If you are finding TLT speed, at around 730 grammes, a bit lardy here are some alternatives. The market reminds me bit of the bespoke cycle parts market that started in the late 1980s. It would be nice to see some more practical alternatives to Dynafit that the G3 Onyx

http://pistehors.com/news/ski/comments/0880-g3-previews-onxy-dynafit-compatible-binding/

I’ve already blogged about the XP50 from Pierre Gignoux. The heel weighs 100 grammes/pair and costs 150€. It has a fixed DIN of 6 (set by the spring). A toe piece is under beta test and is slated to weigh 130g/pair. So that’s 230 grammes for your bindings.

http://pierregignoux1.free.fr/France/Xp50.php

ATK Race have some pretty sexy toe pieces. the all metal construction looks solid. You can’t fit ski crampons, something like the Voile ski crampon posted by Ise would be a possibility.

The NX Extreme toe (309€) weighs 150 grammes and the heel 164€ 120 grammes. The NX World Cup takes 20 grammes off the heel weight for another 15€.

Felisaz PLUM has heels weiging 125g / pair. Toes have had some reported design problems. They are apparently available from Cactus in Geneva, I will have to check them out.

Finally don’t forget Dynafit’s own Low Tech Race which tips the scales around 320 grammes and retails for 600€

davidof - 20 January 2009 10:36 PM

TLT speed, at around 730 grammes

Comparing binding weights is a tricky business. Marketing estimates from manufacturers are usually not thought to be reliable—partly because you’re not sure exactly what they measured. (did they include the screws?).

Anyway for us touring skiers who don’t care about racing, why should these weight differences matter?  Here’s some perspective:

My normal touring setup, moderately wide skis, moderate-weight, Diamir binding with no heel-brakes is about 4.2kg on each leg. (8.4kg pair). If I used a Dynafit TourLite Tech binding they’d be lighter, say around 3.6kg per leg. When I walk around normally in my running shoes, that’s around 0.5kg per leg.

What’s the “load” in my knee-extension muscles (e.g. “quadriceps") which must push the weight forward. Well it’s not just the weight of the ski+boot+binding. It’s also the weight of the flesh and bones in my ankle and foot - (say that’s about 0.85kg per leg), and it’s also about the weight of the flesh + bones between my knee and ankle - (say that’s about 3.15kg per leg). The muscular load is proportional to the “rotational inertia” of what’s being moved, which is proportional to the mass and the square of the distance from the center of rotation (in this case the knee). So rough formula for rotational inertia for the knee-extension muscles pushing the foot forward:
I = 3.15kg*.22m*.22m + (0.85kg + shoe-weight)*.44m*.44m
gives these results for:
** ski+boot+Diamir binding (4.2kg):  I = 1.13
** running shoes (0.5kg):  I = 0.414

So switching to running shoes reduced torque load on my knee-extension muscles by 73%.
what about changing my binding from Diamir to Dynafit?
** ski+boot+Dynafit binding (3.6kg):  I = 1.01
. . . reduces torque load by about 11%

Suppose some ultra-light binding were 0.2kg less per leg than Dynafit TLT:
** ski+boot+ultralight (3.4kg):  I = 0.975
. . . torque load in knee-extension muscles is about 3.5% less than Dynafit TLT.

Big percentage reduction in binding weight leads to small percentage reduction in muscular load.

Anyway most touring skiers have well-developed knee-extension muscles from other activities like bicycling—so I doubt that’s a significant performance “bottleneck” for uphill ski touring. More important are the hip-flexion muscles.

Ken

Sportsmen and women at high level seem to obsess about every gram. I would like to see an ATK Race binding for consumers

http://www.atkrace.com/

but with a good range of boot adjustment, say 2 mondo points plus DIN adjustment. I imagine that Dynafit has some patents on the heel unit that might make this tricky, hence the Onyx rethink at that end.

From a _touring_ perspective, how much speed do we need, and do we need light bindings to achieve it?

300 vertical meters per hour is a climbing pace fast enough to do most ski tours in the Alps (with careful planning and organization). Actually in the summer time an athletic hiker can climb significantly faster than that. Guided ski parties often don’t sustain more than 250 vertical meters per hour.
Like wake up at home at 6:00, drive to a trailhead, start climbing at 8:00 and by 12:00 you’re up 1200 meters. There’s lots of great ski tours in the Alpes du Nord less than 1200 vertical meters. In winter time when it’s colder lots of parties feel safe starting their descent as late as 13:30, so that allows 1600 meters of climbing. There’s only a handful of great ski tours in the Alpes du Nord bigger than 1600 vertical meters (and most of those have refuges along the way to split the climbing into two days).
For real big tours in springtime, another option is to drive to the trailhead the night before, sleep a few hours in the car, start very early. For example park at Ailefroide, start climbing at 4:00 at a rate of 300 m/hr and at 12:00 I’m on the summit of the Dome de Neige des Ecrins (having bypassed two refuges)

300 meters per hour: what’s the require for muscles moving the foot with the extra weight of ski+boot+binding? A turnover frequency of 30 total stride-cycles (including one push from each of the two legs) per minute is not very much (typical turnover by experienced bicyclists is around 60-90 total cycles per minute) (walkers are often around 50, runners higher than that).

