Chicago—Amid all the crowd-attractors at the 2001 National Manufacturing Week show—rock climbers, train sets, even an oxygen bar—one exhibitor was sticking with a display which has stopped engineers in their tracks for several shows now: a new, shiny, red bike.
But the Cannondale bike at Elliott Manufacturing's (Binghamton, NY) booth was no ordinary dirt bike: A system of gears and a flexible shaft connect the front and rear wheels to provide on-demand all-wheel drive when the going gets slippery.
Another company assembles the product and supplies the gearing, but Elliott provides the heart of the mechanism: A flexible shaft which not only follows a curving path from the rear hub to the front, but also allows enough side-to-side motion for the front wheel to turn freely.
And building parts for mountain bikes is only part of their business, according to Thomas Dunn, director of Flexible Shafting Products for Elliott. "Aerospace is a very large part of our business; all the Boeing aircraft thrust reversal systems use flexible shafting," he says. "So is flap actuation on regional aircraft and smaller business jets." Dunn explains that the flexibility helps flaps and reversers deploy in consistent amounts, even on structures which are constantly bending and changing shape according to varying loads.
"When you look at an aircraft wing, the wing is flexing; what you have to do is extend the flaps out and change the profile of the wing," he says. "So they use ball screw actuators throughout the length of the wing, which take rotary motions and convert them to linear motion." Additionally, the flexibility of the shafts allows designers to route them around structural members, wiring, hydraulic lines, fuel tanks, and other components competing for space in the wing's crowded interior.
Dunn also says the flexible couplings perform a more mundane function down on the ground, specifically on Caterpillar tractors. "There's a valve that's located below the cab area somewhere; in the old days the operator had to get out and make an adjustment to the valve," he explains. "Nowadays they connect it with a flexible shaft that comes up to the console. The farmer can sit in his air-conditioned cab with his CD running and just make a simple adjustment with a knob, which adjusts the hydraulic valve for his implement, rather than having to climb out and go in the back and manually make an adjustment."
Other products on display which use the flexible shaft for power transmission or control included scuba tanks, surgical tools, a weed trimmer, thermostats for food processing machines, and a steering assembly for a lawn tractor.
For more information about shafts from Elliott Mfg.: Enter 540