Tackles Flashcards
What is a purchase
Combination of blocks/pulleys rove with a rope, wire, chain
What is a tackle
A purchase consisting of rope rove pulled through 2 or more blocks.
What is a fall
Whole rope used in a purchase. Size of tackle is described by size of fall
Mechanical Advantage
Disparity between amount of force required to move an object and the weight of an object
How do you calculate the MC
Divide the weight of the object being lifted by the force required to lift it.
Ie divide 200lb crate by force required to lift it ie 2
What is friction
When an object moves against another, some moving objects energy is lost to friction. (Can reduce mechanical advantage)
What is reeving
Is how a block and tackle are set up together - either reeved at advantage or disadvantage
When is a tackle reeved at a advantage
It is reeved at an advantage when the rope is being pulled in the same direction that the load is being pulled. Ie away from standing block
When is a tackle reeved at disadvantage
When the rope is being pulled in the opposite direction that the load is moving
Describe single whip tackle
One single sheave block, fixed to a support, with rope passing over sheave
What is MC of single whip tackle
1, no mechanical Advantage is gained
Describe a runner tackle
Consists of a rope rove through a single moving block, 2 parts of fall
Advantage of a runner tackle
2
Describe a double whip tackle
Simplest form of purchase - fall is rove through 2 single blocks. Standing is secured to upper block
Another name for double whip tackle
Gun tackle
MC of double whip tackle
3, if disadvantage 2
Describe Luff tackle
A purchase of 75mm or greater. Consists of a double & single block. Standing part of fall made fast to single block
MC of LUFF
3 or 4
Describe a Jigger tackle
50mm (similar to luff/double & single block) though there is a tail on the double block instead of hook. Standing part of fall is spliced to single block
Describe a handy billy tackle
Similar to luff tackle but smaller the 50mm (one single and double blocks)
Describe a 2 fold purchase
2 double blocks, commonly used to hoist boats
MC advantage of 2 fold purchase
4 or 5
Describe a 3 fold purchase
2 triple blocks
MC of 3 fold purchase
6 or 7
What does it mean to overhaul a tackle
To separate the block further from each other
What does it mean to round up a tackle
To move blocks closer together
