Tinkering with Tech Toes + Axl Springs

The Nitty Gritty:

Zero position (Slic Pin removed) Effective pivot point ~ 50mm behind tech fittings. ~ HH#1-#2

Activity:
How retentive is my home brewed TTS in terms of ball of foot (BOF) hold down, resistance to heel lift, etc.? Comparing the Dyna-Axl to the Hammerhead (HH), both outfitted with standard springs:

The activity level of the Dyna-Axl is not only more than I expected and more than a standard Axl, but the action is very smooth and comes on as soon as you lift the heel/push the cuff. I did not ski the Dyna-Axl with the pin removed, but in carpet tests it had a very neutral feel, on par with a Switchback or 7TM.

Touring Function:
In order to use the free pivot, the heel throw must be “stowed” behind the heel riser. This can be done with skis on by simply squatting down and flipping the lever off the heel, lifting the climbing bar, then slipping the heel throw over the back of the riser. The tech toe is a true free pivot, minimal resistance while skinning means less energy expended, getting in and out of the toe is as simple as flipping the release lever with a ski pole tip. A full 90° ROM for touring is available, even if you never really need that much.

Position 2, ~ HH#4-#5. Effective fulcrum point 80mm behind tech toes, NB's sweet spot.

Lateral heel displacement:
How far does the heel move across the ski under lateral pressure?

This is an area of concern voiced by many interested in TTS. At first glance it would seem that the tech fittings would be insufficient to contain the boot during a hard telemark turn, but this could be no further from the truth. I weigh 200#, driving mondo 30 boots, skiing very low and very fast. As an acknowledged binding breaker, you would think that I’d be blowing out of the toe on every turn, but after hundreds of turns I never had a wiggle. In truth, the tech fittings work in telemark for the same reasons they work in alpine touring, it’s a good design.

Durability:

Position 3, ~HH#6 - #7??

Can the tech fittings and pins take the abuse day after day?

With TTS still in it’s infancy, I can’t say how long the fittings and pins will last before they wear out or fail, but in alpine skiing the tech system has proven itself durable over the years and has become the standard by which other lightweight AT bindings are compared. According to Mark Lengel, his TTS bindings have been skied for multiple seasons with no signs of excessive wear outside of what would be expected from AT use.

Release:
The Dynafit tech binding is a system binding designed with a simple pincer toe that relies on a heel piece for stability and to set both lateral and vertical release. TTS incorporates only the tech binding toe piece, so lacking the tech heel, there is not an adjustable release per se. In ski mode, without the heel engaged, the tech toe piece releases easily, hence my use of the binding in “locked mode” (touring). Lateral stability would seem to be a problem for TTS, but in reality the heel throw and spring assembly provide for some of the missing stability, though less than with a tech heel piece. In bench tests I found that the Dyna-Axl in ski mode (unlocked) would release laterally with about the same effort as a complete Dynafit binding set at a DIN 5. In locked mode the Dyna-Axl took more effort to release depending on the number of “clicks” that the toe piece was engaged, approaching DIN 10.

This short film clip shows the release function in ski mode ~ DIN 5:

In tour mode with the lever locked the release requires significantly more effort, ~ DIN 10.

There are tech bindings that have an adjustable release toe piece (La Sportive, ATK, Plum), but the cost for these bindings is double the Dynafits, so there’ll be no tests forthcoming for this budget garage tinker; plus my wife said no. That said, the Dynafit toe has an acceptable disaster release option for use in avy terrain or when protecting injury prone legs. Additionally, I found the Dynafit toe was quick to re-center when incompletely released, which is a nice trick in case you induce a partial release. I did not get the sense that the system would pre-release any more than  other releasable telemark bindings, but I do believe that the release will be better and more reliable, especially in a twisting fall. I did not ski the binding unlocked since I did not want to release too easily.

Forward rotation and Retention Fade:
My early TTS set ups with the hardwires and spring cable wires did a good job of limiting forward rotation to the point where the boot was ~30 degrees to the ski, but beyond this point it seemed as though binding activity “went away”. In non-engineering terms; I am not an engineer, this seems to be due to the boot arc maximizing spring length early on (zero to 30 degrees), then as the boot continues forward past the peak of the boot arc, the optimal angle of retention is diminished and the springs become less capable of controlling rotation. In contrast, the Dyna-Axl provided continuous retention (activity) throughout the boot arc because the cables are continuously leveraged by the boot, providing a progressive feel, from heel to ski to knee to ski.

