Mechanisms: Cable Ties

Zip ties, Ty-Raps, cable ties; call them what you will, but it’s hard to imagine doing without these ubiquitous and useful devices. Along with duct tape and hot glue, they’re part of the triumvirate of fasteners used to solve nasty problems quickly and cheaply. They’re next up on the list of mechanisms we find fascinating, and as it turns out, there’s more to these devices than meets the eye.

The Well-Dressed Wiring Harness

Like so many products that we take for granted today, the cable tie was invented to solve problems in the aerospace industry. In the prewar years, airplanes were relatively simple affairs with only modest electrical systems, and wiring harnesses were fairly uncomplicated. Bundles of wires could be contained by lacing, an intensely manual process that required skilled practitioners with nimble fingers to weave waxed cords around the wires, resulting in neatly groomed harnesses that were often works of art.

Maurus Logan. Source: Thomas & Betts Co

Even during WWII, with increasingly complex planes carrying radios and radar sets, lacing was the rule for taming the miles of wires now needed to run a plane. But in the booming postwar era, as aircraft manufacturers spooled up their production for the rapidly expanding civilian and military market, the time-consuming and specialist skill of lacing every wiring harness was becoming a liability.

Every liability is a market opportunity for the prepared mind, and Maurus C. Logan was spotted that opportunity and seized upon it. In the mid-1950s, Logan was working at electrical equipment manufacturer Thomas & Betts, and he had seen first-hand the tedious process of hand-lacing aerospace wiring harnesses while touring a Boeing plant. Knowing that there had to be a better way, Logan turned his mind to the problem over the next several years.

US Patent 3,022,557

He went through several design iterations using many different materials before finally leveraging developments in polymer science and settling on a molded plastic strip. The original 1958 patent drawings look very much like the modern cable tie, with a long, toothed ratchet strip that was looped back and inserted into a slot in a small box on the end of the strip.

Just like in current cable ties, the ratchet engaged a pawl to keep the loop cinched up snug around the bundled wires, but Logan’s original design differed from most cable ties today by calling for a separate metal spring as the pawl. It’s easy to see why he would have gone that way, and in fact Ty-Raps use a metal pawl to this day in favor of the integrated pawl with a plastic living hinge favored by most other manufacturers.

A Cable Tie for Every Crime

The cable tie universe has expanded immensely since those first Ty-Raps hit the market, with a cable tie for every purpose. Most cable ties are molded in Nylon; those intended for indoor use are usually the natural milky white color, while those destined for outdoor duty have UV stabilizers that give them a black color. Not all cable ties are created equal, of course, with some much better at standing up to the elements than others — hands up for everyone who has had a cable tie snap while tightening when it’s even a little bit cold. A cable tie tensioner can help with situations like that; basically, it’s a tool that pulls the tail of the cable tie through the ratchet to a preset tension, to both preserve the cable tie and prevent overcompression of the wire bundle.

PlastiCuffs ready for action. Source: Baltimore City Police Department

And of course, cable ties have branched far beyond the initial market for taming unruly wiring harnesses and even beyond the aforementioned applications in expedient repairs. We’ve all seen law enforcement using double-loop ties called PlastiCuffs for mass arrests during protests and social unrest.

Highly modified cable ties are even used as surgical ligatures to control bleeding without crushing tissues like a surgical clamp can. Some ties are even molded from polyglycolic acid, the same material that absorbable sutures are made from, and can be left in the body.

The simple mechanism designed by Maurus Logan has done pretty well for itself in the past 60 years. And so did Logan himself — he rose through the ranks at Thomas & Betts over the years, eventually becoming Vice President of Research and Development. He died in 2007, just shy of the 50th anniversary of his Ty-Rap.