Now I would like to give a deeper insight in the construction of the Kingpin as I had the chance to talk to the engineer. Also I would like to explain the term “Elasticity” in connection with ski bindings. I do not doubt the fact the Kingpin is very stable and has an awesome power transmission which therefore will not be discussed further.
My main critique regarding the Kingpin was my assumption that it lacked elasticity. With ski bindings elasticity is defined as the way a ski boot can move in a ski binding between its quiet position in the middle of the binding and the point where it drops out of it. Especially the latest developments at Dynafit or G3 and also Fritschi showed the importance of the added elasticity in their latest models.
Every ski binding needs elasticity to translate the power of the built in spring into the Z-Value set for the respective skier. Imagine it like this: If your ski gets a hit your binding has to be able to “understand” the difference between a shock where the ski has to stay on the foot, or a fall where the ski has to be released. To this end the spring in the binding has to be able to absorb a force. To to so, the spring needs some distance along which the spring is loaded. If this distance is too short or the spring is too weak, the binding will release too early or at least can not be set to a defined Z-Value. This was the main reason why most skiers locked their Dynafit bindings also when skiing.
This vague release was the problem of the “old” generation of pin bindings like the Vertical or the Radical bindings from Dynafit. That was also the reason they never got ISO certified. Their rear head was just never able to absorb – or load enough energy to be precise – and stabilize the boot before the front pins snapped open. Their elasticity was simply too low.
Therefore Dynafit came up with the rotating front head solution. They introduced it first with the Beast bindings but implemented it for Season 15/16 also for their Radical 2.0 series. G3 went with a higher construction of the pin arms for more elasticity in their front pins. Both brands were therefore able to extend the distance in heel movement where the binding snaps open. Also Fritschi has built a so far unknown elasticity in their slide holding the front pins and was able to present a novelty in the pin binding world with a safety pin system that is now, with the black version, also DIN certified.
When I held the first Kinpin in my hands, I was puzzled as exactly those developments of the other brands seemed not have been implemented. I found the heel piece not elastic at all but just sprang open at a certain pressure. Further the 6 springs in the front had very little holding power, far less than the ION for example. This was in stark contrast to the Marker marketing talking of the powerful “six-pack”. And lastly there was virtually no elasticity in the front pins.
To add more difficulty the boot was jammed in the heel between the piston and the slider plate (mounted on the stopper). This was a third power holding the boot in position. It seemed very difficult to me to master three powers (Front Pins, jamming of heel and rotating heel piston) to work together for a defined safety release system. Together with the assumed lack of elasticity the Kingpin did not persuade me.
Not everything big and beautiful has its source in a master plan or an intelligent design. But to assume the Kingpin was a product of luck and no one in the development catacombs of Marker did really thoroughly think about the limits of pin systems and come up with a vision was not realistic either. So I wrote down my questions and sent them to marker. Eventually I got the contact of Christian Brandl, the head (and probably also the heart) of the Kingpin.
He offered to meet at ISPO 2016 to discuss my questions. In the following weeks we exchanged a few more emails. The more I seemed to know the more questions I had. Generally the purpose was to eliminate my doubts about the lack of elasticity in the Kingpin and the question how such a binding could comply with the ISO Standard. In the end I got more information and insight than I was hoping for. What I hope I understood I would like to explain in the following.
Elasticity of the Kingpin
Of course the Kingpin is elastic and of course Marker did implement the latest developments within the Pin Binding market. Her elasticity is just not sensible with bare hands. Contrary to the Radical 2.0 and the G3 ION, where the spring tension builds up slowly and in a linear way, the Kingpin builds up that tension within the first few millimeters in a much steeper way. The reason for this can be found on the inside of the Kinpins back unit where a the spring is mounted on top of a wheel that sits in a socket. In the first 5mm of side rotation, the wheel has to be lifted up on the edge of that socket.
By comparison, in the Radical 2.0 the back of the boot travels more than double the distance as in the Kinpin until the binding has built up the same pressure. This explains why the elasticity In the Radical 2.0 and the ION can be felt by hand. The spring tension builds up much slower and in a more linear way towards the release point.
Even if one can not feel it by hand, also the Kingpin has an elasticity, which can easily be seen on the chart. It just all happens on a much shorter distance. A shorter distance means less “time to decide” for the binding whether to absorb or to release. That asks for a frictionless travel of the boot to be able to absorb shocks or release the boot according to the set DIN value. More on the reduction of friction in the Kinpin later.
Even though there are many different functions needed to fulfill the ISO 13992 Standard, a reliable horizontal release mechanism of the binding in every possible skiing situation is a key feature. That’s why we focus mainly on this function. By the way, one function that is key for a reliable horizontal release is a length adjustment of the back unit. As you know every ski flexes. If you make a turn the distance between the front and the back of the binding gets shorter. To avoid a jamming of the boot between the front and the back of the binding, the back unit must be able to adjust to the new length. This is usually done by a spring built in between the base plate and the back head.
In the chart above both bindings are capable of an ISO normed side release and therefore both have a length adjustment mechanism. Nevertheless, in reality both work quite differently.
Two curves – two philosophies
My first question regarding the elasticity of the Kingpin and the compliance with the ISO standard was answered. But the grey and green line in the chart above raised more questions.
- Even though both bindings in the graph have very different pressure/travel curves they both got the ISO stamp and are both considered save. What do the different curves say about the behaving of the binding and the skiing performance?
- Where on the curve does the Kingpin release and what is the advantage of the long “flat” part on the top?
