Rigging Errors

RC1

Here’s a couple of rigging mistakes while removing a Robinia this last Thursday. Nothing major but seems as I had the camera rolling I figured it might be worth posting.

The Hobbs ‘winch’ allows the ground-worker to reel-in unwanted rope slack which might occur as a branch/log begins to move after or while it’s being cut. The technique is especially useful where the pulley/block is set below branch/log i.e. blocking down a spar while implementing the notch-hinge technique.

While rigging a spar you wont notice the slack because it all happens so fast….but it happens i.e. when you cut a notch out of a log, what you’re doing is shortcutting its fall-path….kind of like having your feet kicked from underneath you and falling on your knees before folding over face first. So a deep, open-face notch induces more rope slack but is easy to tip, while a shallow notch falls further, minimises the slack but takes more effort to push/pull over.

In the first clip, the ground-worker (usually excellent) somehow manages to fall over while tending the slack but then instinctively grips the rope and causes the log to slam into limb that I’m attached to. Thankfully, it wasn’t my primary attachment point, so I was able to keep my footing easy enough….however, if not for that high tie-in point, I may have been found wanting….it wouldn’t be the first time either.

In the second clip the hobbs winch is utilized to pre-tension the line, so to aid a back-leaning-log, fall in the opposite direction. When pre-tensioning with either the Hobbs or GRCS-Harken (for those who don’t know), several wraps are required to gain the rope-traction needed around the spools to stop the rope from spinning as the winch is cranked….but once the lift/tension is achieved, the operator will more often than not have to remove a couple of wraps in order to then lower the log, unless it were extremely heavy of course. However, on this occasion the ground-worker forgot the second part but I should have really glanced down to make sure anyway.

The rotating log kinda looks like a big fish swimming around a very vulnerable prey….and don’t be fooled by its appearance on the clip, the wide-angled camera lens really squashes everything in so it all appears much smaller than in real life.

WARNING: The latter scene contains bad language so don’t watch if you’re easily offended. Unfortunately, these things slip out in the heat of the moment. Thanks

newguy18

good groundies are hard to find.Geez he almost succeeded in putting you in the hospital.

__________________
Have your say join us today.


old schooler

treesandsurf

I've found the second situation in the video to be the most peculiar when rigging with a lowering device such as the HOBBS or GRCS. I only really have experience using the GRCS, but I've noticed that it can be quite difficult to apply just the right amount of pre-tension before making the cut and not loosing that tension when the ground person removes wraps on the device.

Several times, I've had to have the person on the ground re-take the wraps and crank several times again, to get back to the necessary pre-tension on the line before finishing the cut.

I'm curious if the HOBBS looses much tension when reducing wraps on the bollard? Guess it also depends on rope diameter and the skill of the operator, as removing one too many can mess the whole situation up, as well as leaving one too many on (such as in the video) where too much tension is created and the piece cannot be safely lowered. Good vid.

jp

phill ellison

hell RC1 you looked like you went for a good ride after you took the top off, good video as there is good lesson to be learnt form that to all the groundies, I did have had agood groundie at work who did a great job at lowering but the bugger gone over seas and now i got to train another guy, so your vid will come in handy

Eric Frei

Thanks Reg, I actually loved the commentary on the last one!

Glad all was OK and that log whizzing around could have done you some damage. It could have got twisted into your climbing line too and then a panicked groundy quickly lowered etc ... lots of bad scenarios.

This will be tough for you to hear though, and I'll write it so people understand where I'm coming from... hopefully.

Using the cranking ability of the Hobbs/GRCS to manipulate sections that require immediate slack after the lift in the manner done there on the first lower isn't wise or best practice. You actually have a very bad angle of tension (straight down the lowering line) and in fact create a catapult effect with the lowering line. Watch the video carefully and you'll see the log shoot off like a stone in a shanghai. That then means increased speed, more shock load, less time to transfer wraps. Far better to have the required wraps and be prepared for the quick pull in of rope as the log passes the pulley. A pull rope on the section to get it over is better, plus that then aids as a tag line in the lower process to steer the log down too.

