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Tech tele bindings and release

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  • Tech tele bindings and release

    Forgive me if this has been covered elsewhere. I found a few references, but nothing comprehensive...

    Most tech bindings in alpine mode rely on the heel to release first, then the toe releases when rotated with a free heel. This is good for reducing ACL/MCL injury, but not as good for tibial torsion fracture. More info can be found in this study: Releasable NTN bindings work roughly the same way, but can only release predictably when the heel is flat... when ramped, the springs force the release mechanism into the duck butt or heel. All tech tele bindings (TTS and NTN) apply pressure down into the toe piece via the boot when ramped, making them almost impossible to release from the toe unless released from the heel first (like AT tech bindings, but worse).

    Some tech bindings in the AT world are working on solving the toe release problem. The ones I know of are Fritschi Vipec and Tecton, and the Trab TR2. I'm not counting the Dynafit Rotation because the toe only rotates to help the heel release more reliably, plus the rotating toe wouldn't work for tele anyway. The others solve it with an independent lateral toe release, kind of similar to alpine bindings. It seems to me that predictable lateral release with telemark and tech would have to involve toe release (like Fritschi/Trab) or a frame (like the old Voile CRB). Relying on heel release works when flat, but is a big compromise, and involves complexity/fragility (Meidjo) or a big weight penalty (Freeride etc.). For telemark, I think toe release may be more important than heel release if you have to pick either/or, as the heel is already free in the axial dimension, and held by softer springs than the tech toe... if that makes sense.

    I like the simplicity, lightness, and touring of the TTS system, but the lack of release is a safety concern. For (heel) release, touring, and lightness, I like the Meidjo, but the complexity and sheer amount of plastic has me concerned about taking it places where I'd rely on it to get me home. I think my dream unicorn binding would be TTS with a releasable toe. This would combine the lightness and touring benefits of TTS, with better release than the Meidjo, and without the complexity/reliability problems.

    I did find one test of Fritschis in a TTS setup, but it looks like it was only bench-tested and not skied: More discussion here: I think with either the Fritschi or Trab, a Kreuzspitz-style riser would have to be used so the release mechanism can clear the spring pivot, rather than an OMG/Moonlight-style block. It also looks like the Trab TR2 could work. It's not officially compatible with tech boots, but from what I've read, that applies to the heel, and the toe works fine with tech cups. Of course only a handful of people actually used the Trab, and I doubt any of them are homebrew telemarkers.

    So my question is, has anyone tried a releasable tech toe with a TTS-like setup? Is there any reason the Fritschi or Trab would or wouldn't work? I figured if anyone knows the answer, it's probably one of the people on this forum.
    Last edited by jtb; 29 January 2020, 09:00 PM.

  • #2
    So i have deep dark secret, i used to be a biomechanics researcher, and wrote my honors thesis on binding release.

    you are correct about lateral release at the heel, with one caveat, there are types of twisting falls on hard snow where the heel has to move inward and gets blocked from doing that by the snow. schollarly research on this dates back at least to the late 80's, not in context of tech toes, but in context of bindings in general. i still remember the drawing in one paper on this point and the math behind the increase in tibia stress for the same moment applied to the ski. it is also linked to a higher rate of tibial plateau fractures. Not saying that ;lateral heel release is bad, just not as good as lateral toe release, in most release modes. there are a few where lateral heel can be better.

    what you cannot loose site of is the contribution of friction in any releasable system. friction is bad. its bad, really bad. that is why every real releasable system (and it boot + binding) has some strategy for dealing with it. meidjo does not. freeridedom's do not. in particular, both rotate about the toe, but have exactly zero AFD in the heel pad. any weight on the heel, and the rubber sole will prevent the heel from moving sideways. in addition, either deals with friction on the flex plates either. So i wouldn't trust eitehr to release except in a fall with unweighted boots. 7tm does, plastic on plastic. trp's did, roller belt. voile did not. notice the trend, TUV certified = system to deal with friction, not TUV certified, no system. This is just one example of how friction affects release, there are more.

    my wife has vipec's and before i mounted them, i messed with them. no way are they solid enough to use in TTS. i was not even brave enough to carpet ski them for fear of needing to replace her bindings. Trab looks more promising, as it is more metal. but i have never touched one. but from video's, not optimistic. I have given the trab a lot of thought. both would require some sort of plate to locate the heel and act as a pivot point.

    believe me, i am giving this a lot of thought lately, as i recover from a season ending injury skiing TTS. I am going to make a release system, but it will likely be a bastardization of TTS onto a 7tm release plate. i have pondered other solutions, but none seem as practical, with current boots. 7tm axis of roations in neither heel or toe, it is more arch, but better than toe. but maybe i will be smarter tomorrow than today.


