Help with custom hinge question

I have posted some pictures in the dropbox under HingeX.jpg. Here is my problem. I live on a lake with a high bluff. A couple of years ago, I had
custom stairs made that are hinged on one end and raise and lower on a winch down to beach level. With the recent winds, these hinges have broken. For reference, the stairs are about 32 feet long and drop down about twenty feet. I estimate that they weigh about 800 lbs but dut to the angle of lift on the winch, the force to lift them is probably double that. This does cause inward pressure on the hinges where they attach to the platform and this is probably the only thing that kept the steps from falling twenty feet to the beach when the hinges fractured.
It would appear that the hinges are nothing more than 1 inch .12 thick aluminum tubing welded to the steps and the platform above. The company that made the stairs has apparently changed hands and has no interest in helping me. They are also apparently not setup to weld aluminum portably. The welds held, it was the tube that fractured as you can hopefully see in the pictures. My questions are:
1. Do you think this could be fixed by rewelding on new tubes and could this be done portably in the winter time. What kind of aluminum would be best to use to weld and for strength. Am I likely to find anyone who would do this.
2. Since the hinges failed, would I be better off making bolt on hinges out of stainless steel instead? I would suspect these could be made out of SS tube welded to a plate which is then bolted to the aluminum stairs with a SS pin. Do you think this would be stronger? Would corrosion be a problem putting SS on aluminum? What kind of SS would I use for this?
As you can imagine, the problem is compounded by the hinges being broken which does not allow me to freely raise or lower the stairs but I do think I can safely get them down for repair. At this point, I'm thinking it might be best to try to secure them for the winter and fix it in the spring. I have been reading this group for a while and several of you have answered previous questions. I actually have recently bought an oxy-acet welder and want to learn but don't believe this project would be for a beginner given that strong welds would be necessary and I wouldn't chance that to a beginner.
Any input on my problem would be appreciated.
Thanks
Barry
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.
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Possibly. Depends on where you are. 6061 would be almost Hobson's choice as it is weldable and universally available.

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SS
Saltwater boats mix SS 303/304 or 316 with aluminum frequently, with pretty good success. It's better to isolate the two, but, for example, we often use 303/304 machine screws into aluminum masts with only paste compound between.
SS is, of course, stronger, size for size.

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It is possible to oxy-acetylene weld aluminum (but not Stainless), but it's not easy as, unlike steel, aluminum gives you no clues that it's about to melt. Not a beginner's project. These days most welders use MIG or TIG for aluminum. MIG is easier than gas welding, but this welding is not a beginner's project.
You could, of course, buy new hinges from www.mcmaster.com for a price and bolt them on.
--
Jim Woodward
www.mvFintry.com
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On Fri, 14 Nov 2003 10:41:31 -0500, "Jim Woodward" <jameslwoodward at attbi dot com> wrote:

You can gas weld stainless steel. In fact it welds easier than mild steel if you have a good fit-up. There are SS fluxes available to help reduce the oxidation, and as there is no argon shield layer, the welds tend to be a bit crustier. They pickle ok though. I used to do it a bit before I got my tig - mufflers and exhaust systems mainly Geoff
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Hey man, you need help! You need to find a welder with a portable MIG unit to weld that thing back up. As for the pipe, I would get some extra-heavy wall aluminum pipe and weld it back up. If you use dissimilar metals you will get galvanic corrosion bigtime.
If you are in an emergency situation you can cobble something up with drilled plate and bolts, but I'd try to fix it properly in the spring.
P.S. You will get a lot better response if you post the entire URL e.g.:
http://www.metalworking.com/dropbox/Hinges1.JPG
http://www.metalworking.com/dropbox/Hinges2.JPG
http://www.metalworking.com/dropbox/Hinges3.JPG
It's also often helpful to post your location. If you lived around here you'd get Ernie to help you out.
Grant Erwin Kirkland, Washington
BP wrote:

