Motion System Design

Hanging by a thread

Finagle J. Wurme is a contestant on a new reality challenge show. For his first task he must cross a 1,200 ft gorge, with sharp craggy rocks and venomous snakes slithering below. Wurme expects to find a rickety bridge when he arrives at the gorge but instead sees nothing but a thick rope tied at each side. He is told that he must cross the gorge by going hand over hand along the rope, dangling above the gorge.

His fear grows as he nears the middle of the rope so he decides to take a break and catch his breath. The rope will break if the tension in it exceeds 3 × 104 N. If Finagle's mass is 78.8 kg and the angle of the rope when he stops to rest is 15°, what is the tension in the rope? What is the smallest angle the rope can have before it will break? Disregard the weight of the rope.

Send solutions to [email protected] by May 5, 2006. For last month's full solution and winner announcement, visit

Win a handbook on chains

The winner of this month's problem receives the handbook, Chains for Power Transmission and Material Handling by John L. Wright. This second edition covers design considerations, increased power ratings for roller and silent chains, and how to choose drives with alternate lives. For information, call The Taylor and Francis Group at (561) 994-0555, ext. 2208 or visit

Handbook features

  • Offers consistent procedures when selecting chains for drives or conveyors

  • Discusses installation, inspection, utilization, and lubrication

  • Select chapters include tension linkage chains and steel and flat-top chain conveyors

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