Layout Room EntranceWay Bridges

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beiland

Well-Known Member
#21
Challenge & Imagining/Visualizing Finished Product

Its going to be a challenge, but that will make it all worthwhile to make it work.

What I'm having a problem with right now is imagining how to fit the bridges, that are shorter than my 36" wide opening, and their approaching tracks/piers/grounds onto the lifting portion. Its just something about 'visualization'.

I think I need some images/photos to give me some help with ideas. So if anyone has some please post them.
 

beiland

Well-Known Member
#22



New Idea

After looking at that Jacksonville double track bridge I had a new idea. Instead of utilizing the Walther's bascule kits. Perhaps I could make my arrangement out of 3 regular double track truss bridge kits from Walthers, etc

I would use 2 of those kits end-to-end to provide a nice wide river crossing to my entranceway,...and they would already be a relatively narrow double track arrangement. I could go ahead and use this idea in my planning and building of my RR without waiting to modify the bascule bridges.


Then at some later date I could add the superstructure and counterweight of bascule configuration to one of those regular dbl-track bridges. I would use some of the beam arrangements from that 3rd kit I purchased. And I would have to find an appropriated machinery shed to place in the overhead. Counterweight,..no problem, my bascule bridges are NOT going to be operational,..just for show.



I like this idea,...full width river for the shed's entrance, dbl-track spacing in line with what I have already drawn, and no waiting to resolve details/problems with modifying bascule bridge kits.
 

beiland

Well-Known Member
#23
'Parallellogramming',...squareness

I've returned to working on my entrance-way bridging project. I figured since I had my 3 layers of plywood deck temporarily in place, now was the time to try and finalize this design.

I was pleasantly surprised at how 'square' all of my original metal framework was ! I did end up have to lower one side by 1/32" to get the staging deck crossing to line up.

Then I decided to address the parallel rigidity. I had been thinking about this addition of a 'rectangular plywood plate' at the upper regions as posted in this photo and the following 2 submissions,....



The swinging bridge is a very good idea, I never thought of it.
That aluminum is about 1" wide, and naturally I would thing of T-hinges, just like you did. Then I thought, full size door hinges would be more reliable. But how to attach them? OK, without starting over, I would apply 3/4" ply or 1" lumber to both the swinging frame and the shed.
DougL





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 M



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.
Mark P.




So I added my plywood plate

And I added a piano hinge to the affair.... to be continued
 

beiland

Well-Known Member
#24
Piano Hinge?
I have, and still am, debating with myself on the use of that piano hinge on the upper beam. I have no doubts that it is a more 'exact' hinge than many others, and for that reason is the one to be considered in most cases.

But here is my delimma. Should I be depending on that rotation/attachment point way up there to correctly align my crossing tracks down below. Or should I be building the rectangular frame structure as an entity unto itself to align those 3 crossing tracks/bridges, then simply hinge it at the top to move it out of the way, but without be concerns about the hinging point bringing everything else into alignment??

I went ahead and included the piano hinge just in case this was the route I choose in the final decision. It seems as though I am thinking about alternative ideas to accomplished my goals as I go along with the construction of this fixture.
 

beiland

Well-Known Member
#25
As I posted previously I was pleasantly surprised with the 'dimensional fit' of my original mock-up fixture.












BUT, when I went to add the 8” wide plywood deck to the lower staging level crossing, it did not extend out level across the 3 wide tracks,...rather it drooped at the outer edge away from the frame.


At first I was not understanding why, as all my metal framing were exactly square, and the brackets I had used were all double checked for squareness. Turns out it had to do with drilling those holes to mount those 90 degree brackets at the bottom of my swinging fixture.

















I decided I was going to have to redrill those holes in replaced alum frames using a drill press to get really accurate placement,...and substitute 90 degree 'corner brackets'




I got two of those corner brackets out that I had previously purchased for another project. When I got to inspecting them more closely, and with a metal square tool, I found they were NOT exactly square either,...in several directions !!


