& Bridge Department
Bridge 1 (Cold Springs Trestle)
posts and caps
Scale Lumber Company # HOSCAL81211
Scale Lumber Company # HOSCAL31011
Scale Lumber Company # HOSCAL61211
Scale Lumber Company # HOSCAL6811
Stock from hobby shop
Scale Lumber Company # HOSCAL8811
Scale Lumber Company # HOSCAL2411
Tsp of Black India ink in a pint of Rubbing Alcohol.
Tsp Drizzle Grey
Tsp Antique Brown
Tsp Dark Chocolate
Tsp Opaque Black
Bolt, & Washers
Nut, 4 ½” Washer
Bolt, & Washers
¼” Nut, 4 ½” Washer
the Purgatory & Devil River Railroad is supposed to be a sister
line to the Rio Grande Southern, the Cold Springs Trestle is based on
the RGS prototype. The
RGS was maintaining 111 bridges at the time of abandonment in 1951.
While no two of these bridges were alike, many do share a basic
design. It is this design
that I used to build the Cold Springs Trestle.
For information on the prototype bridges of the RGS I used the
book “Silver San Juan” by Mallory Hope Ferrell and the “RGS
Story” series from Sundance Publications.
I also used scale drawings from the Black Bear Construction
of Trestle Building:
Wooden trestles are a marvel of engineering
and craftsmanship. Each
vertical section is called a bent.
Each bent is constructed of posts with various types of
bracing. All the timber
on a prototypical trestle is bolted together.
This was done with a large rod with a nut and washer on each
end. This not only holds
the bridge together but also allows it to be tightened during
maintenance. Since most
trestles are taller than one single length of lumber will allow the
bents are constructed in panels. The
panels are stacked on top of each other until the necessary height is
reached. On the RGS these panels were usually 10 to 12 feet tall.
bents in a trestle are connected to one another with a horizontal
brace called a girt. Many
trestles also have cross bracing on the sides between bents.
This does add a lot of stability to the structure and keeps it
from racking (swaying). On
the RGS only a small handful of bridges used this cross bracing (I
have only found photos of 2 that did.)
the bents are held together by the girts, and cross bracing if you use
it, you are ready to add the stringers.
The stringers are several large pieces of lumber that are
bolted together and run across each of the bents.
This provides a surface for the ties and rails to sit on.
The stringers on the RGS were usually 8 x 18 timbers.
The RGS’s stringers were built with 3 of these large pieces
of wood running parallel to each other.
Between each piece of lumber is a spacer.
The spacer is a piece of lumber cut from the same 8 x 18
lumber. At the location of the spacers a truss rod is run through all
the boards of the stringers and is bolted on both sides. On the RGS the spacers were placed at the joints of the
stringers. They would run
two truss rods on each side of the joint.
These rods would be located on a 45-degree angle from one
another. (If the upper
rod were in the upper left corner of the spacer the second rod would
then be in the lower right corner.)
top of the stringers the ties and rails are then laid.
Most wooden bridges have a platform on each side that will have
a water barrel. During the days of steam this was a necessity to put out any
hot spots on the bridge. Around
this platform will be some kind of railing.
Along the outer edge of the ties a board was bolted along the
length of the bridge. On
the RGS they typically bolted the boards down every 3rd or
4th tie. This
would help to keep the ties from twisting out of place.
RGS also included 2 guardrails on most of their bridges.
The extra rails were there to hopefully keep any piece of
rolling stock or locomotive that derailed from traveling off the
bridge. Depending on
which bridge you look at, the RGS placed the guardrails both the
inside and outside of the rails.
On most bridges a lighter rail was used for the guardrails.
the Cold Springs Trestle:
Before construction could begin all the
scale lumber would have to be sanded and stained.
I don’t sand the lumber too much because it takes away from
the character of the wood. Railroad
timbers are rough and shouldn’t look too smooth.
I sanded each piece by pulling it through a 220 grit sanding
sponge. Any dust left
behind was removed by pulling the strip wood through a tack cloth.
All of the wood was then stained. The
first step was the base coat of Antique Brown.
Pouring a small amount of paint on a rag and pulling the strip
wood though added the color. The
idea here was to get an uneven coat on each piece so the amount of
paint on the rag varied from piece to piece.
Also changing the pressure of the rag on the wood will affect
the amount of paint applied.
Once the Antique Brown was dry I then
stained the lumber with a mixed stain (for the formula see the list of
materials). I started
with a large airbrush bottle and the paints.
I poured the airbrush bottle about ¾ of the way full with
distilled water and then added the paints.
I use distilled water since the contents of some tap water can
affect the color of acrylic paints.
Once I achieved the color I was looking for I filled the rest
of the bottle with more distilled water.
I stained each piece with the new stain
using the same technique as before.