Cable Pivot point:
The real meat and potatoes of TTS, lots of variability here to optimize the feel. I can’t say enough about the three settings I adopted from the Axl, at 70mm, 80mm, and 90mm from the fulcrum to the tech pins. These settings provide the ideal mix for me as I could see using the third position for racing gates and carving, the middle position for all around skiing, and the first position for softer snow. There is also a zero position with the slick pin removed which I could see being useful for softer boots, smaller skiers, and Nordic styled skiing. What I did notice is that the “optimal” fulcrum position seems to vary depending on the retention system used, so a different spring assembly might need more or less distance between the pins and fulcrum to optimize activity.

In summary, I found that my Dyna-Axl variation of the Telemark Tech System works, and it works well. There remain issues to be resolved such as optimizing retention and fulcrum position, developing TTS specific tech toes that provide for adjustable release, and providing binding kits that allow a non technical person to assemble a telemark tech system. By utilizing the tech fittings, TTS avoids the complications inherent in having a toe and heel that are co-dependent, allowing for a multitude of retention options and a free pivot that is unencumbered by the means of retention.

It’s a sweet trick, that’s for sure 🙂

© 2011

13 comments

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  1. Cool!

  2. Last Spring when Dostie first approached me about this article, I was not satisfied with TTS, in fact I had just gotten back from a frustrating trip to Utah where I wasted a few days flailing about on TTS.

    It wasn’t until this past Fall that I gave TTS another chance, tweaked a few things, burned some midnight oil, that I was finally able to make it work.

    I think one of the things that arm chair critics fail to realize is that much of what is created comes from trial and error, not pure science or engineering, but just re-discovering the wheel over and over until you have a better wheel.

    The TTS Axl is just one way to slide down the hill, it may not be the best for everyone, but that’s not the point of my projects. I build stuff because I don’t like the alternatives. What TTS has shown me is that there is a better way, that millions of dollars in R & D mean nothing if the end product is mediocre.

    If the readers take anything away from my experimentation I hope that is a renewed interest in making telemarking better, and the understanding that what I’ve done and what Mark Lengel is doing, these are just the tip of the iceberg.

    Don’t settle for mediocrity if there’s a better way.

    And don’t forget, some fellow arm chair folks may have thought of this concept before, but you didn’t do it. So, please support Mark Lengel, who did do it, and his efforts to mainstrem TTS, only through your support will TTS become a viable player.

    @ Smelly, thanks for the comment, it helps 🙂

    • Dom on 15Dec2011 at 9:33 am

    Quote: “Since the Axl allows more spring travel”

    Can you be more quantitative? I measured the Voile Hardwire springs as having 30 mm of travel. How much more do the Axl springs provide?

  3. Per Twenty Two Designs:
    “Over 2″ of spring travel for smooth action and durability.”

    Edit: I went home and measured the Axl springs in “complete compression” which I measured as being completely within the nylon spring housing, and the spring travel was ~60 mm.

    This is a 100% increase in spring travel over the “30 mm travel” for the Voile hardwires, so quite an increase and the very reason I chose those springs. The compromise is in the added weight of the longer/bigger springs; which are the single heaviest component.

    Depending on the fulcrum position and the boot flex, the actual binding range of motion can vary. Skiing a pair of modified (read as de-stiffened) Scarpa TX gen 1, the binding did not bottom out in position one or position two regardless of how low I skied; I ski low, some say I ski too low 🙂

  4. I rigged up a Vermont tester to get a better idea of release values. Values are in newton meters. Boot sole length is in mm. Release value is for twist only.

    https://www.vermontskisafety.com/files/CALIBRATER-MANUAL.pdf

    Note that boot sole length, ability, height, and weight are used to determine optimal binding settings (DIN).

    Values were averaged over a series of repeated tests, values +/- 5nm.

    Control: Dynafit Comfort, DIN 5, BSL 305mm = 40nm

    TLT toe, no heel retention, ski mode (unlocked) = 30nm

    TLT toe, no heel retention, tour mode (locked) = 65nm

    TLT toe, heel lever retention engaged, ski mode (unlocked) = 65nm

    TLT toe, heel lever retention engaged, tour mode (locked) = 90nm

  5. @ben,

    Without thinking about it too heavily (so I may be wrong) it seems that, even though it may not be reliable, or DIN/TUV certifiable, the TTS concept theoretically allows a form of safety release when the boot is flexed. Any data to back that up Ben, either experiential or on your kitchen table? Your video, while not exactly a ‘controlled’ environment suggests that, due to the natural twisting of the boot it might work while actually telemarking. You did the tests – what’s your take?

    My understanding is that a lot of the DIN release certification is only for when the heel is flat and level with the toe. I’m not even sure we need more than that, but it sure seems that if there’s a 50/50 chance your foot has the heel elevated, you would want releaseability with the heel raised as well.

    I do recall Rottefella mentioning that the releaseability of their binding was limited, or only reliable when the boot was flat. Though it seemed inadequate at the time I must admit it did work whenever I thought it should so maybe that is good enough.

