Recently, I have been working on a tunnel for my model railway club, and as I was working on it, I decided to do a very similar design to share and could easily be used for a railway bridge.

This design has been designed to be printed inverted and, therefore, will not need any supports. I have printed several of these now without supports, and they have come out well. The tunnel is a stone brick design and has several parts that are enhanced to improve the look.

Whilst researching this design I found that tunnels come in so many different forms, and the surrounding support walls also come in lots of different arrangements. Therefore, as I develop this design, I will be adding several add-on components to help with building tunnels and bridges. (I am starting this project in April 2025 and will add components going into the summer of 2025.) I am also adding a single-track portal and add-ons.

The add-on components I’m looking at adding are:

Tunnel Side Extension Support Walls (also the ability to have two tunnels next to each other) https://www.cgtrader.com/3d-print-models/games-toys/other/model-railway-tunnel-portal-extension-buttress-joiner-add-on Tapered Support Walls Straight Internal Arch - https://www.cgtrader.com/3d-print-models/games-toys/other/model-railway-double-track-tunnel-internal-arches-add-on 2nd Radius Curved Internal Arch 3rd Radius Curved Internal Arch 4th Radius Curved Internal Arch

Curved internal Arches will be made up of 2 degree and 6 degree segments, can also be formed with other arch sections to form exactly what you need that is not 2nd, 3rd or 4th radius.

designed at OO gauge, 1/76.2 scale but can easily be scaled for other gauges.for HO gauge print at 87%, 1/87 Scale,for TT print at 63.5% 1/120 Scale,for O gauge UK at 175%, 1/43.5 Scale,for O gauge International print at 158%, 1/48 Scale,for N gauge print at 51.49%, 1/148 Scale

The examples in the pictures were printed on a Bambu Labs A1 FDM Printer.As normal with my designs, there is a balance between accuracy and printability, hopefully not affecting the look of the model too much.

For FDM printing, I used a 0.4mm nozzle and a layer height of 0.12mm using PLA or PLA+ filament.I used the following Filament: ELEGOO PLA+ Filament 1.75mm Grey 1KG - https://amzn.to/4r1qQIM (Affiliate Link)

use this link to join CGTrader and download my designs.

https://www.cgtrader.com/designers/PJD1974?referral_id=3218445