The On-Line Magazine of Rideable Model Railroading
 NUMBER 102

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© FEBRUARY 02, 2008  

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Signal Bridge for 1:8 Scale Railroads
Working Lights Ease Congestion
 

Working Signal Bridge Automatically Controls Station Traffic

 

Written by Rick Henderson

As the Eagle Point railroad has grown rapidly, many changes are constantly necessary to help keep the rail traffic flowing smoothly. The two track passenger station loading area is somewhat unique in that it is on a curve and not easily visible as you approach from the most common direction of travel. While the turnouts into the area are equipped with motorized controls, you can not see around the corner to see if there is a train sitting on either track, blocking you from stopping in the station area or even continuing through and out onto the main line. There is a by-pass wye just beyond the station area so an engineer needs to know if they can get through the station or must take the by-pass as they approach, well before he reaches the main crossing and has decide which route to take.

One of the great things about having a club is the diversity of skills found within the ranks of the members. The club that works with the Eagle Point railroad has a fairly recent member, Paul Boberg, with good welding skills among other talents. After Paul fabricated a working drawbridge pretty much on his own, something as simple as a two track signal bridge was a snap. All he needed was a few sample photos, which were easily found in adís for models of railroad signal bridges in smaller scales.


After drawing out scale drawings of the signal bridge, Paul built the two legs, cutting and welding parts in the comfort of the EPRR shop.

The two halves of the bridge section were also skillfully produced to make a matching pair.

Once the four pieces were welded together, handrails and a ladder were added. Since this was to be a working signal bridge, mountings for the light fixture bases were considered in the original plans so they would be mounted directly over the two station tracks.

After a primer coat dried a couple of days, most of the bridge section and tops of the leg sections were painted silver while they were easier to reach before being mounted across the tracks.

The finished structure was impressive even prior to the installation of the signal lights.

A final detail before the signals were added was the 1:8 scale walk-way which was made of rain gutter guard.

The location of the EPRR passenger station creates an undesirable circumstance, that being people, members and visitors, walking along the track, especially on the turnout points to get from the crossing to the loading. Since the railroad has a minimum height clearance of 60" in two places, a through truss bridge and a tunnel, the signal bridge was built to a height of 60" above the rails for two reasons; to let riders know the minimum to expect on the ride and to discourage people from walking on the tracks to and from the station. It works well for the first point but further effort was necessary to reduce walking on the track.


 The actual primary function of the bridge is to indicate which tracks are currently occupied. If the light is green, the entire sections of about 100í are unoccupied and okay to use to pass through the station area. If one is red, there is something in that section that will prevent you from getting through. As soon as the first wheel enters the section, the light changes red.

You can just imagine a 1/8 scale maintenance technician from the railroad's signal department reaching over to service these signals from this detailed cat walk.  It was necessary to boost the height of these towers to allow super sized humans to clear without banging their super sized heads as they drove scale locomotives beneath.

An easy to access walkway was installed to further encourage people to keep off of the track.

Viewed from the station platform, it is easy to see the best route to get back to the crossing after a ride.

Most signals on the EPRR are three light block signals controlled by the engineers as they travel the railroad, which controls the traffic flow on the bi-directional single track mainlines. The two station tracks however are each short insulated sections, and there is a two light signal for each track. If there is no train present, the green light is always lit. If any train enters from either end, the circuit switches to the red light immediately, which stays lit until the section is completely clear, canceling the red light and lighting the green. The wheels on the trains complete a low voltage circuit to let the signal board know the track is occupied causing the circuitry to make the necessary change. The exact circuit design of a simple track occupancy system would be a good topic for another author to go into, so Iíll leave that for someone in the future.


The signal lights are actually bright enough to let an engineer know well in advance if the station has a clear passage.

Since the bridge signals have been installed, no train has had to stop and back out of the passenger station when they pulled into what they thought was an empty track.

Even without working lights, a signal bridge is an interesting and attractive addition to a riding scale railroad.

 

Written by Rick Henderson

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