Coming unhinged...

Your carpentry looks very nice!

But I'd be concerned about the forces present on the hinge when the bridge is open. I don't think it will be durable as a means to precisely support the bridge. The long bridge with a short hinge makes for a rather long moment arm giving the bridge a lot of leverage to stress that hinge.

That said, it you come up with some nice cleats on the hinge end to keep it from moving up and down and a good shelf for it to rest on at the swinging end AND you provide a platform for it to rest on while it's open, it might be a workable design.

Regarding dimensional lumber and stability, dimensional lumber isn't the most stable of materials. Especially when there are humidity swings. Might I suggest you consider decent quality plywood instead?  Not AC grade but 9-ply (or more) hardwood plywood. Baltic birch or equivalent is great stuff but is really expensive. If your local home supply store has some 9-ply sold as 'cabinet' grade that will probably be good enough.

I'd also suggest that the 2x4 'leg' I see near the hinge might be enlisted (or a sister leg added) as a place to extend the hinge surface downward allowing the use of multiple hinges which will drastically decrease the leverage the bridge will have against the hinges. Reinforce both the hinge end of the bridge and the abutment carrying the hinge. I prefer to use a box structure for extra strength in the abutments but I don't recall many people saying that I underbuild benchwork so it could easily be 'overbuilding'.

My experience with three swing bridges shows a big problem will be keeping the abutments on either end in precise alignment. It will be all to easy for benchwork to expand/contract or the floor to move up or down over time. Even with a U-shaped piece of 3/4" plywood spanning my current swing bridge it is sometimes very difficult to remove or replace the locking pin (1/8" brass rod in a brass sleeve) without needing to coax (read tug hard) on the abutments to release stress.

If you haven't seen it already you might look at the "Up the Creek column - Plate Tectonics" in the April 2009 issue of MRH where I talk about my swing bridge (literally -- there's a video). It might be of some use.

It's your railroad of course. What ever you do post a bunch more photos. In particular I'd be interested in seeing how you align the track at either end of the bridge (as well as aligning the bridge ends).

I hope this is helpful. Best regards,

Charlie

A piano hinge at the swing end will also help.

The easy way to do it would be to put another leg to the floor directly under the existing hinge, then put a "leg" almost to the floor on the swing end of the bridge below the hinge.  Finally install the piano hinge directly below the existing hinge all the way to the end of the extension on the bridge.  A small cleat on the bench work to support the bridge when in the open position will be a big help to keep it in alignment when open.  Put a flat on the closed end to support the bridge in a vertical plane and then put a vertical at the end of the open position on the bench work and a matching  cleat on the bridge.  Use the last two cleats to install a dead bolt to latch the bridge in the closed position.  The dead bolt will lock and keep the track alignment in the horizontal plane.

That lonesome hinge....

.... will not last long. Can you make it to swing up instead?. This way you will have the whole width of the bridge for hinging purposes, and a small rest piece on the other end (easier to align the tracks). Aisle will be wider also.

Moving stuff ...

Can you move the hinge to the other side?

Can you move the staging access?

Is a swing up bridge feasible? You'd likely have to sacrifice the bridge over the river on the swing bridge concept though.

Charlie

Wish I could use one Russ...

Russ,

Yes your right, a piano hinge would be better.  As I pointed out to Charlie I'm limited by the area underneath the swing bridge being the access to the duckunder for the staging & helix area.  So I'm clearly going to have to be creative in my thinking and engineering on this one.

I'm already thinking that there is an even simpler solution of just having the bridge as a lift out section, would not impede the access to the layout at all, would require very little engineering, would not require much cost to install.  The only downside is that you physically have to remove it and "put" it somewhere at the risk of it being dropped or damaged.

Thanks again for your reply and ideas too.

Decisions, decisions....

Jas...

Hello, we have a new contender...

pipopak,

You may just very well be onto something there!  Thinking about a lift up is an extremely good example of lateral thinking, it certainly would alleviate most of the issues I currently face, and would also provide some positives too.

Your right it would lessen the protrusion of the swing bridge into the aisle, would allow the hinge mechanism to be substantially widened and therefore strengthened.  And it would also mean that the truss bridge and scenery that will be on the swing bridge would be facing into the layout and therefore be protected from being damaged, and that it would also not block the layout area when the swing bridge was opened and against the fascia.

I'll definitely look into your "lift up" idea further too, thanks for the help...

Jas..

