145ft HO Truss Bridge - Single & Double Track

145ft HO Steel Truss Bridge.  Approx 20 inches long when assembled.

Based off the design on Thingiverse by kabrumble (https://www.thingiverse.com/kabrumble/designs).

Two version are available.  Single and Double Track.  They both assemble the same way.

Track spacing for the double track version is 2 ¼" inches.

This is a heavily modified version that is easier to assemble, print, and is sturdier.  Doesn't the have the “X” patterns in the beams.

Clearance height for train inside bridge has been increased to 78mm.

Printed with PLA and uses PETG as the support interface.  But can be printed in PETG as well.

Glue together with clear CA glue or clear Gorilla Glue.  

Clamping during assembly isn't necessary but is advised.  Be sure to allow glue to fully dry at least 24 hours.

The piers holding the bridge can be found here:  HO Scale Bridge Piers - Free 3D Print Model - MakerWorld

Assembly Instructions:

STEP 1 — Assemble the Main Arch Truss (×2)

You will build two identical truss arches: one for the left side and one for the right side of the bridge.

For each truss (repeat this entire step twice):

1. Identify the three truss segments:
   • 1 center curved truss (blue)
   • 2 tapered end trusses (red)
2. Align the connectors of one red end piece with the matching end of the blue center piece.
3. Add a thin layer of glue to all joint faces.
4. Press together and hold until the connection is firm.
5. Repeat on the opposite side to add the second red end piece.
6. Set the first completed arch aside to dry and complete a second identical arch.

✔ When finished, you will have two long, matching, left–right truss sides.

STEP 2 — Assemble the Lower Deck Base

(unchanged, but rewritten for clarity)

1. Lay out the three deck base pieces:
   • Left deck section
   • Center deck section
   • Right deck section
2. Glue them together end‑to‑end to form one long deck.
3. Ensure the deck is straight and level while drying.  (Recommend clamping together).

STEP 3 — Attach the Two Main Arch Trusses to the Deck Base

(Recommended: Assemble while truss is lying flat)

1. Place one completed truss arch flat on its side on the work surface.
   • This prevents wobbling during gluing.
   • It ensures the deck sits at the correct angle relative to the truss.
2. Apply glue to each of the truss‑to‑deck contact points.  (Rectangular holes along the bottom of the main truss).
3. Take the full lower deck assembly (from Step 2) and position it along the bottom edge of that truss.
   • The rectangular beams on the deck will align with the truss’s rectangular holes where you just applied glue.  (Make sure area where the track gets mounted is facing up to the top of the truss section as shown in the picture).
4. Press the deck gently but firmly into position along the truss.
   • Use the flat work surface to keep everything square.
5. Let this first side cure enough so it can support its own weight without shifting.
6. Apply glue to each of the truss‑to‑deck contact points of the second main truss section.  (Rectangular holes along the bottom of the main truss).
7. Flip second main truss arch over and glue it to the exposed deck edge using the same method:
   • Align all deck beams to rectangular holes in the main truss section.
   • Press firmly into place and clamp both sides together along the bottom of the bridge assembly.
8. Allow the assembly to dry thoroughly before moving on.

STEP 5 — Install Upper Support Bracing

These braces reinforce the upper connection between the main truss arches.

1. Identify all the bracing pieces (shown yellow and red in the reference image).  The yellow sections are slightly longer than the red sections.
   • Each piece is an X‑shaped brace.
2. Starting at one end of the bridge, position each brace so that it connects between:
   • The upper chord of both main trusses. (blue)
3. Apply glue to both contact surfaces on each end of the brace.
4. Ensure every brace sits fully into its notches before the glue sets.
5. Repeat along the length of both sides of the bridge.