    • #3
      I have a Voile CRB release kit I'm not currently using. I thought about mounting a TTS binding on that, but after all the $$, it will weigh more than a 3-pin hardwire with the same ski and release characteristics. The 7tm looks like a more modern version of the CRB, and tech tours better than 3-pin... but in the end you're still mounting a binding on a binding.

      As you said, the current crop of releasable tech toes look too fragile for tele. So either someone with money to burn needs to try them and find out what breaks (I would go for the Trab DIN 13 model), or we need a releasable tech toe designed for tele. The latter will happen when we have a lightweight tech boot with bellows and NTN, i.e., never, or until someone makes their own.


      • #4
        Jason, do you think AI tape on the heel piece has any effect on reducing the friction there? Or if not, wouldn't it be possible to make the heel out of some other low friction material as is used in AFDs?


        • #5
          Welcome jtb, great post!

          Sounds like you are really keen on release. Many of us have managed to look beyond it. jasonq is no longer in that camp, as he notes above.

          I don't think I have the technical knowledge that you two possess, but I have a lot of experience messing around with bindings and skiing to the point of pre-release.

          Most bindings will release at some point. The challenge is finding the best place on the continuum from pre-release to non-release that matches your skiing style. Unfortunately, most of the bindings that release, do so in an unpredictable way. Or maybe it is predictable, but unreliable to ski when it does release. So far, I prefer to be in my bindings rather than releasing too early. But maybe if I experienced a fall like jasonq, I'd change my mind.

          Some specifics from my experience for consideration: (I should note that I don't really ever have spectacular falls where a release would be expected)
          TTN: seem to also release as an AT tech toe binding, that is, when the heel is loose, they release.
          - Meidjo: I didn't set the retention (release) on mine when I got them and did pre-release. After I tightened them, I never released.
          - Lynx: I've had the duckbutt clamp come off in deep snow immediately followed by a release. Solution has been to lock the toes. If the clamp comes off for some reason, I can step back in. Although, I'm not sure why but I haven't had the clamp spontaneously come off in a long time (same tension setting).

          TTS (DIY): System with some sort of spring connected at the heel. I thought initially and incorrectly that retention required a strong toe, but retention requires a strong and laterally stable heel. Therefore, you can design some degree of release (non-calibrated) in to the system by allowing softer springs.
          TTS, Long Voile Springs: I would pre-release very easily in these. Too soft and too much lateral play.
          TTS, Long Kreuz with hard springs: these were reliable, but the heel assembly stuck out enough that I would step on them. Solution (a la jasonq) was to bungee up the heel throw to the boot. Worked but needed that bungee.
          note: on both of the above I employed a heel prong that fit into the tech heel to inhibit lateral movement with the foot flat. Depending on the tension of the springs and the quality of the toe I was using, sometimes I'd ski with locked toes.
          TTS, Spike and Double Spike: There was enough forward pressure in this system that I never had to lock the toes and I don't think a release would really be possible, even with the foot flat and no prong.
          Locked toes: I often ski with locked toes. There is a difference between retention strength at one click on the lock and as much as you can pull it. Definitely not scientific though. Although I never did release, I felt like it was more likely with just one click of the lock. Ideally though, we have bindings that we just step into and ski - no locking levers, not pulling on bungees, etc.

          As you note, tech toes do release. With a free heel they tend to release too quickly. With a locked heel, they might not release quickly enough.

          To comment on getting out of the backcountry with a broken binding: It might not be as fun, but you can ski parallel pretty reliably with no heel system and a locked tech toe. And all of the toes are pretty reliable, I think failure would come at a different point in the system. (unless a pin that holds a tech toe arm works its way out, which can happen). I have had to ski out with just a toe more times that I can remember when my DIY systems had issues/failed. Kinda messes up your day, but doable from a safety standpoint.

          I wish you luck as you continue to research and experiment. Keep us posted. As for me, I am quite content with my Lynx for now, which aren't perfect but are as close as I've tried. And my backup, resort binding is an Ion with double spike rear assembly. Feels very similar to Lynx, is step in and has never pre-released on me with unlocked toes. (I built this to tour originally but took off the touring bits to see how light I could get it - about 130g heavier than Lynx per foot)


          • #6
            AI tape is likely Umhw polyethylene sold in bulk as slick strips.
            it has a low coefficient of friction and is resistant to abrasion. So much so that it is used to line steel rock transport chutes.
            Teflon cef is much lower but more fragile. So slick strips are likely the best choice for putting under your heel.