I was just about to walk out the door yesterday morning to go visit a few stores and see what sort of corner brackets they had. My contractor friend happen to stop by and made the suggestion that I simply use a rectangular piece of my ¾ plywood to assure exact squareness of the bottom portion of the swing up fixture. Why didn't I think of that? I had done that exact thing up top?


No need to go searching for premium brackets, and exact drilling of mounting holes. Here it is pictured in its glued up stage. I'll get better/more-understandable photos tomorrow after the glue sets up.



Meantime I went about experimenting with cutting some of my proposed 'angled wood blocks' that would be utilized to 'locate' the swing structure when lowered into place. I cut these on a 10 degree angle,...then went ahead and glued those bottom ones into place.









Ready for fitting the bottom deck tomorrow.
 

beiland

Well-Known Member
#26
2 steps forward, 1 step back

There are times when my progress appears to follow this pace. Case in point, a few days ago I glued up my new plywood reinforcing panels into my metal frame, and left them sit overnight for the bond to fully develop.


Turns out I used the wrong glue. I used my trusty old TiteBond ll. It may be great on wood, but not on smooth alum metal. It cracked right off. I had to clean all those pieces up, and resort to polyurethane glue. I also decided to speed things up by adding mechanical fastenings concurrently. So I had to do a whole detail measuring project AGAIN.

Here is that frame structure with the lower 'squareness plate' glued and screwed in place. I also purchased a couple of 4” brackets that will support the lower staging deck 'bridge'.






Then here is the staging deck placed onto those brackets










Notice my particular good close fit with the angled butt blocks. The tracks shown in those last photos are just representative as to approx location of the 3 staging crossing tracks. In reality I will eventually lay flex track across that deck and joints, and use a razor saw to cut the angles in place.
Here is that swing-up structure raised up to the ceiling


...and that structure partially the way up,...clearing the tip of the peninsula....





You might have noticed those two 'blobs' on the wall that the frame structure is bolted to …

Turns out I had to some extra sanding of the masonite seams/tape in those 2 areas to get a really flush surface for the structure to sit against while remaining in a straight down/vertical attitude.

Its my intention to utilize 2 sliding rod hasp like this one to 'lock' the lower deck in place. I intend to mount those on the underside of that deck piece at either side. And I am thinking I want to mount them at an angle as I have laid them out there.

I have found that MANY of these type sliding hasp are NOT built to very close tolerances, so I have gone looking for better ones, and/or a way to modify this large one to fit my desires.
 

beiland

Well-Known Member
#27
Next 2 Upper Levels

Once I get this bottom deck very exactly in place, and continuously repeatable, I will begin to work on the two levels above it. I have some curtain rod brackets that appear to be just what I need here.





They will be screwed to the alum uprights. As you might see they have slots for those screws. That will allow for them to be adjusted up-down as needed for any small dimensional changes of the frame structure itself.

As I have hinted at previously each side of these decks will be 'individuals',...that is the decks will not be continuous across the span, but rather blank at their centers. The bridge structures themselves will span this center span.....just like real bridges.












There are two reasons for this choice:
1) having the individual ends independent allows for more 'adjustments' in case of misalignments in the future.
2) more realistic appearance.
 

beiland

Well-Known Member
#28
My intention was to utilize 2 sliding rod hasp like this one to 'lock' the lower deck in place. I intend to mount those on the underside of that deck piece at either side. And I am thinking I want to mount them at an angle as I have laid them out here,...​
I have found that MANY of these type sliding hasp are NOT built to very close tolerances, so I have gone looking for better ones, and/or a way to modify this large one to fit my desires.​




I've decided NOT to utilize those sliding bolt hasp. Number 1, they just have too much 'slop' in their fit.


And number 2, why do I need them? I was clamping some pieces of wood just below my wedge shapes in order to hold the whole structure up in place while I rebolted it to the wall. My thought was why do I need those hasp? The bottom deck fit so nice and fine, and with just enough resistance to hold itself in place. So I just screwed two bottom pieces onto my wedge shapes and left it like that. If I ever find a need for more hasp, etc, I can add them later












 
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