Thanks a lot for all the suggestions and idears how to get a new bridge in front of the door. I will come back to that topic next year.
Reinhard
some thoughts.
instead of a single piece of plywood, what about a laminated section composed of some thickness of foam, maybe as thin as 1/4", glued between two pieces of 1/4" plywood or luan. Should be very stiff and lightweight (airplane wing construction techique).
where you show a horizontal section of hinge, what about some sort of ledge on both sides that the laminated section can be supported on. The whole section comes out and is simply laid in place.
track alignment is maintained by simply sliding two rail joiners to align/join at each track joint. I don't think a large gap with a rail joiner will cause any problems except noise.
If removable section alignment with the tracks could be reliable, the track joiners would be unnecessary, but I think this is difficult because of humidity.
greg - Philadelphia & Reading / Reading
Reinhard,
Excellent. A picture is so useful.
I expect you want to keep the area below the layout clear. So I would not use the idea that I presented.
It looks like Mike's idea might be the best. I recommend making the bridge on the right about 30" (the height from the floor). That leaves an approximate 10" bridge from the left. The support for the meeting point of the two bridges will slide out from under the layout at the left. It only has to come out 10", and thus can still be nicely supported after it is extended. I think this asymmetry will result in a better (stonger) bridge.
You will have to attend nicely to details on this, of course. There will have to be a bit of slop in the sliding arm and its support, and you will have to design to correct for this.
Ed
The old gate was "up" and had a hinge at the right side only. I do not like it because it interlocks with a cabinet and permits no free access to the layout when in up position. The gate is open most of the time!
This very old photo explains the situation. The new bridge must also hold a curve at the right side.
The "new" gate will have absolutly no scenery. One soft bump per week is ok :-)
"Up" is hard to do and keep track alignment across the joint while keeping the hinges below the track. To go "up," hinges generally have to be on the top side in order that the track ends don't bind together. In other words, your hinge pivot point would need to sit level with the rail top to go "UP."
There are some specialty hinges around that could be both below the track level and let you go up, but they tend to be special order and expensive.
Mike Lehman
Urbana, IL
Something to plan for is the possibility of damaging scenery on the folding sections when they're in the down position. "Up" would stop that.
Your "bridge" section of 1/4" material is actually too light even if there was no meet in the center that needs support.
I would do something a little different, but let's you keep what ypu've sketched. I would build a T-girder (1x3 material would be adequate) that completely spans the 40".
Beneath the hinge on each side fasten a cleat just enough below the bottom of the bridge section to let the upper part of the T-girder to slip in. The lower, web part of the T-girder will need to be slightly shorted to clear the cleat where it sticks out.
Lift the two halves in place, then slide your girder in from the side. You may need to shim the topp of the T-girder for exact location. This should be solid and leave nothing hanging in the way below the T-girder.
Two heavy duty, good quality of this????
https://cdn.mscdirect.com/global/images/ProductImages/4066825-23.jpg
Cheers, the Bear.
"One difference between pessimists and optimists is that while pessimists are more often right, optimists have far more fun."
A single bridge hingeing/hinging from one side only that opened either up or down would be better. But I assume you already know that.
You can do it hinged on both sides, though, if necessary.
I would recommend a vertically placed piece of plywood underneath each flat one. It would also be hinged on the layout. You would lift up your "bridge" and then swing out the plywood support. And drop the bridge back down onto it. It might make sense to have an adjusting screw on the outer end of the lower plywood piece so that you can adjust the lowered height of each bridge to match.
You might also want to add other failsafing and interlocking items to minimize problems.
I agree 1/4" plywood is propable a bad start. I may change that to 1/2" plywood. But the key problem is still unsolved and I do not find an example in the internet with a similar design. I have some idears how it might (or might not?) work but I prefer to see a layout with a similar two part bridge in operation.
I intend to reconnect the two parts of the layout in front of the door with a light weight bridge made of two hatches. The two elements are made of 4" wide of .25" thick plywood and connected via piano hinges to the layout at both sides. They will both hang down, not reaching the floor, if not used.
The problem:
How to connect the two halves in the middle?
Have you done a similar hatch to bridge a door or do you have a reference to a similar solution?
ps. I had in the past a large hatch connected at the right side and folded to the right side when not in use blocking a cabinet and parts of the layout.