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Hello, DIY forum! It's been suggested to me that I make a thread about the project I'm currently working on, so here we go. I'm working on building a set of digitigrade stilts. Mostly because I want to, really. But it'll also be neat to use around Halloween time. I found out about these things back around like 2015-ish, and I've been working on building a pair as time and money permit ever since. I first built a set based off of this instructable, but found the end result to be far too heavy to use, and my own shoddy workmanship caused too many points of friction, and generally lead to a really bad time using them. On the other hand though, I thought it was an amazing learning experience, and vowed to Do Better Next Time. At least, that's how I justified the ~$300 I spent the first time. After the failure of the Mk I set, I stumbled upon Area 51 and their digilegs. At first, I was ecstatic to find a place I could just buy a set of these stilts from... until I saw the asking price. I live in the USA, so tack on a few weeks to months of waiting for customs, plus hundreds of dollars in shipping fees and everything else. That option was quickly thrown out. However, I am not one to let something be a complete waste. You see, there's pictures on the site. And YouTube is a thing that exists. Unfortunately, it's kind of difficult to find good pictures with scale references, as well as anything with exact information, so while I can kinda fudge a bunch of this stuff, there's certain thing I really need to verify and design for. Thankfully, it's been a few years since the failure of the MK Is, I've improved my skills a bit, I've acquired more and better tools, built myself a workbench, and have access to some expanded equipment selections via work. So I says to myself, I says: "Hmm.... I wonder how much it would cost me to build a set like these? I bet I could do it cheaper than the last set, and actually build them right this time." ... Ok, I'm in. Let's do this. So, for this build, I have a few design constraints that I would like to try to work within: 1.) Make the stilts as light as possible, while not sacrificing the safety of the device. 2.) Make the stilts as cheaply as possible, while not sacrificing the safety of the device. 3.) Use as many generic components as possible, to make it easier to swap parts for either replacement or re-engineering. And that's pretty much it. The form will flow from function, and the baseline will be what I can find and emulate from online sources. So, let's start a build list, here. I figure it'll help me to stay organized if I break the stilt down into build sections, so that's what I'll do. Just from the work I've done so far, it's pretty easy to break the stilts down into 4 sections: The Toes, The Feet, The Legs, and The Cables. I can go over where I'm at with each of these here and now. Starting from the ground up, the toe sections are the parts that, duh, actually touch the ground regularly. Going by A51's stilts, the toes are the rounded bits, which slot into the foot pieces. At first, I attempted to emulate that piece as much as I could, but I was having difficulty getting the sizing nailed down correctly, and so was having issues getting this part started. Eventually, I began to find reports that the Digilegs would cause pain after walking around in them for a while. This lead me to do a lot of thinking and searching, and eventually I stumbled upon this video, of a guy who modded his Digilegs to help ease the pain of walking on them for long periods. Definitely do check out his channel, he does a lot of mocap stuff for movies and games, and his vids are really neat. Fortunately, I was able to discern how his mod was done, and I was able to copy at least some of the basic functionality of it. Currently, the toe pieces I've got going look like this:   I have yet to attach the rubber tread material I've got, as I don't have much, and don't want to potentially waste it until I'm set with the design. I'm currently mostly happy with this though, aside from cleaning up some bits and streamlining things slightly. If it's not obvious by the pictures, the first one is how the toe would look in a standing position, and the second one is how it would stretch out as I get to the middle of a step forward. The spring in the 'heel' is a $30 bicycle shock spring, with a spring rate of 300lbs. I figure that should be soft enough to cushion the impact of me walking along, without sinking down too much every time I settle my weight on to that foot. I can't really think of anything that would drastically improve this design, but I am very open to suggestions. As it stands, I'm considering the toes to be basically complete, until I find something I can improve in them. Next up, we have the foot sections. So named because, well, that's where my feet go. I know, I'm so clever. These things have changed a lot over time, and I'm still not 100% on the final design yet. They started out looking like this:   However, I ended up unhappy with them for a few uh, glaring reasons, which I'm sure most of you are seeing immediately. Not shown is the foot plate and toe pad, which I never got around to making for this design. The eye bolt on the underside was to be an attachment point for a cable tendon, which would run through the copper tube and up the back of my leg. The foot pieces are where most of my