New Boot/Binding Interfaces For Stiff Plastic Telemark Boots ____________________________________________________________ 1 Why another binding? 1.1 Plastic boots pushing today's bindings 1.2 Overview of currently available systems 2 Why another boot? 2.1 Problems with 75mm 2.2 Other interfaces 3 Skiing modes 3.1 Alpine (A) 3.2 Nordic (N) 3.3 Telemark (T) 3.4 Multi-mode: AN, NT, ANT 4 Restricting touring freedom for the telemark mode 4.1 Cleat 4.2 Tether (cable, webbing) 4.3 A telemark release 5 Heel lock-down w/ forward release 5.1 Flexible plate release 5.2 Other systems 6 Can lateral release be improved over existing products? 6.1 Direct release systems 6.2 Plate release systems 7 Accessories 7.1 Brakes 7.2 Elevators 8 Complete Systems 8.1 Dynafit binding / plastic tele boot w/ fittings 8.2 New binding (ANT-75) / plastic 75mm tele boot 8.2.1 Prototype construction 8.2.2 Prototype Evaluation 8.3 New binding (ANT-DF) / plastic tele boot w/ fittings 8.4 New binding (ANT-DF) / Dynafit compatible randonnee boot 9 Conclusion ____________________________________________________________ 1 Why another binding? 1.1 Plastic boots pushing today's bindings It is claimed in trade magazines that the newer stiff plastic boots (such as the Scarpa Terminator and the Garmont Gara) are past the ability of many bindings to handle them. This is probably true and even for some bindings specifically designed for them (e.g. Black Diamond Pitbull), some users have reported screw failures and early cable failures. Clearly a more sturdy interface is needed. In addition, telemark boots have gotten to the height and stiffness of many downhill boots and many skiers are finding they can parallel in the free-heel gear easier than before. Some of these (myself included) would prefer to go all the way and have their tele setup allow a heel lock-down when desired. So for some skiers, a different interface is needed. 1.2 Overview of currently available systems For the purposes of comparison, my brief opinion of the relevant telemark and randonnee bindings follows. (Note: I use "randonnee" instead of "AT", to avoid conflict with my choice of abbreviations: A = Alpine, heels locked, N = Nordic, touring, T = Telemark.) 75 mm interface: Rainey Superloop Best performing Voile compatible binding Pitbull Best performing telemark binding (I like the heel hold down for turning, but it's bad for touring) Voile 3pin/cable Popular system which gives good touring freedom when cables are removed 75 mm release: Voile CRB 1360g, most popular, reliability problems, some skiers report inconsistent release forces Ramer RTB Unknown weight, probably heavier than Voile, but has a more reliable release. Rottefella Unseen in the U.S. Randonnee: Dynafit Tech 4 740g, The lightest, no release in touring mode and skier must remember to unlock front when rear is locked Silvretta SL 1030g, Second lightest, switching modes is confusing, no advantage over Dynafit. Ramer Classic 1300g, This binding is the lightest randonnee binding that works with any boot. The pivot is external and integral to the release. (all weights are from Couloir IX-2 and are per pair) 2 Why another boot? 2.1 Problems with 75mm One of the reasons that 75mm release systems do not compete in weight with the lightest in randonnee gear is the necessity of using a large amount of strong metal plate to grab the 75mm toe. (The Voile CRB 3pin/cable is 620 grams heavier than the Dynafit and 330 grams heavier than Silvretta.) The Dynafit system can be much lighter because it interfaces over a smaller area. Another problem arises when you push the 75mm boot to its limits in mountaineering. The toe is enough of a hindrance that some skiers have opted for using Rainey Superloops and partially grinding the boot toe. 2.2 Other interfaces NNN-BC: Although Voile adapted for NNN-BC, the upper end plastic telemark boot market did not. It does have the advantage that a very free touring pivot is built in. Unfortunately, the amount of torque that can be applied to the narrow bar is limited (in fact grooves under the boot are necessary). The solution to this problem is clear; an interface over a wider part of the toe is needed. Two new interfaces that currently exist that use the widest part of the toe are the Dynafit and Silvretta standards for randonnee boot fittings. Though the Silvretta fittings are used in more boots, the Dynafit has been a clear weight winner due to its ability to integrate the pivot with the fitting. It's not obvious to me if the pivot location is better or worse than NNN-BC, but the fact that the fittings are not exposed while climbing without skis is a huge advantage. The Dynafit fitting and pin interface on the Tech 4 binding may not be strong enough to handle the stress of telemarking (the Tech 4 binding is not designed to release in touring mode). Modifying the anchor of the fitting so the two