Three-rail toy train track provides a distinct advantage for the toy train operator wanting to use the position of trains to operate trackside accessories or to control train action: the track itself can be used for a low-cost, practically invisible, mechanism for detecting a train's location.

The wheels and axles of engines and rolling stock can be used to close an electrical connection across track outside rails.

By insulating one outside track rail from the other, a train's wheels and axles will provide a useful electrical action that can be used for operating accessories when trains enter a designated track area.

O22 switches employ this same mechanism to provide a non-derailing function.

Lionel refers to this action as "wheel-operated electrical switches" and explains it in OSS and OCS Track . Lionel introduced its first "wheel-operated" product in 1921. Our History web page gives more details.

High-rail track is constructed with three rails attached to metal ties with formed metal clips. The outside rails are attached directly, providing an electrical path from one outside rail to the metal tie and back to the other outside rail.

The center rail is attached to the metal ties with insulating paper between the rail and the formed metal clips and ties, electrically isolating the center rail from the metal ties.

Each rail has a steel pin in one end for mechanically and electrically connecting corresponding rails; train power connected to one track is passed to adjacent tracks by the steel pins.

Train power is typically supplied to the track by connecting the "U" transformer post to the outside rails and a variable-voltage post to the center rail. The "U" transformer post and the track outside rails are referred to as train power "common."

An Isolated-Rail Track is constructed from high-rail tracks by insulating one outside track rail from the metal ties.

A track rail is insulated from metal track ties by: loosening the metal clips that hold the rail to the tie, removing the rail, placing squares of an insulating material between the tie and the rail, re- attaching the rail to the ties, and testing to make sure the rail is insulated from the ties.

Any high-rail track section can have an outside rail insulated: O gauge, O27 gauge, straights, long straights, or curves.

"Fish paper" is a good insulating material. It is widely used in the electrical industry for insulating transformers, motors, and other electrical devices. It is also known as "fibroid fish paper," "natural hard fiber," and "vulcanized fiber." A 0.010 inch thickness works well for insulating track rails. Access our Supplies feature for sources of Fish Paper .

Fish paper "squares" are used at each tie location. The square needs to be a little wider than the metal tie, and to extend beyond the ends of the metal clips when they are closed on the rail. It should not be so long as to interfere with wheels or wheel flanges. For O gauge track, a square 3/4 x 3/4 inches works well. A little smaller for O27 gauge track.

The fish paper squares can be prepared by cutting a sheet of the fish paper into 3/4 inch strips with a paper cutter, then cutting individual squares from a strip with scissors.

The following illustrates the process of insulating an outside rail of high-rail track.

1. Loosen the formed metal clips with a sharpened screwdriver blade.
   
   Loosen both clips of each metal tie holding the rail to be insulated.
   Sharpening the screwdriver blade at a 45 degree angle will allow it to better catch the clip.
   
   
2. Open up the clips to clear the tie.
   
   With pliers, bend the clips perpendicular to the metal tie, so the rail can be lifted away from the tie. Lift the rail out and set it aside.
   
   
3. Deburr the ends of the clips.
   
   Use a small file to remove any burrs from the edges and corners of the end of the clips. A few strokes on each clip is enough.
   
   Brush any metal filings away.
   
   
4. Form small squares of "fish paper" over the track rail at each tie position.
   
   A glue stick can help temporarily hold the fish paper squares to the rail.
   
   
5. Position the rail back onto the metal ties.
   
   Center the fish paper squares on the metal ties. The fish paper should fully cover the tie from side-to-side and extend beyond the edge of the both metal clips when they are closed. Make sure excess fish paper won't interfere with wheels.
   
   
6. Snug the metal clips against the fish paper.
   
   Use a wide blade screwdriver to lightly press the clips against the fish paper to hold the rail in place.
   
   After all the clips have been pressed down, inspect to make sure the rail is aligned with the other rails of the track, it is straight between the rails, and the fish paper squares cover tie and clips.
   
   Make sure the distance between outside rails remains 1 1/4 inches.
   
   
7. Lock the metal clips against the fish paper.
   
   Use the wide blade screwdriver to firmly lock the clips against the fish paper and rail. The screwdriver can be given a light tap with the heel of the hand.
   
   A support block under the tie will keep it from collapsing under the pressure.
   
   The rail needs to be securely held, but applied pressure cannot cause the clip to damage the fish paper and contact the rail.
   
   
8. Test the Insulated Rail Track
   
   
   
   A continuity checker or an ohm meter is used.
   
   Attach the continuity checker's probe clips to the insulated and to the non- insulated outside rails.
   
   Test the track to make sure there is no electrical continuity between the insulated rail and the non-insulated outside rail.
   
   With the ends of the track in each hand, give the track a little twist, back and forth. This will reveal most potential shorts between the clip or tie and the insulated rail.
   
   There should be no indication of continuity.
   
   
   If continuity indicates a short between the rail being insulated and metal ties, then the following has occurred:

   • The fish paper square slipped and is allowing the rail to touch a tie.
   • The fish paper square slipped and the end of a clip is touching the rail.
   • The fish paper square is too small.
   • The clip or a burr on the end of the clip has penetrated the fish paper and is contacting the rail. This could mean too much force was applied when locking the metal clips against the fish paper.

   Inspect the track to discover the problem, remove the rail again, and re-install the rail with new fish paper squares. Caution: the metal clips can only be bent back a few times, then they will break.

   Once a good insulated rail track has been made, it can be assembled into an isolated-rail track block and used to control an accessory.

   Sources for fish paper are cited in Three-Rail Innovations' paper Sources for Toy Train Layout Supplies .

   Assembling Insulated Rail Tracks into Isolated- Rail Track Blocks

   INDEX

   
   

   Track sections with an insulated outside rail can be used on a train layout to form an isolated-rail track block for operating accessories. The isolated-rail track block can be of any length, composed of one or more track sections with insulated rails. Even parts of tracks can be used by cutting an insulated rail and inserting a plastic rail pin.

   A plastic rail pin is used on both ends of the isolated-rail track block. Steel pins are used to join insulated outside rails of tracks within the isolated-rail track block.

   

   An isolated-rail track block installed on a train layout needs to be tested for continuity from the insulated rail to the non-insulated outside rail and from the insulated rail to the rails connected on each side with a plastic track pin. There must be no continuity from any of these tests.

   The continuity test must be made before any accessory is connected to the isolated rail; continuity will always be indicated, through the accessory and transformer, once connections are completed.

   The electrical connection from the accessory is made to the insulated rail.

   Train power is connected to the center rail. Train power common and accessory power common are connected to the outside rail that is not insulated.

   Three-Rail Innovations paper Making Invisible Connections to High-Rail Track describes a useful technique for making electrical connections.

   Now you are ready to use isolated rail track blocks to operate trackside accessories. Click the following bar to see how.
   

   Operating Accessories with an Insulated Track Rail

   
   
   
   

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