This bearing is no wallflower

Boston-When Brewer's Ledge founder Jeff Brewer designed a rotating climbing wall called the Treadwall, his challenges included making it affordable to health clubs and military training centers. Going down that path was a test almost as formidable as scaling the 10-ft obstacle.

Design of the Treadwall included a mechanism for adjusting its angle. The fitness equipment uses a cable-and-winch system with two cables and one active moving part-a tubular steel rod that extends through the center of the wall. The angle adjuster tube runs through the two side channels that guide the climbing panels around the machine. The point at which the tubing passes through the channels requires a bearing that must frequently withstand up to 200 lbs of direct force.

"We considered several options for the bearing in this system," says Brewer. He preferred using inexpensive schedule 40 pipe for the tubing, but ball bearings were ruled out because the shaft's surface would require machining.

Brewer also considered using bronze bearings, but thought they were too expensive. Furthermore, he could not guarantee that the rough surface of the pipe would not cause excessive wear on the bronze bearings.

Early versions of the Treadwall included bearings fabricated out of plastic. He mounted them into fabricated brackets welded into the guiding channels. But Brewer deemed this option too expensive.

His solution was the iglide M250 bearing from igus Inc. (East Providence, RI) "Testing indicated that the bearing would handle the load and abrasion requirements with minimal wear," says Brewer. "They are also inexpensive and very easy to use."