30 total stride-cycles is 60 individual steps per minute, or 3600 per hour. For 300 meters that means raising the weight on each foot by
8.33cm elevation per individual step by each foot.
Not very much.
Or assuming about climbing with switchback “conversion” zig-zags at an average climbing slope angle of 16 degrees:
30cm of forward advance per individual step by each foot.
Not very much.

If the goal is to complete great ski tours (rather than compete with touring partners), I think for most tourers that rather than saving weight carried on each foot, there are much bigger gains to be had from better organization (and taking shorter rest breaks).

Ken

Hi Ken,
I agree, I was thinking more of a binding with less plastic parts rather than saving weight which is why the ATK’s looked interesting. F’example I’ve just noticed that the front locking lever on my Comfort’s is broken although it should continue to work.

davidof - 21 January 2009 05:07 PM

I would like to see an ATK Race binding for consumers . . . hence the Onyx rethink at that end.

Yes it’s great that we’re getting lots more options now for Dynafit-compatible bindings.

For serious _touring_, reliability of my binding is more important than saving 100-200g. I’d want to be out on long-proven Dynafit TLT bindings, rather than taking the chance that some ultra-light Dynafit-compatible is going to _break_ when it’s just me and one ski partner and an unguarded refuge.

I have carefully purchased all my boots in the last ten years to be Dynafit-compatible, even though currently I usually tour on Fritschi Diamir bindings. (I mean all my Alpine Touring boots. My _truly_ light boots for long gentle tours with _truly_ ultra-light skis and bindings were all carefully purchased to be SNS compatible).

I do own a light AT setup with Dynafit binding, Scarpa F1 boot, Atomic Tourcap Guide skis—but I don’t often ski on them because I only have space in airline luggage for bringing two pairs of skis to France. So the Dynafit setup stays home and instead I bring (1) my heavier AT setup for better downhill performance in difficult snow conditions, and (2) ultra-ultra-light SNS binding skis.

Ken

Well it is true that you certainly climbed PDQ when we met up.

davidof - 21 January 2009 05:28 PM

I agree, I was thinking more of a binding with less plastic parts rather than saving weight.

Yes I agree that new Dynafit compatible bindings could be _more_ reliable—and I’d be interested to hear more details - (though most of the emphasis so far has been on saving weight).

Extending the analysis of “load” on muscles to the hip-flexion muscles . . .
(important for moving the ski up and forward, but perhaps less well-developed from bicycling than the knee-flexion muscles). The calculation for hip-flexion muscles might be more complicated because might include a significant component of moving the weight of the ski+boot+binding _upward_ (especially when breaking trail)—while the knee-extension move was mostly only about sliding the ski forward.

I’ll assume that the mass of the flesh and bone of my lower leg (below my knee and including ankle and foot) is about 4kg, and the mass of my upper leg (between hip and knee) is about 6.5kg and the distance between my hip joint and knee joint is about 0.38 meter.

Forward—for the inertial “load” of sliding the ski forward, we want to calculate rotational inertia about the hip joint. If the mass of the upper leg were distributed uniformally along its length, then the effective “radius” for rotational inertia would be 0.22m—but actually the mass is skewed closer to the hip, so let’s use .19m instead. If the lower leg were just a “dead weight”, I’d just use hip-knee length as “radius” for its mass, but actually the lower part of the lower leg is itself being accelerated forward (by the knee-extension muscles)—which adds more inertial “load”, so I’ll put in an “extra load” factor of 1.5, so the rotational inertia for hip-flexion is:
I = 6.5kg*.19m*.19m + (4.0kg + shoe-weight)*.38m*.38m*1.5
gives these results for:
** ski+boot+Diamir binding (4.2kg):  I = 2.01
** running shoes (0.5kg):  I = 1.2
** ski+boot+Dynafit binding (3.6kg):  I = 1.84
** ski+boot+ultralight (3.4kg):  I = 1.84
. . . so the Dynafit versus Diamir reduces inertial load by 6.5%
. . . ultra-light versus Dynafit TLT reduces inertial load by 3.5%

Upward—for the gravitational “load” of lifting the ski upward—there’s no load when the knee is vertically below the hip at the start of the step, but there’s substantial torque load when the knee is lifted up at the finish, say the upper leg is then around 45 degrees from vertical—say the average angle is around 25 degrees. Assume the effective “force radius” for the mass of the upper leg is around .16m (less than half of its length, because its mass is not proportionally distributed).
gravitational Torque = 6.5kg*.16m*sin(25) + (4.0kg + shoe-weight)*.38m*sin(25)
gives these results for:
** ski+boot+Diamir binding (4.2kg):  gT = 1.76
** running shoes (0.5kg):  gT = 1.16
** ski+boot+Dynafit binding (3.6kg): gT = 1.66
** ski+boot+ultralight (3.4kg):  gT = 1.63
. . . so the Dynafit versus Diamir reduces gravitational load by 5.5%
. . . ultra-light versus Dynafit TLT reduces gravitational load by 2%

Big percentage reduction in binding weight leads to small percentage reduction in muscular loads.

