Layout Room EntranceWay Bridges

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beiland

Well-Known Member
#1
I'm building a double deck layout in its own handi-house shed It has a large wide door at the entrance that needs a couple of 'entrance bridges' that can be moved aside relatively quickly. Because of the large width of the opening I am thinking it should be a 'split bridge' type like the bascule type where both of the two sides would swing up.

And it likely needs 3 bridges to carry 3 levels of tracks across the opening,...staging tracks, main level tracks, upper level tracks. Actually the span only needs to be 36" as that will be the width between the side decks at this entrance, even though the shed's door is 42"



Here are a couple of photos of my train shed doorway, (disregard the former cardboard shelf mock ups,...things have changed)









 

beiland

Well-Known Member
#2
This was one of my original thoughts after discarding a 'twin tower, lifting span' idea


Here with just two of those alum extrusions (uncut in length) strung across it at the two levels











The extrusions I happen to have collected,...








perhaps side by side...
 

beiland

Well-Known Member
#3
Subsequent Thoughts


Construct a light weight, rigid, rectangular metal frame that would be as wide as the entrance opening I intend to have (36"?), and tall enough to have all 3 track levels (staging, bottom deck, top deck) attached to it,...plus extra height to go above the shed's door to reach a horizontal hinging location above the door.


In other words the top horizontal leg of that metal rectangle would form the rotation axis about which the 'frame' would rotate upwards (swing upwards) towards the ceiling. Then it would be only necessary that the width of the bridge structures, etc be limited by the clearance to the top of the ceiling when the frame is swung upwards into it's raised position.


These 'bridges' could be of many different types / styles, and not to limited to their scale heights. They would be attached to the metal lifting frame via their sides facing the frame, leaving their opposite sides facing the room. Only the bridge structures themselves would appear to cross the space between the open spaced metal frame


The inside of the shed's door would be painted as a body (river or bay) of water, and would act as the backdrop for the bridges when it was closed. When the door was left open there would be hollow spaces between the bridge structures that a person could view thru to the inside of the shed.


The bridge might simple be a trestle across the water with multiple legs that don't actually touch on any base, but appear to do so as a result of the water backdrop?? .....somehow melt the bridge structure itself (minimized) into a backdrop painting on the inside face of the shed's door. .....


PS: I had originally thought of making that 'rectangular frame' a solid piece of plywood with the backdrop painted on to itself. But that would mean that even with the shed's door open, no one could see inside. So that's when I began to think of a 'hollow core' to that framework.
 

beiland

Well-Known Member
#4
Crude Mock Up


Here is just a rough mock-up of flat panel that would hang from the front wall by some sort of piano hinge (blue tape). It would swing up to the ceiling like shown below. It would also be a 'hollow frame structure' rather than a solid board,..to allow for vision in and out when the door to the shed is swung open.




















And yes in an emergency I could scoot out under it.
 

beiland

Well-Known Member
#5
Yes I could duck under the 60" high tracks, but then what do I do about the two other levels at 40" & 32"?


I entertained quite a number of ideas in the beginning,...like vertical lift bridge, etc








Now that you mentioned it, a vertical lift bridge just might be easier to construct for the entrance......no worries about locating pivot points so accurately for track alignment and support in the middle of two side sections, etc I like that idea.



I could stack one on top of the other for my double deck trackage, and sort of hide (disguise) the connection between the two layers. Have to see if I have room under the ceiling height.
I'm looking to make it simple (KISS principle), so NO mechanization,...just a nice smooth raise or lower by hand for multiple entries
 

beiland

Well-Known Member
#6
I think I have come up with a real simple way to get all 3 bridges out of the way rather quickly. I'm going to work on that today.

I use that shed door SO OFTEN that I wanted it to be as 'easy as opening a door'. Thats why the swing up idea appealed to me,...just swing all 3 bridges up to the ceiling in one easy operation, then back down for all 3 track levels.


AND I was hoping that my choices of bridge styles for the two main levels would NOT be dependant on the overall idea. In other words I might be able to have any variety of bridge styles on either of those 2 upper levels


I actually am currently entertaining the idea of a double track bascule bridge for the lower level. BUT there is not one on the market. So I'm considering putting two Walthers ones side by side like this.



In this situation those bascule bridges would NOT have to actually operate,...just sit there creating that image.
 

beiland

Well-Known Member
#7
I'm going to utilize this very stiff, thick sidewall, 3/4 alum beams to make my 'rectangular frame' I spoke of above. Basically all I need to use to make the this frame 'in-square' and strong enough are a number of stiff metal corner brackets. Here are a few pics of the materials,...











Here are 3 decks, staging at bottom (3 tracks wide), main deck (2 tracks wide), top level (2 tracks wide). This is just an initial mock-up with foamboard pieces inserted to show how decks might be laid.














Likely the bottom staging deck crossing will be a piece of the 3/4" plywood I am using for the decks all around the room. The crossings at two upper levels may be just the bridge structure themselves?
 

beiland

Well-Known Member
#8
Initial Metal Frame for Bridges across Entrance





Here is my initial stage development of the metal frame that will support the 3 bridging tracks across the entrance to my train shed....


basic frame hinged down






basic frame hinged up to ceiling






mock-up with one bridge for upper level track, and 3 staging level tracks at bottom






ceiling hanging






'see-thru' feature of this concept



Sorry for photo contrast due to very bright outdoor lighting verses structure itself. But basic idea that the trains can run across these bridges while the shed door is open to outdoor breeze and light, and layout can also be viewed from outside the shed while trains are running.


