zip line beech

[educated arborist]

cool pics, dave can you talk me through yor 3 in 1 set up please, i see the pulley and friction hitch which i get, then i see the tail end heading back up to the tree through another crab and pulley??

 

don't mean 2 piss on some1's chips but it is not a 3-1 to do this involves at least 7 pulley wheels! it will be a 'true' 2-1 or some people call it a re-directed 2-1. Treevo made this mistake at the A trade fair during a demo & allthough we work with big safety factors in arb i think its advisable to be aware of the forces involved.

[Amelanchier]

don't mean 2 piss on some1's chips but it is not a 3-1 to do this involves at least 7 pulley wheels! it will be a 'true' 2-1 or some people call it a re-directed 2-1. Treevo made this mistake at the A trade fair during a demo & allthough we work with big safety factors in arb i think its advisable to be aware of the forces involved.

 

You sure? IIRC mechanical advantage is calclulated by simply counting the number of rope sections in tension. So two pulleys & three sections of rope between them in tension = 3x mechanical advantage (force needed /3 but 3x distance of rope needed).

[Stephen Blair]

:biggrin:nice one tony not just a legislation guru, i would be very surprised if monkey-d was wrong:001_huh:

[David Humphries]

You sure? IIRC mechanical advantage is calclulated by simply counting the number of rope sections in tension. So two pulleys & three sections of rope between them in tension = 3x mechanical advantage (force needed /3 but 3x distance of rope needed).

 

 

That would be my understanding of this particular set up

 

 

nice one tony not just a legislation guru, i would be very surprised if monkey-d was wrong:001_huh:

 

 

The Monkey is but a student Stevie, misunderstanding & learning along the way, via experience and interaction.

 

 

 

 

 

Right,

 

the fact that this is my 5000th post, I'm now gonna do something I've been promising myself for a while, and have a wee break from the "talk".

 

So, I bid you all a fond fairwell & adieu

 

 

No beter way to depart than qoute the great Verbal himself........

 

 

"The greatest trick the Devil ever pulled was convincing the world he didn't exist.

 

And like that.......poof........ He's gone."

 

 

.

 

 

 

.

[Ian Flatters]

I undersatnd it as a 2-1 pulley system too.

 

2 pulleys so line going to the hitch doesn't count. Line 1 heads from the isc block to the pulley and the return rope is only used for tension. So 2-1?

[markarb]

sean what size line are you using for the speed line?

thanks mark

[Amelanchier]

I undersatnd it as a 2-1 pulley system too.

 

2 pulleys so line going to the hitch doesn't count. Line 1 heads from the isc block to the pulley and the return rope is only used for tension. So 2-1?

 

A 2x (2:1) mechanical advantage system is what gets you in the tree as you pull a rope over a branch (friction reduces the actual efficency which is why we get a ropeguide involved), both lines are in tension so its twice as easy to pull yourself up but you pull twice as much rope...

 

The rope section after the hitch/pulley will be experiencing as much of a force as the rest of the line as its pulled so it's definatley involved.

Edited March 21, 2010 by Amelanchier
spp.

[educated arborist]

why bother replying? who reading this post is to know whats right or wrong? Its v.basic physics but it doesn't matter if you don't understand just carry on making it up & if anyone chalenges you intelectually just shout louder & if that fails, just make fun & call them names instead! Real Mature. If you google physics for dumbies, mechanical advantages i'm sure u'll c what a 2-1 4-1 6-1 & 8-1 advantage is. It has to go in even numbers when using ropes & pulleys, the only way to get an odd advantage is to set up 2 tripple pulleys in a draditional fiddle block rig then set 1 pulley with the rope passing off the fiddle block & onta an anchor then pull on this pulley by its narrow end. I'll draw a picture & scan it in if i get a chance.

[educated arborist]

hopefully this will not only upload but make it easyer to understand.

[Amelanchier]

Wind your neck in son. I see your source and I raise you diagram 3...

 

[Pulley - Wikipedia, the free encyclopedia]

Edited March 21, 2010 by Amelanchier