Rigging assessment.

[jfc]

Thanks guys for this info, just printed a load of it off to start learning. I am happy with all the practical stuff as I do it regularly anyway, yep even do cradle/spider sometimes (though it has been some time). 

 

I had never seen the Husqvarna sponsored NPTC sheets, thanks Harry_L.

 

Sorry to be slow replying I needed some time off over xmas and tried to forget about work work a couple of weeks (being self employed it can take over your life a bit!).

[wood cutter]

All you need to know is the jargon in the nptc book. Log mass flow chart ect and the forces for static and dynamic rigging. The practical is easy

[jfc]

So I've got my assessment tomorrow and just wondering if someone can check I have this correct.

 

I have a 12mm sirius bull rope MBS 3500kg, so SWL is 1/10=350kg.

 

For snatching situations the load is 14.3x log mass.

 

so 350kg/14.3 = 25kg  is this the max recommended load for snatching? Even if you double it for each leg of the rope it is only 50kg.

 

Or have i got this totally wrong! 

 

cheers,

 

jan. 

[wood cutter]

one big thing is to learn the forces  in play and how it effects the type of rigging

 

static rigging - pulley above material to be lowered, ( branches are 2x heavier)

 

dynamic rigging - pulley below materials to be rigged ( 14.2 x heavier)

 

also though to work out the weights of  a section of timber is to use a log mass flow chart, measuring the tree at dbh, x by oak or something like that as oak is the heaviest timber we have?? lord knows, that is what i got taught on my rigging course about 5 years ago now.

[Mick Dempsey]

9 hours ago, wood cutter said:

one big thing is to learn the forces  in play and how it effects the type of rigging

 

static rigging - pulley above material to be lowered, ( branches are 2x heavier)

 

dynamic rigging - pulley below materials to be rigged ( 14.2 x heavier)

 

also though to work out the weights of  a section of timber is to use a log mass flow chart, measuring the tree at dbh, x by oak or something like that as oak is the heaviest timber we have?? lord knows, that is what i got taught on my rigging course about 5 years ago now.

How do you mean, branches are 2x heavier?

[Mark Bolam]

Because there is twice the force on the pulley, the weight of the branch and the equal force on the rope required to hold it.

[Retired Climber]

55 minutes ago, Mark Bolam said:

Because there is twice the force on the pulley, the weight of the branch and the equal force on the rope required to hold it.

It's just the easiest way to think of it isn't it. Trainers aren't mathematicians, so it's an easy way to teach it. It's not exactly x2 though is it. 

[Mark Bolam]

I don’t like to overthink it really mate.

Big piece = chunky anchor point and big rope.

[Retired Climber]

3 minutes ago, Mark Bolam said:

I don’t like to overthink it really mate.

Big piece = chunky anchor point and big rope.

Yep, definitely the way to do it. you could easily spend half the day calculating stuff otherwise. Equally, exact calc's are imposiisible in our industry due to the variables in just about everything we work with ( hence the simplification) .

[Steve Bullman]

When it comes to rigging trees there isn’t much that isn’t covered by common sense. Even the best maths brain would be lost in the trees without it