Shackle Load Pin
Morehouse is well known in the industry for calibrating loadcells of all types to the highest accuracy.
And for 50 years, we have scratched our heads at the poor performance of load pins compared to all other types of loadcells. Even the slightest change in loading conditions causes drastic changes in load readings.
These errors can go completely unnoticed in a standard calibration. Just taking the load pin out of the shackle and putting it back in we see reproducibility errors up to 10 %.
After years of iterations, Morehouse has redesigned the shackle load pin and taken it from the accuracy of a fish scale to a precision measurement instrument.
Shackle Load Pin Test
We compared one of our shackle load pins to that of one of the better manufacturers on the market.
One might be curious about how we define one of the better. That’s easy; running a calibration lab, we see all kinds of instrumentation. When we calibrate an instrument, we look at the history of that device and similar devices from the manufacturer.
When the current calibration compares well with the last calibration, we feel good about the calibration. If it doesn’t, we become more vigilant in finding out why.
Until now, we were completely biased that this one manufacturer had the best shackle load pin. Knowing who we perceived as the best manufacturer of shackle load pins, we made our decision on what manufacturer to test the Morehouse shackle load pin against.
The test we did was simple. Put the shackle load pins in our Morehouse 30k deadweight machine with weights known to be within ± 0.002 % of applied force.
Use the same setup and adapters with each load cell. Exercise the shackle pin load cells three times. Then record readings over the range. Record another set of readings to obtain repeatability data. The importance of this step is we do not move or change anything in the setup.
Then we take the pin out of the shackle load pin and put the pin in the other direction (180-degree switch shown in Figure 2)
Shackle Load Pin Data
Figure 1 Morehouse Shackle Load Pin Test
The data was collected based on the above test to calculate repeatability and reproducibility.
The maximum relative repeatability error without rotation for the Morehouse unit was 0.04 %. The maximum relative reproducibility error with rotation was 1.17 %.
Note: The maximum relative reproducibility error of 1.17 % was the worst at the first test point.
Figure 2 Other Manufacturer Reproducibility Test
The maximum relative repeatability error without rotation for the Other unit was 0.36 %. The maximum relative reproducibility error with rotation was 4.42 %.
Note: The maximum relative reproducibility error of 4.12 % was the worst at the first test point. Both units have the maximum relative reproducibility error at the first force point.
Comparing the Two Units
Figure 3 Comparison Ratio Morehouse vs Other
Relative Repeatability Error Between Both Units
When we look over the comparison data, we see, at a minimum, the repeatability data of the Morehouse unit is 4.72 better and, on some points, up to 231.60 times better.
If we take the average of all data points, the Morehouse unit is around 39.56 times more repeatable than the other manufacturer.
Relative Reproducibility Error Between Both Units
When we look over the comparison data, we see, at a minimum, the reproducibility data of the Morehouse unit is 3.76 better and, on some points, up to 43.5 times better.
If we take the average of all data points, the Morehouse unit is around 57.06 times more reproducible than the other manufacturer.
Shackle Load Pin Conclusion
The results speak for themselves. We are thrilled with the performance of our new shackle load pins. Though we also want you to test these for yourself. If you have any load pins, please run the same test plan.
What are the results? We are willing to bet they might be worse than what we are showing for the other manufacturer’s shackle load pin.
If the results are not what you want them to be, we feel we have a solution.
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Everything we do, we believe in changing how people think about force and torque calibration. We challenge the "just calibrate it" mentality by educating our customers on what matters and what causes significant errors, and focus on reducing them.
Morehouse makes simple-to-use calibration products. We build awesome force equipment that is plumb, level, square, and rigid and provide unparalleled calibration service with less than two-week lead times.
Want more information, visit our page on Morehouse Shackle Load Pins
Contact us at 717-843-0081 to speak to a live person or email for more information.
