Before leaving the subject of floor trusses, two machines deserve special attention, the Tiger Cat and the Structur-Span. Both included features that were way ahead of their 1970s provenance and both were markedly faster than even present-day machines. Both plated the truss with a single pass, and both powered trusses out of their jigs. But these machines also had memorable challenges that I encountered as a supplier, and in two truss plants where I worked.
The Tiger Cat from Hydro-Air, MiTek’s predecessor company, promised to emulate the success of their record-setting Glide-Away roof machine, upon which it was based. The Tiger Cat included automated pressing, not markedly different from Gang-Nail’s Press-O-Matic which had debuted a few years earlier. Initial feedback was that the machine was too fast. Later I went to the plant to find out why. But first, I walked through an apartment job being framed with a huge quantity of trusses produced by the Tiger Cat. Then at the plant, I saw two men on opposite sides of the narrow table, laying down plates on a truss in a jig, moving smartly just ahead of the automated press head. Shortly after completing the pressing, the truss was automatically ejected, and the process reinitiated. Since the truss didn’t have to be flipped and back plated, the cycle time was markedly reduced, and it worked with two rather than three operators. But unfortunately, the Tiger Cat’s multiple mechanisms needed sophisticated controls that were not yet available. And this worthy concept came to an ignominious end when one of the heads ran off the end of its track and would have run into a crew member if it hadn’t been halted by a snapped hydraulic hose. [For all images, See PDF or View in Full Issue.]
The Structur-Span was the mainstay of 4x2 truss production at Hall-of-Famer Don Hershey’s Tru-Trus in Phoenix. It, too, was a mechanical beast, with a constantly moving conveyor mechanism that propelled the truss through a pair of finish rollers. After I left Hershey’s plant, its efficiency encouraged me to buy one for the Virginia plant I ran. But credit is due both to Jim Adams of J.D. Adams who invented it and to Don Hershey who perfected it – mostly. Like with the Tiger Cat, plates were placed on both the top and bottom of the truss, though they had to be hammered as is done on a roof gantry. Then the conveyor was engaged, and the truss was moved through the first roller press, partially seating the plates. Just after the truss emerged from the roller it encountered a deflector which turned the truss slightly, imparting a “predetermined” camber, shown in the diagram in exaggerated magnitude.
Yet, we often couldn’t predict exactly how much camber would result. Since the truss is being put under stress by deflectors, the resulting camber could vary if the stiffness of the chords varied over a run of trusses. Though this was quickly addressed by adjusting deflectors, the following truss may also have had unacceptable camber. Experience lessened this challenge, but completed trusses had to be rejected, especially when changing from single to double chords. Maintenance of the constantly moving conveyor was also a challenge.
Truswal aimed to resolve these issues upon its purchase of J.D. Adams. As inventors of floor truss technology, they apparently believed they would bolster their market leadership by enhancing and re-patenting the Structur-Span. However, they changed little of the functionality of the machine, but improved its adjustability and the consistency of the camber imparted. However, in Truswal’s effort to perfect camber, they added at least two and as many as four additional rollers to the Adams’ mechanism. This excessive complication was deemed unnecessary as camber became built into most machines, and its control ceased to be a sales advantage. As Truswal ceded its machinery manufacture to Klaisler, the Structur-Span faded into oblivion, and the much simpler “Fatman” mechanism became the industry standard (see Floor Truss Technology, Part V and Part VI). Now, nearly 50 years after Ronnie Wright set this standard, a new vision for floor truss manufacture has been made possible by robotics. But, to displace Wright’s standard, robotics will need to address the diversity of floor truss details (see Floor Truss Technology, Part VIII: Inside Floor Truss Details), thereby further lowering production costs and boosting competitiveness.