Fun little rigging job last week.

[Steve Bullman]

roger, trainers = sneakers

 

cracking photos mate.

[rbtree]

Yup, I fingered that out, big fella!

 

some folks at the Treehouse had some criticism as well, including Pete McTree... I welcome that. I've been climbing for 35 years, but in all reality, I didn't know squat till I joined the ISA in 1989 and started reading. Then, starting with the old ISA message board, and now visiting 4 main ones regularly, Arbtalk the newest, I'd say I've learned a whole heck of a lot more. The sharing of knowledge, jobs, tips, tricks amongst working arborists as happens online is a fantastic resource to have.

 

Pete and a couple other's commented on using biners for rigging....I agree that this use is sketchy, but here's what I said in response:

 

"

the spine is being loaded laterally in those pics

 

sure, Pete, maybe 15-25% of the load is lateral....that is, the portion of the load that is actually transferred to the biner, which is very minimal when rigged the way I teach my crew. I didn't see what Mickey was doing or would have insructed him to do it the better way. The way Mickey rigged it, and on smaller diameter wood, the side load would be higher.

 

I know that a few times, I've rigged stuff a bit too heavy.....but also have checked the tension on the biner after the lowering...and it is minimal compared to the load...even considering what the dynamic loading could have been.

 

In my non-scientific (or backed up with dynamometer evidence) I'd venture to say that the peak force on a biner of a properly tied setup would never go beyond 1/4 of the total load, as it is spread out, starting at the marl. So, say a 500 pound load is butt hitched, and let run a fair bit, applying 3500 pounds on the rigging point, and 1750 pounds on the load. That is about 450 pounds on the carabiner. Now no more than 1/2 of that would be a side load force, I'd say. Now tell me, do you really think that would break a 50K rated biner?

 

And that is worst case (well, besides a snafu such as snubbed load which could apply 10x the force on the rigged load), I think. As well, i've never butt hitched a 50 pound load with a biner termination, and won't.

 

Part of my reasoning is to offer, that hard and fast rules, such as one handed chain saw use, and this new OSHA bs ruling, while they may have merit, aren't necessarily the end all."

 

Anyhow, the way I teach biner use is to terminate it the way a running bowline is terminated...looped around the rope and clipped back to itself. This not only further reduces the load on the biner by a fair bit, but reduces possible sideloading as well..which WILL be present when a biner is used to tie off a small diameter stem.

[rbtree]

Oh yeah, I see that Brian was wearing sneakers.....He owns Wescos (lineman boots), and likes them. In fact, he had them on the truck. Me personally, I won't wear mine on the ground...they're not comfy for ground work, and offer only minimally more protection.

[High Scale]

Lovely clear shots, nice camera/work.

[Drella]

Not to sound naggy but, you may want to consider retiring about 10' off your work line.

 

That's the all too common point of failure. I've had two embarrassing experiences with the same issue. One was false-crotching a giant Austrian Pine,, luckily no one was injured. And the other a mammoth Shag-Bark Hickory, same M.O. with the rope. Both times it had snapped at that exact same spot, right where yours is about to....

 

 

[Tommy_B]

Not to sound naggy but, you may want to consider retiring about 10' off your work line.

 

Good eyesight Drella!! I guess you don't need that eye patch!!!

[rbtree]

Oh, I know, guys. Good eyes, too! That line is overdue for replacement.

But that nick isn't super bad. Prolly no more than 10-20% strength loss. I don't think we picked anything over 800 pounds on that job (picked, not butt hitched), so we were within 10-1 SWL factor.

 

And, I'd stupidly left the static line at the shop.....

[Mac McLennan]

Nice photos......Thanks for posting:001_cool:

[Pete Mctree]

Yup, I fingered that out, big fella!

 

some folks at the Treehouse had some criticism as well, including Pete McTree... I welcome that. I've been climbing for 35 years, but in all reality, I didn't know squat till I joined the ISA in 1989 and started reading. Then, starting with the old ISA message board, and now visiting 4 main ones regularly, Arbtalk the newest, I'd say I've learned a whole heck of a lot more. The sharing of knowledge, jobs, tips, tricks amongst working arborists as happens online is a fantastic resource to have.

 

Pete and a couple other's commented on using biners for rigging....I agree that this use is sketchy, but here's what I said in response:

 

"

 

sure, Pete, maybe 15-25% of the load is lateral....that is, the portion of the load that is actually transferred to the biner, which is very minimal when rigged the way I teach my crew. I didn't see what Mickey was doing or would have insructed him to do it the better way. The way Mickey rigged it, and on smaller diameter wood, the side load would be higher.

 

I know that a few times, I've rigged stuff a bit too heavy.....but also have checked the tension on the biner after the lowering...and it is minimal compared to the load...even considering what the dynamic loading could have been.

 

In my non-scientific (or backed up with dynamometer evidence) I'd venture to say that the peak force on a biner of a properly tied setup would never go beyond 1/4 of the total load, as it is spread out, starting at the marl. So, say a 500 pound load is butt hitched, and let run a fair bit, applying 3500 pounds on the rigging point, and 1750 pounds on the load. That is about 450 pounds on the carabiner. Now no more than 1/2 of that would be a side load force, I'd say. Now tell me, do you really think that would break a 50K rated biner?

 

And that is worst case (well, besides a snafu such as snubbed load which could apply 10x the force on the rigged load), I think. As well, i've never butt hitched a 50 pound load with a biner termination, and won't.

 

Part of my reasoning is to offer, that hard and fast rules, such as one handed chain saw use, and this new OSHA bs ruling, while they may have merit, aren't necessarily the end all."

 

Anyhow, the way I teach biner use is to terminate it the way a running bowline is terminated...looped around the rope and clipped back to itself. This not only further reduces the load on the biner by a fair bit, but reduces possible sideloading as well..which WILL be present when a biner is used to tie off a small diameter stem.

 

Your maths is better than mine! and methods are well founded. I agree that in that configuration the side-loading forces will be minimal, compared to the peak loads at the marl. The doubling back, clipping onto the line would further reduce the load, and as you pointed out in your later post you were working with a factor of safety in excess of 10 to 1.

With your massive experience, ability and attention to detail, I have little issue with such usage. It is when a less experienced individual mis configures the system, or by mishap the marl or half-hitch drops off the cut piece that I would worry, especially on larger wood, and if the load was not allowed to run to dissipate some of the energy.

 

I'm still learning- and do every day in this game. I like to understand the limitations of the methods I use, and the implications in the case of mishap. I am a firm believer that if more people understood the benefits of learning and research, there would be a reduction of accidents and the HSE here in the UK and the OSHA for you in the US will leave us the hell alone!

 

There is some information out there on the side loading of biners, I will attempt to source it but i don't know if it's available yet.

[rbtree]

Hey Pete, we meet again!

 

I'm now ordering my rigging lines with eye splices which will pretty much preclude use of a termination knot on the spliced end. A shackle will of course be the choice for heavy loads or butt hitching.

 

And, I stopped by Ben's today. He'll have new 1/2 inch line for me in pronto!! I've been putting that order off for quite some time!