With the shed door closed, a backdrop painted/attached to its surface will provide a watery scene the bridges are traversing.
 

santafewillie

Well-Known Member
#9
Novel concept. My only concern would be how far back the center "blob", mainly on the uppermost deck, will have to be in order for the frame to clear when operating. If it were my layout, I would leave out the staging level crossover, make the lower operating level removable, and make the upper level one stationary. At 60", it would be a simple matter to duck under and there probably isn't any layout materials that large once the the interior decks are in place.
 

beiland

Well-Known Member
#10
Forgot to photo this image yesterday






Turns out those hinges at the top are plenty strong to hold the frame structure, but they are too slender to resist the bending that will result with long term usage and heavier weights that will be added to the structure. So I will likely add another crosspiece up top just under the one mounted to the wall, and that will also allow for 3-4 hinges to be utilized across that upper bar.
 
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beiland

Well-Known Member
#11
Potential Hinge Modification


Turns out those hinges at the top are plenty strong to hold the frame structure, but they are too slender to resist the bending that will result with long term usage and heavier weights that will be added to the structure. So I will likely add another crosspiece up top just under the one mounted to the wall, and that will also allow for 3-4 hinges to be utilized across that upper bar


Just to follow up on that observation about the hinges, here are a couple of photos that depict that weakness i spoke of correcting. Actually it not presently as bad as it looks,...more of an optical illusion due to the overlapping feature of the tapered arm of those hinges.












So I will likely add another cross piece to the rectangular frame at the upper location, and it will be tied in via those corner braces as I did down at the bottom (just a short representative piece taped in place here). That will give me another whole cross piece to mount several more rectangular hinges to,...so then at least 4 hinges up there.






 

KB02

Well-Known Member
#12
Can you reach whatever latch you have on the door with the bridges down? That would be my only question. Even with the fans, it might get hot in there in the summer and you might want the door open.
 

bnsf971

AKA Gomez Addams
Staff member
#13
Brian, now that you've gone to all the trouble of doing this, why not make the "bridges" on tracks, like a roll-up garage door? It would take up less space than the swinging gate.
 

beiland

Well-Known Member
#14
Can you reach whatever latch you have on the door with the bridges down? That would be my only question. Even with the fans, it might get hot in there in the summer and you might want the door open.
I'm going to change out the 'stock' door latch to another arrangement that is both more secure, and easier to reach from inside with the structure down for running trains.
 

beiland

Well-Known Member
#15
Brian, now that you've gone to all the trouble of doing this, why not make the "bridges" on tracks, like a roll-up garage door? It would take up less space than the swinging gate.
I think that might have been even more 'involved' than the structure I have now, and the curved metal tracks for the roll up door mechanism might have more difficult to place out of the straight line of the crossing tracks.
 

beiland

Well-Known Member
#16
Alignments

That's a neat concept no doubt. But I'm worrying about how the cut ends of the rails on the bridges will have to pass sideways across the cut ends ends of the rails of the fixed tracks as the bridges arcs down. It'll be almost horizontal movement close to the end of the arc.


Depending on the radius of the bridge frame arc, would the rear bridge track ends have to pass across the ends of two or three sets of the fixed track ends? Maybe there's more room for error than with a vertical movement of each single bridge rail against its fixed mate one gets with a lift-up, drop-down or lift out section?


As well as beefed-up hinges, maybe you'd need to add some diagonal bracing to the frame to stop it from "parallellogramming" on the way down and letting the bridge tracks bump into the fixed tracks?


Pete the worrier.

Being a structural engineer, I can tell you that the corner braces you're using will most likely allow the swing gate to rack much too far left and right. In short, they probably don't make the structure stiff enough in the lateral direction.
You can easily improve the lateral stiffness by at least an order of magnitude by simply adding small triangular (say three inches or a bit more on the sides bordering the 90 degree angle) gussets at each corner of the frame. Welding them in place would be best, but self-tapping screws would probably work well enough. I would avoid bolts for that, since the clearance holes would still allow some lateral movement.

Lets see if I can tackle both problems that have been brought up here recently.


My plan to address both,...
a) any 'racking / parallellogramming' of the rectangular frame, and
b) the cut ends of the rails on the bridges having to pass sideways across the cut ends ends of the rails of the fixed tracks,...is to employ a wedge shape phenomena.

Both ends of that plywood piece that bridges the staging level will be cut at a narrow angle across their width, and in such a manner that the edge facing the shed's door will be shorter than their opposite edge that faces the interior of the shed. Those angled ends will mate up exactly with wedge pieces added to the plywood deck/shelves on either side of the entrance opening.


When the framed structure is lowered into position the matting wedges will force exact alignment horizontally regardless of any racking, and the angled faces will prevent any of the rails passing directly perpendicular to one another.

At both ends of the plywood bridge, a bolt action fastener placed on the bottom surface of the plywood, and matting up with its reciprocal on the deck plywood,... will ensure firm fore-aft placement, and height alignment.

Need a little sketch?
 
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beiland

Well-Known Member
#18
Didn't have enough height for the top bridge, then what would I do about the lower ones?

And I did not want to have to operate 3 independent bridges each time i wanted to run in and out.

I wanted a 'single entity' that could operate as easy as opening a door.

And I wanted to be able to have a variety of bridges to display.

I think I have accomplished this with this design,...just needs a little tweaking during the finishing steps. Those steps will not be completed until the track is laid across the 3 bridges, then cut at the appropriate places.
 



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