Help explaining "rigged to advantage/disadvantage"

[a70duster]

First off I am an electrical type so bare with my potential to misname stuff. I have a guy at work doing a presentation on rigging. He has "rigged to disadvantage" pretty well nailed down. He uses a 4 part block and tackle as an example for the compounding force as the rope winds itself through the pulleys. His rigging references come from cranes and all of the information is about "rigging to disadvantage".

Does anyone have any good links to "rigging to advantage"? We have calculated the force in each line with a moving pull line but he is not feeling comfortable with the results.

 

[a70duster]

PS - I made up a few simple drawings but I do not know how to embed them in my post - any suggestions appreciated...

 

[a70duster]

Rigged to disadvantage

http://i268.photobucket.com/albums/jj37/a70duster/pulley2.jpg

 

[a70duster]

Rigged to advantage - is this correct?

http://i268.photobucket.com/albums/jj37/a70duster/pulley1.jpg

 

[MikeHalloran]

When I need rigging, I call a rigger. Cheaper than hospital bills.

I haven't heard of "rigging to {dis}advantage", but the way I learned in high school physics says if you're pulling up to lift the load, you're part of the solution, and using the hardware more efficiently.









Mike Halloran
Pembroke Pines, FL, USA

 

[a70duster]

We are riggers (well the mechanical types are). I work at a ski resort and we are improving our knowledge. Our biggest rig is resplicing the haul ropes and that is a horizontal load.

 

[hydtools]

Here is a wikipedia description:

http://en.wikipedia.org/wiki/Block_and_tackle

Ted

 

[a70duster]

^^^ I did some searching and that is where I found "rigged to advantage/disadvantage" but it doesn't go through tension increase from pulley friction.

 

[hydtools]

Try this ref, it includes tension added by friction:

http://www.globalsecurity.org/military/library/policy/army/fm/55-17/ch6.htm

Ted

 

[a70duster]

Thanks hydtools