45KN = 4500kgs?

[Rod]

how do you put more than one quote on

 

sorry for not quoting you targettrees

[Rupe]

Also im using 2 blocks to reduce pressure on each block so instead of a single at 45kn the weight pressure from the rope is spread so if my maths are right using half the block (90 degrees insteasd of 180 degrees) would increase this to around 67.2kn per block? I think? If someone could tell me if im right or wrong please

 

 

Not quite. Using two block and the line spread out reduces the force on the anchors of each block. You could in theory then lower a larger load as the force is distributed bettween the two blocks. So your sort of right, but you can't magicilly increase the SWL load of either block, but in theory you could now lower a 672kg (your maths, not mine!!) piece instead of the 450kgs you had previosly.

 

Word of caution though. These are pulleys and not blocks. 450 kgs will knacker them pretty quick, and you don't want to go anywhere near that amount of force. The cheeks will close up at the top and the pulley will fail loler inspection fairly quickly.

 

Blocks cope with higher forces much better.

[Ian Flatters]

Not quite. Using two block and the line spread out reduces the force on the anchors of each block. You could in theory then lower a larger load as the force is distributed bettween the two blocks. So your sort of right, but you can't magicilly increase the SWL load of either block, but in theory you could now lower a 672kg (your maths, not mine!!) piece instead of the 450kgs you had previosly.

 

Word of caution though. These are pulleys and not blocks. 450 kgs will knacker them pretty quick, and you don't want to go anywhere near that amount of force. The cheeks will close up at the top and the pulley will fail loler inspection fairly quickly.

 

Blocks cope with higher forces much better.

 

Yeah its only going to be used for branch reductions over houses really prob not even going to get close to 200kgs at max velocity of weight. Bought them because my main cast blocks are heavy and these are light and easy to move about in the tree. yeah its 67.2kn between the two blocks not per block (maths were not my strongest subject:lol:).

[Rupe]

If you set you existing block as the top anchor, and then carry those pulleys round the tree with you, attaching them wherever you need a lowering point, that will give you a good set up.

[Ian Flatters]

If you set you existing block as the top anchor, and then carry those pulleys round the tree with you, attaching them wherever you need a lowering point, that will give you a good set up.

 

My plan is to set my cast block high in the tree then one isc pulley 45 degreesish down from that, then the second isc pulley just above the branch i want to reduce.

[Mark Bolam]

I'm just about to order said pulley for that application.

 

Can it be also be used on a 13mm rope for the trolley on a zip-line?

[Ian Flatters]

I'm just about to order said pulley for that application.

 

Can it be also be used on a 13mm rope for the trolley on a zip-line?

 

I can't see why not? higher swl than the red petzl tandem too. You could also balance the load better if you used two i guess?

[john dawson]

there is an easier way y'kno............

 

 

 

just climb out further, cut said branches in smaller lengths and hand throw to target. D'oh!!!!!!!

 

even better you could use two 60cn slings and a steely krab?

[educated arborist]

OK firstly the SF (safety factor) arborists apply to hadware in rigigng operations is 5:1 not 10:1 so the SWL of your pulley is 900kg. It is not designed for snatching & must hand freely when in use not leaning or bending against any branches. The SF takes account for allot but it is worth bearing in mind that a main rigging pulley will be loaded with a 200kg log & have a 200kg aposing force at the capstan end meaning that a 200kg log loads the pulley with 400kg when being lowered. When setting up re-direct pulleys it should be beared in mind that a shallow re-direct angle will exert lateral forces on the tree against which it is far weaker. These pulleys can be linked in a train of two when speedlining but its best to buy a purpose built tandem pulley IMO, ISC make a real nice stainless steel one which is stronger that the petzl tandem and accepts 16mm rope if required.

secondly yes, for arguments sake 45kn is 4500kg, depending on your altitude on earth etc etc etc put lets not get anal

Edited March 11, 2010 by educated arborist
typo

[Rod]

OK firstly the SF (safety factor) arborists apply to hadware in rigigng operations is 5:1 not 10:1 so the SWL of your pulley is 900kg.

 

"for arborists rigging, with dynamic loading, high wear, and dirty conditions, a design factor of 10 or greater is recomended" {the art and science of practical rigging ISA production}

 

i'll belive the book thanks:thumbup: