Building Skewed Bridges
RailModel Journal April 2008 (pages 6-14)
By V.S. Roseman
Bridges are one of the those significant "scenic" features that need to be positioned when the layout is still in the planning stages, prepared for the benchwork stage, installed when you lay the track, and above all, matched to some specific prototype. Most railroads have a variety of bridge installations where the road, railroad or cannal they are crossing passes beneath tracks on an angle, forcing the bridge itselft to be skewed.
Picture 1 (Ride Side)
View of my East Ferry Street bridge seen from the right of way.
My model of East Ferry Street bridge built from an old Vollmer truss bridge model with Bachmann signal bridge girders.
Pennsylvania RR (Northeast Corridor). Stone skewed arch at Commerce Place in Elizabeth, New Jersey.
North Broad Street arch at Elizabeth, New Jersey with a portion of the station platform on top.
Kibri stone arch bridge with skewed construction similar to Elizabeth, New Jersey, but with a much smaller bore.
Baltimore and Ohio RR bridge over Western Avenue at Port Ivory, New York showing the angled abutment, which is not perpendicular to the direction of the bridge.
While many models of bridges are available, no kits have been offered that permit the finished model to cross an obstacle at an angle. In fact, rivers, roadways, canals and other features requiring railroads to bridge them seldom just happen to be at 90 degree angles to the right of way. In some locations such as in narrow stone canyons or over city streets, there is not enough room to place the abutments for a conventional bridge, so the bridge supports are placed parallel to the obstruction and at an angle to the right of way. The bridge is a parallelogram instead of a square, and the bridge is said to be "skewed." There are several ways to skew model bridges, and some easy methods are shown here.
The girders of this bridge seen from below. The support girders beneath the tracks are termed "stringers."
There is a concrete wall above the abutment, which appears to keep ballast from falling into the street. This bridge is not actually parallelogram shaped, but has girders of the same length arranged on the bias.
The Baltimore and Ohio RR, crossing above Western Avenue at Port Ivory, New York, built a stepped abutment that permitted using the shortest possible stringers (girders to support the rails) while staggering or skewing the position of the heavy side girders as shown in the photos and plan. You can see the angle on the map view, plus some details of this plate girder bridge.
My friends Don and Hiram and I designed a similar plate girder bridge model that started life as an inexpensive Lionel item. The model supports the mainline loop on the Showcaseline S gauge display layout. Rivets holding the original steel floor were cut off to remove it from the cast sides. A new skewed floor was cut from aluminum, and holes in the floor now accommodate boIts and nuts to hold the cast plate girders.
These plate girder bridges are easy to work with for they have ballasted floors instead of complicated openwork floors. Multiple-track plate girder bridges usually have low plate girders between every track as in the photo showing the former Central RR of New Jersey mainline at Elizabeth, NJ where it was squeezed down to four tracks.
The Central RR of New Jersey Newark Branch was built at an angle to the grid of streets. The grade-separated line had to cross above many streets on skewed bridges. I have simulated the structure at East Ferry Street using a Vollmer bridge as the start point. I needed square ends, which meant leaving off the nice angled girders that came in this kit. I used parts from a Bachmann signal bridge to form the upper lattices. I simulated the size of the Vollmer parts to make the triangular
BALTIMORE AND OHIO RR. BALLASTED TYPE SKEWED PLATE GIRDER BRIDGE:
WESTERN AVE. PORT IVORY. N.Y.
Plan view and elevation of the Baltimore and Ohio's Western Avenue bridge shown in the photos.
Central Railroad of New Jersey's former four track mainline east of Elizabeth, New Jersey crosses Broad Street at an angle as evidenced by their abandoned plate girder bridge showing the construction of a multi-track skewed structure.
My friend's model of a skewed pattern plate girder bridge with ballasted floor on his display layout for Showcaseline S gauge model trains.
View of front of the skewed plate girder bridge with Mt. Ferraro resort station on the left.
Detail shot of the skewed plate girder bridge from the open cut leading to the tunnel.
Sketch showing the construction method of this model.
Overhead plan view of the East Ferry Street installation of the CNJ in Newark.
Central Railroad of New Jersey crossed Ferry Street, Newark on this bridge. You can see that it has ordinary construction except for the triangular girder work at near and far ends of the bridge.
Ground view of CNJ skewed truss on Ferry Street, Newark showing the construction of the track support girders.
The Lehigh Valley crossed the Central Railroad of New Jersey mainline at Aldene, New Jersey on this bridge, which is a skewed truss type.
Plan view of the Lehigh Valley Aldene bridge.
My Atlas model Warren through truss bridge, which has been skewed to fit on a model layout.
The Atlas Warren truss bridge floor has been replaced with .060-inch-thick styrene. The gussets provide a good gluing surface to hold the trusses on.
end segments. I have taken some artistic license as the Vollmer model is not the same kind of iron bridge as in my prototype.
