Building a Large Curved Trestle on a Grade – Part 2

Processing Reclaimed Wood

I have a house that is over 100 years old, and in the past got a load of cedar channel siding that was reclaimed from a similar house. Many of the pieces were only 1-2 feet long, so not very useful for repairs, but very useful for model bridge building (and other scale lumber use) because it is all old-growth cedar as shown in Photo 1. It is very likely that you can find a recycled building material company in your area where you can obtain old cedar or redwood.

Raw Material

Photo 1 – Raw Material

I did quite a lot of research into reclaiming wood on the internet to learn from pros. There are a few things that need to be done to prepare reclaimed wood for processing. First, reclaimed wood is likely dirty. Hose and brush it off thoroughly to remove dirt and small stones. Next, and most important, remove all nails and screws before cutting or ripping with power tools. A nail will ruin a saw blade and perhaps cause dangerous kick-back. Suitable tools are medium hammer, pry bar or pliers. If you can’t pull a nail because of the tight bond with the wood, you can drill right next to the nail with a small bit to relieve some of the pressure holding it in place. Use an old or cheap bit, as it will get dulled by contact with the nails.

Use a sander to remove irregularities and smooth the surfaces for easier handling on the saw. Remaining nails may show up after sanding, as they will perhaps be shiny, but don’t count on that. Old, rusty square (iron) nails are not shiny.

Magnet Nails and Wood

Photo 2 – Magnet, Nails and Ripped Wood

Completely hidden nails can be located using a rare-earth magnet  suspended with fine string or fishing line as shown in Photo 2. This can be passed closely over the wood surface, and will be strongly attracted to any remaining iron or steel. Mark the location with chalk so you can easily find it later. The magnet allowed me to find a ½” piece of square nail that was completely inside the board – no head and nothing visible on either side.

The severe weathering of the siding only extends a little ways in from the ends in most cases, and a fraction of an inch in depth. Note in the photo how tight the grain is, and how nice the cedar coloring still is even after 100 years except where rust has discolored the wood.

To prepare the wood for ripping, I took a small amount off the edges of each piece to provide a straight edge. If both edges are too uneven to get a good rip cut, temporarily nail a straight board slightly overhanging the ragged edge to run against the rip fence.

I finish the ripped wood using 60-grit sandpaper in a palm sander to smooth the sides and get to correct finished size.

Next time: Mass-production of Bents.

Tool List

  • Stiff brush
  • Medium-sized hammer
  • Wood chisel
  • Regular and needle-nosed pliers
  • Small pry bar
  • A drill with a small bit
  • Rare-earth magnet
  • Palm sander with sandpaper

 

Building a Large Curved Trestle on a Grade – Part 1

Materials

This is the beginning of a semi-regular series describing how I go about building a complex trestle. I am writing this series so that, hopefully, others may benefit from my experience and (probably more than a few) mistakes. I model in 1:20.3, but will provide many measurements and plans in 1:24 as well.

Building-Pt-1-Photo-1

Photo 1: Prototype Photo of remains ca. 1970?

I am modeling the Rio Grande Southern and one of the bridges I am building for my railroad is the Butterfly Trestle.  This will be a great example as it is curved, on a grade and very tall. This trestle is built using framed bents, which are divided into manageable sections called stories. The bridge has 20 bents of varying heights, up to 3 stories tall, with two bents carried on very large beams.

Building-Pt-1-Figure-1

Figure 1: Butterfly trestle plan

The top member (that the stringers rest on) is the cap which is 12×14 x 14 feet, which scales to 5/8”x11/16” x 8.5” (1/2”x9/16” x 7”). Each story is about 16 feet tall, which scales to about 9.5” (8”), with 12×12 posts with the two outer posts on a 3-in-12 batter. Between stories are 12×12 sills, and a 12×12 mud sill at the bottom. The 12x12s scale to 5/8”x5/8” (1/2”x1/2”).