            • #7
              I always thought the vipec toe would make a very releasable TTS binding. I have a pair of them. They even have inserts for the cocking lever that have multiple shapes so the toe of the boot can actuate a release if it rolls forward to far, which would mitigate the problem of a heel up situation where the binding might not release.

              As far as NTN goes, I always thought that a claw with a single bearing at the center and a detent on the boot's duckbutt to recieve the crown of the bearing would be a much better claw than the one rottefella used. Once the bearing pops out of the detent the boot rolls free on a bearing... The only issue would be a directly upward motion against the claw, which could be solved with a pivot at the claw longitudinally, which is loaded in place under spring tension...
              the fall line is your friend.... resistance is futile


              • #8
                for an AFD on the heel pad, i don't think teflon, UHMW, low COF plastics will work well. My reasoning behind that is that every binding made for rubber soles that has a contact point in the the rubber sole uses a mechanical AFD, ie a sliding AFD. Look at all the grip walk/walk to ride/AT compatible alpine bindings and frame AT bindings, and the common theme is a sliding ADF if it is a rubber boot contact point. Also, look at the brakes for bindings like G3 Ion/Zen or dyanfit rotation, marker kingpin, they have slidy bits to not add resisentece to the heel moving sideways. if they didn't need that, they wouldn't use it, its more complicated and expensive than a piece of telfon.

                as far as release/pre release, on of the gating factors there is "elastic energy storage". you will often see some version of that referred to even in gear reviews, like on blister. it is really important. it all boils down to, with little or none, a small sharp jolt will cause the ski to release. but with enough, the energy of the jolt get stored in the spring, and then return to center. the idea is that the jolt, while it might be of high force, it is of short duration, therefore low energy, and can be absorbed. Also, your leg and knee are part of a system with the ski, boot, binding, and all have mass, and all the dynamic behaviour that does with that. so a short whack won't cause much displacement at your leg because it has to move all the mass. but a longer push, even at lower force will be a larger energy than the spring can store before releasing the boot. the end result of this is that there is an optimum spring rate/defelction before release. in constant force, you can think of that as the DIN release torque. But if you deflect farther before release, you use a lower spring rate, and the energy stored in a spring is 1/2 k x ^2, so the effect of 2x the deflection is way more than the 1/2 the rate in storage. and this is why folks usually talk about how many millimeters of elastic travel a binding has. becasue since DIN defines the static release torque, which is basically spring rate x elastic travel, then the binding with the most elastic travel has the most energy storage.

                that was a long way to explain why TTS tech toes will pre-release, they have almost zero elastic storage. the energy storage of that system comes from the cable springs, and the deflection where your boot release is independent of the springs used. so the only way to increase storage is to increase spring rate. that is why soft springs = pre - release, stiff springs = less. keeping in mind the amount of energy the cable spring can absorb when a whack is applied depends on how much the spring was compressed right then. so heel down, less storage, heel up more. this explains why things like jim's prongs lessen pre release, they block the heel motion when the binding is in its minimum storage condition.

                now the next question is why "elastic" energy storage, and the reason is you want the binding to return to center after the hit. if instead a damper was used (friction) it would absorb the energy of the hit just as well, but not return to center, and then the next hit, ratchet, release.


                • #9
                  PS, since i have all this time on my hands, and i actually have a set of vipecs on unused skis, maybe i'll mess with those too. won't have acess to those skis for a couple months. still think they will need a plate binding of some sort to give a rotation point for the heel. picture a Bomber with a tech toe, but i'd hope lighter.


                  • #10
                    I think the title of this thread needs 'palaver' in there too....


                    • #11
                      Originally posted by jasonq View Post

                      that was a long way to explain why TTS tech toes will pre-release, they have almost zero elastic storage.
                      So, to get release we mount the tele binding on a releasable plate.... a la old Silvrettas. Which, is why I started telemarking in the first place - to have a reliable binding for more aggressive backcountry skiing and get away from those things! I suppose the 7tm is the vastly improved 'modern' version.


                      • #12
                        How would something like this work as far as using the main springs for elastic storage, and encouraging "return to center"? The image from below shows an exaggerated "conehead" shape to the part of the boot where the heel throw would go. As the boot heel moves to the side, it cams the wheel on that side backward, further deflecting the spring(s). Yes, if you're already bottomed out, you're SOL, but that problem should be addressed anyway, for other reasons. And yes, the cable would have to attach to the heel throw lower than the tread of the boot, so the boot was free to move fully to the side in a release situation (which is kind of impossible as-drawn, but this is just a rough concept). This would likely still need to be partnered with an AFD on the heelpad, perhaps like the tank tread on the old Rottefella TRP. Of course this same concept could be employed on an NTN claw and reshaped duckbutt. Might be easier and more effective that way, actually.

