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Locking cuff ski/walk mechanism for TX Pro/Rush hybrid Franken boot

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  • Locking cuff ski/walk mechanism for TX Pro/Rush hybrid Franken boot

    I haven't been completely satisfied with the way these boots ski since replacing the OEM cuff with a Scarpa Rush (3-buckle Maestrale) cuff. The ski walk switches didn't provide the range of motion for touring that I had hoped to achieve, so I first tried skiing them without a ski mode. Tele turns in good snow were fine but everything else was pretty rough. No power and no back seat to lean into when I need to.

    I made a simple ski/walk mode from a chunk of plastic and a bungee. That helped but I really noticed that the lack of a locked cuff still wasn't doing it. So I tried attaching a steel bar to connect the cuff and the shell. It proved the concept but it was way too clunky. So I had a pair of shorter rods and rebuilt the back of the boot with that to make it a little less inelegant.

    The first picture is the short rod secured to the hole where the Rush ski/walk mechanism was with a shim made from 6 mm delrin (original Voile Plate material), an M5 T-nut, and a 14 mm M5 pan head posidrive machine screw.

    The second picture is the boot in walk mode. I still need to cut out the side of the bottom hole to allow it to slide in and out of ski mode when I loosen the wing head screw..

    Some numbers I got comparing to the standard TX Pro are:

    Weight Pro = 1869 g
    Weight my frankenboot = 1609 g
    Walk mode Pro = +10.2 deg
    Walk mode Franken = -3.1 deg

    Ski mode 1 Pro = 14.2 deg
    Ski mode 2 Pro = 19.4 deg
    Ski mode Franken = 17.5 deg

    Total ROM Pro 1 = 4.0 deg
    Total ROM Pro 2 = 9.25 deg
    Total ROM Franken = 20.6 deg

    Tour mode difference is 13.3 degrees.

    I am ready to call this a success. I already know they ski ok without the locking cuff. Performance should be a bit better this way, especially in manky snow and technical terrain. I'll see soon but my foot is still numb so I'll wait a little longer.
    Click image for larger version

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    Click image for larger version

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  • #2
    previous years were year devoted to binding tinkering. seems 2020 is the year of boot tinker.

    elegant, simple. minimalist version of the la sportiva solar lock. Only the solar uses a notch in the bar so you can swing it away to the side.

    do you think you will have any problems with the bar rotating down and hitting stuff while in tour mode? If so, a wave washer under the pivot screw, or between the bar and delrin block, might add enough friction to keep it in place. Or if you spaced it out farther so it could rotate up 180, then add a bend to make it mate with your nut/stud. Then you could add detent, velcro, elastic, or second stud at 180, and just switch the nut up there to keep it out of the way during tour.

    btw, the original voile plate, ie the one mounted below a 3 pin binding with the bungie heel throw, the plate itself was made out of UHMW. I think the little plate locator/heel pad mounted to the ski was likely delrin, but could have been nylon, been a while. Mine were bright pink, and matched my bright pink Anses skis.
    Last edited by jasonq; 2 March 2020, 11:23 AM.


    • #3
      Thanks Jason. It rotates to the side. I just didn't cut the notch in last night. That is the last step that I will do today. I did it on a longer bar that I used to test the concept and posted in the thread about removing the cuff. This time I decided to give it its own thread.

      In the picture I rotated it 90 degrees, as far as it will go, only so it didn't interfere with the view of the notch I cut into the cuff to maximize ROM. It would only rotate a few degrees and is held tight by the friction of the top screw.

      Yes, I might grind a little off the cuff to the outside so it would rotate 180 degrees but I don't think it will be necessary and would require pulling the pants out of the way more to do that every time. I think just moving it to the side will be enough and I don't think it will fall back down into ski mode. It's pretty tight.

      Didn't know the original Voile plate was UHMW and not delrin. Thanks again!
      Last edited by cesare; 2 March 2020, 02:37 PM.


      • #4
        Good on you for giving the lowly wingnut a chance.

        You are a kind and compassionate man.


