Load Pin Selection
When selecting or designing a Load Pin, two of the first things you need to know are 1) the size of the required load and 2) the amount of space available for pin installation. While Load Pin diameter is an important factor in determining how much applied load a pin can support, sizing a Load Pin can be more complex than simply matching diameter to capacity.
Why Load Pin Diameter Matters
A Load Pin functions as both a mechanical component and a Force Sensor. As an applied load passes through the pin, the pin experiences mechanical stress and slight deformation. Strain gauges installed within the Load Pin measure this deformation and convert it into an electrical signal proportional to the applied force.
Increasing the diameter generally increases the Load Pin’s ability to withstand applied force. For a simple cylindrical section, even a relatively small increase in diameter can produce a significant increase in mechanical strength.
However, a Load Pin is not simply a solid cylinder. Instrumented Load Pins typically incorporate specific areas for strain measurement, including reduced sections or internal strain-gauge pockets. These features allow the sensor to produce a useful, repeatable measurement, but also influence the mechanical strength of the finished pin.
Load Pin Capacity Depends on More Than Diameter
The relationship between Load Pin diameter and maximum applied load depends on the complete mechanical design. Important factors include:
- Pin diameter and geometry
- Distance between the supporting structures
- Load direction and loading arrangement
- Shear and bending forces
- Material and heat treatment
- Strain-gauge pocket dimensions
- Expected static and dynamic loading
The way a Load Pin is installed is particularly important. A pin supported at both ends with the load applied between the supports experiences a different combination of stresses than one installed in a different configuration. The mounting structure itself must also be capable of supporting the applied load.
For this reason, increasing the diameter is not always the best or most practical solution. A larger Load Pin may provide greater mechanical strength, but it may not fit the existing equipment or provide the desired measurement characteristics.
Choosing the Right Load Pin Size
For a new application, Load Pin sizing should begin with the maximum expected applied load, rather than simply selecting a diameter from a chart. From there, the required safety factor, mounting dimensions, loading conditions, and environmental requirements can be used to determine an appropriate design.
This is especially important when replacing an existing mechanical pin with a custom Load Pin. Here, the goal is often to maintain the original mechanical dimensions while adding load measurement capability. In these applications, the Load Pin must be engineered around the existing mounting arrangement rather than selected solely by its diameter.
At Rugged Controls, custom Load Pins can be designed around the specific requirements of the application, including load capacity, existing dimensions, loading conditions, and environmental factors. Our Load Pin Request Form allows customers to provide pin specifications and engineering drawings to help determine the appropriate design.
Summary
Load Pin diameter is a critical part of determining load capacity, but diameter alone does not determine how much load a pin can safely support. Proper Load Pin sizing considers the entire mechanical system to ensure the sensor provides both the required strength and accurate load measurement.