fittings are connected and anchored to a large part of the boot sole will be necessary. It might also be necessary to modify the fitting shape. The simplest modification would be to simply make the holes deeper, in which case the telemark boot might still be compatible with a Dynafit binding. If necessary though the holes could be wider as well. The Silvretta SL interface appears to be (or could be made to be) laterally rigid enough for the telemark application, but in order to achieve the free pivot needed for touring, an external mechanism on the binding is necessary which might add weight and complexity to the project. Also this fitting doesn't seem to be taking off and Silvretta is now concentrating on the new lightweight version of the 404. The Silvretta fittings are also somewhat compromising in extreme rock climbing situations. The third randonnee interface uses a normal DIN toe and heel. This is only possible in a telemark binding if a flexible plate is used which is laterally very rigid and yet flexes smoothly for the tele position. My guess is that this will be difficult to do well. 3 Skiing modes 3.1 Alpine (A) Having locked heels is something many telemarkers ask for, but for some reason, manufacturers won't oblige. Perhaps this is for reasons of liability, though with a good lateral and forward release the risks are reasonable enough for alpine skiers. Having heels locked allows one to handle uneven snow in parallel mode with less of a chance of face planting. Also on icy snow when the parallel edge is for many more effective, having the heels locked makes this terrain easier to ski. 3.2 Nordic (N) The Nordic or touring mode, is a big issue to any skier who uses their gear beyond the lifts. It is clear that a system with a restricted touring motion (such as the Pitbull with the cables tight) will not do well touring in soft snow (skis dive), and for all snow, this system is more tiring. Randonnee systems have a very free touring pivot but allow for no bending at the ball of the foot which some skiers (myself included) prefer. 3.3 Telemark (T) The telemark mode has some advantages over the alpine mode in addition to being a fun turn to learn. With a little kick wax, rolling descents are easier to handle and certain types of snow such as low angle deep powder seem easier to telemark than alpine for some skiers. 3.4 Multi-mode: AN, NT, ANT Most bindings sold today are in two classes: AN (or randonnee) and NT (telemark bindings). An ANT binding would combine these functions together. In the next section, the components making up this binding are covered. 4 Restricting touring freedom for the telemark mode It is hard for most skiers to telemark well with a free pivot at the toe. Paul Ramer can ski this way on rigid boots, but most telemarkers prefer to have the ball of the foot on or fairly close to the (trailing) ski. This is demonstrated by the need for Cable Track on NNN-BC to telemark effectively. 4.1 Cleat One way to hold the ball of the foot on the ski is to have a cleat on the sole that is latched to the binding in a way that does not inhibit the lateral release. It might be possible to design a metal cleat with a rubber cover. A similar possibility is to use two fittings up on the side of the sole near the ball of the foot. These could be similar to a Dynafit fitting. 4.2 Tether (cable, webbing) The most common way to get telemark performance out of a binding currently is to use a cable either underneath the boot or around it. Under boot routing protects the cable from cutting, but there is still a problem with metal fatigue. One solution to this problem is to use regular climbing grade webbing instead. As long is there are no sharp edges, the webbing should easily last a season or two and can be easily replaced for low cost. Ideally, adjustments of the point where the webbing pivots would be possible (not available with the Pitbull). If these can be done easily while skiing, a binding for 75mm that does not have an external pivot could still adapt for N and T modes by pushing the pivot point forward or backward. 4.3 A telemark release There have been problems with bindings ripping the screws out of the ski during hard forward falls using plastic telemark boots. It is worth looking at mechanisms to release from telemark mode to nordic mode. If a plate release is chosen (see Sect 6), the cable could be attached to the plate and the plate could be designed to release in forward falls. The mechanism I planned to use on my ANT-75 prototype is similar to the heel lock-down in the next section. 