The toe support bracket can be seen at the beginning of the video. It is a somewhat rectangular bracket bolted to the frame under the toes of the shoes. The toe support will reduce the stress on the shoes which has advantages. Keep in mind that we are pushing these cycling shoes into a use they were not designed to support. The load differences between the two uses are significantly different.
The very nature of a bicycle pedal nearly eliminates the torque loads on the shoe interface. In cycling, the loads on the shoe are restricted to predominantly axial loads (compressive and tensile) and a small amount of shear force with miniscule torques that are essentially the shear load multiplied by a lever arm that is 1/2 the height thickness of a pedal (about a centimeter).
In comparison, the primary load a monofin transmits to the shoe is torque. The fin generates nearly equal parts shear and axial loads and these loads are multiplied by a lever-arm that is at least 25 times larger than the bicycle pedal's lever arm, which results in very large torque at the shoe interface. These loads need to be resolved, and the frame on the Pilot2 does this by resolving the torque into force couples that result in axial loads at the bolt interface to the shoe.
The larger the radius on the force couple the smaller the axial forces to balance the torque. The frame on the Pilot has a radius that is double that of the basic Look bolt pattern. The Look pattern also has an imbalance in that it is a triangle orientated such that the swimmer's largest power stroke applies the maximum tensile load to a single bolt at the toe end of the interface. I'm proposing to eliminate this bolt and use the other two bolts in a balanced force couple so that the swimmer's power stroke shares the maximum tensile loads through these two bolts. Combined with the doubled radius of the lever arm, this system will cut the maximum stress on the bolt interfaces to the shoe by a factor of 4 over just using the basic Look system as it was designed for cycling.
Adding the toe support creates a nearly equal force couple for the swimmer's return stroke. The return stroke is generally not as forceful as the powerstroke, but now it will have the same level of protection against breaking the shoes.
The frame also supports the sole about 1/2 the length out along the length of the sole, so the sole of the shoe only needs to be half as strong as if it were unsupported. All are good measures to minimize the chances of having structural problems with the shoes.
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