Hey Marc, Everyone has
Hey Marc,
Everyone has their methods, and there are different approaches for different situations, but here is what I did, which might give you some ideas. I would echo Dave's advice in that you have solid benchwork on both ends (maybe even overdo it). I would also echo Bruce's advice in that you get the straightest lumber for the bridge itself, age it (ie: store it in your layout room for a month, maybe more, before installing it), and build up the benchwork and bridge and everything before you lay track on it. I didn't seal everything as Bruce mentioned (most if it was painted afterwards), but it is worth the time to seal everything before assembly.
As Bruce mentioned, it is very important to secure the rails of the track to keep everything aligned (this was a failure with a liftout a family member put together). Bruce's method has been used successfully by others. I went a step further, and used a method I saw on an N-Track module with a lift up gate: I secured copper PC board to the wood, and soldered the rails to them. Don't forget to cut a path in the PC board between rails so that you don't short things out.
Above you see another trick that I picked up, I staggered the rail joints, so that only one wheel is over the gap at the same time, which smoothed things out very nicely. Please excuse the sloppy look of the solder (it was cleaned up). Later, guard rails were added (one step smaller in rail, IE use code 83 guardrail for code 100 main rail), and I topped the PC board off with some diamond plate patterned styrene to give it a more industrial look. In between the tracks on the bridge, you see a small metal plate. When the bridge is raised, a cabinet magnet, which is mounted to a block, which is then mounted on the ceiling, locks onto this magnet, and keeps it up. I do not use the magnet to "hold" the bridge up. The bridge is balanced so that it will stay up on it's own, but the magnet keeps it from being bumped down easily.
For alignment, I used the tried-and-true V-block method for aligning the bridge. Here the bridge is up:
And here the bridge is down. You can see the MDF V-block that snuggly fits into the groove:
I also added a cabinet magnet and plate to keep the bridge secure in the down position. This and the up-position magnets provides for one-handed operation up and down. Plus, I added a micro-switch that is wired to a relay. Most people will turn off power to the tracks approaching the bridge when the bridge is up, in order to stop trains from running off the edge, but for a consist of 3 sd40-2s in HO, your looking at 3 feet "buffer tracks", which I really couldn't do. Instead, I isolated a foot (in one case only 6 inches) of buffer tracks, and wired up the relay so that it reverses the feed when the bridge is up. That way, as soon as a loco enters the buffer zone, it causes a short, power is turned off to all of the tracks, and it really gets your attention.
On the hinge end, I used cabinet hinges, which allows a thick board to butt up flush and snug against the frame when closed. This saves a lot of space for me, and made construction easier. Here it is in the up position:
And here it is in the down position:
You can see how the bridge tracks clear the base tracks when the bridge is up, and line up nice and flush when the bridge is down.
Good luck!
Jon, ---jps