5 Heel lock-down w/ forward release 5.1 Flexible plate release A very simple system to handle forward releases from the heel is an interface of a rigid plate and a flexible spring steel plate. I implemented a crude retrofit of a Voile release to test this method and it seems like it could work at least for low DIN settings. It might be possible to move a screw that secures the flexible plate to control the release or if required, different thickness plates can be made. 5.2 Other systems It is possible to use a similar mechanism to any of the heel locks of AT bindings as long as they do not inhibit the lateral release. They simply need to be designed with almost no return force in the lateral direction. 6 Can lateral release be improved over existing products? "All I can tell you now is that I do have plenty of reports among the anecdotal ski injury reports I have received of significant knee injuries in plastic boots with releasable bindings that didn't release.", Mike Tuggy, MD, mtuggy@u.washington.edu, http://weber.u.washington.edu/~mtuggy/sfm/telepag1.htm Lateral release must happen at the toe in a telemark binding, but the point of pivot varies and advantages of the different locations are often debated. I have not prototyped any new releases, but my understanding of the problem is that there are essentially two solutions. 6.1 Direct release systems Ordinary alpine bindings are what I would call direct release systems; there is no plate attached to the boot after a release. This might make for the lightest release system, but is not as easy to do with a telemark binding as it is with a randonnee binding. One idea is to release directly from the fittings (altering the shape of the fittings if necessary) so that torque applied to the boot tends to compress the male end of the fitting (on the binding) and let the boot release. The spring that keeps the male fittings tight against the boot might be challenging in this design, since it is difficult to see how it can be fitted in front of the toe piece. 6.2 Plate release systems There might be a slight weight penalty, but the use of a release plate allows several advantages: 1] The ability to use a simple brake which deploys when the plate is removed (e.g. Voile), 2] The possibility of having a 75mm release work on the same ski (with a different plate), 3] It enables a cable to be used more easily, and 4] The part that releases can be designed to have the high cost, so that the ski mounting hardware is cheap and quivers can be covered with less cost. 7 Accessories 7.1 Brakes Some skiers report they would feel safer if their skis would release and not stay attached if they are in avalanche terrain. Brakes are incorporated into the Voile system and some of the randonnee bindings (though some of these brakes do not function if the ski were to release in touring mode). This leaves a market for a retrofitable brake for Ramer Classic/MT-2000 and RTB, Dynafit Tech, and Silvretta SL as well as systems where brakes are available but heavy or expensive. The only design easily adapted to all existing brakeless bindings is one that does not use information about whether the boot is in the binding. A simple tether that is attached to the boot or sturdy gaitor strap, could deploy a brake when it was pulled hard enough (release tension could be adjustable). The normal style brake will work fine for plate release systems, and might work well for direct release as well. There could be a lever underneath the toe of the boot which does not actuate the brake during the boot's touring motion, but deploys when the boot is completely off the ski. An advantage of direct release brakes are that when you are entering/exiting the binding, the brakes are deployed and the risk of loosing a ski is lower. 7.2 Elevators Elevators are very useful as most randonnee skiers know. They can be mounted on the ski directly or under the heel. For designs that use a cable, it is very reasonable to swap the striker position from the ski to the boot. The piece that attaches to the heel of the boot can be then as thick or slightly thicker than the shim under the ball of the foot, which with some bindings is somewhat substantial. This piece can house the compression spring (instead of in front of the toe as with Black Diamonds Pitbull), as well as house 2 metal bail type elevators. The advantages of elevators on the heel piece are 1] access to elevators with he tips of your poles is improved over some of the current elevators (Rainey Upheel, not included, since I haven't tried this one yet), 2] if mode A is not desired, one can have a binding without any screw holes in the rear of the ski and there is no problem with the striker plate being in the wrong position for different boot sizes (as in a rental operation). Most quality elevators are currently mounted on the ski, and this may still be the best placement for new bindings since: 1] the heel lock-down unit is already there and has to be adjusted to the heel anyway. Elevators can be simply integrated to this part. 2] if the cleat method of restricting touring freedom for telemarking is used, there is nothing at the heel to use to mount elevators to. To avoid the problem of many ski mounted elevators being hard to control with a ski pole, they should be designed to not lie flat on the ski during use (though they could fold flat for transport). 