Tunnels in the model railway layout

Tunnels are essential to break up the view of the tracks and avoid the loop-track effect, like a ‘hamster running on a wheel’. Thanks to tunnels, we can hide those parts of the track plan where the tracks take on less than orthodox shapes to optimize space utilization.

Inside a tunnel, we can insert helix ramps (see below), a staging yard (fiddle yard), and other ingenious solutions. A tunnel must be long enough or positioned relative to the scenery in such a way as to prevent the spectator from seeing the front of the train exiting the tunnel while the tail has yet to finish entering.

Bridges and overpasses

Our tracks will necessarily cross each other, meaning we will have to build overpasses.
By making the necessary calculations (see below), it will become clear that the minimum clearance between 2 tracks where one passes over the other is 8 cm in a hidden area, while it becomes about 12 cm in a visible area (for example, via a bridge).

This means that with a maximum gradient of 4 percent, the climbing section must be at least 2 meters, which equals the measurement of a circumference with minimum radius (radius 36cm = 2 x 3.14 x 36 = 226 cm).

Our senses are programmed to appreciate movement, and the crossing of 2 trains on multi-level tracks enhances these sensations.
A viaduct running diagonally across the middle of the layout, crossing other tracks, will definitely create a beautiful effect. If possible, let’s avoid running bridges and viaducts too close to residential buildings. 

The helix ramp

The helix ramp is generally hidden and serves to allow the tracks to overcome one or more height differences in the smallest space possible. Usually, helixes are used to lower the tracks below the reference baseboard level and lead them toward staging yards, or to climb tracks in hidden areas, only to exit via a mountain tunnel. 

Straights

A train running along a straight stretch usually has its own charm, but unfortunately, there is no room for long straights in the visible part of the layout. Let’s try to find a place for them on viaducts and other background sections.

Curves

In our track plan, we should avoid keeping curves greater than 90 degrees visible as much as possible, because they look unrealistic.

Click here to continue reading >>>