CATALOG OF THE MECHANICAL COLLECTIONS 3 



MODELS OF MECHANICAL POWERS 



U.S.N.M. nos. 307593-307599; 307913-307919; 307942-307946; 308030-308043; 

 30S121-308122 ; 308227-308232; 308324-308327, all inclusive; 45 models; 

 made in the Museum ; not illustrated. 



These models are exhibited to illustrate the mechanical powers and 

 their simpler combinations in man-powered machines. 



There are about 45 models illustrating the various orders of levers, 

 including straight, bent, and rotary levers, and their applications 

 to such simple machines as cranks and windlasses ; the inclined plane 

 and its application to ramps, wedges, screws, and jacks; and rollers 

 in the forms of axles, load rollers, pulley blocks, and wheels. 



ROLLER, LEVER, AND INCLINED PLANE 

 Plate 2, Figueb 1 



U.S.N.M. no. 181251; model; made in the Museum; photograph no. 39008. 



This model shows a group of men moving a block of stone along 

 a ramp with the aid of rollers and a crowbar. It illustrates a present 

 every-day use of three mechanical powers in their simplest forms. 



CHINESE WINDLASS 

 Plate 2, Figube 2 



U.S.N.M. no. 307599 ; model ; made in the Museum ; photograph no. 24926C. 



This elementary form of the differential hoist (see below) is said 

 to have been in use in China for many centuries. 



The windlass drum is made of two sections of different diameters, 

 which turn together as one piece. The rope is so attached that it 

 winds upon one section of the drum as it unwinds from the other, the 

 net lifting or lowering effect being the difference between the length 

 of rope wound upon the drum and that unwound. By making the 

 sections nearly alike in diameter a large mechanical advantage is 

 secured without making the drum too slender for strength or the 

 crank too long for convenience. 



HAND HOISTS, 1928 



Plate 2, Fiqtjbe 3 



U.S.N.M. nos. 309507-309510 ; originals ; gift of the Yale & Towne Manufacturing 

 Co. ; photograph no. 6232A. 



Three complete hoists and a sectioned operating one are exhibited 

 in the Museum to illustrate the principles of the modem differential 

 pulley block, the screw-geared block, and the planetary spur-gear 

 hoist. 



