D&RGW PIN-CONNECTED DECK TRUSS IN 1:48 O-SCALE. (On3, On30) RETIRED
A nice deck truss was my second model. The D&RGW had replaced an old wood deck span at the entrance to the Black Canyon near the town of
Cimarron in 1891. It is yet another recycled bridge from the D&RG mainline, as were the missing connecting girder spans. The span is a bit under 120'
long. There is another span just like this one. The "High Bridge" over the Animas River near Tacoma, CO is the twin transplant from the D&RG. It is still
in use on the old Silverton branch. However, it has suffered from a disfiguring but necessary strengthening to support the big Durango & Silverton
Narrow Gauge Railroad locomotives.
The bridge kit comes with all the parts for the superstructure, you supply the track and piers.
These prototype photos are from a
CD I received courtesy of Glenn
Farley. I studied all the photos I plus
other drawings and data to get it right.
Compare the model to the prototype. I
have captured all the details of the
lacing, rivets, bracing and beams.
Proportions and thicknesses of the
model parts are very reasonable too. It
will of course include full-length steel
stringers for strength so your heavy MMI
locos won't end up in the river.
I will not be including the end support
frame (the part with the sign). Simple
I-beams to an abutment would suffice or
as an alternative, the High Bridge uses
wooden trestles to connect to solid
ground, so the choice will be yours.
Compare them to the photos of
the model below...
|This kit was run 2012-2013 and is retired. Thanks for all your support!
copyright by John Palecki page update 11/7/13
These are photos of master parts. I decided to use stereolithography to
make the masters for my cast parts. I can get contours and variable wall
thickness that I could not make with hand-made styrene parts. Plus, I don't
have to emboss all those rivets myself.
Fineline Prototyping provided the STL services. They did a nice job
grooming my CAD files and making the parts.
The photo below is a rendering from my CAD for one of the vertical beam
sides. The photo at left is a close-up of the rivets from the stereolithography
process. I selected a high-resolution process that lays down .002" thick layers
of material. You can barely see the thin layer lines in the rivet domes as well as
the shape of the domes from the CAD simulation of a spherical surface. They
will not be visible on the model. The next photo down is the floor beam. I have a
prototype photo below it. Nice!
The etched brass came out
beautifully. I employed a rarely used
technique of a two-pass etch. This gives
a multi-level part rather than just two
levels. I wanted to simulate the
overlapping lacing bars with a joining
rivet. This also allowed me to design
alignment features on the backside of
the parts for ease of assembly.
Thanks to ParaGrafix for the great
job in laying out the parts, aligning
the layers and controlling the etch.
You get four of these frets in each kit!
This is a close-up of the lacing for
the vertical beams. Note the three
layers- bottom bar, top bar and the rivet.
Those strips are only about 25" wide.
Etched brass is the best way to get this
detail in a complex part other than really
expensive injection molds.
The many tabs are necessary to hold the
thin parts in place during two etch runs.
That includes re-applying resist,
exposure, development, etc. The tabs
cut easily with a honed X-Acto #17 blade
on a glass surface, or use Xuron brass
part cutters. I have suggestions how to
cut them out plus the web has more hints
than I can think of.
Here is a photo of the lower chord.
The beam sides are complete with rivet
detail, and the lacing matches the beam
side rivet locations. Just like it should be.
I use Zap-A-Gap to assemble the
beams. By tacking down a couple
connections to hold alignment, you can
then bond each point with the beam in
Four beam types are to the left Top down are:
Upper chord (inverted)
End vertical beam (with sway brace brackets)
The beams assembled easily but are a little fiddly,
especially the first one. I am including instructions
on how to make a few simple fixtures that will make
the assembly easier and better.
And note that I am coloring the resin so the parts
are an easy-to-paint gray.
This bridge is beautiful!
I am quite pleased how it came out. About two
years of work was needed to get to this point. The
bridge is very strong- the bracing adds
considerable rigidity just like on the prototype.
The detail of the sway bracing is captured in the
model as are the overlapping lacing bars on the
beams, the pin-connected joints, the shoes, and so
on. It is not too difficult to assemble either- just lots
of prep work and repetitive assemblies.
Beam sides, shoes: Cast resin
Lacing, plates brackets, clevis: Etched brass
Rods: Brass & styrene
Eyebars, pin nuts: Laser-cut styrene
Stringers: Steel bar