. The American artist's manual; . one horse, andcan with the same ease push round thehorizontal beam in a 40 foot walk; butthree of the same men will push round abeam in a 19 foot walk, which a horse(otherwise equal to five men) can butdraw round. A man turning an horizontal windlass bya handle, or winch, should not have above30 lbs. weight acting against him, if he isto work ten hours a day, and raise theweight at the rate of three feet and a halfin a second. This supposes, however,that the semi-diameter of the windlass isequal to the distance from the centre tothe elbow of the handle ; for i
. The American artist's manual; . one horse, andcan with the same ease push round thehorizontal beam in a 40 foot walk; butthree of the same men will push round abeam in a 19 foot walk, which a horse(otherwise equal to five men) can butdraw round. A man turning an horizontal windlass bya handle, or winch, should not have above30 lbs. weight acting against him, if he isto work ten hours a day, and raise theweight at the rate of three feet and a halfin a second. This supposes, however,that the semi-diameter of the windlass isequal to the distance from the centre tothe elbow of the handle ; for if there bea mechanical advantage, as there usuallyis, by having the diameter of the axle, onwhich the rope winds, four or five timesless than the diameter of the circle de-scribed by the hand, then may the weight(taking in also the resistance, on account,of the friction and stiffness of the rope)be four or five times greater than 301b.;that is, so much as it rises slower thanthe hand moves. In this operation, the effect of a manV. ?>rce varies in every part of the circle de-scribed by the handle. The greatest forceis, when a man pulls the handle upwardsfrom about the height of his knees ; andthe least force when (the handle being atlop) he thrusts from him horizontally ;then again the effect becomes greater, asa mean lays on his weight to push downthe handle ; but that action cannot be sogreat as when he pulls up, because heiays on no more than the whole weightof his body ; whereas, in pulling, he canexert his whole strength. Lastly,he hasbut small force to pull the handle towardshim horizontally, when at its lowest. Let us suppose a man of moderatestrength to weigh 140 lb. he may in thetour principal parts of pushing and puliing, in the whole circumference of motion, exert the following forces, viz. in the•strongest point, a force equal to 160 lb.;in the weakest, a force equal to 27 lb.; inthe next strong point, 130 lb.; and in thelast, or second weak point, 30 lb Let usa
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