It wasn’t enough for Jack Schmitt, President of Truswal, to introduce wood-web floor trusses. He also had to demonstrate how to build them, and that required a special machine. Schmitt turned to his trusted associate, Carl Virta, to come up with a process, and Carl knew who could help him. On his next trip to Triangle Truss in Windsor, Wisconsin, he collaborated with Don Steffenhagen and Jim Lee on the possibilities. Lee suggested building the truss on a solid surface and passing the entire assembly through a final roller. So, they roughed up a 4x2 truss, fastened it to a sheet of plywood, and hammered truss plates onto the topside joints. Then after adjusting the clearance on their fixed-in-place finish roller, they ran it through and saw that they achieved the full embedment of the plates. They then flipped the truss over, tacked plates onto the joints and, reversing the rotation of the roller, sent the entire assembly back through, and celebrated the first successful fabrication of a wood-web floor truss. [For all images, See PDF or View in Full Issue.]
Crucial to the success of this experiment was their use of the short-tooth roller plate that Schmitt had recently acquired from Ronel Corporation in Florida. However, by using that plate, he precluded selling his machine to the large majority of CMs who used longer tooth plates; that is, unless they switched to Schmitt’s plate. That was just the type of opportunity that stirred Schmidt’s sales-savvy instincts, and put him on the road, promoting floor trusses. And, for a time, he had the best “mousetrap,” and it could be had for little or no cost, if he got the plate business. This strategy was remarkably successful, and quickly catapulted Truswal to the forefront of the plate industry. Given that Truswal was ten years late in joining the industry association, this was quite an accomplishment and, at the same time, a stimulus to the competition to develop their own machines.
Because Gang-Nail and Hydro-Air hadn’t yet developed a roller plate, they had to design vertical hydraulic press machines. Their immediate reaction to Schmitt’s innovation was to adapt their roof machines to the task. Gang-Nail followed Schmitt’s method, running the same type of assemblage in and out of their Gang-Nail Compress machine, which had been introduced in 1969. To accommodate the greater depth required some adjustment of linkage connecting the upper and lower beams of the press head.
Hydro-Air rushed a reconfigured version of their Mono-Press right after the introduction of Schmitt’s machine. They added a second floor track parallel to their standard base track and raised both tracks up on Unistrut channels to provide for varying truss depths. They envisioned an operator maneuvering a modified C-frame press head around the perimeter of the truss. While this design worked for flat roof trusses, the pedestals were too unwieldy to be adjusted to the shallow floor truss depth and it took too long for the C-frame to press twice the number of joints as roof trusses. A later design mounted the tops of the pedestals on a new structure that ran the length of the table. A notable feature was air clamping in the duct chase, which tightened the diagonals and eliminated accumulated web tolerances. However, like the early Gang-Nail solution, this was only a stop-gap measure, and both companies went back to the drawing board.
Hydro-Air released its Tiger Cat in 1973, borrowing two press heads from their Glide Away machine. Each head traversed the length of the truss on powered carts opposite each other, preceded by assemblers who set plates both on the top of the truss and on floating plattens beneath the truss. Unfortunately, the Tiger Cat’s intricate maintenance requirements hindered its potential, and rarely did it achieve the savings that would have accrued from its operation with only a two-man crew.
Gang-Nail released its own partially automated machine, called the Gemini, in 1976, incorporating a feature they called Press-O-Matic. This involved presetting mechanical limit switches at each joint, and at the end of the run, permitting the press head to travel the length of the truss unattended and return to the center of the machine. This was a much narrower version of its generally reliable Mark 4 and Mark 5 beam presses with two in-line setups, so that operators could assemble the parts of a second truss while the press was engaging the first.
Throughout the early 1970s, other manufacturers were busy developing their own faster and more reliable versions of a floor machine, which ultimately would spread floor truss technology across the nation. But at the same time, engineers and software developers had to figure out how to efficiently design parallel chord trusses. And their task turned out to be much more challenging than they had presumed.
Next Month:
Floor Design Intricacies
Articles in This Series