Self locking folding hinge


Have been asked for advice on making a folding wooden walking stick for a large heavy man. So its got to be something a bit stronger than usual. Was thinking of something like using 2 inches (5cm) by 3/4 inche (2cm) in cross section size.
I searched and read the preferred wood for making aircraft is Douglas Fir, so i thought that would be good for this stick. (good strength to weight ratio) but I guess that is difficult to buy already cut to size here in London. U.K.? Would some kind of building grade plywood be stronger, I wonder?
The tricky part would be some *self-locking* hinge. Does such a hinge now exist? I remember very many years ago seeing such a thing (I think on something agricultural). Would be grateful if anyone had advice on this. Thanks.
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I don't know of anything that would work - doesn't mean there isn't one, just that a walking stick presents a lot of problems. Not much cross sectional area, round and not square, could be subject to fairly high stress and if it fails there's a _huge_ problem.
What about modeling your cane after one of the folding canes already on the market? The typical ones have nesting aluminum sections that are held together by an elastic cord.
The two most likely approaches: - wrap wood veneers around a store bought cane and then gussy it up - start with metal tube sections and cut solid wood to fit the tubes. Cut a piece of wood in half, use a core box bit to hollow out the two sections, then epoxy the two pieces back together around the tube and turn it on a lathe.
Either way, inlays and metal banding would dress it up and strengthen the connection points.
R
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How about hinging with a regular hinge and fitting a sliding metal collar to prevent lateral movement of the joint. When the user wants to collapse the stick they slide up the collar and use the hinge to fold it. When they use the stick, the open it out and let the collar slide over the joint (obviously with a stop to prevent it sliding all the way down the stick). A more tricky question might be what you do about the handle as this would take a great deal of stress if jointed to the stick.
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The problem with sliding latches and locks is that they leave room for human error. A walking stick that is not fully locked is very dangerous. Very. Lawsuit and broken bones dangerous. The bungee cord (shock cord to some of you folks) solution keeps the pieces under constant tension, is very quick to assemble and disassemble, and it is immediately obvious if the sections aren't fully locked in place.
There's a big risk in such a project, and a very large downside. I don't know that this is the time to be reinventing the wheel. Then again, maybe it is - just make sure the thing is foolproof, not susceptible to wear, and way stronger than needed.
R
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Whilst true, if done correctly, the user would pick the stick up by the handle, it would automatically unfold on the hinges enabling the collars to slide down the stick into position.
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If the collars could slide freely, there would be play, play leads to wear. Downward spiral. A sliding collar lock is doable, but there'd have to be a way to lock it in place and it couldn't more too freely.
This is one of those threads that I really hope that the OP posts an update with his solution. I'm very interested.
R
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Why make one?
I use a Leki 'Wanderfreund' walking stick (cane). They are a 'get up and go' cane. They are collapsable and have several cool attachments available. At least take a look.
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john hamilton wrote:

When you say, "walking stick" do you mean a cane (30-36" or so long) or a longer staff?
If the former, 2" x 3/4" is overkill. I make my own cane shafts (round) taper from 1" to 3/4". Each end is further reduced to accomodate a brass ferrule (cut from brass water pipe nipples) between 1" and 1/2" long.
I wouldn't suggest Douglas fir as a wood, better to use a hardwood; I use hickory, do not know what you have there but would think oak would be fine.
Regarding the hinge, why do you/he want it to fold? Would two or more independent sections work? If so, hanger bolts work. Those are a fastening with bolt threads on one end, screw threads on the other; the bolt end is epoxied into a hole in one part of the shaft, the screw end is screwed into a hole in the other. A 3/8" diameter one would be sufficient. They can also be used to attach the handles but I just use 5/8" threads in the wood itself.
As to actual hinges, I know of nothing ready made but both Ricodjour's and Nowell's suggestions could be made to work. So could ferrules attached to each section with ears welded or silver soldered to each...ears on one side with a pin so the sections pivot, ears on the other side with a thumb screw or removeable pin to lock/unlock the sections. Any way, you'd probably need a way to keep the folded sections together so they don't flop around.
--

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On Fri, 20 Aug 2010 13:49:36 +0100, "john hamilton"

Is this a walking stick as in a stick to help balance, test foot-holds, and throw snakes out of the way while hiking--- or to help a disabled person navigate his house and sidewalks?
If the latter- then talk to his physical therapist & do what they say-- which will probably be 'buy a proper device'.
If the former-- then you need to decide whether strength, weight, or foldability is the most important feature.

Doug fir would make a heavy, [compared to nearly any commercially available stick] weak stick that would be difficult to hinge-- but you could join two pieces with a ferrule.
I think in the UK, Yew would be much stronger but a bit heavier.

I have a longbow that comes apart at the handle- joined by a metal ferrule. It was used for 30 years before I twisted the limbs while stringing it one day and some laminations were broken. The ferrule was just fitted tightly. On a walking stick, I'd use a button lock & maybe a piece of elastic to keep the pieces together.
Jim
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On Fri, 20 Aug 2010 13:49:36 +0100, john hamilton wrote:

============================================================================ Your basic idea is used on tent poles:
http://onlinemilitaria.net/shopexd.asp?id 9
Ash is sometimes used for walking sticks, thumb sticks and of course Boy Scout poles.
Cic.
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Baseball bats, AIUI, are either Ash or Hickory (or aluminum ;). These are used because of their strength. I would think the requirements for a cane material would be similar.
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Interesting. That does look like a reasonably easy to build solution. The OP might also want to check to see what patents have been granted. Here's a start: http://www.freepatentsonline.com/result.html?query_txt=hinged+folding+pole
R
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john hamilton wrote:

Then prettify it with a nice knob.
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Also spruce. And what about doing like a blind mans stick.
Where you use elastic inside the core from top to bottom and then have a brass ferrule on the female piece to prevent it from splitting where they join. That would in effect be a hinge.
On 8/20/2010 8:49 AM, john hamilton wrote:

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Does this person currently use a cane? Does he want a folding cane, or is this some well meaning other person dictating the requirements? I've been a cane user for more than ten years and have a number of canes. Some are collapsible and some are not. Those that I can collapse are almost never collapsed. I've found that the most important attribute is whether or not I can hang the cane from something or have it lean upright against a wall. This requirement typically means some sort of rubberized or foam grip.
Hinged canes tend to be fixed length and the length of commercial models is never quite right. The same goes for the push button collapsible canes. A custom model should be a "perfect" fit for the user and this will require discussion with a physical therapist or other health professional. Also, it might be better to make three canes as the "perfect" fit varies. I move my push button canes longer or shorter at times to accommodate wear and tear on my back, shoulder and arm, but there is a reasonable range.
You might consider making a cane using the Lee Valley hardware suggested in another post and giving it two removable central elements: perfect, and long. Short would be accommodated by omitting the central element.
Both of my 'custom' canes are perfect length in cherry and both are ovals of about 3/4" on the major axis. Two inches seems excessive to me.
Good luck, and please let us know what you end up doing.
LD
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