attention currently is devoted in this project. I've spent the last month-ish redesigning them from the ground up, and am currently working with this design:    This new design is a bit more straightforward, utilizing stronger bolts, and not-hand-curved metal. It weighs about the same as the old design, but still substantially less than the original design I followed years ago. The plate you see in the 2nd and 3rd pics are one of the first fully custom pieces I've utilized for this build so far. They are 1/16" stainless steel plate, taken from the scrap bin at work. I have more holes and slots to make in the things, and then I will be bending them into a box shape for my feet to go in. The sides will be bent up 90 degrees, with slots running between the two holes for the straps. The thinner-width section will bend up at 45 degrees, until nearer to the end of it, which will bend up another 45 degrees, to form a flat front edge. The entire plate will be covered in adhesive-backed neoprene cushioning, and will bolt into the angle iron on the sides of the main section, as well as have some reinforcement in the 45 degree section to help take my weight. Overall, I'm happier with this design, but it still has a few issues I'm looking to work out. The impetus for this thread was me asking about attaching the cable tendons to these things, and getting an absolute ton of ideas from the DIY quick questions thread. I feel it could still be better, and am very open to ideas on how to improve the design of these pieces. Next up, since I mentioned them, are the cable tendons. These things have been an interesting challenge for me. Almost literally nothing exists on them regarding their usage in the Digilegs. I know that their main functions are to help keep my legs locked into that bent-up digitigrade stance, and to help transfer some of the strain from being in that stance from my ankles/calves up to my thighs, to make walking and standing easier. I know the cable is braided wire, and that it is adjustable. One of the common mods I've seen for these stilts is to add a way to quickly de/attach one end of the cable, which allows the stilts to be put on and taken off while standing. So that's one design requirement I'm hoping to stick to for this build. Unfortunately, that's about all I've got for this part of the project. I don't have a cable yet, because I don't know what size I need for these things. I don't know what sort of forces they're going to experience, so therefore can't buy cable, therefore can't actually install it into the build. If anyone knows how to calculate out the forces that I will need to account for, please either post in here, or DM me, or something. Finally, we have the leg pieces. These, I thought, would be the most straightforward pieces of the build, and so I've been saving them for last. The basic function of these parts are to give the stilts ample room to be strapped on to me, and also to serve as the other endpoint for the cable tendons, so that my thighs can take the extra strain of walking around. Mostly, these pieces currently exist as a placeholder:  Originally, I was going to use bent metal bands in place of the large black plastic bits you see in the Digilegs. I opted to get away from the plastic because I broke way too much of it falling over on my old stilts, and it's way too expensive to just be replacing all the time. Of course, that idea's gone out the window more and more the longer I've had to think about it. You can kinda tell, because the band over the thigh section is riveted in place, while the shin section is just held there with a clevis pin. Things I still need to do for these pieces are: 1.) figure out how to attach them to my legs. I can do straps around the backside of the calf/thigh, but I need to figure out a way to secure them solidly to where they would need to be without introducing a vulnerability that would shatter if I fell over. "securely" in this case means that the stilts don't want to move once attached. They should not slide up/down my leg or twist around my leg. 2.) figure out an attachment point for the cable tendons. I know where they will attach, on the thigh, directly behind the knee, but not exactly how yet. I'm hoping to make the thigh attachment point be easy to un/latch so that I can hit that aforementioned goal for the cable tendons themselves. 3.) triple check the length of the calf and thigh sections to ensure that they actually line up with my knee and ankle joints. The current length is longer than necessary by design, so I can cut them down later. Honestly, these pieces are currently at the back of my mind, except for trying to find a solution to issues #1 up there. Finally, you might be interested in exactly how I'm doing the moving joints of the stilts. I'm pretty happy with how this turned out at the moment. The knee and ankle joints are set up like this:   The 'anchor' side of the joint, shown here as the lower side, is the structural metal, a washer stack, and then a small cap piece, held together by a rivet. The 'moving' side is the structural metal, then the actually moving piece, then the cap piece, held in place with washers and a clevis pin. And that's pretty much it, so far. I welcome any ideas, feedback, questions, suggestions, constructive criticisms, and whatever else you can provide to help this project along. To recap, my main problems I'm looking to work through at the moment are the following: 1.) Figure out how to decrease the weight of the foot pieces. 2.) Figure out an attachment point/method for the cable tendons to the foot pieces that allows them to be adjusted, to allow for adjusting the tension of the cable tendon tension. 3.) Figure out what sort of forces I need to spec to for the cable tendons. 4.) Figure out how the best attach the cable tendons to the thigh sections to allow me to easily detach and reattach them. 5.) Figure out the best means of securing the stilts to my legs. Beyond that, it's just cleaning up the design, then testing them out, then doing a full write up and parts list. neogeo0823 fucked around with this message at 02:37 on Feb 14, 2023 |