We use a lift up as well

Tracks cross the main entrance to the layout from our office area at the WRMRC.  We have used two different swing bridges in the past but were not happy with reliability.  Both of the old swinging bridges sagged and had alignment issues when they were closed.  Our current method is a hinged lift section, and it has worked flawlessly since we put it in.  We have double track on a superelevated curve, and it lines up perfectly every time.

It isn't casual construction, though.  We used hinges suitable for a bank vault, reinforced the doorway with steel angle stock to prevent it from being affected by humidity and designed an adjustable V-channel to receive the end of the track section when the gate is closed to make sure it centers properly.  We also have it electrically interlocked and use an electromagnet to keep it locked down.

The best advice is not to leave anything to chance; give the track no choice but to end up where it should, and definitely allow for adjusting the free end's latching or guide mechanism, because anything made of wood will move over time and you need to be able to account for that.

Jas, more info ...

If you are planning for the lift rather than the swing type, then this may be of some help to you. Don (dfandrews) has a blog here that discusses this and some additional info is included in that thread from George Booth:

https://forum.mrhmag.com/post/layout-7-the-lift-bridge-12188337

I hope this will help you with the design.

JL&T Railroad - Swing Bridge Construction - Take 2...

​Well guys the swing bridge ain't swinging anymore, it's lifting up!  Firstly thanks to those who provide some great feedback this morning and alternative ideas for the bridge.  Jurgen & UPWilly thanks for the posts and links to other lift up bridges, they helped spark the inspiration to try a different direction.

The actually moment that the idea came to me, occurred this morning when I was getting my breakfast and opened one of our kitchen cupboard doors, they use a recessed hinge system that is ideally suited to creating lift up bridges for model railroad layouts.

So this morning full of beans, and a million ideas running through my head Lachlan and I went of to our favorite hardware store, Bunnings.  So we came back and I was into it, I first mocked up the end supports in pine and bolted these to both sides of the layout framework fascia, then I constructed the middle section and clamped this in place.

I then placed some temporary plywood tops onto the frame work and screwed these down, I then marked out the positions for the recessed hinges and installed these.  I then screwed the hinges and lift up section in place and tested in out.  Well proof of concept worked and worked really well.  The beauty of these hinges is that have several adjustments in them to ensure perfect alignment.

I also be adding further adjustment on the other to, but this will be in a future update.  Anyhow a few photos & video below of what we managed to achieve in a very productive day on the JL&T...

The JL&T - Lift-Up Bridge - Version 1.0, in place with the single track/truss bridge...

​Walthers single track/steel truss bridge in place and river bed cut out of frame...

​Shot showing the box frame secured to the layout benchwork frame fascia, bolted through using 1/4" bolts...

​​The remaing lift up section will be constructed either with hardwood like the box frame or using marine grade plywood (9 ply).  This will add more strength to the section and durability as opposed to the current dress pine and light plywood.

The secret weapon for the lift up section are these "kitchen cabinet - recessed hinges...

​Shot showing the bridge abutment and recess on the hinged end of the lift up...

Lift up end of the bridge, leading into the interchange crossover & intermodal yard area...

​Checking curve clearances and bridge strike points using a TT 89' Flat Car - the longest rolling stock on the JL&T...

​Thats all for tonight, I"ll post some more updates soon as I progress and update the design and refine it more.  Please feel free to offer more advice too, if I can get to this stage so quickly with the help I've received to date anymore would be gladly appreciated.

I'll be posting a JL&T - Video Update #5 on the "Lift-Up Bridge" shortly...

Cheers all,

Jas...

This is the plan of our

This is the plan of our bridge:

Here I have rotated the lift section:

You can see that we have used a conventional hinge, but were still able to position it below the track grade.  All you need to do is bevel the cut in the roadbed in such a way that it can move away from the fixed portion without binding.  You can also see the way we extented the free end track so that it drops into a slot in the fixed benchwork at that end.  This is where we have the V-slot to receive and center the bridge tracks.  The added benefit to this design is it recesses the joints in the track away from the edges of the bridge so that you can't snag the rails with your clothing (ask us how we figured out that was a problem...)

Maybe these drawings will give you some more ideas.

Excellent!!

I was thinking about a piano hinge, but your way is a lot better. I would add some kind of positive stop for the open position, maybe with a magnet to keep it up. This is a long bridge with a long lever action on the hinge screws. And a pan on the hinge side to collect all the river water that is going to spill with the bridge up!!.

keeping it open

You will want the cut in the roadbed at least half an inch back from the hinge so that your top surface can rotate past 90 degrees.  You want the center of gravity to be past the hinge line to keep it from wanting to fall back down.  This is where a relatively thin bridge is a good idea.  We use a block of wood on the door frame for the bridge to rest against for now, but we are thinking of making something on the (as yet unbuilt) valance above the bridge to hold it eventually.

