2^8 «OMPOUNb BARK EL AND WJfNCH. 



Ini795orx796. Mr. Mc Kean communicated the idea to me a few day* 



Dcfcripiion. aft^r it firft occurred to him, in the year 1795 or 1796 ; his 



plan differed, however, in two points^ from that defcribed in 



your Journal ; for, firftly, he made ufe of handfpikes apphed 



into holes in the end of the largefl: barrel, whenever the winch 



did not afford him fufficient power; and, fecondly, when he 



found it neceifary to raife any thing above the level of his 



windlafs, he added two other puUies for the rope to pafs 



over. 



Dimenfionsand About the year 1797, Mr. Mc Kean ereded a faw-mill 



ZmTuni°^^ worked by a fleam engine, at Bordenton in NewJerfey; 



terrel. where he employed this crane to raife his logs, from the ground 



to the frame on which they were to be cut, being a height ef 



about twelve feet ; the circumference of the largeft barrel was 



about fix fee tj and its length three feet; the fmalleil barrel 



was of the fame length, and its circumference three feet, 



making the difference of their circumferences three feet ; and, 



confequently one turn of the barrels, raifed the log one foot 



fix inches ; and eight turns only were fufficient, to elevate it 



the height required. 



Its power as one This windlafs was turned with handfpikes fix feet long ; 



90 twenty. which, at the place where the power is generally applied, 



would defcribe a circle of about 30 feet ; fo that the power 



obtained, is as one to twenty. The length of rope neceflary, 



including that which paffes round the pullies, and from thence 



to the barrels, is about 55 feet. 



A common Now in order to raife a weight 12 feet high, with a power 



tackle would ^^ ^^^ ^^ twenty, by means of the common block pullies, 



have required • /• • i • i 



five rimes as r>o lefs than 270 feet of rope is neceifary ; there is, however, 

 much rope; this difference in the fizes of the ropes, that, in the former 

 but thinners cafe fupporting one half of the weight to be raifed, whereas 



in the latter it has only to fuflain one twentieth part of it. 



This windlafs '^^^ windlafs has the peculiar property of holding the weight 



floes not run at any part of its rife or fall, without needing a ratchet-whee] 



^own* ^^^ catch ; by reafon of the two parts of the rope pulling on 



oppofite fides of the barrels ; and although one pulls on a 



longer lever than the other, yet it is not fufficient to overcome 



the fridion on the axis, whiclimufl of neceffity be large, iti 



order fo give the requifite flrength to the machine. 



Itpromifes to be I have lately introduced a fmall windlafs of this kind, into 



fuu"'^^^'^ a piece of piachiner^ requiring altefpate elevation and de- 



preffionj 