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Looking at your photos, I would say that the hinge design is inexcusable. You have two strong beams running down the sides to support the treads. The treads are not required to be of such heavy-gauge material. The hinges now attach to the treads, and this is a recipe for failure. Abandon that design!
Since this is going to be exposed to weather, corrosion, side loads and who knows what other abuse, you should think about VERY robust hinges. Personal safety is an issue! Think about something which will not fail catatrophically, as it looks like your present design might have. (Think about being three steps down, carrying a cooler full of beverages when those wimpy hinges let go.) Your stairs are nice and obviously cost a pretty penny. Don't gamble it all on hinges which could send the whole stair down the cliff in a tangled wad of meat and metal.
My first "go" would be to bolt heavy plates, say 3/8 inch thick, two feet long, and as wide as will fit between the flanges on the stair beams. Matching plates to be bolted to top landing frame to overlap the stair plates. Ordinary salvage-yard steel would do just fine if you use standard corrosion control to prevent rust and galvanic action between aluminum and steel. Hinges to be LARGE pins (one inch steel) through matching holes in the plates. Do the job now, while the stair is held in place so that after you bolt on the plates, you can drill straight through both pairs of plates for the hinge pins. No chance of misalignment. No chance to damage the stair (or yourself) in the process of taking the stair down.
To minimize damage by winds in the future, provide a support for the free end when the stair is in the "up" position.
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Sounds like a heavy duty solution which I like. I'm not sure how I would bend such thick plated into an eye hook configuration to accept the pins or am I misunderstanding what you are saying? Any clarification would be greatly appreciated. Need all the help I can get.
Thanks
Barry

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I think he's telling you to bolt on plates *edge up*, parallel to the stair runners, and extending out past the ends of the runners. Matching plates are bolted to the landing, also extending out past the landing. The two sets of plates overlap, holes are drilled through the overlapping plates, and a large hinge pin is inserted.
Gary
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Just because the company has changed hands does not mean that they do not have liability for the design. manufacture, and instsallation of them. I have not looked at the pic's. But as has been said the hinges seem to be of poor design. I would go back to them and point this out to them. Might even have an attorney write them a letter. Once you start working on them you assume the liability.
Good luck
Chuck
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Pilgrim wrote:

Yup. Spend $10,000 on a lawyer instead of $20 to fix it.
Ted
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\ Inexcusable design. Now understand that I am not an engineer, however those hinges are way too small for such a structure. Just my 2 cents worth. How about a much beefier "piano hinge". It would distribute the loads better.
Lane
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I am going with Lane. A Stainless Steel 316L piano hinge would do better than aluminum. That is to much weight on those little aluminum hinges.
Glenn Houston, TX
On Fri, 14 Nov 2003 10:17:39 -0800, "lane"

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And don't forget to claim this loss on your homeowner's insurance. - GWE
m5bmw wrote:

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Ironically, I was trained as an engineer but have not worked as one for twenty years. When I first saw the hinge design I was amazed as I also thougt it was flimsy. Figured though this is what they do so they must know. I like the piano style hinge Idea and will look into this.
Thanks
Barry

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Thanks for all of the good ideas. I kind of like the idea of a bolt on steel piano hinge. Unfortunately getting that installed in this weather will be tough but doable. I see McMaster has SS Hinge that has .25 thick leaf and a 5/8 inch pin. It is not cheap but if it does the job that would be OK. Do you think this would be heavy duty enough? I estimate that the current homemade aluminum hinge has a pin of about 3/4 inch diameter. The other option would to use a regular steel hinge and try to isolate it from the aluminum . Not sure how I would do this but it would be less expensive to try and if it worked well could then splurge for SS one. How would you isolate it from a corrosion standpoint. I know this is probably common knowledge so I apologize for asking but whish one would corrode, the aluminum or steel? I assume you would do the bolting with SS bolts even if you used a regular steel hinge.
Thanks
Barry

