Global Fastener News

February 15, 2005 FIN – After a seven-year, two billion mile journey strapped to the side of the Cassini orbiter, the Huygens probe decelerated 12,000 mph in less than two minutes before parachuting last month to the frozen surface of Titan, Saturn’s largest moon.

Fasteners had to travel the equivalent of 450,000 round trips between Los Angeles and New York as the spacecraft explored Saturn and its moons without loosening or failing under shock, vibration or the extreme temperatures of rocket launch, atmospheric reentry or sub-zero space. Earthbound manufacturers can use adhesives, deformed threads, nylon rings, prevailing torque nuts and other traditional means of preventing loosening. “To survive the vibration and high temperatures of launch, we required the most reliable locking engagement thread,” NASA scientist Dan Harpold explained. “With conventional threading, however, screws loosened up and backed out under testing.”
With no ability to tighten or replace loose or stripped fasteners after launch, Madison Heights, MI-based Spiralock used its thread form with a 30º “wedge” ramp cut at the root of the female thread. Under clamp load, the crests of the threads on any standard male bolt are drawn tightly against the wedge ramp. That eliminated sideways motion that causes vibrational loosening and distributed the threaded joint’s load throughout all engaged threads.
NASA conducted tests including “bake outs” where screws and matching internal thread forms were heated to 300° C to simulate temperature-induced thread loosening.
“To date, not one has come loose that I’m aware of,” Harpold observed. ©2005/2013 Fastener Industry News
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