Method for coupling a sensor to a piece of equipment, such as a golf club, baseball bat, or tennis racket, that ensures that the sensor is in a known position and orientation relative to the equipment. Compensates and calibrates for degrees of freedom introduced in manufacturing and installation. The method may include manufacturing a sensor receiver that aligns with equipment in a fixed orientation, and that holds a sensor housing in a fixed orientation relative to the receiver. Remaining uncertainties in sensor position and orientation may be addressed using post-installation calibration. Calibration may include performing specific calibration movements with the equipment and analyzing the sensor data collected during these calibration movements.

A hollow golf club head comprises a head main body made of a metallic material and having a bottom portion including a first portion and a second portion being connected with the first portion having difference in level, and at least one weight member having a specific gravity larger than that of the head main body and attached to the second portion of the head main body.

A ball bat extending about a longitudinal axis and includes a handle portion, a barrel portion, an injection molded element, and a tubular insert. The handle portion has a generally uniform outer diameter. The barrel portion has proximal and distal regions spaced apart by a central region. The element includes a tubular inner wall defining a longitudinal bore. The element is non-removably attached to the handle member. The element includes a tapered proximal region, a barrel engaging region, and an insert engaging region for engaging the insert. The insert engaging region includes a stop for inhibiting longitudinal movement of the insert. The barrel engaging region non-removably engages the proximal region. The bat having a total length measured from a proximal end of the handle portion to a distal end of the barrel portion. The handle portion has a length that is less than 70 percent of the total length.

An apparatus for engagement with a barrel of a bat includes a cup and at least one cover. The cup is secured for securement to a distal end of the barrel of the bat. The cup defines a cavity and includes a first connector portion. The at least one cover has a second connector portion cooperating with the first connector portion to releasably secure the cover to the cup over the cavity.

An apparatus for engagement with a barrel of a bat includes a cup and at least one cover. The cup is secured for securement to a distal end of the barrel of the bat. The cup defines a cavity and includes a first connector portion. The at least one cover has a second connector portion cooperating with the first connector portion to releasably secure the cover to the cup over the cavity.

A length adjustable golf club includes a club head attached to a shaft at a lower end. A length adjusting kit includes a shaft insert that attaches to the shaft at an upper end. The shaft insert includes a coupling port that accepts one of an extension block or a grip adapter. To provide length adjustments of the overall club length, one or more extension blocks may attached between the shaft insert and the grip adapter. A grip assembly having a reinforcing sleeve connects to the grip adapter and extends over the shaft and any extension blocks. The grip assembly couples to the shaft through a grip adapter and grip coupling. The grip adapter and grip coupling are axially moveable prior to securement with a retaining fastener. The grip coupling may be rotationally constrained or rotationally adjustable relative to the grip adapter.

A stiffness characteristic measurement device holds a golf club head with a face surface facing upward, drops a collision rod vertically toward the face surface, and calculates the stiffness characteristic of the golf club head based on a detection value of an accelerometer attached to the collision rod. Every time the measurement point on the face surface is changed, a drop distance changing step of adjusting the drop distance of the collision rod is performed so that the collision velocity of the collision rod to the measurement point is substantially constant.

A tennis racket fitting method according to the present invention comprises: a first step of preparing a plurality of test tennis rackets, at least one type of racket property that influences swing for hitting a ball being defined for each of the test tennis rackets; a second step of causing a reference tennis racket to be swung at least one time by a user in order to hit a tennis ball, and acquiring a measured value by measuring transition in at least one of the position, the velocity, the acceleration, and the angular velocity of the reference tennis racket in at least a portion of an interval from when the swing starts until when the swing ends; a third step of calculating at least one evaluation indicator to be an evaluation of the swing of the reference tennis racket based on the measured value; and a fourth step of, based on the racket property, selecting a tennis racket that can improve at least one evaluation indicator from among the test tennis rackets.

A tennis racket fitting method according to the present invention comprises: a first step of preparing a plurality of test tennis rackets, at least one type of racket property that influences swing for hitting a ball being defined for each of the test tennis rackets; a second step of causing a reference tennis racket to be swung at least one time by a user in order to hit a tennis ball, and acquiring a measured value by measuring transition in at least one of the position, the velocity, the acceleration, and the angular velocity of the reference tennis racket in at least a portion of an interval from when the swing starts until when the swing ends; a third step of calculating at least one evaluation indicator to be an evaluation of the swing of the reference tennis racket based on the measured value; and a fourth step of, based on the racket property, selecting a tennis racket that can improve at least one evaluation indicator from among the test tennis rackets.

The present application is directed to a method for use in a system implementing a reference golf club, one or more sensors associated with the reference golf club, and a computing device. The method comprises receiving from the one or more sensors, by the computing device, swing data relating to a swing of the reference golf club, analyzing, by the computing device, the swing data to determine recommended shaft parameter values for each of a plurality of shaft parameters using an algorithm, accessing, by the computing device, a shaft database comprising actual shaft parameter values for each of the plurality of shaft parameters for each of a plurality of shafts, determining, by the computing device, at least one shaft from the plurality of shafts based, at least in part, on a comparison between the recommended shaft parameter values and the actual shaft parameter values, transmitting, by the computing device, information relating to the at least one shaft; and displaying, by the computing device, the information on a display of the computing device.