Sway bracing is 4×10, which scales to 7/32”x1/2” (3/16”x7/16”), and longitudinal braces (girts) are 8×8, which scales to 3/8”x3/8” (5/16”x5/16”).

The two larger openings provide clearance over the waterways where a bent in the center is carried by eight 9×30 beams, as shown in the small plan at the bottom. These scale to 7/16”x1-1/2” x about 17.5” (3/8”x1-1/4” x about 16”).

The track is supported on two sets of 3 stringers of 8×18 wood, which scales to 3/8”x 7/8” (5/16”x3/4”).

I used a spreadsheet to calculate about how much wood of each size I will need as I am going to rip my own material from cedar reclaimed from very old siding.

Piece and Size Quantity (feet)
Cap: 5/8×11/16 (1/2×9/16) 13
Post: 5/8×5/8 (1/2×1/2) 245
Brace: 7/32×1/2 (3/16×7/16) 168
Beams: 7/16×1-1/2 (3/8×1-1/4) 27
Girts: 3/8×3/8 (5/16×5/16) 95
Stringers: 3/8×7/8 (5/16×3/4) 29

Figure 2: Rip list

Well, this will keep me busy for a while! Next time, I’ll describe what I learned about processing reclaimed wood.

Bridge Terminology

Batter – the angle of posts to provide lateral stability, typically measured in inches of offset per 12 inches.

Beam – the members that are supported by the truss that in turn support the stringers and track.

Bent – the term for the vertical assembly of one or more stories that support the stringers and track-work.

Brace – diagonal members used to enhance the structure of a bent.

Cap – the top timber that the stringers rest on.

Chord – the horizontal pieces that run the length of the truss on the top and bottom.

Deck – the assembly of beams and stringers that supports track-work (ties and rails).

Girt – longitudinal braces between trestle bents.

Mud Sill – the bottom-most sill of the bent that rests on the footing, pier or the ground.

Plate – the piece at the ends of the chords that rest on the piers.

Rods – typically the tension members of a truss.

Sill – the bottom timber of the story.

Story – The vertical section of a bent between sills.

Stringer – Beams that run parallel to the track which support the ties.

Truss – the whole assembly of chords, compression members and tension rods that form the support structure on the sides of the bridge.

Wall Brace – Braces between trestle bents on the outside of the structure.

 

Visit to 7” Gauge Ride-on railroad

RollingStockWe were invited to visit a very impressive 7” gauge ride-on steam railroad. It is located in a suburb southwest of Portland. There was a large amount of rolling stock, obviously used for “operating” sessions. In the foreground you can see some cars for full-size passengers.

 

 

D&RGW C-16  K-38
The motive power was diverse, including two SP engines (standard gauge prototype, not pictured), a C-16 D&RGW (left) and a K-38 D&RGW (right). Just like the prototype, these are both coal-fired steam engines, about 1/5th the size. And, just like the prototype, they must be oiled, have the tender filled with coal and water. Note the glow from the firebox in the bottom-right photo.

EngineOil  TenderCoal

TenderWater  FireboxGlow

The railroad was about 1 mile long, with two tracks so that on a ride you would cover the distance twice. The road features a very long trestle and a tunnel.

Trestle  Trestle.2

The day was very enjoyable for all.

Hypertufa

Hypertufa is a method of using cement to create light yet strong rock-like castings or scenery. I plan on using a lot of artificial rock scenery in my railroad instead of moving literally tons of rock and earth. The mixture is simple to make. Here’s my take on a recipe:

Hypertufa: 1 part patching cement, 1.5 parts perlite and 1.5 parts peat moss. It will take 0.5 to 0.75 parts water to make this the right consistency.

Note: The cement dust is very irritating to skin. I learned that gloves are very important. I got a rash where my hand touched the dust on the bag when scooping out the cement.

On the left is hypertufa on hardware cloth. I had the mixture too thin, but it still worked okay. I would probably “paint” another coat over this and do some sculpting. On the right is an aluminum foil casting. Both methods are likely to be used.

Hypertufa