Special Bearings for a Special Needs Cycle

For children who cannot pedal a conventional bicycle, the Step'n Go from Treadle Power Inc., provides an answer. Unlike a traditional bicycle, the three-wheeled Step'n Go eliminates the difficult circular pedaling motion and replaces it with a more natural up and down stepping action.

"It's more like walking than cycling," says Stuart Lindsay, president of Treadle Power Inc., manufacturers of the Step'n Go cycle. But a bike isn't just pedals. It is also handlebars, steering, and control."

"We like to think that the riders design our cycles," says Designer Mark Walker. So when a physical therapist suggested tilting the steering column back towards the rider so that a little girl with spina bifida would be able to fit the cycle, the engineers at Treadle Power were willing.

But the original nylon bearing was not. The design of the steering column used a flange nylon bearing, located on a pin welded to the front axle. "This caused problems for the nylon bearing which had no self-aligning feature. It would just fracture when we tilted the steering column," says Walker.

Lindsay requested samples of the oil-impregnated bronze Spyraflo (Peachtree, GA), a self-clinching, self-aligning bearing that offers a ±5° self-alignment capability. "We chose the oil-impregnated bronze bearing for its rugged construction, as well as the self-lubricating feature, which would keep the carbon steel alignment pin from corroding," he says.

With the Spyraflo bearing in place, the steering column can be positioned where the rider needs the handlebars, without inhibiting rotation of the column. "Most people probably won't use the full 5° self-aligning feature, but we can use it to the maximum, and the steering column still works flawlessly," says Walker.

Lindsay also appreciates the self-clinching feature of the Spyraflo. As the bearing is pressed into the bore, the tapered sides force material up into an undercut below the flange. The serrations act as multiple cutting edges that increase the flow of material into the undercut. When finished, the flange of the bearing is flush with the surface, and becomes an integral part of the assembly.

Article written by Laurie Touplin, Contributing Editor, Engineering News

For further information contact:

Spyraflo, Inc.
404 Dividend Drive
Peachtree City, GA 30269
t. 770-631-9990
e. sales@spyraflo.com