8 Complete Systems All of the previous ideas might have merit in incorporating into existing or new designs, but it is worth considering some complete systems to see how some of the ideas interact with each other. 8.1 Dynafit binding / plastic tele boot w/ fittings If the plastic telemark boot can be made competitive with Dynafit compatible randonnee;e boots in terms of weight and support and the fitting is compatible, randonnee;e users may consider it as an alternative. They will have a harder time kicking steps without crampons, but they will gain a more ergodynamic touring stride. 8.2 New binding (ANT-75) / plastic 75mm tele boot The 75mm standard will be around for a while, and it is worth having a binding to handle these boots. I thought of modifying both the Voile and Ramer release platforms to get a start at this binding, and ended up starting with the Ramer. 8.2.1 prototype construction To prototype the ANT-75, I used a Ramer Classic with the plate cut in half and a side-throw style Rainey Superloop connected to this plate. There are 4 positions (6 mm apart) for the Superloop toe fore-aft positions. A non-release pivot lock-out for telemarking is implemented by a sliding plate that latches on the Ramer plate. No heel lock has been implemented, but a similar mechanism to the modified Voile telemark release (sec 5.1) should work for the heel also. The limiting of travel in telemark mode is done by webbing that comes up through one of three holes (15 mm apart) drilled in the Superloop bottom plate and runs underneath the boot to a short piece of Ramer plate with the Ramer rear bail adjustment. One Superloop side throw spring is used under the heel for tensioning the webbing, but a different length and stiffness spring could be substituted. A bail was constructed in a similar shape as this year's Superloops but with two tapped holes which accept screws coming from a right angle piece mounted to the 75mm side plates. By using different washers above the bail, it is possible to adjust toe tab height (something Tom Turiano requested in Couloir IX-2). 8.2.2 Prototype Evaluation In the touring mode, when the boot was all the way forward of the touring pivot, it feels like being in a normal Ramer Classic since there is little bending at the ball of the foot occurring (the pivot actuates very easily). With the boot all the way back, it feels more tiring (the pivot is harder to actuate). The middle two positions both felt reasonable. In telemark mode, the front webbing pivot felt as free as a 3 pin binding, the middle position felt about like a Pitbull (the position is about the same), and the rear position was a bit too far back for my size boot. The lateral release seemed relatively unaffected by the telemark mode pivot lock out. I showed this prototype to Paul Ramer in March 97 and he was not interested. 8.3 New binding (ANT-DF) / plastic tele boot w/ fittings This the market with the most potential, but I haven't done any prototyping yet. Either direct or plate release with the associated brake could be used. Either a cable or cleat could hold the ball of the foot down. Heel elevators may as well be part of the heel lock down unit. 8.4 New binding (ANT-DF) / Dynafit compatible randonnee boot This possibility would probably not be very common, but if the ANT-DF is either cheaper than the Dynafit binding or if the skier wants a touring release for avalanche terrain (which Dynafit does not have), but yet the skier prefers to use rigid boots for climbing and touring, the ANT-DF might be a good choice. It is thus probably worthwhile to make this binding handle these boots. 9 Conclusion The time has never been more ripe for a new interface for stiff plastic tele boots. These boots are now high-performance, popular, and made by several manufacturers. They are capable enough as a randonnee boot as long as the heel can be locked down. A new binding with all modes (ANT) and a good boot can be competitive against many randonnee systems in modes A and N, so randonnee skiers may cross over and maybe even try the T mode when conditions are right. An ANT (or an NT restriction) binding can be competitive with other release NT systems currently on the market. Finally the 75mm market is not going to die tomorrow and having a 75mm compatible version might not be a bad idea in terms of total market share. If any of these new ideas are worthwhile, I'd be interested in working with others to pursue them further. My academic background is in Math/Electrical Engineering, but I'm happy behind a grinding wheel as well. Contact Info: Dara Parsavand | parsavan@prony.colorado.edu 735 Pine Street, Boulder, CO 80303 (303) 417-1445 (press #2 after connection)