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Author Topic: Threading Pulleys  (Read 1518 times)

johnnie58

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Threading Pulleys
« on: November 21, 2009, 05:00:23 pm »

New member and I don't know where to put this,but here goes anyway.
 There are some recent pics of the tug boat Imara in close up  and I noticed the threading of the 2 and 3 sheave pulley blocks especially the set over the port side life boat,so I guess they have all been threaded the same.
 The three sheave pulley block is attached to the davit arm the haul rope is threaded over the centre pulley rather than over one of the side sheaves as this can cause the  block to move out of perpendicular causing the  the rope to jamb between the sheave and block.The lower block (2 sheave) is set at 90 degrees to the 3 sheave and this minimises the amount of chafing on the haul rope.
  If I can locate the set that I have will try and submit a pic of what I mean.
                                                              John the Aussie bloke.
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Bryan Young

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Re: Threading Pulleys
« Reply #1 on: November 21, 2009, 05:24:33 pm »

I did a "how to" on reeving lifeboat blocks a while ago. Check out the search engine.....I can't remember where it is. BY
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Notes from a simple seaman

Bryan Young

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Re: Threading Pulleys
« Reply #2 on: November 23, 2009, 03:12:35 pm »

"Threading Pulleys" is good enough I suppose....personally I'd prefer the term "reeving of blocks", but not to worry.
As the previous poster said, the blocks (for a 3 sheave set-up) are right angles to each other, however, stopping chafing is not the prime reason for this. It is so the blocks can be reeved so the hauling part can exit out of the top centre sheave. This keeps the blocks upright when the weight come off and so prevents "toppling".
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Notes from a simple seaman

Jimmy James

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Re: Threading Pulleys
« Reply #3 on: November 23, 2009, 08:50:48 pm »

Nice clear model wish I had a pound () for every time I've Reeved one of those off
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