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    Design shortcomings


    In funklabs thread " Putting together a wheelchair tool bag " he makes mention of a shortcoming of the folding back locking hinge mechanism on his TRA.
    Has anyone else experienced this issue and if it is design and or metallurgy, has TiLite addressed this??
    Do they trial their new designs to prove longevity and robustness before putting into production?

    I have been looking without success, where can I find an exploded diagram of this hinge mechanism?

    Originally posted by funklab View Post
    ..... The TRA is fine, it does the job. Unfortunately the new folding back design seems incredibly flawed. It locks in with two non-removeable tabs that could easily have been made to be replaceable. They seem to snap off after somewhere between 3 and 18 months of what I consider very light use, necessitating the replacement of the entire $700 back hinge. Other than that I don't have too many complaints.....
    Last edited by slow_runner; 25 Aug 2021, 6:27 AM.

    #2
    TiLite has a few hinge designs they've used. The parts manual has most of the diagrams. Unfortunately, the most recent time I looked for the backrests, it didn't include the one on mine, which seems to be even newer. It doesn't appear to use any tabs, or lock in, either. It is just a friction mechanism that holds it all together.

    The specific model's owner's manual also has a good diagram and a description of how it all works for adjusting it.
    "I have great faith in fools; self-confidence my friends call it." - Edgar Allen Poe

    "If you only know your side of an issue, you know nothing." -John Stuart Mill, On Liberty

    Comment


      #3
      I'm still getting used to this new way of posting photos. Slow_runner, I think you asked me for some pictures in the other post, but I totally forgot. My apologies.

      In the post with my hand in it you can see the quick release bar locks onto a silver colored cylindrical locking tab type thing. In the picture without my hand you can see that the one on the right is missing.

      If one fails then the other is taking the whole load and in addition to not securely keeping the back open, it generally breaks as well within a few days. I haven't quite had my TiLite TRA for two years yet and this is the second set I've broken. The first set lasted a little over a year (apparently the warranty period for this part), but the second one lasted less than three months, so hopefully they'll just send me a set. We shall see whenever I get around to asking them. It takes a lot of mental energy to do battle with the DMEs and manufacturers.

      Comment


        #4
        No worries, try this image vehicle funklab, it works quickly. https://postimages.org/

        In an earlier thread I posted about this TRA that I hope to have. A member spoke of the poor design for caster locking, I thought that the comment related to the earlier of method; now I am thinking it was this newest design. IMO it is expediency over function.

        I found an excuse for what I need to see and I am not impressed with friction fit, what were they thinking?
        Ease of use trumps solid fixture?
        I will be speaking with Permobil about the possibility of the earlier version.

        Have you had issues with the friction lock on the front caster funk?

        https://www.permobil.com/us/product/precision-lock/


        Oncetherewasagirl had a similar problem as yours funk
        https://www.carecure.net/forum/sci-c...-help-identify

        Hey funk, is that rear bracket alloy, composite, plastic or a mix of materials? I prefer steel.
        Can you post images direct on from the back with the back in both its upright and folded positions.
        I'm thinking that a full width bar may solve that poor design? There are big loads, often sudden as we move and stretch, on that semi supported latch pin.
        Last edited by slow_runner; 30 Aug 2021, 12:46 PM.

        Comment


          #5
          Originally posted by slow_runner View Post
          Hey funk, is that rear bracket alloy, composite, plastic or a mix of materials? I prefer steel.
          Can you post images direct on from the back with the back in both its upright and folded positions.
          I'm thinking that a full width bar may solve that poor design? There are big loads, often sudden as we move and stretch, on that semi supported latch pin.
          Couldn't swear to you what the bracket was made out of. It's all metal, but I have no idea what kind of metal. The metal post (is latch pin the technical term I'm looking for?) that keeps breaking is a solid chunk of some kind of metal and snaps off where the stress is, which isn't a particularly thin portion of it. It's just not substantial enough to do the job I guess. Perhaps if it was full width it would. I often hook an arm around the back of my chair when leaning forward, supporting some of my weight on the single latch pin. If it went all the way across perhaps it would be able to share the load. Probably just needs to be bigger as well.

