Bridge over the Entrance Way

Colonel Nicholson: Reeves, if this were your bridge, how would you get it underway?

Major Reeves: Get it underway, sir? Well, first of all, I wouldn't build it here.

Colonel Nicholson: Oh? Why not?

Major Reeves: As I was trying to tell you a while ago, sir, the Japanese couldn't have picked a worse location. There's no bottom. You see those piles? They're sinking. Our chaps could drive those piles 'til doomsday and they wouldn't hold.

- From The Bridge over the River Kwai (1957). 

Well, I have been working on my layout for about 18 months now and up until a week ago had no idea how I was going to bridge the entrance way. Oh sure, I had seen lots of ideas online with hinges, swing and lift gates, electrical cut-out switches, and the like, but I still wasn't sold on them. Some looked complicated to build, and others required that both sides of the layout be perfectly stable already. That isn't the case with my layout, as the two sides of the chasm are subject to movement depending on humidity and whether I accidentally kick the legs while walking past the benchwork.

So, I had two goals for the bridge: (1) It had to accurately allow for the rails on either end to be lined up when in the closed position, and (2) It had to hold the benchwork together when in the closed position. Thus, plans for a simple lift-out bridge wouldn't work. I needed something that was hinged on one end that dropped down or swung over and pulled the other end tight. I found a video on Youtube which was pretty close to what I wanted. Now only was it easy to construct, but it had positive alignment from the bolts that extend below the end of the bridge (used for power interlocking). I don't plan to incorporate a circuit which will cut power to the bridge when the layout isn't in use, but it is a nice feature for those who need it. 

I bought a board that was 3.5" wide and 36" long, and two pieces of 1" square dowel. After drawing a centerline down one side to aid in track laying, I flipped it over and glued and screwed the two dowels along either side. At this point, it was oversize but pretty stiff. I could always cut it down to the necessary length on my chop saw, but I liked how the dowels kept the board from deflecting. And, they would prevent derailed trains from taking a dive off of the bridge. Then, I flipped it over and discovered to my horror that the resulting 1.5" width between the dowels was insufficient for a train to comfortably pass through. A boxcar could just squeeze through but that was asking for trouble!

So, I flipped it over again and my bridge with the deck below the girders turned into a bridge with the deck above the girders. A little bit of re-engineering was required, but I swear every one of my projects is like that. To make it work, I cut one end at an angle to clear the layout side when it lifts up. Then, I glued some 1/2" square dowels on the now upper side at the edges to provide some protection for the trains. I left the dowel overhanging the lifting side so it rested on the top of the layout and prevented the bridge from falling down. By doing it this way, I didn't need to figure out a complicated stop to go under the beveled edge of the bridge.

The hinges were secured and the bridge worked great. Then, I laid track which ran over the hinged area and ran into another problem. The video had showed the hinges mounted on blocks elevated above the track height. This I think prevented binding of the track at the hinged area. I didn't think it was important when I built my bridge and mounted the hinges below track level. So, when I laid the track the two edges of the rails crunched into one another at the joint! Panicking, I quickly went to plan B (or am I up to C now?) when I should have just stopped to think it through some more. Instead of just raising the hinges, I instead removed them completely and turned it into a full lift-out bridge.

I glued small sections of 1/2" square dowel outside the overhanging wooden side rails to keep the bridge lined up and I beveled them for appearance. For the track crossing, I used some cut-up Atlas code 83 rerailer sections and they may provide some sort of help should trains derail approaching the bridge. I used caulk to secure it and made sure the track was in perfect alignment and my test cars rolled over with just a slight click. Unlike other areas on my layout, I didn't solder any rail joiners here because I am not sure how much expansion and contraction will affect the bridge joints. Wiring just involved two long wires soldered to the rails, and then joined to a plug which ties into the bus wires through an existing hole in the end of the benchwork section. It isn't pretty, but it works. (If the hinges were used, I could just wire the track to them and they would pass the current across the joint. That would have been snazzy. If only it worked.)

D&H Postcard of Hadley, NY

All in all, this bridge is nothing like I originally planned! It doesn't hinge up, it doesn't have power automatically fed to it when it is in place, and it doesn't have any means of pulling itself tight to the two benchwork sections on either end. But, it was cheap- about $15 including the special Atlas track rerailers- and it will be easy to modify or replace down the road if I want to. I can still add hinges pretty easily by gluing some "1x2" lumber on one end (thus raising the pivot point of the hinges), and I purchased some door latch hardware which can easily be retrofitted to the other end. But, more than likely it will become permanent. If only it were as picturesque as some of the real D&H bridges.

And, just as important, my main line track is now 100% installed. Last week I had soldered feeder wires to the main line track on the last corner module and yard section last week. With the bridge in place it is now theoretically possible to run a train completely around the layout. However, none of the switches have motors or any other way to keep the points set yet so I am holding off on running trains. But, a box of Tortoise machines arrived in the mail a couple of weeks ago and that will be my next project.