                        Click image for larger version  Name:	RollerThrow01.png Views:	0 Size:	26.3 KB ID:	99445

                        Click image for larger version  Name:	RollerThrow02.png Views:	0 Size:	22.5 KB ID:	99446

                        Click image for larger version  Name:	tanktread.png Views:	0 Size:	568.1 KB ID:	99447

                        Edit to add: Ah crap, someone kinda beat me to it, like 15 years ago. But they didn't have the luxury of a "conehead" boot heel to fine tune things. As far as I know, most boot heels have been more or less just the back half of a circle. Now, we can 3D print a bolt-on conehead in like an hour.

                        Click image for larger version

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                        Last edited by bobbytooslow; 30 January 2020, 03:10 PM.


                        • #13
                          i think the answer is mostly yes. that heel throw, would obviously need some sort of plate to go with it, but roller there aren't really needed for a rotate about heel because it is acting close to the axis, and is a fairly low friction interface.

                          the skyhoy is a rotate at the toe release at the heel, IMO, kingpin heel is a conceptual copy of the skyhoy heel. also notice the sliding AFD device at the heel.

                          I think you could do a decenct AFD for a duckbutt/NTN/TTN, rollers at the butt, and a AFD plate that pivots up at the toe and runs all the way to the duckbut. then a AFD device on the heel pad.


                          • #14
                            Jasonq said-
                            for an AFD on the heel pad, i don't think teflon, UHMW, low COF plastics will work well. My reasoning behind that is that every binding made for rubber soles that has a contact point in the the rubber sole uses a mechanical AFD, ie a sliding AFD. Look at all the grip walk/walk to ride/AT compatible alpine bindings and frame AT bindings, and the common theme is a sliding ADF if it is a rubber boot contact point. Also, look at the brakes for bindings like G3 Ion/Zen or dyanfit rotation, marker kingpin, they have slidy bits to not add resisentece to the heel moving sideways. if they didn't need that, they wouldn't use it, its more complicated and expensive than a piece of telfon.

                            I agree that this seems right, but the Campbell study said otherwise.

                            Also its better than nothing!


                            • #15
                              Good link to the Wildsnow article from 2014. I recently met one of the authors of that article, Rick Howell, here in Vermont, when I was pumping gas, wearing my tele boots. He was curious to see what type of ski boot, allowed me to drive my car!
                              We spent quite a while discussing AT bindings (which I tour on now) versus Tele setups, and I showed him the tele binding, on the skis, in my car, the Outlaw. We also spent time on some later phone conversations.
                              He felt that a tele binding has a reduced chance of knee injury (ACL)compared to Alpine bindings, because of the relatively softer upper on a tele boot. So the knee can move laterally in a fall. And of course , we are protected in a forward fall, because the heel lifts up as we fall forward.
                              As for an AT "pin" binding, fixed heel, (and by extension TTS?) because the ski boot has to rotate about the toe piece, depending where forces are applied to the ski, the Tibia may reach a failure level before the boot releases from the heel pins. OTOH, because an AT heel releases to the side, there may be more protection for the knee, (compared to resort Alpine bindings) with lateral release at the heel, in an AT binding. You have to study Rick Howells graphs quite a bit to understand this.

                              A regular Alpine binding, that rotates around the heel, as the toe piece releases to the side, does protect the Tibia, more than an AT binding, but knee injuries are more prevalent. Rick Howell was adamant to me that an AT setup, particularly skied hard, at the resort (which I do on occasion) is dangerous, because of the increased risk of a serious spiral tibia injury.
                              To summarize,
                              If lateral-heel release tech bindings became the in-bounds standard, I would predict a tick up in tibia injuries and a tick down in ACL injuries (assuming bindings are adjusted to appropriate levels)
                              If you want , I could call him, and see if he would like to discuss these issues, with you. I did ask him if he would like to test any of my Tele bindings (NTN) such as my Freedoms, or Outlaws for forces that occur, before a binding release.

                              In the Wildsnow article comments section seen below, I asked the authors about injury patterns , with modern Tele/ NTN bindings. My comments are identified as VTskier, as in Vermont skier.
                              Last edited by chamonix; 30 January 2020, 07:58 PM.