Swing bridges are movable sections that turn laterally to allow passage. While many of the advantages and construction techniques are similar to lift or drop bridges, there are some additional things to consider when choosing this option.
- Larger footprint: A swing bridge will occupy as much room when it is open as it does closed. For multi-level layouts or other installations where vertical clearance is at a premium this may still be a better option. Plan accordingly.
- Larger hinge: Because all of the weight of the bridge will be placed on one side, additional support is recommended. A piano hinge works well. For large or heavy bridges, a support post and caster may be required.
- Tapered open end: Like a lift bridge, the end opposite the hinge much accommodate the radius of the swing. On a swing bridge, the easiest way to accommodate this is to make this end a 45° angle. You can also measure and cut a curved radius.
- Multi-level: Although more complicated, a swing bridge can be built to move several levels at once.
- Kill Switch: Getting power to the bridge is as simple as a flexible wire connection. But what about an open bridge? Prevent disaster by wiring the track on the bridge and its approaches as its own block. Installing a kill switch (a push button or mechanical relay will work.) This can shut off power to the bridge and the approaches when open.
- Protection: Additional fall protection can be provided by installing shields of plexiglass or other materials to the sides of the bridge. Faux bridge girders are a common option. These only need to be high enough to prevent a fall in case of derailment.
Another option for building a swing bridge is to mount it directly to a door. If you choose this option, there are several factors you should consider:
- Building Code:Adding a section of tracks, even a narrow one, to a door will reduce the amount of walk-through space when the door is open. You should check with building codes in your area to ensure you maintain minimum safe egress requirements. If you are fortunate enough to have the option, installing a wider door may be one solution to tight clearances.
- Clearance: The wider you make the track, the less room you will have when the door is open. This will also impact the angle on the open end of the bridge which must continue the swing radius into the track section.
- Opening: The door must open away from the layout room.
- Security: As with other swing sections, a kill-switch to prevent trains from falling into an open bridge is a good idea. Since people on the other side of a closed door may not be able to see if trains are running or not, some additional precautions may be in order. An interior lock, external warning light, or at least a "please knock" policy on the other side of the door is also a good idea. A warning light could actually be wired into the same circuit that cuts the power to the trains when the door is open.
If attaching the benchwork directly to the door is not an option, consider building a seperate swing or lift bridge beside the door.
In either case, the security measures above would be a good idea to prevent an accidents from doors or people slamming into a closed railroad bridge.
The bridge shown in the photograph is attached to a hollow-core door that connects the railroad room and woodshop. Since esthetics is not a priority on the opposite side of the door, the bridge is attached to plywood strips.
These strips are fastened with large bolts to additional wood braces on the other side of the door which also support a small section of pegboard for storage. This prevents the weight of the bridge from damaging the thin veneer of a hollow-core door. For more finished home installations, a solid door would be a simple solution.
Notice that the backdrop and fascia (still in progress) also continue across the door. When complete, the door will blend in seamlessly with the rest of the railroad and room.
A latch on the fascia helps secure the door and prevent opening from the other side. (A moot point since the shop will not likely be occupied during a railroad session anyway, but an added insurance nonetheless.)