The Lehigh Valley RR at Aldene, New Jersey crosses at an extreme angle above the Central Railroad of New Jersey's mainline on a heavy steel truss bridge. The plan view shows the angle and mounting of the bridge on its abutments. As there is no model of this bridge, I used an Atlas Warren through truss model of a much smaller bridge to show another easy way to skew a truss bridge kit. I copied the width of the Atlas bridge floor in .060-inch-thick Evergreen styrene, and sketched the final form onto this using the two kit trusses to get the length. I fitted the bridge to the situation on the layout and instead of a plain angle for the end, I stepped the ends for two walkways and the track as the Atlas model has. The walkways were scribed and painted, and the track was mounted to the center. I used .060-inch square strip styrene for the guardrails seen on bridges to help keep trains from falling off. These are bent inward at the ends, and most have a casting that joins the two p arts, although I have found bridge guardrails in the pattern I used.
The small gusset parts that lock into the floor of the kit should have these tabs on the bottom cut off. The gussets are to be glued to the vertical girders of the side trusses, and make good gluing surfaces to attach the trusses to the bridge floor.
Strictly speaking, the only solid bridge floors I have ever encountered were ballasted decks of various types of bridges, and I believe that the correct way to build this model would be with an openwork floor made up of girders similar to the CNJ skew truss that was photographed from below.
Walthers timber trestle kit, 933-3147 is a useful model and can be fitted to more situations on a layout if built as a skewed bridge. The bottom rail support beams are notched, and you can fill these with squares of .0 1 5 or .020-inch-thick styrene. I left mine without filling, and they hardly show. The bents can be set at any angle you want. If you wish to strengthen the model, drill through from the top at a few points where the supports meet the rail support beams .030-inch and fit a piece of .030-inch brass wire to reinforce the joint between the bent and the top section holding the track. Setting the wooden bents on simulated concrete or stone slabs permits you to place this bridge across a stream or river, and this will look much more logical if the supports are parallel to the flow or direction of the river. To make guardrails, you can add .060-inch square styrene strips inboard of the rails (be sure to check your wheels as thick wheels will be forced to lift off the rails if the guardrails are not placed correctly).
At Elizabeth, New Jersey the Pennsylvania Railroad (now Northeast Corridor) was grade separated on an earth berm through the middle of town. This important rail line between New York and Washington crosses over streets that are at odd angles to the railroad right of way. The result is the Elizabeth arches as shown in the map and photos. Instead of creating the usual barrel-shaped arch interior, the designer set up a series of flat arches side by side, with each one skewed by about two feet to the next. This technique can be used in model form by using the two faces of any stone arch bridge k i t and tracing the outline of the arch onto several thicknesses of Foam core board. ( foam faced with plain paper.) Cut out each arch carefully and set them in a stack, then skew the pieces sideways to any angle you might need, and glue them in p lace sandwiched between the two plastic detailed bridge faces from your bridge kit. For smoother looking arches, you can glue a sheet of paper to one side of each of these arches, and cut a fan shape from the center of the arch to the edges, then fold the paper around the inner edge of the arch and glue on the other side using either Elmers or tacky-type glues. Then sand off any locating pins on the back of the stone faces and glue these with contact cement to the core you have built. I cut a three-step end for the top of my mode l to fit easily to abutments. Cutting the bridge diagonally can work too, provided you do not have to cut into the ties or rails.
Many stone arches have smooth bores, and I found a number of these on the New York Connecting Rail road (connects Penn Station, NY with the New Haven RR ) , and the photo shows one of these located in Astoria, Queens. On the Long Island RR in Long Island City, New York, an industrial freight track over the street is supported by skewed supports parallel to the street. RMJ
The Walthers wood trestle model with the bents skewed to accommodate the flow of the river. I set the bridge up on simulated concrete footings made of Northeast wood.
The Walthers wood trestle model showing direction of the bents (supports). I used rail to simulate the guardrails on this model.
Bottom view showing the skewed supports.
Sketch showing the installation of the Walthers simulated wood trestle (a plastic kit) where a rail line crosses a river at an angle.
Map showing the location of the downtown arches at Elizabeth, New Jersey with both Pennsylvania RR and Central RR of New Jersey mainlines.
To build a skewed stone arch, trace out several arches on Foamcore board or similar thick material. (I had black Foamcore boards.)
Kibri stone arch bridge with skewed layers of Foamcore board.
Complete skewed stone bridge model beginning with a Kibri kit.
Stack as many layers of these arches as you need for your bridge and glue in skewed order as shown. Then glue the kit's stone facings to the outside.
A smooth-bore skewed-arch bridge on the New York Connecting RR approach to the Hells Gate bridge at Astoria, New York.
This support beneath a long Island RR single track is set parallel to the street rather than perpendicular to the track.
Central Railroad of New Jersey's South Third Street bridge at Easton, Pennsylvania. Walkways are clearly shown on this mainline skewed bridge.