The 3 main features that appear to be limiting the performance of the FreeMotion boot are the lack of a hard rear stop and forward lean adjustment for the exo cuff and an adjustment means for the U spring that would allow a range of low resistance rotation of the cuff before the resistance provided by the U spring is introduced. It is also important to have a monoplanar boot board with a ramp angle in the order of 2.5 to 2.7 degrees or, preferably, the ability to substitute boot boards with different ramp angles to allow experimentation to determine the optimal angle or range.
In researching the history of the FreeMotion ski boot, it appears to have evolved out of the Kneissl Rail soft boot introduced around 2002. Perhaps Simon can confirm this.
The Kneissl Rail is shown in the graphic below.
Like the Freemotion, the Kneissl Rail does not appear to have a hard rear stop for the exo cuff. But the Rail appears to have a dial on the spine that suggests some sort of adjustment for the U spring that might permit a range of low resistance rotation before it is introduced or perhaps a tension adjustment for the u spring. The Rail also has a constraint plate over the instep that is secured with a buckle, a feature the FreeMotion shown below in Figure 1 from the patent, lacks.Since the investment in prototypes and production molds is substantial, aesthetic considerations and production costs typically take priority over functional considerations.
Because of this, my preferred option is to use purely functional, low cost prototypes that are easily modified as research vehicles to prove out the functional aspects of a technology. Prototypes such as the Birdcage (shown below) can be designed and fabricated at minimal cost compared to the costs of sophisticated aesthetic and production prototypes.
The photo below is of an early research prototype called the Lab Rat that was developed for a recent project. The open architecture of Birdcage and Lab Rat formats permit instrumentation to be incorporated and visible observation of the effects of the technology on the foot and leg to be conducted, something that is difficult, if not impossible in aesthetic prototypes, especially ski boots.
The photo below shows a second generation version of the Lab Rat call The Fit. It is more compact and much lighter than the Lab Rat.
The 4 photos below show the modifications I made to address structural inadequacies and interface issues of the first generation mold generated post Birdcage prototype called the P1. The instep was reinforced with a formed stainless structure and the internal plastic components were replaced with reinforced fibreglass and Tig welded stainless steel components. While these modifications did not lead to a marketable prototype, they validated the conclusions of the analysis that explained why the prototype failed to deliver the expected performance.
In my next post, I will offer some suggestions for potential grafted-on modifications for the FreeMotion ski boot that may clarify the options required to address the issues that I flagged that were confirmed by Simon. It would be helpful if Simon can provide his comments on whether this approach is viable from his perspective.