LIFT OUT BRIDGE PROBLEM !!

Have you thought of using a 45 degree angle on the sides of the lift out? The variance sounds like a moisture problem, maybe a dehumidifier would help you with not having a spacing issue.

I have helped a friend with a lift-up bridge about 4 years ago. One thing was track alignment or cutting of track on the bottom side to help with the lift-up, another thing to help is using an extra long track pin or nail for tubular track.

Lee Fritz

Lee Fritz-- I do think it is because of humidity....I can not change the tables on either side of the lift out....I have also thought of using O27 track on the lift out with several joints in each track.  I would use the  spacings at the rail joints to lengthen/shorten the bridge tracks as needed.  The rails would not be tightly screwed down, and I would use ¼'' strip wood  guides for holding the rails in place....sounds like a hassle?

John,

It could be humidity if you are up north in the USA.

I have year round humidity issues being in southeast Florida(WPB). I use a lot of stainless steel track from Gargraves.

Lee Fritz

Lee- yes, I am in NY...thanks for your thoughts....John A

How about a metal lift out?  You can get varying sizes of aluminum angle stock and flat stock at you local big box store.

You could also try PVC fence balusters (big box store).  They are about 1 1/2" square.  They can be glued or mechanically fastened (all thread and some nuts) into whatever width you need; light and strong.

Your idea to mimic the bascule bridge rails would probably work as well.  Maybe taking a piece of track and re-engineering it to fit over another piece, this would give you electrical continuity.  You would need grind the top rails and inside of the outside rail to give a smooth transition.

Have fun.

Yes, Dan, I am thinking along those track ideas.....I think it is the layout (4 feet by 51 feet)  that is "growing/shrinking"...the "bridge" is ¾'' plywood, painted on all surfaces...argh!!!

\

Get a dehumidifier.

Dennis

How real railroad lift bridges allow for expansion of rail joints:

What kind of track are you using? With tubular track you can cut off the bottom part of the movable rail ends so it drops over and overlaps the pins of the fixed rail ends. Good for gaps of 1/4" or so if you use extra-long track pins.

Three tracks on one bridge complicates the matter. Hopefully the rails and approaches are straight. Got pics?

I think your original idea is the simplest. Occum would likely agree.

The main support should be abutments, that would allow a thinner metal on your "rail caps" for a smoother transition, but the bumps causeing a major issue is slim in a straight shot with pizza cutter flanging... i think.

Llittle rollers go trough worse on Super O clips daily. Though sprung, the pole vaulting effect still exists on an occasional clip, but its bi-annual rare when a clip lifts and a bigger bump than I think youll get anyhow.

If you run 0-27 profile you might try a full length or cap of O. Its pin diameter is larger so might be a perfect fit if cut well...? The downside is its a thicker gauge metal.(unless you find a thin aftermarket version (seen it) or if lionel thinned the metal used on full O from that of postwar.?.)

It is your bench expanding, the bridge isnt long enough to grow that much. Its a per foot thing.

Unless the bridge is copper or brass with lots of heat or cold blowing right on it. Those would expand a lot but the temp difference would have to be pretty steep.

A dehumidifier is the best answer. It's getting pretty juicy in the area for the wood to swell 1/4". A humidity and temp monitor from home depot will be useful. (see attachment)

I like the suggestion of the 45° cuts at the joints. Same direction with the table over on one side and the bridge piece over on the other side. That would permit expansion. remove the approach tracks and hit it with a circular saw. Then build a new bridge to match. Fit on a juicy day.

Replace the table supports/framing in that area with 3/4" plywood ripped to the same width as the existing framing. A sawzall is handy for the cutouts. Splice with plywood plates.

I would think you would have to determine what is moving. Get a measurement of the gap (tables) and the bridge material at the swelled and shrunken states.

Putting a bump in the track (sliding cover plate) is as hard as a gap on the trains.

You need to resolve the humidity or the offending structure

Dennis posted:

Get a dehumidifier.

Dennis

Ditto.

I have two running in the train room.  They work well. 

But, buy a good one.....check ratings.

KD (Michigan)

1/4" expansion of common unsealed wood within 50 linear feet is some what low in the expansion/shrink dept.  In the future, using metal stud framing and Advantech decking will reduce your moisture expansion/contraction issues to .0001%.

We have had 1/2" gaping problems with HO track on a 50' run. 

Going back to my flooring career, we instructed homeowners to maintain 35% to 55% humidity with a minimum 55 degree temp when using solid wood flooring.  Engineered wood flooring is more stable but not by a whole lot.  Any numbers outside that range will void product warrantys.

Sealing the wood is another helpful step.  Seasonal humidity balance is essential.

For a down and dirty fix I like your multiple track joint idea,  Mild nuisance but doable.

Elevated humidity can bring on a host of other much more serious problems.

John A posted:

Yes, Dan, I am thinking along those track ideas.....I think it is the layout (4 feet by 51 feet)  that is "growing/shrinking"...the "bridge" is ¾'' plywood, painted on all surfaces...argh!!!

\

That would be my guess as well. Is it a free standing layout? I would lean towards installing locating pins on the ends or could you install it one end hinged and pins on the opening side? That's what we did. Maybe a picture? I'm sure guys here have encountered and solved this issue in various ways.

Gentlemen--- appreciate your input!   John A

It's probably not so much the expansion/contraction of your lift out section as it is the rest of your layout that is causing the problem. you might look into Gargraves (or is it Ross?) track, which offers vertical "blade" style rail joiners, which might work better for filling the gap at your bridge.

Bill in FtL