top, temporarily affixing it with modest spots of the Dap 230 caulk.  When I go back to build the permanent bridge-trestles, I will replace the hardboard patterns with the Central Valley bridge girders, just as I did at Cascade Creek.  Then I can build and install the trestle towers.  The inspiration photo for this blog taken at Salt Creek Trestle will give you an idea of the effect I am striving for.  I will paint my trestles black, as they were until the early 1960’s.

Temporary bridge girder pattern installation at Salt Creek Trestle.

Bridge track installed on top of temporary bridge girder patterns at Salt Creek Trestle.