Snatch Blocks

[jojam]

Hi, can anyone tell me if you are winching using 2 snatch blocks (pulleys), if this triples your pulling power or not? Also what is the correct way to setup 2 snatch blocks if there is one. We have a 4.7m diameter at breast high Elm to winch up a steep bank.

thanks:confused1:

[Peter]

As I understand it, if the rope runs up and down three times (ie through 2 pulleys and then to the puller, then for every foot of rope you pull through the system the load travels 4 inchs, so effectively you have tripled the pull, less friction loss and rope stretch.

 

How far do you need to pull it? If its a fair distance you'll either need a long rope or a way of attaching the mechanical advantage system midline.

 

If at all possible, the top anchor needs to be up off the ground, to help lift the load and stop it digging into the ground.

 

What are you pulling with and does it have enough pull to drag one third of the total load uphill?

 

Thats some badass Elm btw!

[madmatt]

4.7m diameter at breast hight thats nearly 16feet in diameter?!

[skyhuck]

4.7m diameter at breast hight thats nearly 16feet in diameter?!

 

Surly he means circumference????????

 

If not ring record breakers!!!!!!!!!!!!!!

[penfold]

Surly he means circumference????????

 

If not ring record breakers!!!!!!!!!!!!!!

 

not to mention you're going to need a bigger winch unless you get skyhucks mog and skidding winch on it

[treequip]

If not ring record breakers!!!!!!!!!!!!!!

Or Back Breakers :scared1:

[jojam]

Yeah ok you got me cirumference. It will be felled down the bank and then pulled back up with an Igland 8tonne winch on a valmet and two snatch blocks for a bit of extra heave.

[skyhuck]

Yeah ok you got me cirumference. It will be felled down the bank and then pulled back up with an Igland 8tonne winch on a valmet and two snatch blocks for a bit of extra heave.

 

That sounds like a very good setup for the job!!

[penfold]

better than your mog,skyhuck?

[Arbocop]

wow wee thats a big one, alas the simple answer is not that, as you need to make allowances for how many wraps there are on the drum of the winch, the moore there are the less efficheant, abut a 5% to 10% loss on each pass throufh a sheaving due to friction, a resistance allowance in referance to the slope of 1 per 1 degree of slope up to 54 degress where is maxes out, use a low anchor piont on the wicn as when pulling up hill funky things happen to the vector of force on the tractoee that can cause premetur rearing etc ohh it goes on and on, there is a really good book ohn the subject if you have about 400 quid, or you could just hook up and see hehehehehe

 

seriosly look hear

 

http://hse.gov.uk/pubns/afag502.pdf

 

and

 

http://hse.gov.uk/pubns/afag703.pdf

 

and