How Does a Cable Binding Work?

[lowangle al]

I think moving the cable connection closer to mid foot would lead to broken legs like with the old cables and early alpine bindings.

[JohnSKepler]

I find myself wanting to make a simplified dynamics model of these systems and run it in Matlab/Simulink. […] I don't know that I'll actually do this since I'd really rather be out skiing and I do similar things at work. […> All it would do is verify what users have already reported.
Oh, it would also let me vary the configuration and put a stake through the heart of the physics debate!
Maybe worth it after all???

@JohnSKepler If you have time at some moment, it would be great to see an updated version of the first post diagrams, with the difference that the cables would be routed through somewhere around mid sole. Already, it is nice to have a summary of the lengthy Physics Debate content in this thread. Thanks

I could do that. In the original diagram, I didn't even intend to make the cable connect at the right point. Just drew it for reference. But updating it is a good idea since, well, this board is world wide and we all have reputations to protect!

I may add another diagram as well. It was not lost on me that the physics debacle debate left out the other two axes of control. It was centered almost exclusively on the moment* (or not) the cables (or not) imparted (or not) to the ski when there are three control moments, one each about roll, pitch, and yaw - not at all unlike an airplane, that are significantly affected by what the cables and foot do. (In the drawing below I've placed the axes origin at the balance point of the ski but where it is doesn't matter.)

The orientation of the forefoot on the ski plays a huge role in how the body, through the flexible linkage of the femur-tibia-foot imparts torque to the yaw axis. Flat forefoot - loads of controllable torque. Standing on toe, much less torque and much less controllable. It affects roll, as well, but has a smaller effect. Not saying that controlling roll has a smaller effect, it's how you get on edge, but the position of the forefoot doesn't effect controlling that axis as much. In fact, my gut tells me that the way the skier controls yaw may be the lynchpin of the telemark turn. I can't say I know how that is done, but from a consideration of moment and force and how it gets to the ski, the flat forefoot is huge. Negative pitch torque (the cable and shins-to-boots**) improves directional control. Positive pitch torque helps you float on powder. So, the cable not only pushes the tips into the snow, improving directional control, it also keeps the forefoot on the ski, improving directional control. This all hit me the other day and that's why I started thinking about an Xplore/cable frankenbinding!

Please note that I've been stuck in boring (but necessary and productive) reviews at work this week and when my subsystem isn't on deck I have to have something to think about! So I'm not out to prove anyone right or wrong, just sharing my admittedly geeked-out daydreams with a few people here who might find some of this interesting. (My wife doesn't care about any of this.) None of it is new or revolutionary, it's just the way the tens of thousands of engineers in my field think about problems. Feel free to pity me. My wife does, but she likes me anyway because I'm so good at fixing crap around the house.

*Moment - a torque applied about an axis
** Shins-to-boots - @fisheater , best tip ever!

If there are any young, bright mechanical engineers on this forum, there are a bunch of Ph.D. dissertation topics in this. I'm an old guy and it just sounds like too much work, but it's fun to think about.

[Capercaillie]

The first thing I'd neglect is sole bending other than at the toe. Too hard to model!

Wouldn't a rigid plate (heel to behind the ball of foot) connected to a leaf spring (ball of foot to toes) be a good approximation?

[TallGrass]