Method of selecting the foot plane angle in a sliding activity

Abstract

In various sliding activities or sports, such as ice skating, a desired angle for the foot plane within a boot is selected. When conditions change, such as going to a different location or even changes within the original location such as temperature changes, the original foot plane angle is no longer appropriate to give the best convenience and performance results. In order to determine the more appropriate foot plane angle the friction coefficient of the surface for which the original foot plane angle existed is determined and then the new friction coefficient is measured at the new location or under the changed conditions. The change in initial friction coefficient to the new friction coefficient is then used to determine what change should be made to the foot plane angle.

What is claimed is: 
     
         1 . In a method of selecting the angle of a foot plane of a foot in the boot used in a sliding activity wherein the foot plane is originally at an original angle for a surface having an initial friction coefficient, the improvement being in changing the foot plane angle when the friction coefficient between the boot contact edge/surface and the surface of the sliding activity changes, comprising the steps of determining the initial friction coefficient, later measuring a new friction coefficient for the surface of a sliding activity, decreasing the foot plane angle from the original angle to a new angle when the friction coefficient increases, and increasing the foot plane angle to a new angle when the friction coefficient decreases. 
     
     
         2 . The method of  claim 1  wherein the new foot plane angle is obtained by the use of a shim inserted in the boot at the heel or at the ball of the foot. 
     
     
         3 . The method of  claim 1  wherein the boot is a hockey skate boot, and when the friction coefficient changes in the range of 0.00677 to 0.01488 the foot plane angle is changed by an angle in the range of less than 1 degree. 
     
     
         4 . The method of  claim 1  wherein the boot is a hockey skate boot and the foot plane angle is changed in accordance with the change in friction coefficient on The Hockey Skate Graph. 
     
     
         5 . The method of  claim 1  wherein the boot is a speed skating boot, and when the friction coefficient changes in the range of 0.00282 to 0.01008 the foot plane angle is changed in a range no greater than 0.8 degrees. 
     
     
         6 . The method of  claim 1  wherein the boot is a speed skating boot and the foot plane angle is changed an amount based on the friction coefficient change in The Speed Skating Graph. 
     
     
         7 . The method of  claim 1  wherein the boot is a figure skating boot and when the friction coefficient changes in the range of 0.01373 to 0.04070 the foot plane angle is changed in a range of less than 2.5 degrees. 
     
     
         8 . The method of  claim 1  wherein the boot is a figure skating boot and the foot plane angle is changed by an amount corresponding to the friction coefficient change in The Figure Skating Graph. 
     
     
         9 . The method of  claim 1  wherein the boot is a roller skating boot and when the friction coefficient changes in a range of from 0.04 to 0.075 the foot plane angle changes in a range no greater than 2 degrees. 
     
     
         10 . The method of  claim 1  wherein the boot is a roller skating boot and the foot plane angle changes by an amount corresponding to the change in friction coefficient in The Roller Skating Graph. 
     
     
         11 . The method of  claim 2  wherein the boot is a ski boot and when the friction coefficient changes in the range of from 0.02 to 0.06 the foot plane angle changes in a range of less than 2.5 degrees. 
     
     
         12 . The method of  claim 1  wherein the boot is a ski boot and the foot plane angle is changed by an amount corresponding to the change in friction coefficient in The Ski Graph. 
     
     
         13 . The method of  claim 1  wherein a tribometer is used to measure the friction coefficient. 
     
     
         14 . The method of  claim 1  wherein friction is determined based on temperature measurement. 
     
     
         15 . The method of  claim 1  wherein the foot plane angle is selected to maintain a reaction force at the surface of the sliding activity aligned with the center of gravity line of the person in the sliding activity. 
     
     
         16 . The method of  claim 1  wherein the foot plane angle change for a stable sliding contact surface is calculated by the inverse tangent of the initial friction coefficient minus the inverse tangent of the new friction coefficient and for an unstable sliding contact surface the foot plane angle is calculated by 2 times the difference between the inverse tangent of the initial friction coefficient and the inverse tangent of the new friction coefficient. 
     
     
         17 . The method of  claim 1  wherein the foot plane angle is changed by the addition of a shim to the heel or to the ball of the foot wherein for a stable sliding contact surface the angle is calculated by the heel to the ball of the foot length times the tangent of the difference between the inverse tangent of the initial friction coefficient and the inverse tangent of the new friction coefficient, and for an unstable sliding contact surface the foot plane angle is calculated by the heel to the ball of foot length times the tangent of 2 times the difference between the inverse tangent of the initial friction coefficient and the inverse tangent of the new friction coefficient. 
     
     
         18 . The method of  claim 1  wherein the method is repeated when there is a subsequent change in friction coefficient whereby the previous new friction coefficient is treated as the initial friction coefficient and the previous new foot plane angle is treated as the original foot plane angle. 
     
     
         19 . A method of selecting the angle of a foot plane of a foot in the boot used in a sliding activity comprising of obtaining a balanced sliding position by measuring the coefficient of friction between the boot contact edge/surface and the surface of the sliding activity, and using the coefficient of friction to determine the foot plane angle by a technique selected from the group consisting of:
 a) for a sliding sport in which the sliding contact area is straight in the xy plane or has at least two contact points that are on the xy plane, the angle of foot plane is equal to the inverse tangent of the sum of the coefficient of friction between the contact materials and the foot-plane angle relative to the horizontal, when the length of the conceptual line from the center of gravity to the ball of the foot (where the conceptual bisect lines through the angles formed between the connecting body parts torso, upper leg, lower leg and foot are perpendicular to that line) is at a minimum and when the person is the non-sliding balanced position wearing his/her activity-specific footwear;   b) for a sliding sport in which the sliding contact area is curved, the angle of the foot-plane is equal to twice the inverse tangent of the sum of the coefficient of friction between the contact materials and the foot-plane angle relative to the horizontal, when the length of the conceptual line from the center of gravity to the ball of the foot (where the conceptual bisect lines through the angles formed between the connecting body parts torso, upper leg, lower leg and foot are perpendicular to that line) is at a minimum and when the person is the non-sliding balanced position wearing his/her activity-specific footwear,   c) for a sliding sport in which the sliding contact area is straight, a lift, in either under the heel or under the ball of the foot to attain the angle, is generally equal to the distance between the heel and the ball of the foot multiplied by the sum of the coefficient of friction between the contact materials and the foot-plane angle relative to the horizontal, when the length of the conceptual line from the center of gravity to the ball of the foot (where the conceptual bisect lines through the angles formed between the connecting body parts torso, upper leg, lower leg and foot are perpendicular to that line) is at a minimum and when the person is the non-sliding balanced position wearing his/her activity-specific footwear; and   d) for a sliding sport in which the sliding contact area is curved, a lift, in either under the heel or under the ball of the foot to attain the angle, is generally equal to the distance between the heel and the ball of the foot multiplied by the twice the sum of the coefficient of friction between the contact materials and the foot-plane angle relative to the horizontal, when the length of the conceptual line from the center of gravity to the ball of the foot (where the conceptual bisect lines through the angles formed between the connecting body parts torso, upper leg, lower leg and foot are perpendicular to that line) is at a minimum and when the person is the non-sliding balanced position wearing his/her activity-specific footwear.