Location Design and Trackwork

by Bill Donovan, Real Trains Inc

Introduction

This information is written for someone who is starting to design their track layout and who has limited on no experience in this work. It covers all the basics but does not go into some specific areas such as the building of switches (turnouts) or bridges.

Location

Your location should be large enough to allow the full size of the track plus at least several additional feet along both sides of the track. This allows for the width of the train equipment and the passengers. It is not recommended that the track be placed near trees, posts, edges of high walls, etc. because a derailment could cause the train and passengers to hit or fall over these objects.

You should select a location for your track that will prevent people and pets from having to be on, or tripping over, the track. If vehicles must cross the track you should try to develop a design that minimizes the number of crossings. Crossings located on straight sections of track, commonly called “tangent track”, are always best. Completely avoid foot or vehicle crossings at switches or other complex trackwork.

Drainage

Consider the existing flow of water, both streams and runoff from rain or melting snow. Tracks are usually raised somewhat above the adjacent ground and can quickly become a dam. Small flows can use a culvert (pipe) under the track, Larger flows may require a bridge.

Ground that slopes towards the track will result in flow towards the track. If uncontrolled, this may wash mud or debris into the rock ballest making it unable to properly hold the track. The usual way of addressing this is to place a V-bottomed ditch along one or both sides of the track to turn the water flow parallel to the track and route it to a point where it will either flow away from the track or can be ran into a culvert, drain or stream. Lowering the track below the surrounding ground (commonly called a “cut”) will require a ditch on both sides.

Curves

Curves are measured by the radius to the center of the track (half-way between the rails). You should always make any curve follow the largest possible radius that your space allows. Tight curves limit the types of equipment, especially steam locomotives, that you can operate. The actual minimum value depends on many factors. It is best to contact the manufacturer or designer of anything you plan to operate and to inquire as to the minimum radius they recommend.

For 1-1/2 inch scale, small locomotives such as a four wheeled switch engine can operate on curves as tight as a 10 foot radius (3 meters), but sometimes do so only at low speeds. Most home layouts try for a minimum radius of 30 to 40 feet (9 to 12 meters). Clubs often use 70 to 100 feet (21 to 30 meters). Smaller scale equipment can go somewhat tighter than this while larger equipment must have larger minimums. In each case areas that are only operated at low speeds or are not used very often may allow tighter minimums. Be sure that whatever minimum value you use is maintained everywhere since sudden kinks can develop when you are laying track and they will be much less than your minimum.

Cars are not discussed since most North American prototype cars use individual trucks and the minimum radius is determined mainly by the wheelbase (center to center distance between wheels) which is usually much smaller than a locomotive. One issue to be aware of is what is known as a reverse curve (see drawing). If you have a curve that turns first one way, then the other you can create a problem if the two sections of the curve are too close together. This is not an issue of wheelbase but of coupler swing between two cars (or a locomotive and car) and usually shows up with your longest car, especially if it is coupled to something much shorter. To prevent problems separate the two curves by the length of your longest car (X in the drawing). You can reduce this somewhat if you have a tight place, especially since such an area will probably be limited to low speeds. Also be aware that this applies to the curve within a switch followed by either another switch or curved track.