Advantage Snafoos

by Burt
(ARK)

I'm thinking...if the moving block is below the fixed block (which is mostly normal)...then- in order for the hauling part to travel same direction as load (or upwards in most cases)....I contend that, in most cases, an advantage is impossible...unless...hauling part.. goes thru a single pulley affixed on a tangent, beside the fixed block...which would,technically, put us back to a disadvantage....

MY QUESTION...keeping in mind,the losses of power from friction, multiplied by each shieve & a possible loss from using smaller pulleys (which should put more pressure on the axle-hence more friction)( my own conjecture, learned from using both big & little well pulleys...daily...as a boy.

With these factors in mind,using 3/16" galvanized cable...3" shieves...with a 7 to 1 - worm drive hand winch, no ball bearings on axels...with all these factors considered...HOW MANY SHIEVES in BLOCKs until point of diminishing returns ????? much obliged for your answer...
I will be lifting max of 700 lbs....

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Block and Tackle
by: Anonymous

Have a look at http://en.wikipedia.org/wiki/Block_and_tackle





Lifting Tackle
by: Mike

F is the mechanical efficiency

N is the number of falls

S is the number of sheaves

K is the sheave friction factor, for plain bearing sheaves with wire rope it will be approximately 1.09, (this value can be obtained from the block manufacturer)



This does not take the worm drive hand winch into consideration.





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