Another crazy idea... looking for curved aluminum, stainless, or steel/iron

You guys helped me figure out a really strange request for an extruded aluminum profile for my roof rack (bathroom stall headrail), so let's take another shot.  Photo for example:

Mom wants one of these to go over a little stream on their property.  She isn't finding what she wants so she asked me if I could fabricate it.  She found all steel or all wood, and she wants a steel frame with a wood deck.

So I'm looking for some kind of arched metal as a source for the basis of the curved deck.  My first thought was the bent steel frame of one of those old-school C-band satellite dishes, but they just don't exist much anymore.  What else can you think of that might have curved metal in it that I could scavenge for a walking bridge.  The bridge will be about 6-8' long and only needs to be about 2-3' wide.  I can weld steel and stainless, but not aluminum

Nothing coming to mind for scavenge right now, but pie cutting a bunch of tube would do it.

Not really pie cutting, though.  One cut through 80% of the tube, every 2 inches or so, put tension on it and then start tacking.

In reply to Mr_Asa :

I like that.  Make a quick plywood jig and just cut kerfs in the bottom face and sides.  Bend, weld, done.  Cut it every 6" so I leave a flat surface to screw down deck boards.

If it's only for pedestrians, this should suffice and be easy to find for free. It come in sections, but you can weld them and they usually have some nice galvanizing for something over water.

In reply to fanfoy :

Love that idea.

Yeah, I'd honestly just slip a couple coffees to the dump attendants and suft their metal bin.  Destoryed trampolines and tubing abound there! 

In reply to Curtis73 (Forum Supporter) :

Here you go Curtis. One 20' piece of 2 x 3 x 0.120" 11 gauge rectangular tubing cut in half to 10'-0" spaced 4 feet wide with 2x6 deck boards. The board gaps are too wide, I would space them 1/8" using a 16d box nail and they will shrink to a 1/4" gap. I can modify it but I did this to keep the dimensions simple for a proof of concept first attempt. 

10 degrees included angle is just right (above), 15 degrees is too steep for the first and last segment of the bridge (below).

I have a roller that can do 1.5" & 1.75" round tubing and 1" square tubing. Likely too small for what you need, but an option for you. You know where I'm at and it's a bit of a drive unfortunately. What about a flat bar for the top rail? I built this set of railings for my neighbor, but a curved rail wouldn't be hard at all. 

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A walk through the local scrap yard might yield a find that could work. Every few weeks I head to the local scrap yard for a stroll.

Shame you're quite a ways away, I'd roll up some material for you.

I also see that you're a TD. I might even have some rolled steel you could use that was formerly a fly bar for a moderately-sized theatrical line array, but A) it's huge and B) it's heavy (2" x 3" x 1/4", I believe). 

Here is what I came up with for railing and tie down steel axle stakes or screw in trailer house anchors. If only you could find some pieces of old corrugated round grain bin panels.

If you'll be screwing boards to steel, use angle steel not square shapes so it doesn't get filled with water and rust. 

In reply to OHSCrifle :

Where can you buy cold roll formed U channel that has a uniform thickness that would be bendable like tubing with a uniform thickness? I don't see how C channel with its tapered top and bottom flanges would work with out completely cutting out each piece and then welding them up (which might be easier just using a metal chop saw instead of using a side grinder to cut out all those notches). I was thinking that the tube ends would have to be left open for drainage. Can tubes be powder coated on the inside? How tall of a piece will fit into Curtis' bake oven? We should make it all modular to fit in the booth.

How about not making it arched and put two or three 7" steps or two ramps up to a gang plank crossing the creek? And use regular C channel.

lotusseven7 (Forum Supporter) said:

A walk through the local scrap yard might yield a find that could work. Every few weeks I head to the local scrap yard for a stroll.