        • #5
          Originally posted by aqua toque View Post
          Good on you lowly wingnut.
          What did you call him?

          Function in disaster, finish in style.


          • #6
            I'll take it! ;-)


            • #7
              The last time I skied in these boots on the v2 Lynx, I had a bit of trouble. The stiffer Lynx required me to lean on the cuff more than I am accustomed to doing and I ended up with a bad case of shin bang after a few runs trying to keep up with a younger alpine skier in the steep sidecountry at Teine. Something had to be done and I'd been thinking about it for a while this summer. I finally solved the problem.

              I started by removing the wing head screw and replacing it with just a regular M5 screw because it was not as easy to switch modes with the wing head screw as I expected and there was always the risk of losing the screw. I had to add a lock nut behind the T-nut to hold the screw in place, then loctited and smeared JB Weld around the whole assembly inside the shell to hold it tight. The tension of flexing the boot keeps the ski mode bar in place under pretty heavy carpet testing and I am confident it will not slip into tour mode while I'm skiing. And when I am skinning, the boot will mostly be in backward ROM that will prevent it slipping back into ski mode. I think...

              Click image for larger version  Name:	IMG_8256.JPG Views:	27 Size:	1.56 MB ID:	104314

              Then I went to work on the shin bang problem. I cut the front off a pair of new 100 yen shop insoles, wrapped them in contact paper, and double side taped them to the tongue on the shell. The left one was perfect but the right one still killed me. So I started searching for a placement of another pad to take the pressure off my shin. I found it above the medial ankule bone. I also trimmed down the arch supports that I had taped into the shell to compensate for the removal of footbeds. That lowered my foot in the boot a little more and between those two actions, I solved the problem. A final round of vigorous carpet testing out in the hall of our building confirmed that I could crush the tongue of the boot now with more force than I ever need and the binding feels totally fine now. It's another month or so until enough snow to ski but we have had snow at higher elevations for the last week or so. The proof will be in the skiing.

              Click image for larger version  Name:	IMG_8255.JPG Views:	27 Size:	1.81 MB ID:	104315
              Last edited by cesare; 17 October 2020, 04:02 PM.


              • #8
                looking nice.

                if you have an issue with the bar staying in the mode you want, you could try adding spring point set screw as a detent. looks like you could put it into your delrin spacer block and either have it locate in a hole in the bar. Or have it exposed on the side so the bar has to swing thru the detent to change modes. if you can locate it in the right place, you might be able to use just one to make a detent for both up and down. migth be fiddly to get just the right detent strength?

                something like this maybe?

                another option if your bar is magnetic, to use a rare earth magnet in your delrin spacer. either recessed underneath the bar or on top of your spacer on the bottom left side as seen in pic one. Something like that would hold the bar in the ski mode well i think, and shouldn't be too fiddle to get just right.


                • #9
                  A very low tech way to keep the bar in the right mode would be to cover the metal near the open end of the notch with some duct tape. Or, slightly better, put a small bit of some urethane glue on it. Just something that will (A) take up some space and close the notch off a bit so the bar can't accidentally change modes but (B) is slightly flexible so you can push the bar into the other mode with a tiny bit of force.


                  • #10
                    Thanks for the ideas, gents. I really think it will not change modes that easily because the fit on the upper screw that is the pivot point is pretty tight. It takes some effort to move it and if there is any tension on it from leaning on the cuff it will not budge at all. And when I'm in walk mode the notch will not be anywhere near the screw most of the time. But if it does happen, I will go through your suggestions from simplest to more complicated to see what works. It was REALLY difficult to switch modes with the wing head screw locking it up tight because it wouldn't allow the notch in the bar to swing off the screw until the screw was almost all the way off due to the difficulty in maintaining a neutral cuff angle while bending over and manipulating the screw. And that was barehanded. With gloves on the screw always ended up falling out. My biggest worry now is still losing the screw but I think there is enough loctite and epoxy stuffed all around it that it should stay put. I have extra screws in my repair kit now just in case.