Rigging forces

[stewmo]

I see. They changed how they want it explained.
 
When I did the course there was a separate question on estimating the weight of the log, where a species correction factor and a safety factor (the 1.3) came into play.
 
Then for the load at the rigging point it was 2x and 11x log weight. 
 
14.3 is a much easier number to use. I'm really good at my 14.3 multiplication table. 
 

Thanks for that. That’s quite interesting! How long ago did you do your ticket?

I really don’t get it myself, the size of the bits are tiny. No one could possibly rig like that.

Even with your x11 it doesn’t really make much difference. It’s the safety factor on the ropes mbs, 5:1 rather than 10:1 that frees you up a bit.

With my example above the limit on size of rigged piece would mean that once the stem was approaching 2ft you simply couldn’t rig anything negatively without double blocking and even then it would be tricky.

[Blah]

May 2017. 

 

It seems that things are slightly different in real life, yes. That's from my own experience, and watching respected climbers like August Hunicke and Reg Coates.

 

It's  trying to simplify a really complicated calculation of dynamic forces to cover different tree species. When I looked into it properly after the rigging course, even the scientific papers concluded that basically, it's impossible to calculate the forces accurately.

[stewmo]

May 2017. 
 
It seems that things are slightly different in real life, yes. That's from my own experience, and watching respected climbers like August Hunicke and Reg Coates.
 
It's  trying to simplify a really complicated calculation of dynamic forces to cover different tree species. When I looked into it properly after the rigging course, even the scientific papers concluded that basically, it's impossible to calculate the forces accurately.

Yes exactly.

Real world scenarios I’ve rigged big sections on 16mm rope. Now unsure how safe anything is.

And then just to further complicate, this from the AA with a Treemangineers research showing 8 x mass plus 500kg.

Who knows haha

[BenR]

On 02/03/2021 at 19:35, stewmo said:

 

Thanks for that. That’s quite interesting! How long ago did you do your ticket?

I really don’t get it myself, the size of the bits are tiny. No one could possibly rig like that.

Even with your x11 it doesn’t really make much difference. It’s the safety factor on the ropes mbs, 5:1 rather than 10:1 that frees you up a bit.

With my example above the limit on size of rigged piece would mean that once the stem was approaching 2ft you simply couldn’t rig anything negatively without double blocking and even then it would be tricky.
 

 

It's based on the assumption that there is minimal rope in the system and that the piece is not let run. The numbers are basically there to illustrate a worst case scenario and encourage people to be aware of the potentially high forces that could occur if operations go badly.. eg, f-all rope in the system low to the ground and operator does not let pieces budge an inch (excluding the rope stretch) results in mega high peak load at the high point.

[Khriss]

Include in this a directional pull, as if yr fellin top off - the yank as the hinge breaks 😳 K

[wood cutter]

static rigging = x2 heavier ( pulley above material to be rigged)

 

Dynamic rigging = 14.2 times heavier (pulley below material to be rigged)