Building A Bridge
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Author:  Perryo [ Fri Apr 15, 2016 10:07 am ]
Post subject:  Building A Bridge

We needed a bridge to cross the Cooper River into Camden City on our Camden & Mount Holly Railroad (C&MH RR). The "river" is really just a dry stone bed to handle water runoff during heavy rains but crossing it required two, 5ft long, spans for single tracks at two different heights; The C&MH RR mainline track elevation is about 11 inches higher than the lower level trolley line.

The upper span was to be a simple through-girder type bridge. However, I wanted the lower span to have the appearance of a drawbridge which in my imagination would open to allow barge traffic to travel up-river to a small dock facility (a future project ;) ).

An internet search revealed many photos of really neat railroad drawbridges. Most were way beyond both what I needed and my modeling skills. However, the Amtrak bridge over the Bush River at Perryman, MD seemed simple enough to give me a few ideas for a plausible looking small drawbridge. The Library of Congress online photo collection has several pictures of this bridge which was built back in 1913 and is still in use. This photo provided what I needed - ... 6313pv.jpg

This is how the bi-level Cooper River bridge turned out. Building it on the workbench was a fun wintertime project.

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C&MH BRIDGE 4.jpg [ 202.78 KiB | Viewed 13592 times ]

Author:  Perryo [ Tue Apr 19, 2016 1:42 pm ]
Post subject:  Building The Cooper River Bridge

I thought that I would post some info on how I went about building my Cooper River bridge for anyone on the forum who might be interested.

At first I intended to build the bridge supports from stacked concrete paver bricks. That would have been prototypical, workable, and inexpensive, but I happened to find two G scale steel support structures online that I could use as-is to give the bridge a little bit of a different look. It remained for me to build the two, 5ft long, bridge spans themselves.

For rigidity each span uses two, 5ft x 1-1/2" x 1-1/2", stamped steel angles held together in several locations with steel tie plates pop-riveted into place across the bottoms of the angles. These items were obtained from my local home improvement store. All nuts, bolts, screws and pop-rivets used are stainless steel.

The side girders for the upper span were made from a 5ft piece of 2-1/2" square PVC rain gutter downspout. The plastic downspout was split twice along its length. The two resulting "C" shaped pieces were turned inside out, ]_____[ and pop-riveted to the outsides of the steel angles. Scraps of the PVC material were cut and glued in place to make vertical stiffeners on the outsides of the girders. The span was painted flat black and labeled with the railroad's name using self-stick vinyl letters. Pieces of 5ft x 1-1/2" x 1/4" pressure treated wood lattice, stained brown, were screwed down to the angles to make the two maintenance walkways. The final result was a simple, relatively inexpensive, 5ft long bridge span.

For the lower span I chose to start with the pre-made girder bridge side pieces now available from Colorado Model Structures. These molded plastic side pieces can be used as-is in many situations but I decided to do some cutting and gluing to make them the basis for the drawbridge span. Pieces of styrene plastic from my local hobby shop were used to finish-off the cut edges of the girder structures and to make the faux "lifting gear" mechanism. These pieces were then bolted to the sides of the steel angles and painted flat black. Pieces of stained pressure treated wood lattice were again used make the two maintenance walkways. A chunk of pressure treated wood, painted gray, was hung from the bottom of the span to simulate the drawbridge's concrete counterweight. A bridge tender's shanty was made from an old caboose body shell and styrene. The shanty was added to the end of the drawbridge span to finish the project.

BTW: The caboose body shell was donated by a member of our local garden railroad club; just one of many good reasons to get involved with a local club if you can.

Any questions or comments are welcome.
If you have a favorite bridge on your railroad please share it!

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DRAW%20COMBO%203S.jpg [ 143.74 KiB | Viewed 13568 times ]

Author:  paulrace [ Tue Apr 26, 2016 8:41 pm ]
Post subject:  Re: Building A Bridge

PerryO, this looks great. I'll forward the link to CMS.

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