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Component Manufacturing dverti$ dverti $ er
Don’t Forget! You Saw it in the
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December 2023 #15293 Page #134
The Last Word The Concrete Truss Machine Joe Kannapell, P.E.
N
ew inventions may fade away, but most provide valuable lessons, like the concrete truss machine. Not many of these were built, but they seemed to Cal Jureit to be the logical match for his new truss plate, and they set the course for all his future machines.
Jureit had to have been exasperated when he realized his great invention of the truss plate took dozens of tons of pressure to put to use. Each tooth was much thicker than a nail, each joint had many teeth, and each truss had many joints. Only a hydraulic press was suited to the task, as Bill Black, Sr. had recently demonstrated. But such a press was heavy, difficult to move among joints, and often had a hard time seating Jureit’s plates. Carol Sanford had introduced a more expensive, but faster, machine with multiple beam presses that spanned across the truss, but it required a finish roller to complete the job. Both machines were slow setting up and pressing trusses, especially on difficult designs. So Jureit devised a design that would shorten pressing time dramatically while being cost-competitive with Sanford’s approach. Jureit’s concept was a “super press” that could seat all plates simultaneously for the hypothetical 99% of all trusses. He figured that this required a massive hammer-like device, wielding 100 tons of force. If such a beast were designed from steel at $0.12 per lb in 1960, the cost would be $24,000 ($250,000 today), but with concrete at $14.00 per cubic yard, the cost would only be about $4,000, including reinforcing steel. Thus, in late 1960, was born the first and only concrete press. Jureit proposed that Gang-Nail fabricate and ship a hollow, reinforced steel shell that CMs would fill with concrete onsite, since a gargantuan 100ton machine couldn’t even be moved onto the streets of his plant in Hialeah, Florida, much less across America. Once installed, this machine would be able to press with a single stroke, trusses up to 9 feet tall and 40 feet long, at about a pitch of 5/12. “The few trusses longer than 40 feet can be put through lengthwise,” Jureit stated at the time.
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