Abstract: Skate propulsion mechanisms are provided. In some embodiments, skate propulsion mechanisms comprise: a base plate; a drive wheel couple to the base plate; a shoe plate to which a user's foot can be coupled, which shoe plate can be moved relative to the base plate in response to movements in the user's foot; and a drive mechanism, coupling the shoe plate, the base plate, and the drive wheel, that propels the drive wheel when the user's foot is moved in a first direction and that permits the drivel wheel to operate in a free wheel mode when the user's foot is stationary.

Abstract: Handles providing shock absorption are provided. In some embodiments, handles comprise: a handle core having an axis; core permanent magnets mounted to the handle core; a handle sleeve surrounding the handle core; sleeve permanent magnets mounted to the handle sleeve which generate repelling forces radial to the axis from at least some of the core permanent magnets; and an adjustment screw used to control a force longitudinal to the axis.

Abstract: In some embodiments, devices for measuring strings of a racket include a housing and a button. The devices also include a setting device that determines the frame size of the racket in response to the button being depressed and a spring system that adjusts pre-tension of the strings in response to the button being depressed. The devices further include a calibrated leaf spring having strain gages and an adjustment screw which is affixed to the button and which makes the starting measuring pressure onto the calibrated leaf spring adjustable. The devices still further include a fixing part which becomes fixed to the housing when force is applied to the button that causes the spring system to reach a specified level of compression and a display that reflects pressure on the strings in response to pressure applied to the strain gages.

Abstract: Devices for determining the string tension of racket strings are provided. In some embodiments, devices for determining the string tension of racket strings comprise: a body having a front surface indicating different combinations of player and racket characteristics, windows corresponding to certain types of rackets, and an axis perpendicular to the front surface; and a rotary disc which is rotatably situated on the axis behind the front surface and which has numbers indicated thereon representing racket string tension values that can be viewed through the windows for the different combinations of player and racket characteristics.

Abstract: Devices for determining the string tension of racket strings are provided. In some embodiments, devices for determining the string tension of racket strings comprise: a body having a front surface indicating different combinations of player and racket characteristics, windows corresponding to certain types of rackets, and an axis perpendicular to the front surface; and a rotary disc which is rotateably situated on the axis behind the front surface and which has numbers indicated thereon representing racket string tension values that can be viewed through the windows for the different combinations of player and racket characteristics.

Abstract: Skate propulsion mechanisms are provided. In some embodiments, skate propulsion mechanisms comprise: a base plate; a drive wheel couple to the base plate; a shoe plate to which a user's foot can be coupled, which shoe plate can be moved relative to the base plate in response to movements in the user's foot; and a drive mechanism, coupling the shoe plate, the base plate, and the drive wheel, that propels the drive wheel when the user's foot is moved in a first direction and that permits the drivel wheel to operate in a free wheel mode when the user's foot is stationary.

Abstract: Handles providing shock absorption are provided. In some embodiments, handles comprise: a handle core having an axis; core permanent magnets mounted to the handle core; a handle sleeve surrounding the handle core; sleeve permanent magnets mounted to the handle sleeve which generate repelling forces radial to the axis from at least some of the core permanent magnets; and an adjustment screw used to control a force longitudinal to the axis.

Abstract: Devices for measuring strings of a racket and ball quality are provided. In some embodiments, a device for measuring strings of a racket comprises: a housing; a button; a setting device that determines the frame size of the racket in response to the button being depressed; a spring system that adjustments pre-tension of the strings in response to the button being depressed; a calibrated leaf spring having strain gages; an adjustment screw which is affixed to the button and which makes the starting measuring pressure onto the calibrated leaf spring adjustable; a fixing part which becomes fixed to the housing when force is applied to the button that causes the spring system to reach a specified level of compression; and a display that reflects pressure on the strings in response to pressure applied to the strain gages.

Abstract: A ball-hitting instrument for playing ball games, comprises a handle and a flat head part (preferably a tennis racket bearing a screen in the head part) and an apparatus for programming and controlling the seizing of the handle and the guiding of the instrument during a player's motions for hitting a ball. The apparatus is mounted on the handle and contains an electronic circuit comprising an on-off switch, a perceivable signals-emitting device such as a buzzer, an integrated circuit chip, a potentiometer and four noiseless, quick-response switches each having a travel path and a circuit-making mercury or magnetic body movable back and forth along that path to make or break circuit.

Abstract: A device for testing the stringing tension of a racket is made up of two components. The first component has a racket support surface with a recess therein. The second component is a cylinder containing a spring in compression with a slot in the cylinder indicating the compression load on the spring. The components are connected together with a connecting bolt passing through the racket. A spindle mounted on the connecting bolt and the first component applies pressure between the two components, acts on the strings of the racket and indicates racket tension by the amount of compression applied to the spring of the second component. The connecting bolt can also be threaded and the second component cylinder can be threaded thereon to apply pressure between the components. Distance sensing electrical contacts in the recess of the first component indicate when the reading is to be made.