Regarding the second question Christian has sent me the draft on the left. According to his understanding this is the optimal pressure/travel ratio that every binding brand wants to get close to. Especially of course for alpine bindings. On one hand the 15mm of travel until the boot is released have proven optimal of time. On the other hand one tries to get the steepest possible curve on the first few millimeters in order to keep the boot in position as long as possible and make sure one has the best possible power transmission.
Respectively, regarding my second question, the Kingpin releases the boot at the far right end of the “Table” the green curve describes. The curve is flat on top because the maximal holding pressure according to the set DIN Value (before releasing the boot) is already reached. From now on the boot travels another 5mm up to the total 12mm on the maximal resistance before being released. After falling out of the binding, the pressure in the binding falls rapidly as there is no resistance from the boot anymore. Thus the fast decline of the green line. The advantage of this “Table” shaped curve is the fact that the boot is held better in position while skiing. The binding absorbs shocks up to the set DIN Value with a minimal amount of travel of the boot in the binding. The flat part of the curve ensures one does not experience unwanted pre-releases of the binding. Even shocks with a pressure close to the set DIN Value will not make the binding snap open, since the boot still has to travel the full 12mm (15mm in an optimal case) before the boot is released.
A “vulcano” shaped curve (the green line in the graph) means the side release kicks in with every small hit or shock and the ski boot moves a few Millimeters to the left or right. One could describe this behavior as spongy, which can in an extreme case lead to a feeling as if the boot is not properly attached to the ski.
It’s in the nature of the classic Dynafit-like back head construction (Dynafit, G3, Plum) that the spring load of the side release is built up in a linear way up to the 12 or 13 mm of travel. In the image on the left you can see the spring in a Dynafit binding in a relaxed state. For a side release the back head is rotated an thus the spring needs to be pressed over one or the two edges built in the cylinder. It is quite intuitive to see that the spring does not build up much pressure when rotated sideways a little bit. Also one can imagine that the pressure or the spring builds up quite linear as the head is rotated further.
Whether one can really feel the “spongyness” of the Radical 2.0 or the ION depends on the ski and the skier. An average weight skier with average speed on a “normal” touring ski will probably not feel anything. At Kundalini we mounted way over hundred Radical 2.0 and ION’s on Freeride Skis over 100mm width and had virtually no complaints. Of course we skied the two mentioned models ourselves and even if we were aware of the facts described in this article, it is hard to confirm with certainty there was a “spongy” feeling in a binding. We believe it is for a large part the riding style of the skier and his sensibility if this fact can become a problem.
Kingpin – going all the way
To comply with ISO 13992 pin bindings must provide a reliable safety release especially also under difficult circumstances. To test so, skis are bent (like in turns), layback positions and rotational falls are simulated to see, if the bindings still release at the set DIN value. In all these kind of tests, the friction between boots and bindings grows and in worst case the boot gets jammed or locked in.
Regarding these kind of tests, the Kingpin is strongly exposed in two ways. First, the steep resistance curve or in other words, the short way of elasticity in the Kingpin makes her very sensitive to frictions which could lead to lock-ins. Second, the jamming of the heel of the boot already provides a lot of friction which can become even more in a layback position.
Christian Brandl had to find a way to reduce friction even in the most extreme ski or body positions. To let the boot smoothly glide sideways out of the binding, the slider on which the boot stands was armed up with small metal rolls and thin metal plates for them to roll on. I know of no other binding that provides this kind of technique. Normal bindings just let plastic glide on plastic. With this sophisticated sliding plate, the boot has much less resistance to the side due to friction.
But there is a second issue with the piston. As every boots heel is round, also the piston has to be round to embrace the heel of the boot and clamp it down. Now, as the same piston needs to release the boot to the side, there is an immanent danger the boot is locked on the edge of the piston when moving sideways. For the same reason, by the way, the back of every new-generation pin bindings is rounded in the opposite direction.
In order to solve this issue, Christian Brandl had a look around in the K2 group to which Marker belongs to and found inspiration at the Inline Skate department. He then integrated a pair of ball bearings in the sides of the pistons enabling the boot to “roll out” of the binding with much less friction and with no danger of locking in.
The third force holding the boot back when moving sideways, are the pins in the front. In order to move sideways, the boot has to press the pins open. Here again the allegedly strong „sixpack“ of springs enters the play. As the Kingpin is constructed in a way that all holding power should come from the heel, the pins in the front clamp only very little. Thus the reason for the “sixpack” is not power but diameter. The smaller the springs the lower the standing hight. In that logic it makes sense to use three weak springs than two stronger ones. Accordingly, there is no other binding that has a lower sand hight. Dynafit is about the same, depending on the model.
These three aspects make it clear: Marker was very much aware of possible issues of their ambitious construction and they went all the way to prevent any problems.
One can say the Kingpin ranks among the best when it comes to stability, power transmission and safety. If you are willing to take the small extra weight you can’t make a better choice than the Kingpin.
On the other hand it would surprise me if Dynafit or the design team around Matthieu Fritsch, with whom I did an interview in Aschheim about the Radical 2.0, is not attacking the problem of the „spongyness“ as I write these lines. The image of the Radical binding above makes if clear that there is room for optimization in the transition between the spring and the cylinder.
Also, I would be surprised if Fritschi would not pick up the idea of the alpine-like piston the Kingpin uses. In combination with her unique toe-piece they could present a binding that combines the best of many worlds.
Things certainly remain exciting.