That is a well designed Lift Up bridge...

Jurgen,

Your design is very effective, but also very simple in design.  Which should mean that it should perform without any issues for a very long time, sometimes simple and uncomplicated ideas are the best ones.

The Version 1.0 that I have built yesterday for the JL&T is working well, I can see a few ideas from your that I'd like to incorporate that I think will benefit the JL&T Lift Bridge.  I like your v groove design for aligning & centering the tracks, I'm going to do something along the same lines but ours will use the side wings to do this.

Thanks again for posting your drawings, very much appreciated...

Jas... 

JL&T - Lift Up Bridge / Video Update #6

Hi All,

Just a quick video update on the progress of the lift up bridge for the JL&T for those following.

Cheers,

Jas...

My post is not SPAM...

It don't mean a thing ...

if it ain't got that SWING!

Good job!

Charlie

Thanks...

Nicely built bridge

Can't wait to see an intermodal crossing the great divide.

It will be that or a coal haul Alan...

Nice lift up

I like those recessed cabinet hinges too.  That's what I used on our kitchen cabinets in our last house when I renovated the kitchen there.  I was going to suggest something like them  after reading your post but I am late to the party!

If anyone is looking for a supplier of these hinges online or in the US & Canada, my favorite place to get hardware like this is Lee Valley, they have a hinge for just about every situation I think.

Nice job on the bridge Jason, thanks for the updates on what you are doing.

Nice Work

It looks like you've found a great solution Jason.  I may have to steal some of your ideas here for my own situation. I've acquired the rest of my layout room and because I wasn't ever planning on getting access to the rest of the room, it will force me to have some kind of lift bridge section in order to expand. I like the kitchen cabinet hinge idea. Thansk for sharing this and keeping the camera ABOVE the benchwork.

Thanks Kevin, Fantastic links...

Kevin,

Those hinges are fantastic for this type situation, something I didn't even consider until I was opening the kitchen cupboard doors.  Your suggestion for the hinges are very interesting, if I had seen them prior I would have seriously considered them for the lift up bridge.

I like the idea of the entire hinge being hidden, would look very neat.  I also like the action and clearance that they provide when in the open position too.

Thanks for the comments and thanks again for the links, they have been "book marked"...

Jas...

Steal as many as you want...

Kevin,

Feel free to use whatever you need, although the link that "Kevin R" (Sorry Kevin, all corrected) provided for the entirely concealed hinge is a very good and workable hinge that may work even better than the type I have used.

Great to hear that you have gained some valuable space for expansion, can't wait to see the planning/development of that and the construction process.

Thanks for the comments.

Jas...

No longer a swing, lift up, but a lift out...

Hi All,

Well there has been another change made recently to the JL&T bridge, it is no longer a lift up but is now a lift out.  I struck a major issue with the design of the hinge mechanism, the location and operation of it was causing the track to bind when the bridge was lifted.

So after some thinking I have decided to simple turn it into a lift out.  This is simplistic in design, does not have any moving parts, and is easy to remove and place back in.  The traffic using this aisle won't be that much and as such it wont be an issue to remove it once in a blue moon.

The new lift up bridge installed & wired...

I was trying to figure out how to align the track at both cut ends of bridge and decided to use an idea that was showed by Charlie with his swing bridge.  I took one other step and actually soldered some track feeders to the drywall screws.  This way if I ever need to remove the track it can be done with ease.

Soldered track feeders, and drywall screws in place...

​I also had to come up with a wiring solution that would allow power to the bridge/lift out section, and to both ends that would also stop expensive locomotives from meeting a untimely sudden stop, and the end of a short drop.  This was achieved by incorporating a toggle switch into the positive wire feed that feeds the wiring block for this area, this was then extended around the door frame to the other side and feed back into the opposite end and the bridge.

Shot showing the wiring block, toggle switch and wiring for the lift out bridge...

Toggle switch for power to the wiring block, this is the left side of the layout...

And the opposing end on the right side of the layout, here are the two removable connectors that power the bridge section...

I've also done a quick 5 min video of the wiring block, wiring, and toggle switch installation too.

More to come as I hopefully start to do some scenery once the bridge track is down, and the bridge painted and weathered...

Cheers,

Jas...