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SS against aluminum is not that good an idea unless yuu "Isolate" the parts. Each bolt hole must be drill oversize and a plastic bushing installed. Under the bolt heads and nust you must use plastic washers. If you don't the aluminum will corrode to white powder on each contact surface. My choice would be to have a hinged assembly made up out of aluminum with stainless hinge bolts properly bushed. The item could be made up in a fab shop then bolted to your stairs and landing using stainless bolts appropriately isolated. Fabricating and welding is costly and slow when done on site. I hestitate to suggest a piano hinge because the leaf of the hing is not really heavy enough and long enough to transfer the load a foot or two into the stair stringer. A piano hinge is ideal when the load is vertical and the hinge pin is vertical such as in a conventional door but the hinge is not designed for carrying the ramp load at right angle to the hinge pin. Randy

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On Fri, 14 Nov 2003 16:48:09 -0500, someone who calls themselves "BP"

I went and looked at
http://www.metalworking.com/DropBox/Hinge18.JPG
and I wouldn't go with a piano style hinge like the "professional" <sic> fabricator that built the stairs used the first time, there is way too much weight, dynamic loads and lateral loads for that pipe sleeve they used.
You have the weight of the stairs, lateral loads from wind when it's up and surf when it's down, lateral loads from the hoist mechanism (since it doesn't look to be at the balance point), and it all has to be safe to hold up the dynamic forces of a few thousand pounds of people running and jumping up and down on it.
If you have a dozen kids all bounding up or down the stairs at once, they don't walk down stairs sedately. "Last one in is a rotten egg!" will get them to skip every fourth step, and the stairs will be bouncing for five minutes.
I was going to do some ASCII Art to show what I was thinking, but that wouldn't work. Look in the dropbox for hingeidea1.bmp done in MS Paint - came out rather nice for something drawn with a touchpad mouse IMNSHO.
I would go BIG with the rebuild - weld 1/2" or 3/4" sheet aluminum plate on the inner and outer flanges of the stair stringers with a heavy wall (3/4" wall at least - think gun-drilled bar stock) pivot tube welded inside extending through to each side. And weld it everywhere you can - weld the sleeve in place to the C-channel stair stringer first, then weld on the fishplates, then weld the fishplates to the sleeves. Get the TIG gun inside the channel and weld the sleeve to the backside of the outer fishplate. You want to make the ends of the stringers one big structurally monolithic block.
For the fixed side of the hinge, make a matching set of thick blades on a big plate bolted both to the wood support structure below and the aluminum deck above. Gusset the outer blades so they can't bend, the inner blade gussets can't be too large or someone will trip on them. You could even use two more pieces of your hinge sleeve on each fixed leaf to make it more bombproof.
And some beefy bolts as hinge pins - 1" x roughly 8" stainless bolts, with Nylock nuts (or castellated nuts and SS cotter pins) riding in Teflon sleeves and washers for galvanic isolation.
How close can you get a portable welder's truck or trailer to the stairs? This is going to take a beefy TIG rig or a big MIG with a spool gun to do structural work on aluminum.
(Disclaimer: I AM NOT A LAWYER, CERTIFIED WELDER, OR STRUCTURAL ENGINEER. I'm just a home hack welder that can do passable work in MIG and gas - but I'm also a professional maintenance electrician that knows when public safety is involved and it isn't your specialty, you can patch it back together temporarily and call another pro. In your case, you go to a structural engineer to whip up plans from your ideas for a solution, and a certified structural welder to do the work.)
--<< Bruce >>--
--
Bruce L. Bergman, POB 394, Woodland Hills CA 91365, USA
Electrician, Westend Electric (#726700) Agoura, CA
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Very nice - thanks. This may be the answer. I could make a very firm attachment to the platform by utilizing the the wood you noted below which is actually bolted to a 10 inch I-Beam. I could actually go all the way through to the I-beam. One of my concerns has been how solid would the attachment to the platform be as it is just a 3 inch aluminum C-Channel. ( Though this is the only thing the upper hinge is attached to now). The wood actually forms a platform that I lift a Zodiac inflatable boat onto using the davit lift in the pictures. The lake can get quite rough so you have to be able to get it out if the storms kick up.
