Instron Corp.

During my time with Instron Corp., one project that I had a hand in was the “Warwick project.”  In this project, the customer had one of the largest products available oriented upside down with several custom components on it for crushing metal I-beams for strength analysis.  The problem with this project was that the hook and crosshead apparatus (pictured below), which would launch down, was subject to so much force that the crosshead would wobble on its way down to crush the beam.  This was not noticeable to the naked eye since the crosshead would reach the I-beam in a few milliseconds. Using a high-speed camera, it was determined that the hook wasn’t releasing fast enough around the pin and was causing the wobble issue at the initial release.  To put the figures below into perspective, the machine stood over 12 feet tall and the hook was almost 2 feet in length.  The crosshead was under the force of two springs and a pressurized piston that would release the hook.  The size, shape, and weight of the hook were the only aspects we were able alter to allow for a more linear release of the crosshead and more accurate data for the customer.  

To redesign the hook, I was tasked with finding the exact forces on the hook from the pin.  Using the time of hook-to-pin contact from the high-speed camera and the known initial conditions, in-depth equations were developed to analyze the forces on the hook. The equations were run in Excel so that we knew the forces for each increment of time.  When the forces during release were known, our team used the data to better redesign the hook which ultimately had mass removed without sacrificing structural integrity to lower the weight and optimize the moment of inertia.  An example of the equation notes can be seen below, which was used to setup the more precise Excel equations.  

The wobble issue was resolved, but another issue remained which was the magnitude of the machine’s impact on the customer’s test facility floor.  The impact was enough that the whole building would shake.  To resolve the problem, an elegantly simple solution was attained by sourcing D3O pucks to place on the feet of the machine nearly eliminating the shock. 

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