Block and Tackle?

[Q228]

Can anyone out there explain to me whata block and tacle is? Is it a 4:1 add on system? This name or term was never brought up in the NYS Rescue Technician class.

Thanks for your help.

[SPFDRum]

A "block & tackle" is a mechanic advantage system that uses a series of pulleys with a rope to hoist. 4:1 advantage means on a 100# object, you would pull 25# on the rope. The disadvantage is that for every 4' you pull on that rope, the load only moves 1'. The term comes from a block-pulley in a frame, and tackle-set of ropes and pulleys.
Hope this helps.

[Q228]

So a block and tackle is the actual pulleys or a 4:1 mechanical advantage system (add-on as known here, being that you can add it onto the main line with out looping it as you would a z rig) a 4:1 add on is a two double pulleys where a seperate haul line is looped through to provide a 4:1 mechanical advantage. this is then attached to your main line with a gibbs or tandem prussiks. this is of course backed up with a load releasing hitch tied into the main line with a gibbs or tandem prussiks. Is taht what is generally known as the Block and Tackle? or is it any set up of pulleys for mechanical advantage weather it is a 3:1 z rig 4:1, 5:1 or 6:1 add on system?

thanks for your help

[resqtek]

Block and tackle is simply another name for a haul system. It is usually used when describing an add on system. Some rope access workers will use two small block and tackle systems to move from anchor point to anchor point when working under an overhang while cleaning windows. PEtzl has a good picture of this technique at:
http://www.petzl.com/petzl/statique/work/ENG/tech/html/20-21_WR02/21b.html