This would be a large project that I am not likely to get done before the bad weather hits. My main goal now is to get the steps secured for the winter. Today I attached an additional sfaety cable on the outboard end to support it. I will also likely run vertical cables this year from the winch support directly down to the inboard side of the steps for vertical support. I have not done this in the past but if the hinges were to go and allow vertical collapse, it would be a disaster unless the inboard end has some type of support which now is really only the hinges.
Surprisingly, the steps today show no signs of vertical instability at the hinge ( not that I believe they're safe) when I raised and lowered them. This is probably due to the horizontal force component of force when being lifted due to the angle of the winch cable. I may think about running some cables diagonally from the deck to the outboard part of the stairs for lateral stability in the winds over the winter. I have thought of this in the past but before the hinges went, the lateral movement was minimal. However, it is now a different story. The other day in the winds, the hinge to the lakeside was actually separating from the platform by upwards of two inches as the stairs swayed. This makes me believe that the hinge failed due to fatigue. Even with the two inches of separation, there was no tendency in the winds for that side of the steps to drop relative to the platform. I'm not sure I can explain this except for the direction of the winch cable pull which is up and has a significant component of horizontal force pulling the steps toward the platform.
Tomorrow, I will go out and take some measurements after I take a better look at your diagram and see if there are any obstacles to this idea but I can think of none. Thanks.
Thanks
Barry
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Hey Barry,
I wouldn't really want to walk out on that as it appears now, but a picture showing the hinge area from the stairs would help. Also, a shot from a bit further back showing the whole arrangement, hoist and all. And I'd immediately get some sort of blocking (2 X 4's??) to raise the "safety chains" up so that if the hinges do finally fail catastrophically, the unit won't "fall" 4 inches or so onto the railing bottom stringer. Make it so the chains are already "snug" and "lifting-rather-than-pulling" so to speak. A couple of el-cheapo wire rope come-a-longs or web belt ratchets would provide that "snugness" better than chains, or put bear-claws on the chains.
Anyway, that hinge mount is the cheapest easiest way they could do it. Much better and stronger would be an outboard pivot bearing mounted to each side on the stair stringer channels. You'd want to be well and safely secured, but bolting through the sides would negate having to weld. Even a strap there temporarily would help.
I suspect that this damage was caused by the twisting that a high wind causes, like the a Stop sign flutters, only horizontally rather than vertically. So, the further outboard the hinge point can be made, the better.
As this appears to be mounted parallel to the shore, is there any way to provide a brace from the top of the embankment to the water's end of the stair case while it's in the raised position? Might help in the future.
Looks like you have a nice view. There is shoreline similar on both Lake Huron, south of Grand Bend, and along parts of Lake Erie, and Lake Ontario at the Scarborough Bluffs. Whereabouts are you located?
Take care. For sure!! And good luck.
Brian Lawson, Bothwell, Ontario. XXXXXXXXXXXXXXXXXXXXXXXX

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I'll try to take some additional pictures today and post them. The place is lake Erie just outside of Erie Pennsylvania. I agree the damage was likely due to side to side twisting. I never apreciated how much the hinges were resisting this movement. Before they broke, the side to side movement at the far part of the steps from the hinges even in wind when the steps were raised was really minimal. Now that the hinges are gone, the movement is significant Probably at least a foot. . I hope to attach some additional safety chains today and see what I can do with blocking it up.
Thanks
Barry
wrote:

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The hinge is inadequate. Once you arrive at a new design consider adding a few padeyes and safety chains should the hinge fail again. You don't want a QM2 type failure
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