Instrumented Clevis Pins for Sheave Applications

Many Strainsert Instrumented Clevis Pin designs are incorporated into sheave and pulley systems. The user has the option of either designing a sheave around our standard CPA Clevis Pin series or having a custom pin manufactured for an existing sheave design with a tailored measurement capacity and geometry, allowing for simple installation and optimized measurement capacity. The Instrumented Sheave Pins are often used to measure line tension by monitoring reaction load on the pin. Using the equations provided below, the line tension can be determined.

 

Constant Wrap Angle

For a sheave with a constant wrap angle, the resultant load can be oriented in relation to a single force sensing axis and the following equations apply.

*Axis of Maximum Sensitivity: Align Keeper Flat of Load Sensing Pin perpendicular to Axis of Maximum Sensitivity which is at one half the wrap angle. For this example, wrap angle = 105 degrees and Ø/2 = 105 /2 = 52.5 degrees. See specification drawing below. Ø= Wrap Angle T = Line Tension P = Resultant Force on Sheave Pin

Line Tension (T): To measure the tension in a line by measuring the reaction force on the sheave use the specification drawing and formulas: P = 2T cos(Ø/2) or T = P ÷ 2cos(Ø/2) Example:For a Wrap Angle of Ø = 105 and measured sheave load of 10,000-lbs. The Line Tension (T) can be determined by the formula: T = 10,000 ÷ 2cos(52.5) and T = 8,213-lbs

 

Constant Wrap Angle Specifications (opens in pop-up window)

Instrumented Clevis Pins Online Catalog

Specification Drawings

 

Variable Wrap Angle

For a Sheave with a varying wrap angle, the force direction varies with respect to the force sensing axis. To address varying wrap angle applications, an instrumented pin with two sensing axes oriented 90 apart, measure the orthogonal X and Y loads. The X and Y outputs can then be used to resolve the magnitude and direction of the Sheave force on the pin, as well as the line tension. The following equations apply for a bi-axial sheave load pin with a variable wrap angle.

The cross section of the bi-axial clevis pin illustrates gage alignment. The gages marked Y will sense load component Py, while the gages marked X will sense loads in the Px direction. Given the outputs from the two bridges as Ex and Ey, and constants (Kx,Ky), derived from calibration data*, the resultant force P is determined by: Px = Kx Ex Py = Ky Ey and the resultant force P = Square root of [Px]² + [Py]²

The Line Tension (T) and Wrap Angle (Ø) can be determined by: T = Px² + Py² ÷ 2Px and Ø = 2 inverse cosine( P ÷ 2T) *Where P, Px and Py are adjusted for cross-talk effects. For further discussion of bi-axial load pins see bi-axial pins under the Clevis Pin Optional Features.

 

Variable Wrap Angle Specifications (opens in pop-up window)

Instrumented Clevis Pins Online Catalog

Specification Drawings

Pin Design: For quotations on custom sheave pin designs, complete the Contact form below. Include additional drawings, comments, or special requirements as applicable.

Please request our specialized custom sheave pin questionnaire form and a link will be emailed to you.