I need to find one around here.  The only one I know of is a certified scrap recycler.  By law, once it enters their facility, it is considered hazardous waste and can't leave for consumer use.  Only way it can leave is shredded on a truck.  There used to be one in Indiana, PA that was brilliant.  Massive football-field sized piles sorted by type.  I used to go in there and get stainless for 13 cents a pound.  Ah, the good old days.  Unfortunately it was deemed an eyesore and the town made them so unwelcome that they had to shut down.

In reply to VolvoHeretic :

Steps came to mind, but I think part of why mom wants this is because she's 77 and just bought her first electric wheelchair.  She only uses it for big days out at like the fair, or museums.  She's just not walking quite as well as she used to.  She wants to be able to visit her best friend next door, and I think this bridge is a veiled way of saying she's starting to lose confidence in straddling the creek to get there.

In reply to VolvoHeretic :

And THANK YOU for the schematics.  Very helpful.

VolvoHeretic said:

In reply to OHSCrifle :

 Can tubes be powder coated on the inside? How tall of a piece will fit into Curtis' bake oven? We should make it all modular to fit in the booth.

The booth can pretty easily do 6' sections, and in truth this bridge could be only 6' long.  The creek in question is a drainage trickle from a spring.  This is more to get over the muddy part around that drainage.  During a big storm, the "creek" might be 8" wide.

So I could do it with arches that bolt together in the middle.  Make a couple sorta trusses to tie it all together.

I can't powdercoat inside tubing.  There might be a special attachment for the gun to do it, but I don't have it.  I've been looking for stainless tubing/channel/pipe on FBM because it would be easy to pick up a spool of stainless MIG wire, but haven't found any suitable yet.

I think I also have mom talked into using composite deck boards.  Aside from an occasional pressure washing (which she loves as much as I do), no upkeep, and it will last for a very long time.

You are welcome.

Curtis73 (Forum Supporter) said:

I think I also have mom talked into using composite deck boards.  Aside from an occasional pressure washing (which she loves as much as I do), no upkeep, and it will last for a very long time.

Composite boards aren't as strong as 2x6s so you will have to have an intermediate arch in the middle. I think the bridge needs to be at least 4' wide and I'm not sure composite will even span 24" whereas I'm sure treated 2x6 will span 48". You will also have to have a bottom rail on top of the decking to prevent the wheel chair wheels from running off of the edge of the bridge.

Depending on how much height you want under the bridge, it might have to be pretty long to keep the slope to code which was 1:12 but might be changing as I had to design a HUD wheelchair ramp at 1:18 several years ago. Granted, you can build anything you want, It's just that I can't draw anything that isn't up to codes that I know of and nothing I draw on this forum has been engineered or stamped. 

I used composite decking on my deck and it was limited to 16" span. Check whatever type you decide on to see what's recommended. Also, my decking has split wherever there is an exposed screw head on a top surface. Water sits and freezes in there. The main deck has short screws inserted from the underside through a thin flange of galvanized steel. It's fine after more than 15 years.

You're both right.  I would have to do no more than 16" span.  The plan was to do a 32" bridge with three arches.  I could likely stretch that to 18" spacing and 36" wide and no one would die.

In reply to VolvoHeretic :

Yeah, she's not concerned about code.  They live in the middle of nowhere and this is for her convenience, not an actual solution to a handicap problem... yet.  I just want to be sure that it's future-proof for when she actually needs the wheelchair.  Let's just say, I'd like to give her the option.

So, I tried to come up with modular handrails out of 1.5" 11 gauge square tubing joined together with screw on tab connectors. The deck is made from 4" C channel and is held together with angle iron. I wonder if the included angles should be reduced to 5 and 10 degrees or maybe 7.5 and 15 degrees instead of 10 and 20 degrees.

The deck could also be made entirely with angle iron. I am just guessing on the material size of the structural members and it should be checked by someone who knows more than I. 

The hand railing would use SS self drilling 1/4" screws.

The deck sections lengths need to be recalculated for the use of composite decking since they won't shrink and the spacing would be preset at 1/4".

Those drawings speak my language.  Amazing.