Jeff Markham wrote:I'm trying to understand this DIN stuff, so bear with me...
Isn't Harald saying that the combination of a persistent force/torque coupled with the spike caused by an irregularity (e.g., rut) causes the total force to exceed the DIN release point? So, if you normally exert less torque/force (binding-wise), it would require a larger "spike" to release? Conversely, if you are torquing on the bindings a relatively smaller spike will cause you to release?
I guess the question is: does a PMTS skier exert less torque (releasing) force on his/her bindings than a non-PMTS skier? How could this be objectively tested?
Yes, that is what is being said, but the physics doesn't back up the hypothesis.
Suppose you are making a LH turn, and twisting. The rotational force you exert is pushing your toes to the left, so you are pressuring the left arm of the toepiece. You have a low edge angle and are skidding the turn.
Now, as you near the end of the turn, you skid into a bump. The bump will push the ski in the direction that the skier is twisting it. The lateral force is not an additive force, it subtracts from the force on the left arm of the binding. So the physics says, twisted/steered turns can actually assist keeping the ski's on!
This skier will only loose a ski if the bump overrides his torque and the right arm of the toepiece releases. A properly edged skier will not loose the ski. But, it's not the skiers torque that assisted in the ejection, it's the high lateral force received by skidding into the bump due to a low edge angle. The hypothesis that the torqe ADDS to the ejection force is incorrect here.
BTW: This is the concern when bump skiing, and why you can't lower your DIN in the bumps.
Now, suppose that the skier is making another steered LH turn. This time, the skis are rotated at the top of the turn and bump hits inside edge of the RH ski only, prior to getting to the fall line.
I can't imagine how quickly the skier would need to be pivoting their feet to overcome the speed that the traverse to the right that brings them past the bump for this to happen. I'd think it's beyond anyones capacity, unless they are moving extremely slowly/stopped are parallel and manage to fit the bump between their skis just when the turn starts.
For the ski to be dislodged when traversing perpendicular to the fall line, they'd have to twist with the same force that would release the binding when standing still! There is no additive force.
Moreover, it can't happen at all in a wedge!
In conclusion, I see no evidence to support the hypothesis that steering torque assists binding release due to irregularities in terrain.
Is there some piece of this analysis I've missed?