Room Access Lift Bridges - picture heavy

There has been a few folks asking about Access Lift Bridges lately. Since I had to build a few for the Railroad that I am currently building, I thought that I would post a topic of what I have and how I did it. This is not a How-To, but some "must know" information, techniques, and pictures.

My railroad room is one-third of my three car garage, which is really a shop rather than a place to put our cars. The Railroad room is about 23 feet long and 9 feet wide. It also has two doors. An inside door to access that rest of the garage area, and an outside door that is seldom used anymore. My Railroad has two levels and is a shelf type 18 to 24 inches deep with a peninsula on one side. The lower level is around the walls and across both doors. There is a nolix that goes up to the upper level which is only on two walls. The nolix also goes around the room and across both doors. I have four Access Lift Bridges, two at each door. Each is slightly different, but all of them are lift up types, and have a few things in common.

There are generally three types of access bridges that modelers build. One is a swing bridge, which is mounted and operates like the bottom half of a door. Another type is a drop bridge, which hinges on one side and swings down. The third type is a lift bridge, which hinges on one side and swings up. During my modeling career, I have built all three types. Each has its advantages and disadvantages. To me, the easiest and most reliable is the lift bridge, and that is what I have used at both doors to my Railroad room, and that is the type that I will explain in this post.

Here are my reasons why I have chosen lift bridges:

1. They will not fall down or open when a train is on them.

2. They do not have to be locked in the down position.

3. They can be set in place without using hinges until you have made sure things are right.

Here are a few of my rules when making lift bridges:

1. The hinge pivot point MUST be higher that the tops of the rails. (If not, you will deform the rails/track when lifting the bridge.)

2. When the bridge is lowered, it MUST close and come to rest in the same place every time.

3. You MUST provide a way to power the track that is on the bridge. (The more reliably you do this, the less problems you will have.)

4. You MUST make sure the bridge will not fall down when they are up or open.

5. You SHOULD provide a lip at each end on the stationary part of the opening so the bridge does not rely on support from the hinges. (This helps with the alignment.)

6. The bridge itself MUST be sturdy enough that it does not change shape when in use.

7. When track is mounted on the bridge, all ends that span a gap MUST line up every time the bridge is down.

Now that we have covered the basic needs, let's take a look at my bridges. I will first show you the doors with the bridges up, then down. Next I will show you how the bridges are made, how they are hinged, what keeps them in place when down, and how they are held open. I have numbered the pictures so you can refer back to them so they don't have to be posted more than once. I have also numbered the bridges A through D.

Number 1. The outside door with the bridges up.

Number 2. The outside door with the bridges down.

Number 3. The inside door with the bridges up.

Number 4. The inside door with the bridges down.

Bridge A is the simplest one. It is made from a 1x4 board, (Rule 6). The hinges on the right have been mounted on a piece of 3/4 inch thick plywood. 4 of them. Two are on the stationary side and two are on the bridge side. The hinges are screwed to these and the top is higher than the top of the rails will be, (Rule 1). Under both ends of the bridge are other 3/4 inch thick supports that are fastened to the underside of the sub roadbed, (Rule 5).

On the left end, there is a wood dowel fastened to the bottom of the bridge. It enters a hole on the support lip of the sub roadbed when the bridge is down, (Rule 2). When the bridge is up, it leans back quite far so it will not fall closed if bumped, (Rule 4).

Now for a couple of building notes. When building this bridge, the stationary ends (sub roadbed which is 3/4 inch thick) were fastened to the walls first. Then the bridge lip supports were added to one end. The bridge board was then set on the support lip and lowered to the other end. A line was then drawn on the bottom of the bridge board, and the board cut. Next the second support lip was put in place and the bridge board set in the opening span to check for the proper fit. Once that was done, the hinge blocks were cut and mounted and the hinges screwed in place. The guide pin hole for the dowel was drilled into the bridge board from the top, and on into the support lip, at the non hinged end. A dowel was glued into the hole in the bridge board and cut to length. The end of the dowel was also shaped to a rounded point to aid its insertion into the alignment hole in the support lip. Then everything was primed in anticipation of some paint, ground cover, and ballast after the track was laid.

Bridge B is almost the same as bridge A, but there are two differences. First, it is wider and was made from a piece of 3/4 inch thick plywood. Second, there was not enough room under the sub roadbed on the left side (hinged side) to put a support lip. However, Rule 5 is still in play because if you look closely, the hinge blocks that are part of the moveable bridge board are longer, and the hinge pivot is set back from the stationary edge, which allows the hinge block to rest on the top of the sub roadbed at that end. Notice also that the hinge blocks are not as tall or high as the ones for bridge A. This is because bridge B is going to be used as an interchange yard and carry 4 tracks, all of which will be fastened directly to the sub roadbed.

Bridge C is almost the same as bridge A except for the hinges. Instead of hardware store hinges, I had to make the ones for this bridge because the end supports or piers were too narrow. What I did was make pivot points using 1/4 inch 5 or 7 ply model aircraft plywood. This is a very strong and rigid plywood. All of the rules apply. The hinge pivot point is higher than the rails and uses quarter-twenty extremely short carriage bolts. The holes have had Thin CA glue applied to them to reduce any possible wear.

As for rule 7, this was accomplished in the following way: A section of road bed was cut from quarter-inch Luan and the ballast profile was cut on it too. Two of these were used, one on the stationary piers at each end. The bridge itself is made from a 1x2 poplar board. The top surface of the board was level with the top of the Luan roadbed. The track installed was about four to six inches longer than the bridge. It is held to most of the bridge with caulking. The last two inches on both sides of both bridge gaps or separation points were spiked between the ties, then super-glued to the roadbed. Once this was done and the glue allowed to dry thoroughly, the rails were cut at the bridge gap.

Feeders were soldered on the bridge track and routed along the bottom and into an angled hole in the bridge pier.

This bridge had bridge sides built from styrene and glued to the bridge board, then painted. The track will be ballasted later. This bridge has a hold-up button that holds the bridge in the up position.

Bridge D is a unique shape. Because it simulates a water channel under a Railroad bridge, it had to be built differently. The basic framework used is cut sections of L-girder that was left over from my last layouts bench work. These L-girder sections are at the stationary ends of the opening, and the ends of the moveable part of the bridge itself. The bottom of the bridge is quarter-inch Luan that has been braced or reinforced with 1x2's. There will be a two-track swing bridge (Walthers) to carry the tracks across the water channel.

As you can see from the photos below, the hinges have been elevated, the bridge rests on a lip at each end, and the lift end is keyed by two dowels in the support lip. This bridge also has a hold-up button, plus a foam protected rest so that it doesn't contact the upper bridge pier for bridge C.

Two things that some modelers think is necessary for access bridges are the ability to remove power from the approach tracks at each end of an access bridge; and some form of sides to prevent equipment falling to the floor. I do not do either of these things because: I stop all trains when I lift my bridges; and the brides and their tracks are leveled from side to side, speed is kept low, and stray parts do not got on the track. I do try to blend my access bridges into my scenery as much as I can.

So, I hope you found this post informative, and it will help you if you ever have to build an access bridge.