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Feb 13, 2023 02:53
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Happy Hallmark Holiday, for anyone who has a significant other to spend it with! If you do not have a significant other, then happy Launching Of The Bismark day! Anyway, today I ran a test. Over the weekend, I bought a $5 bicycle brake cable from a local bike shop. I took a small metal plate that was roughly the same size as the tube steel on the foot piece, and I cut some slots in it to thread the ends of the cable through. Then I threaded the cable through the foot piece, and looped the middle over a second piece of tube steel. Then I placed the loop and steel on a stool, and suspended the foot piece about an inch off the ground, and held the upper piece of metal to the stool with my hand. The result looked like this:   I then gingerly stepped one foot onto the foot piece. Followed by the other foot. Then I jumped on it about a dozen times. The result was an intact cable, and a very slightly bent piece of metal plate. I figured the plate would bend. It's a relatively flimsy bit of metal that I can reinforce pretty easily. But the cables? I'm super happy with that. I think I'll be able to use these. And the fact that they're $5, is just 
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Feb 15, 2023 01:35
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One thing I will add here, without having any direct experience in either (haven't done a metal project in about a decade) is that decent welding machines and metal laser-cutting services have both become incredibly cheap and so as you approach more viable iterations of this apparatus you will be able to get them built "properly" much more easily than even back in 2015. I look forward to seeing this progress!
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Feb 15, 2023 07:00
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slurm posted:One thing I will add here, without having any direct experience in either (haven't done a metal project in about a decade) is that decent welding machines and metal laser-cutting services have both become incredibly cheap and so as you approach more viable iterations of this apparatus you will be able to get them built "properly" much more easily than even back in 2015. I look forward to seeing this progress! Ooh, I haven't even thought about getting any parts made professionally yet, but I am definitely excited about that prospect. So far, everything is being done by hand, with limited help from some power tools at work, time permitting. I'll bet this thing'll look amazing with all the supports professionally cut and trimmed and all that. Anyway, I'm currently trying to work out how I want the tendon cables to attach to the stilts. I had originally asked this question in the DIY quick questions thread, and I received a lot of really good feedback on the idea, but now as I'm doing testing and getting conceptual ideas in place, I'm realizing that what I thought I wanted wouldn't work out right. Originally, I thought I'd need something like this:  But I've come to realize that if I put this on the stilts, that the way I'm imagining the cable adjustment working would put the threaded rod backwards with respect to how I was thinking this would go. Either that, or the adjustment point for the cable would be at the wrong end of the foot piece, which wouldn't work once you needed to attach the toe piece to the stilt. Hopefully this illustrates my thoughts well enough. This would be a side view of what I'm thinking of doing:  The idea is that the mounting plates are bolted into the tube steel, and are in a fixed position. They have holes drilled in them for the threaded rod, but the rod merely passes through the plates. The holes are smooth, and not threaded. The threaded rod has nuts on it that stay in place on the rod, locking it into place on those mountain plates. The one on the far right end acts as a bolt head for turning purposes. The metal block would likely be aluminum, and would have a hole drilled and threaded for the rod, and hole(s) drilled for the cable(s). Once the cable is attached to the rest of the stilt, simply turn the rod via the rightmost nut to adjust the block, thus tension, to the desired place. If I use the two large bolts holding the ankle brackets in place, I can get about 4 inches of adjustment room out of such a setup. Does this seem practical? Efficient? Does it seem like it's The Best Way To Do This? I legitimately have no idea. As always, I'm open to all ideas and input on this. Especially if those ideas and that advice help me to reduce weight and/or cost and/or make the parts easier and more accessible to obtain.