    Even though I just stated it would be nice to have releaseability when your heel is raised, I’m not sure I want it to ever let go while I’m in the middle of a tele.

  6. Of course you’d have to ask for a release when flexed, and of course I would have my bindings torn apart and strewn across the work bench. Friday is my day off, so fun, fun, fun.

    TTS would release while skiing, but it would be so variable that I’m not sure it be possible to measure accurately, I’d expect the increased pressure on the tech pins to lower the release threshold. A way to simulate “under pressure” releases would be to increase the preload and see how release changes. My Dynafit Radicals will be here this afternoon, so once I have them back together I’ll try some flexed releases.

    In terms of developing a predictable release, the heel lever is key because it is a secondary source of friction. The HH levers hang up a little more than the Voile levers due to the aggressive hook. I think a heel could be modified to allow for easier release, but you could lose some lateral stability and pre-release could become a bigger issue. A heel lever with wings like a alpine ski binding would be a neat trick.

    I have this “vision” of a modified tech heel: a teflon spacer between heel and boot for minimizing friction during releae, the existing pins would control later movement, a hook to retain the heel when the boot is flexed forward, and a ramp at the base of the heel for step in. By using the existing spring turntable of the heel this would provide the release and would be settable.

    Then there’s the possibility of making the heel usable for AT use, so you have tele and AT all on the same rig…

  7. As posted by Big Sky on TTips:
    “My question is this: Are the people commenting on this binding skiing it hard, like really hard? Not that I’m some crazy ripper but it should not have released and I’m skittish now. I’m very familiar with dynafit and I even had the toes totally locked. I also made sure the snow was clear of the inserts but my understanding is the binding won’t lock if there is snow build up in there. ”

    Big Sky, I weigh 200#, mondo 30 boots, skiing a compact stance. I have done a fair amount of hard charging on firm snow in my TTS Axl and have not had a single release or pre-release. The tech toe is not prone to releases any more than other AT bindings unless there is snow/ice packed into the boot and/or binding. If you released in tour mode, then it was most assuredly an icing issue.

    Do I ski hard? Hard enough to destroy more than a dozen sets of NTN bindings. Some would say it’s my style, but suffice to say that I have not had any failures with TTS and no toe releases to date, and I have not “cleaned up” my style in the interim 🙂

    Got a new TTS rig on the bench, going to Utah on Friday, review to follow.

    • Ben Kadas on 27Nov2012 at 8:33 am

    Just an update on the TTS Axl: No problems to date with this set up, the binding works awesome, no bottoming out even with knee to ski turns,  tech toes and scarpa dynafittings are unblemished by hours of use both on the up and down.

    It’s pre-season right now, so not a lot of skiing going on, though I did order some new Scarpa boots on Black Friday. I am working on an improved TTS Hammerhead that will be lighter than the TTS Axl and equally powerful, estimated weight will be less than 1500gm, still not as light as the official TTS, but plenty powerful. I’ll post up a review here (if allowed) once I have the design worked out. Here’s to another great TTS season!

    • rob on 28Nov2012 at 8:33 am

    I love reading about TTS. Untill I upgrade from duck bills to a boot with tech fittings all I can do is day dream and let you guys work the bugs out. Keep it up! I think TTS will kill NTN in time.

    • mtnguy3 on 7Feb2013 at 8:52 am

    Hey BenKadas
    How is that TTS Hammerhead project coming?  Looking forward to seeing some pictures and a review.

    • BenKadas on 7Feb2013 at 5:43 pm

    The TTS Hammerheads were built and skied last season, I then sent them to Dostie in the Spring and they have gotten buried under all his other “product testing”. They skied well, as good as the TTS Axl, though the stack height is significant. The easy way to try them out is to mount your tech toe directly to the HH shim. I don’t have the bindings or shims handy, so I can’t give you any measurements. I remember Dostie saying something about trying them out in Dec-Jan, then sending them back…

    • BenKadas on 14Mar2013 at 7:24 pm

    The TTS Hammerheads went to Dostie last Summer and he’s still got them, not sure what he’s using them for, possibly an ashtray, but they are done and I skied them quite a bit last year on my carving skis. The HH works well for a TTS hybrid and could be retrofitted on the cheap by simply mounting the tech toe directly onto the shim. The only downside of an HH TTS is the stack height; though for racing/hardpack it’s just fine.

    Honestly, I mostly skied on the TTS Axl last season and so far this season I am mostly skiing the TTS as developed by Mark Lengel. I prefer the lighter weight TTS, though I have to be more careful when skiing low so the cartridges are not overly stressed.

    Mark has a proprietary TTS toe and is tooling up for a proprietary “long travel” cartridge, look for a complete ready to mount TTS for next Fall (2013).

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