          I haven't had any caster issues, but I haven't adjusted them at all either. I think I've popped the casters off twice for cleaning, haven't even needed to replace my 1.5" wide casters yet, though it looks like I will soon.

          Comment


            #6
            Is that latch pin a moving item or fixed for the latching arm to lock and locate?
            Last edited by slow_runner; 26 Aug 2021, 1:43 AM.

            Comment


              #7
              Originally posted by slow_runner View Post
              Is that latch pin a moving item or fixed for the latching arm to lock and locate?
              It’s fixed to the lower portion of the back hinge.

              it’s actually welded in there or something (hard for me to see exactly). It could easily have been a bolt that went all the way thru with a hex nut on the outside so you could extract it if it snapped off. But then when they broke i guess they’d only get $5 or $10 for a broken part instead of $700 for the whole hinge assembly.

              Comment


              • slow_runner
                slow_runner commented
                Editing a comment
                Have you still got the broken hinge units funk? Down this way we have a 'Consumer Guarantees Act' that trumps any guarantee that a manufacturer might offer. It works on the premise of what time might be reasonably expected of an article.
                If something fails without neglect or abuse just outside of the guarantee, the item has to be put right or replaced.
                If Tilite refused to honour their responsibility on a component that fails within a reasonable expectation of the life of that component, especially where (in my opinion) the problem lies with design and metallurgy, then that's not a right thing.
                Last edited by slow_runner; 30 Aug 2021, 12:44 PM.

              #8
              It's a mating of a steel pin into an aluminum bracket that's only 3/16" wide. Aluminum is too soft and too thin to screw a weight bearing steel pin into, so they welded a steel grommet/spacer into the aluminum bracket for the pin to seat into. The pin appears to be both threaded and epoxied into the grommet on my Aero Z. There is epoxy squeeze out around the edges and coming out the center of the steel pin (it's hollow). It might just be a compression fit with epoxy, but the end of the pin looks like it is designed to accept a hex tool, implying a tool needed to thread it on, but it's hard to tell with all the dry epoxy in the way. If mine ever falls out, I'll inspect the inside the grommet it's mounted to, with a pick, to feel for threads in there. It's at a weird angle for looking into.

              And, despite using this hinge on most of their chairs, for at least the last 2 years, neither the parts catalog nor the owners manuals (that I can find online) have been updated. They both still show the previous hinge design.

              Mine pins are both still quite solid feeling after just over 2 years.
              "I have great faith in fools; self-confidence my friends call it." - Edgar Allen Poe

              "If you only know your side of an issue, you know nothing." -John Stuart Mill, On Liberty

              Comment


                #9
                Normally an insert will be cast within the aluminium. Without seeing it, this is what I suspect has been done. If it is an insert that has been epoxied or similar, I am less impressed. From the thread by Oncetherewasagirl I can see that the pin has been drilled then broached to accept an Allen key. I suspect it has been hardened, maybe not tempered. The thread form looks crap China like and there is no radius at the diameter intersect. That pin will fail eventually by loosening or fracture.
                There is too much load on a single support. Maybe it relies on the cradle below it?? Not good.
                I imagine that there is some form of worm drive within. Does it rely on friction to maintain position? I cannot see a lock for that function.
                Why they ever went from the previous version with a fully supported pin to a cradled pin design , only Dog would know.

                Any capable person can adjust the angle on the previous design. If it was wanted to present something tidy, just a nicely molded cover would have sufficed.

                Odd, have you had issues with the means of locking the caster?
                You mentioned that there are no exploded diagrams of this bracket mechanism- perhaps it was never intended to be a repairable item? .....
                Last edited by slow_runner; 30 Aug 2021, 12:52 PM.

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