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Feb 16, 2023 02:48
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So, I was planning on making a post this weekend about my progress so far, but I've hit a couple snags that are gonna make we wait a couple days, so I'll instead post about some philosophical poo poo. In my OP, I laid out some design constraints for the project: 1.) Make the stilts as light as possible, while not sacrificing the safety of the device. 2.) Make the stilts as cheaply as possible, while not sacrificing the safety of the device. 3.) Use as many generic components as possible, to make it easier to swap parts for either replacement or re-engineering. These are well and good and fine constraints. However, they are merely goals to be achieved. Exactly how will I achieve these goals? I need to implement, and stick to, a design philosophy. See, two very easy traps to fall into are feature creep, as well as over-designing various bits and parts. For example, the mock up from my last post, about anchoring the cables within the foot pieces? Yeah, completely over-designed, and also set up to be very annoying to fix or modify. So how do you get around that? I'm going to roughly-quote a person, whom I will not name because I heavily disagree with literally everything else about them, but broken clocks, etc etc etc.. They basically said that when you're designing a thing, there's 5 things you need to do, in a specific order. Technically, I see only the first 3 as applying to this project. These things are: 1.) Make your design requirement less dumb. Your design requirements are definitely dumb. 2.) Try very hard to delete the part/process. If you're not adding some things back in, you're not deleting enough. 3.) Simplify/optimize. This is 3rd because it's a very common error to attempt to optimize a part that should not even exist in the first place. The 4th and 5th things were about speeding up and automating things, and realistically, I'm going to ignore those for this project. They might work better in a future project, but in this one, I'm going to take my time and I'm not able to automate anything here, so v0v. Moving back to the cable tendons, the main issue with the previous mock up, was that I wanted the anchor point to be inside of the tube steel of the foot piece, and also I wanted it to be adjustable from the back end of that foot piece. This is a Dumb Design Requirement. I need to make this requirement Less Dumb. So, gently caress it, attach it anywhere and any way that works and does not compromise the safety of the device. Cool and good. Next, we need to delete as much of this mock up as possible. ...You know what, I think I see a shortcut here. See, the Digilegs website, as previously mentioned, has pictures, which I can use as reference. These guys have had at least a decade to refine their design, so why not cop that as much as possible?  So, you can see here how they did it. Simple metal attachment point, in-line cable anchor with threaded rod that they use to adjust things. Simple, elegant, light, easy. How can I replicate that, while still adhering to both the project design constraints as well as the overall design practices I just laid out? Over the last week, I'd been looking into various cable anchors and other means of creating an in-line thing like that. Most of the answers have been expensive and underwhelming. poo poo like $20+/ea cable anchors that look like they should work, but claim they will not give any sort of strength rating because these are not meant for lifting, and etc. Eventually, I settled on this as the next iteration of the mechanism:  That's 3/8in threaded rod, cut to 6in(which I can cut down further, if needed), the accompanying acorn nuts, with 3/16in holes drilled in the middle to allow the brake cable to fit through, then a couple of lock nuts and a corner brace that I trimmed down(but not enough) as the mounting point. Total cost was ~$10 for more than enough for both legs. The acorn nut screws down about 5 threads onto the rod, so I know it's getting maximum hold on that, and I'll locktite it in place and make sure it will never move, once I finalize that design. At this point, I just need a way to curve the cable around the heel of the stilt without kinking it, and I'm pretty much set, as far as I can tell. Unless someone has a better idea, which I am all for hearing about.
