Strawberry Gulch Railroad

In June of 2020, I was given permission by the CFO and creative director of the Colorado Front Range Railroad to construct a outdoor 1:29 Railroad. Some of the challenges of the railroad are steep grades and limited area for return loops. In addition there are several new fruit trees that were planted and needed to be accessible.

A survey of the landscape was performed to the Colorado Front Range Railroad constuction group and a plan was devised. The planning department requested that the railroad grade be kept to a minimum. There is a small right of way in front of the retaining wall that is wide enough to house a set of double tracks. A large trestle will be built to keep tracks at the same grade while being able to create a return loop.

The surveyors have laid out stakes to show the location and height needed to construct the Strawberry Gulch Trestle. From the surveyors measurement the planning department was able to construct a CAD model of the right-of-way. From this model the structural department was able to design a bridge for this route.

A blueprint was created of the trestle bents by reviewing plans found in the the Grandt Line Resource library. These plans are for a standard gauge Rio Grande Trestle dated 1907. The one change made from this standard plan was the fact that the trestle is curved instead of straight. A design to build angled stringers was developed.

From the Trestle blue print a jig was made to build the trestle bents. Several other jigs were made to aid in the trestle construction. A angle jig consisting of a 80 degree and 85 degree side was used on a disk sander to form the correct angled end on the angle posts of the trestle bents.

All lumber used in the construction of the trestle was cut from 5/8"x 6" x 10 ft redwood planks on a Porter Cable 9" bandsaw. There are 25 board feet of lumber used in the construction of this trestle. That is approximately 24,350 scale board feet of lumber to build the trestle in 1:29 scale.

As seen in the middle image above double sided nails (fabricated in-house from commercial nails) were used as drift bolts like the actual trestle. All joints are mechanical (nail or screw) bound and glued with Titebond III outdoor glue. Redwood was chosen because it is natural weather resistant. A clear polyurethane coat was also sprayed on the trestle protect it from the elements.

In total 28 bents were built for the trestle ranging from 3 inches in height to 38 inch in height. The total length of the trestle is 24 feet from end to end. The trestle also includes a 3 ft long (87 scale feet) Deck Truss Bridge to cross the retaining wall drainage path.

After the completion of all the bents the curved stringers were all cut to length and holes were drilled in them using the stringer drilling jig. The screws holding the stringers together had to pass thru the stringers orthogonally. This means the distance between the end of the screw and its hole center was different depending on if it was the outer or inner stringer. the drilling jig was designed so that all the construction department had to do was insert the stringer in the jig fully and drill the holes. No measurements necessary. there are a total of 156 stringers on the bridge. Custom angle plates were made from 5/8"wide x1/8" thick aluminum bar stock. The angle plates were all cut to 1.5" long. Holes were drill in them using the drilling jig so they would match up with the stringers. The angle plates were bent to a 10 degree angle as specified in the blueprints developed by the planning department. This was done using a vice and a hammer. Each angle plate was checked against a digital protractor to verify the correct angle. In total 156 angle plates were fabricated.

Six different length stringers were produced to make the curved trestle each size was marked to indicate is length. 3 different angle plates were made as well. This is because the hole location varies depending on where it is used on the stringer deck.

The stringer deck was assembled in 6 major pieces. Each joint is comprised of 6 stringers, 3 angle plates, 4: 1-5/8" 2-56 stainless steel screws, 4: 2-56 Stainless steel nuts, and 8 #2 Stainless steel washers. The screws we made intentionally long to help assembly they were later cutoff.

The next step after creating the 6 major stringer segments was to clamp them together so that bridge ties could be added. Several custom clamps were made from bridge ties and 2-56 screws to hole the stringers the proper distance apart while ties were glued and nailed in place.

Once the ties were added to the stringers it was time to start connecting the bents to the stringers.

After attaching all the bents to the stringers cross bracing was installed. All connects are glued with Titebond III waterproof glue and also nailed in place.

The trestle was built in 3 segments and spliced together at the end of construction.

Construction of the trestle is completed and installation has begun.