Model: 028 Pulley Lifts
Two types of "block and tackle." The first has a lower pulley block with three grooved wheels or sheaves and the upper pulley block has four sheaves. Its lifting ratio is 7 to 1, therefore it will lift seven pounds when one pound pull is exerted on hand rope. Used most generally in construction work. The second contrivance is known as White's pulleys, and has a ratio of 6 to 1.
[Virginia Downward & William M. Clark, 1930]

[Editor’s Note: There are four Clark models on pulley force-lift devices, 25-28.They differ from the closed system belt and pulley mechanisms of model 5. The pulley-lift is an open mechanism; the single cable is connected to an external driver. The right hand model was likely copied from Figure15 of the 1868 catalog of Henry T. Brown on mechanical movements. FCM]

Francis Moon 2005-00-00

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