Monk Subdivision - Building a Lift Bridge

When I designed the Monk Subdivision current staging room, it was clear I need to cross the doorway. In my mind, it would be simply a drop in module with tracks screwed in place. No hinges, no fancy systems... and sure I did build it and it worked until I tried to take out and it stuck because of wood expansion.

The plywood flat rest against a 2 inches shelf

I swore I would not replicate this system and decided to design a lift bridge with two hinges. However, I didn't throw away my previous module and a few basic ideas. First, I liked how the module was sitting flush on the layout due to two birch plywood overhangs. The plywood rest on a small notch were I didn't put fiberboard. This was, even if I use hinges, the module weight isn't resting on them.

In closed position, the hinges only serve for alignment.

On the other side of the doorway, I installed double bead catches as an alignment device but also as a way to lock the panel in position. Sure, it isn't as strong as a bolt, but so far, I've been impressed with the result. It's both strong, easy to adjust and convenient.

Cheap, strong and self-aligning: double bead catches

However, one shouldn't expect a moving device such as a bridge to work perfectly out of the blue and Louis-Marie helped me to adjust it until performance was optimal. A few styrene shim under the hinges, some careful sanding to get a perfect assembly and making sure the catches were on the right place did a lot to improve the finished product.

Pre-drilled PC board ties

As for track, the birch plywood used at both ends is also a way to provide a solid foundation to fix the track. A strip of plywood is also provided at each ends of the layout. The first ties on each side of the gap are Fast Tracks PC board ties nailed in place with their height adjusted as best as I could.

Flextrack was laid continuously over the gap and plastic ties removed where PC board ones were provided. I then soldered the rails on the PC boards to get a strong link. Using flextrack also helped to make sure both the gauge and rail height were a perfect match.

Rails soldered and with their gap

The nice thing with this method is that if the PC board tie tops aren't 100% flush, the solder will fill the gap. Once the rails cooled down, I cut the gaps with a cutting disk and tested if the lift bridge was working as expected... and sure it did! The key, indeed, is to make sure the hinges pivot is higher than the rail head to provide enough space for the bridge to fold over without ripping the track.

In open position, no risk at all.

I certainly won't win an award for this lift bridge and I know that humidity variation will have an impact down the road, but I made sure to provide enough adjustment room here and there to be able to make alterations if ever required.

Lessons learned with this experiment are most likely to be applied to the other lift bridge in the scenic part of the layout. I never liked the cumbersome swing bridge I built a few years ago and will cheerful disassemble it when the time comes!