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Feb 25, 2023 19:23
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I'm kind of confused by this cable, does it need to actually function as a bowden arrangement or does it need to be inside the tube for routing or what
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Feb 26, 2023 00:00
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slurm posted:I'm kind of confused by this cable, does it need to actually function as a bowden arrangement or does it need to be inside the tube for routing or what Originally, I wanted it inside the tube steel because I thought it would look cooler to have the tendon be hidden away a bit, to help keep the outside of the foot pieces as clean as possible. That was definitely not the right way to go, though, as that's deriving function from form, which is entirely backwards. Functionally, the cable will act like an Achilles tendon. It has two main purposes, and one secondary purpose in this build; Mainly to keep my feet in alignment with my thighs, for that dog leg look, and also to help with balancing my center of gravity. Secondarily, it will allow my thigh muscles to pick up some of the work from my ankles and heel, to help reduce the risk of straining them. Plantigrade legs, like humans have, are not made for the stresses that would normally come from what is effectively walking in ultra-high-heels, with a shoe that's an extra one or two feet longer than you've had your entire life. I pulled some pictures from around to hopefully help elaborate on the difference. Firstly, here's one of the difference between human and horse legs:  You can see normal horse, and human, on the left and right respectively. Middle is some weird thing where the horse leg is uh, meeting the human leg in the middle, so to speak. I'm pretty sure Google pulled this from an article on how horses can injure their legs, which is apt, since this cable basically prevents this in the user. The green, yellow, and red are where the achilles tendon slash the tendon cable come into play. As another example, here's a quick mock up of the above, just in simpler terms.  The tendon would be the red segments of each leg. In this drawing, it doesn't matter what creature the leg belongs to. Notice how the upper and lower segments of each leg are roughly parallel. The tendon helps with to keep the foot locked into parallel with the thigh, more or less, while also allowing the thigh muscles to help with moving the feet. Finally, the cable helps to maintain center of gravity. For this one, I have the Digilegs tech specs to help demonstrate:  For this part, the cable tension keeps my legs at the correct spot so that I don't fall over in one direction or another. Super important for making sure I can walk in them and wear them for more than a minute at a time. Does this help explain things at all?
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Feb 26, 2023 01:27
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No I mean you're using like a brake cable that you can push/pull in a Bowden arrangement with a sheath? Or is it just that you need to be able to tension the cable.
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Feb 26, 2023 07:46
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slurm posted:No I mean you're using like a brake cable that you can push/pull in a Bowden arrangement with a sheath? Or is it just that you need to be able to tension the cable. Oh! No, I just need to maintain tension. There's no push/pull going on; The cable is only going to be experiencing varying amounts of tensile forces.
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Feb 26, 2023 20:44
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neogeo0823 posted:Oh! No, I just need to maintain tension. There's no push/pull going on; The cable is only going to be experiencing varying amounts of tensile forces. If you really want lifting rated stuff it's out there ie https://www.mcmaster.com/product/3475T53 but it seems like you've perused your options. Just in case you need custom stuff though.
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Feb 28, 2023 16:45
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slurm posted:If you really want lifting rated stuff it's out there ie https://www.mcmaster.com/product/3475T53 but it seems like you've perused your options. Just in case you need custom stuff though. Yeah, I had seen those, but at $21/ea, they're a bit pricey. If I need them in the end, I'll pay for them, but that threaded rod and two acorn nuts, plus the lock nuts and a pair of those brackets were like $10, so...  Currently, the snag I'm thinking of how to work around is in the bracket and threaded rod, and the positioning thereof. See, I drilled a single new hole, and widened two other holes, then trimmed down the sides of the bracket so it would fit into the space on the side of the tube steel. It started off looking like this, and ended up looking like this:  I'm sure you can spot the uh, small problem there. I'm thinking I can buy a couple more brackets, drill open the hole on the lower edge there, skip the upper one all together. Then trim the side, but maybe not the bottom of the bracket. Or maybe just flatten the pointed tip of the bottom instead or something? The issue then becomes that the bottom of the bracket will stick out below the tube steel and hit the ground slash prop up the stilt in that spot. The solution for that that I instantly go to is buying more brackets and just placing them on each side of the tube steel, so as to create a 4 pointed footprint. But of course, that has very obvious drawbacks that would make the whole putting-the-stilts-on-while-standing part kind of difficult, as well as increase weight, though admittedly not by much. I dunno. Anyone got any thoughts here? Ideas? Comments? Anything?
