2:1 or 3:1 Mechanical Advantage

[Colin]

Tom

You're an SRT man so maybe you got confused with the 2:1 application shown in the RH pic of this diagram.

 

[Tom Dunlap]

Eric,

You illustrated the RADS mechanical advantage. Nice!

 

[TheTreeSpyder]

Though Zer0 actions on line in 2nd drawing, lines 1,2,3 each have 1/3rd load, red has 2/3rd; above that is full load. thus you must pull line 3, 3x lift distance and gives 3x power.

System is a 1/1 static/still; 3/1 dynamic/ motion. Statically there are 3 supports pulling up versus load pull on 3 lines down for 3/3. Dynamically/ under motion / lift we pull 1 support leg with hand, that in turn delivers 3 pulls on us as load, for 3/1!

A safety rope grab of prussik or cam on top pulley facing towads the '2' gives each line 1/2 load at static/hold - safety on, but then pulling @ '3' gives 1/3 load to each line; as safety now moves.

Locking off line 1 to lower pulley gives our DdRT of 2/1 dynamic; but still would be 1/1 (with load shared between legs of support) static.


Orrrrrrrrrr something like that /forum/images/graemlins/crazy.gif!