03/05/07

During  October of  2006, I finally got around to building a Swing Bridge to replace the duck under I had been using to gain access to the train room.  To my surprise it was actually very easy to do and only took a few hours.  Please bear in mind that I have the carpentry skills of the average rock, so you should be able to do it even quicker.  Due to formatting, this page is best viewed in full screen.

Decisions, decisions..

When installing a swing bridge a series of questions / issues need to be answered.  As with any construction process the more of these issues you deal with prior to the commencement of construction the better.  Of course, I didn't do any of that and just built the thing on the fly.

(1) Swing Up or Swing Down? The placement of the hinges determines if the bridge swing up (hinges on the top and viewable) or swings down (hinges under the benchwork and hidden).  The key point is the width of the bridge and the type of scenery your going to install on the swinging portion.  If the bridge swing down the scenery will be exposed to damage in the down position if someone walks to close to the bridge when entering the room.  If it swing up, the scenery is better protected from damage but the hinges are visible.  Its the age old problem of function (swing up) vs. aesthetics (swing down).  Since the opening for the bridge is a narrow door frame (roughly 30 inches), I decided to have the bridge swing up to protect the future scenery that will be installed.

(2) Track Connections:  As the level of the track will not be on the same plane as the hinge, you need to figure out how to allow for room to swing the bridge open (on the hinge side for a swing up or the non-hinge side for a swing down).  This can be accomplished by cutting the benchwork, roadbed, and track at the same angle or putting in removable track sections to provide enough space.  I elected for removable track as cutting everything at the same angle was beyond my meager carpentry skills and I didn't have full use of my left arm at the time of construction.  The three straight track sections on the hinge side are removable.  I cut the plastic links that hold the rail to the ties to allow the rail connectors to slide up and down the rails.  Using a pointed tool, I can slide the connectors up into position to link the track sections when the bridge is down (see the picture above).  When I want to raise the bridge, I slide the connectors down and remove the three track section - as shown below.  You'll also notice that there is a gap in the cork road bed of 1/2 inch.  This gap allows enough space the roadbed on the bridge itself as it swings upward.

(3) Free End Guide:  I don't use connectors on the free end (the non-hinge side) of the bridge as the track is fixed in place.  In order to make sure the bridge goes down into the same exact position when closed, I built a simple guide from two pieces of 1x2 and a piece of 1x4 attached to the end of the bridge.  Since this bridge swings up, gravity is my ally in holding the bridge in place

(4) Electricity Connections:  When installing a swing bridge one does need to sever the electrical connections at both ends.  This is a fairly easy issue to fix but the electrical connections need to installed from the hinge side for obvious reasons.  While not ideal electrical connectors, the sliding rail joiners described above also work as passable electric connections.  The turn out on the bridge the installation of a plug connector for the turnout control.  When the bridge is down, I plug the connector in and the turnout controls work.  When I want to raise the bridge I have to unplug the connection, which acts as a bit of a safety device to help ensure the bridge is opened only when it should be.

(5) Bridge Safety (Human and Models):  The last item to consider if Swing Bridge Safety - the bridge should only open or close when you want it to, not when it wants to.  This requirement is more important with a bridge the swings up and (and therefore can slam down) as the "wham" point is apt to have someone's hand in the vicinity or their head in the passage way (trust me I know).  To lock the bridge in the upright (open position) I used 2 eye bolts and a carabineer to hold it in place.  As long as the laws of gravity remain constant, I'm not that worried about the bridge suddenly swinging open  from a closed position so I rely on the turnout connection to act a as a reminder.  If the laws of gravity do change to the point where the risk of the bridge flying up becomes a real concern I think I'll have other, more important, worries than swing bridge safety!

Now that we've secured humans from most bridge mishaps, what about the trains?  Despite the momentary Addams Family'esque joy of seeing a train crash to the floor in a shower a scale detail parts, its a bad thing when this happens.  I'm fairly safe on the hinge side, as we remove 9 inches of track.  The free side will require a wooden block to be installed at the "end of the line.  I'll also be installing rail guards on each bridge end to ensure a derailment doesn't take some cars over the side.

Comments? Please Email us at:

Bosco@clarksville-balt-and-ohio.com