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Mar 2, 2023 00:51
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this is cool as hell fyi
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Mar 2, 2023 01:15
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A Wizard of Goatse posted:this is cool as hell fyi Well, thank you! My big hope is that this thread is at least mildly interesting to folks. This sort of half-cerebral-half-wildcard-adventure kinda DIY is my jam, and there's not much I love to do more than share neat poo poo I find and figure out with people. So, I bought a couple of new brackets. I have yet to drill or trim them. I'm gonna see if I can do so tomorrow at work, when I'll have access to the nice drill press and those fancy metal cutting drill bits and such. Actually, due to corporate contracts, we have to use drill bits supplied by Grainger, and frankly, they're hot garbage that you can actually feel get dull after you use them once or twice. It's kind of uncanny. I really need to invest in a new set of quality drill bits. If slash when I ever get a house, a drill press is high up on my list of must-get tools. Anyway, brackets. Here's a picture of the modded one next to the new one:  I colored in the area where bolts would obstruct the tendon anchor. Unfortunately, it looks like the lower right corner of the modded bracket is out as a spot, because even though the hole will fit there, the nut that would need to go on the backside would get blocked by the cross bolt. The small hole on the left side miiiiight work? If I can sort of, drill it down towards the bottom of the piece as I widen it? Maybe? Does anyone have any advice on doing that? Other than that, I'm kind of scratching my head on where to go with this particular means of securing the anchor. I'd welcome any ideas anyone has on how to proceed.
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Mar 3, 2023 00:34
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Dang, has it really been over 3 weeks since I last posted in here? Time flies when you're workin' overtime. Anyway, I'd love to post a bit of progress, but unfortunately, I've stalled slightly while I figure out my own lack of skill in what I'm doing. Long story short, I had attempted to mark and drill some holes, and welp, that didn't pan out correctly at all, so I'm currently working the kinks out of that operation before I finish the parts I was working on. When it's done, I'll post an update on the foot pieces and the tendon cable mounting point. For a slight spoiler, I've decided to try to completely re-design the foot pieces. Again. It would be disappointing, but that's the game, you know? The previous designs weren't failures, I have simply found other ways that don't work for what I need. No, my biggest gripe about the coming redesign is that it forces me to discard one of my design constraints for this specific part of the project. However, I have also realized that all of the other pieces have at least one component that's doing a similar thing. So, I'll try to stick with it in the future, but sometimes, you have to do what you have to do to make it towards the goal, I suppose. I do feel kinda bad though about the lack of content over the last couple of weeks, so for at least a bit of content, have the video that started this whole thing.  EDIT: Hmm, apparently the video won't play when embedded here, and that also breaks the timestamp. If the link doesn't go straight to the reveal, skip to 1:01. So, I first saw that video quite a while back, when I was younger, poorer, and with far fewer tools. Back then, I just thought the costumes were really frickin' neat, and wouldn't it be cool if I could make that for myself. I ended up with a shabby imitation for that Halloween, but decided I wanted to Do Better. I wanted a creature that was more otherworldly, looked more unsettling, and moved in a more interesting way. One thing lead to another, and I found an Instructable to make a set of werewolf stilts. From there, it's been iterating and attempting to Do Better ever since. When I finish this project, and I've got a set of working stilts that I can walk around in, my next plan is to create some sort of modular set of mounts for them that'll allow me to un/bolt pieces on and off the stilts so I can use them in multiple costumes.
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Mar 25, 2023 03:47
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Just read through this real quickly. It's an interesting problem to solve. The real answer is to have a turnbuckle that you hide in the pipe and leave after the correct length of pull is set. There's a reasonably common mechanism with an eye bolt through some bushings to set tension, depicted below (hopefully).
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Mar 26, 2023 20:23
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how would you secure that to the inside of the pipe? Brazing?
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Mar 27, 2023 17:21
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