Tree anchors expressed in kilonewtons

[peds]

8 minutes ago, AHPP said:

Wanted a load cell for ages. Bought a GRCS recently. Want one even more now. 

And yeah, load cells are great fun, been such a useful tool the few times I've played with one. Definitely an investment worth making if you can make it work for you.

Not sure we can afford one this year, fingers crossed for next year!

[Will C]

No figures but you can winch a stuck lwb shogun and 8” chipper (both on their belly across a field from a ft round connifer. That was with a 5.5t pull winch that tripped the thermal overload out till we ran a double line back to the truck so in theory a potential 11ton pull! Anchor strop was a couple of ft up the stem which didn’t move. 

[peds]

Figures be damned, that's a nice meaty pull. No worries dangling two people and a stretcher off a 12" conifer then, I'll make a note of it in our training manual.

 

 

[AHPP]

19 minutes ago, peds said:

Those Clutches do all the clicking for us. Such a pleasing noise!

 

My mistake. Didn't realise they clicked. I thought they were just a slicker guide plate. Your holiness restored. 

[peds]

That's all they are, a pretty slick 800euro guide plate, but with a pulley built in. Awesome bit of kit, huge improvement on the Pretzl IDs they replace.

 

Still got a heap of IDs for general use, but for the centrepiece of the masterpoint... Clutches rule, hard. 

[Mr. Squirrel]

I caused root plate failure of a 25cm alder and a similar sized lime using them as winching anchors while pulling logs around. Separate occasions. The lime was in waterlogged soil while the alder was in about 10cm of soil on top of hard core. I’ve anchored onto little bushes and the likes plenty though. Soil and roots play a massive part. 

[john87]

Slightly off at a tangent, but this will be found interesting..1.pdf

[Dan Maynard]

10 hours ago, Mr. Squirrel said:

Soil and roots play a massive part.

I was thinking this, shallow soil with stunted trees on the side of a mountain being particularly difficult to judge.

[peds]

Absolutely, some could just be a paper thin sheet of roots hidden under a blanket of moss on a solid rock slab, but some could have big thick roots wrapped between and around a pile of half ton boulders. Tricky one to judge. 

[Dan Maynard]

23 hours ago, peds said:

Wrist thickness or more for climbing on (depending, of course, on so many factors), so two wrists for a rescue load, times it by ten for a safety margin... twenty wrist thickness?

For simple bending theory (say in consistent material like aluminium) the strength goes up with 4th power of diameter, so 2 wrist thicknesses is 16 times as strong.

 

The thing with rigging is use force direction to your advantage, so pulley on the stem and then redirect pulley lower and further out so that the force vector from the redirect is straight back down the branch.