Ken

davidof - 21 January 2009 05:07 PM

Sportsmen and women at high level seem to obsess about every gram.

How true.
. . . (but it should not apply so much for most tourers, see more details below)

For rando racers (and for those many touring skiers who cannot resist competing with their partners) that obsession might make sense: concern about “every gram” which is attached to the _foot_. That’s because unlike pedaling a bicycle, climbing on skis does not have “gears”.

How fast you climb is the product of: (a) step length; (b) one separate step each for the number of legs; (c) turnover (frequency of complete stroke cycles with one step each by both legs). Since (a) is limited to some reasonable distance (not more than 1 meter), and (b) is fixed for humans (though dogs get double the number)—the main thing a racer can work on for higher climbing speed is (c) turnover frequency.
I think most touring skiers seldom achieve a frequency more than 40 per minute (of complete cycles with one step by each of the two legs), but racers can sustain 55 or more per minute. (Experienced bicyclists easily sustain 70-80).

The problem with frequency in ski-climbing is that torque load on the specific hip-flexion and knee-extension muscles for moving the ski forward depends on _more_ factors other than just ski+boot+binding weight. The specific load is also proportional to (a) the skier’s overall speed and (b) the _square_ of the turnover frequency. So ski-rando racers really are pushing the limits of torque load on those specific hip-flexion and knee-extension muscles. Anything they can do to reduce that load will yield something resembling a proportional improvement in sustainable climbing speed.

Touring skiers can avoid the problem of extra load from ski-boot-binding weight by playing this principle the opposite way: _reduce_ the turnover frequency. Suppose a skier can climb 400 meters per hour at a frequency of 40 per minute. Climbing with zig-zag switchback “conversions” at an average upward angle of 16 degrees, gives a step length of 30cm (not much, about a foot) and vertical gain per step of 8.3cm (not much, about three inches). If the same skier decreases their striding frequency to 30 per minute, but increases their step length to 36cm with 10cm vertical gain, they are climbing at 360 meters per hour.
. . . which is 10% slower than 400 meters, but the torque load on the muscles is only _half_ of what it was at 400 meters per hour (because of the much lower frequency).

Touring skiers have other strategies available to reduce load on those specific muscles _much_ more than by trimming weight off the binding.
. . . (Even if using a Diamir binding rather than Dynafit would tend to increase muscular load by as much as 10%, natural compensating motion adjustments can make the impact much much smaller.)

Also as the season progresses, each time skier does another tour, those hip-flexion and knee-extension muscles develop more strength and endurance for their special task of moving the weight of the ski forward.

Ken

The logical conclusion of the calculation is clear: put your skis, binding and boots on your back and climb with your running shoes

But the usual experience is that it’s less tiring to climb on skis, one reason being that there is more regularity in the moves.

So there are many factors. I agree that for non-racers, even at speed higher than 300m/h, the weight of the equipment is not really a critical factor (fitness is!): a few minutes difference at the summit are key in a race, not in a tour…

ericlodi - 22 January 2009 07:29 AM

But the usual experience is that it’s less tiring to climb on skis [than on boots carrying skis], one reason being that there is more regularity in the moves.

I agree that it often feels harder to boot up a hill carrying skis - (and that’s a good warning against the simplistic reasoning that “less weight attached to the feet is always better").
I offer these typical reasons for why it happens:
(a) people tend to take a steeper more direct line up the hill when booting.
(b) people tend to take more vertical in each step when booting - (the steps are too high).
(c) sometimes the snow is soft or difficult.
That is, booting feels harder because it’s been made _actually_ harder.

Going up a gentle/moderate slope on firm (but not icy) snow, I think booting up and carrying skis on the pack is faster and easier for athletic non-racers than climbing with skis on. Or if you had a well-designed non-steep _stairway_ to walk up, then carrying skis would be faster and easier.

But out in the real snow, the problem is that it takes a lot of extra _work_ to create a boot-line as “friendly” as a ski-climbing track. For the person kicking the steps, it’s less work to go straight up the hill, and less work to create fewer steps with more height between them.

I think the big problem is with (b)—some of the steps are too high. Because then no matter how slow you climb, you have to make a “strength” move to raise your whole body weight plus the skis, up to the next step. Such moves engage the “Fast Glycolytive” (FG) muscle fibers, which soon get fatigued—then soon after that every step up feels fatigued.

A good ski uptrack avoids those problems—with little extra work by the leader - except to make the slope of the track gentler than the leader would require.

Ken

KenR from USA - 24 January 2009 03:43 AM

Going up a gentle/moderate slope on firm (but not icy) snow, I think booting up and carrying skis on the pack is faster and easier for athletic non-racers than climbing with skis on.

An old timer would add that it saves the skins, that wear out fast on hard snow

Ski Trab have presented a couple of binding projects at the ISPO 2009. There is a Dynafit clone similar to the ATK and another “revolutionary” composite aluminium/magnesium binding slated to weigh 560 grammes with 14 DIN with proper front boot security. The Trab TR1 binding will be out for the 2010/11 season.