Blocks and Pulleys

[klimbinfool]

So Tom , I gather out of all of this , that, that illustration is a considered block .

Greg

 

[Mahk_Adams]

The formating in my last post just disappeared so all of the paragraphs were lost. That makes it look like just a large jumble of words and it's difficult to read. Hope that doesn't happen here.

My dictionary says that the word 'sheave' may be pronounced either 'shiv' with a short 'i' or 'shev' with a long 'e'. Two different pronounciations for the same word.

My dictionary says that the word 'shiv' is a knife; it is also pronounced 'shiv' with a short 'i'. Same pronounciation for two different words. Confused? Wait till you read below.

Interestingly, the dictionary says that 'sheave' is "...a pulley for hoisting or hauling..." Apparently the guy in the hardware store was right. A 'sheave' is also a grooved wheel. For arborists, 'sheave' usually refers to the grooved wheel in a pulley or a block over which the rope runs. In a block, the smaller grooved wheel that holds the sling is usually called the bushing, although it too is also a sheave (a grooved wheel).

The glossary in The Art and Science of Practical Rigging (ASPR) says a bushing is "a metal tube that acts as a guide or bearing for moving parts...; or the nonrotating sheave used to increase the bend radius for the sling attachment".

Bearings can be either bushing bearings or ball bearings.

In short:

A pulley is light duty and requires a connector for the sling.

An arborist block is heavier duty, has extended cheek plates and does not require a connector for the sling.

The sheave is the grooved wheel over which the rope runs in a pulley or a block.

The bushing is the smaller grooved wheel over which the sling is placed in a block.

Bushing may also refer to the tube-like sleeve that acts as a bearing and reduces friction between the axle and the sheave.

Bearings can be either bushing bearings or ball bearings

As a side note, ISA is putting the finishing touches on an Arboricultural dictionary. It will include everything that is in the glossary of the Certification Study Guide, the glossary from ASPR plus a lot of other industry terms.


Mahk

 

[Tom Dunlap]

Dave has a \"heart\" I think

I mean the picture that he posted looks like a rigging heart. It looked like what I've seen aboard wooden sailing ships. These hearts are part of the standing rigging. Most of the time I've seen them mid-ships mounted on the gunwales. A large line comes down from the masts and is attached to the top eye of the heart. Then smaller line is rove through the grooves. The whole works becomes a block and tackle. IN this case the block doesn't have a sheave on an axle. The sheave is the rounded grooves in the heart.

http://www.pbenyon.plus.com/B_S_M/Blocks.html

http://www.pbenyon.plus.com/B_S_M/Blocks.html

 

[glens]

Mahk,

This third post appears to me to have the same (proper) formatting as your second from earlier. No need to delete it again! I didn't see the first before you got to it with the eraser.

If this one seems to give you trouble when you see it in the future, shoot me an email before you do anything with it.

Glen

 

[Nickrosis]

I hope you used cut-and-paste, too! /forum/images/graemlins/smile.gif