I didn’t shake up the bottle after the initial mix.
The settling of the paint in the bottle created various shades
of color as I worked. This
effect gives some of the bridge timbers a more weathered look than
ones next to it. Once all
the lumber was stained I left it to dry overnight.
All of the necessary pieces and parts were
then cut on my Northwest Shortline Chopper.
I then used the mixed stain and a small paintbrush to touch up
the ends of each cut. All
of the lumber was left to.
Since I can make the posts on the bents from
one solid piece of wood I constructed a “False Panel” bent to take
advantage of the added strength.
Using scale drawings,
the bents were assembled with Super Z - RC56 glue.
The first step was to glue the top cap and the posts together.
After each post was laid in place and the cap glued on the
horizontal braces were added. These
are not only the supports for the girts they also represent the top
cap of each panel in false panel construction. After the horizontal pieces are in place the cross bracing
was glued on. On RGS
trestles they typically had two cross pieces on 45 degree angles on
the lower panel and only one on the upper panels.
Once all these pieces had a chance to dry the bent was turned
over so the horizontal and cross braces could be added to the other
side. The bents were left
to dry before adding the NBWs (Nut, Bolt and Washer).
next step was to add the NBW castings.
Each NBW was first painted with Ceramcoat Cinnamon.
Next I drilled a hole at the location for each NBW with a #69
bit. The NBW was cut off
leaving a small amount of shaft underneath.
This tail was then dipped into Elmer’s white glue and then
placed in the hole. Each
NBW was pushed in until flat on the surface of the wood.
On the horizontal braces I used the larger of the two NBW
castings. All other
locations received the smaller castings.
Each full bent on the Cold Springs trestle required 44 of the
larger castings and 88 of the smaller ones.
This totals 132 castings on each of these bents.
There are a total of 1248 NBWs on the bents of this trestle.
The stringers required another 57, as did the outer rail on the
deck of the bridge. This
brings the total number of NBWs to 1361.
This does not include the dozen or so that slipped out of the
negative tweezers and shot across the room.
(The $20 spent on NBWs was more than the cost of the scale
all the bents had their NBWs attached I then set the bents up in my
Midwest Products Trestle Buddy. This
allows you to evenly space the bents and support the entire bridge
during construction. I then added the girts to the trestle. These were glued in place based on the scale drawings as well
as photographs of various RGS bridges.
This assembly was left to dry.
Since the RGS did not use cross braces between bents on most of
their bridges I also chose to forgo the cross bracing.
stringers were constructed next.
During my research on the RGS bridges I found that the
stringers were usually built to span between 3 bents.
Since I could purchase scale lumber that was long enough to
make the stringers in one long length I chose to do so.
This I felt would provide better strength to the structure.
I found in several old photos that most stringer sections would
span between 3 bents on the outer edges of the trestle and sometimes
span just between two bents on the inner pieces.
I chose to use this type of design on the Cold Springs trestle.
To simulate the seams in the bents I used a razor saw to scribe
a seam in the outer edge of the stringers.
I then placed the spacer blocks behind this seam and placed
NBWs on either side of the seam in the same manor as the prototype.
the entire visible track on the P&DR’s El Lobo Division is hand
laid Code 70 rail I did not use flex track for the bridge.
The ties were cut from the 8 x 8 lumber to a length of 10 scale
feet. These were stained
in three batches. I used
the same method as above where I first stained several of the ties
with the Antique Brown and then the mixed stain. A second batch of ties was done with just the mixed stain
without the Antique Brown base coat.
The third batch of ties was stained with a coat of the
‘Opaque Black’ from Createx and then the mixed stain.
This was only done to 7 or 8 ties to simulate newer ties on the
both sides of my trestle is a platform for the fire barrel (one on
either end of the bridge). The
ties here were cut to a length of 16’ to act as the platform base
for the fire barrel. The
railings around the platform were made from scale 2” x 4” lumber.
Again the design was based on photos of various RGS trestles.
The timber bolted along the edge of the ties was done with the
same lumber that I used for the girts.
Every 4th tie I used the smaller of the NBWs to
‘bolt’ it down.
all the wooden parts of the structure were in place I applied a coat
of Alcohol and Ink stain over the entire trestle.
I next painted the rails to give it the rusty look.
The paint is mostly Floquil Rail Brown with a dash of Floquil
Rust added. This was
applied with an airbrush. After
cleaning off the bottom of the rails they were coated with a thin
layer of Pliobond glue. Once
the rail was in place I ran a hot soldering iron along the rail to
melt the glue and bond the rail to the ties.
I placed my guardrails on the inside of the rails.
I chose this because I use several D&GRW Mikados, which are
outside frame locomotives. With
the wheels being inside the frame and the counterweights on the
outside I was concerned that the counterweights would strike the
guardrails if they were on the outside.
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