Both devices (Hobbs/GRCS) free spool to pull in slack as the log passes the pulley, great for minimizing shock load. However the window of opportunity to switch from 3 wraps winching to 1.5 wraps running in a spilt second is too challenging and risky IMHO.... the first part of the video this mainly refers to.

In situations where lifts occur usually there's no slack in the transition from lift to lower (the second lower of your video), for example winching a limb up over a roof, turning it then lowering it.

In the 2nd lower on your video due to the angle of the lowering line the log had little chance of going any way but toward the lowering line, again pretension not really necessary. When you watch it a few times you'll see the section "fell into" the lowering rope and went the right way really well, just was over wrapped or wraps crossed over each other.

On sections where the lowering block is beneath the load (top stropping) on non spooling devices like the Port-A-Wrap I have my wraps in, stand back clear, have sufficient loose rope straight behind me, gloves on loosely holding the rope and a bow in the line between me and the device so that there's slack to be "consumed" to prevent shock loading. It also helps assure the piece clears the climbers feet... sort of like loosely feeding rope then braking the system.

However with spooling devices just pull in the slack as the sections passes the pulley and have gloves on, light grip and let it run prior to braking.

Attached Thumbnails

 

__________________

Phased1

Hey RC1

Good video,

If I understand the use of the Hobbs/ Grcs correctly, then the groundie needs to have more wraps on the device to pre-tension the piece than to lower it, so sometime between pre-tensioning it (or pulling it over) and the piece falling the groundie has to remove some wraps..... correct?

It makes me wonder if the advantage of pre-tensioning the rope is worth it.

In the first vid it looks like you could have pushed the piece over as the kerf was already opening a little when you finished cutting. If so, the Grcs/Hobbs could have been rigged for lowering from the start.
Also if the line wasn't pre-tensioned but the groundie had the Hobbs/ Grcs rigged properly for lowering then any small amount of slack in the system wouldn't matter that much if the groundie was able to let the piece run, no?

Just my 2 cents, as I don't have a Grcs/ Hobbs..........yet.

I'm not trying to be overly critical here, just trying to understand the pros and cons of the device before I use one myself.

What do you think?


Phased1

PS. I see Ekka has posted a reply while I was writing this so some comments may have been addressed or duplicated, he must type faster than me, damn, I was using BOTH fingers too

OutofMytree

Firstly, congratulations to you RC1 in posting a video with mistakes in a public forum. We can all talk about how good we are and post photo's and vids of our victories but mistakes are less commonly seen. Kudo's to you mate.

I use a porta-wrap so I cannot comment on either the HOBBS or GCRS. I will stick to men on the ground issues. That your groundie knew to have less loops in the first situation speaks well of prior communication. I make a point to discuss each cut before lowering so everybody knows whats going on and it seems you do too. Hey, anyone can take a tumble whilst looking up and not at where your feet go. My concern is mentioned by Ekka. I ALWAYS have 2 groundies on a job where I lower branches or blocks. 1 on the porta-wrap and one on a guide rope. The one with most muscle gets the guide rope and the one with most brains gets the lowering device. In that second scenario the only way that it could have gone pear shaped is if BOTH groundies messed up. Hasnt happened to me yet so I figure this simple system is effective. The only time I have ever had rigging issues like this have been directly MY FAULT.

Keep the vids coming folks, I am learning something every time I watch one.

RC1

Eric

That’s what happened Eric, the rope was tight but not pre-tensioned. Perhaps you mis-read the post, or did I not explain it properly? Also, a pull-rope in this instance would have served no purpose what-so ever as the rigging point was ideally situated for the landing.

Not only was the second log leaning back but it was also leaning towards me (perhaps not obvious from the lens position), so then consider that a tag line was impossible to apply from the left because of the obstructing-adjacent trees, the pre-tension was absolutely necessary…..and was also the reason why the log didn’t sit down on the saw upon completing the cut.

The sole reason that it ‘fell into’ into the lowering rope and went the right way really well is because I set it up that way. And there were no crossed wraps….just additional wraps that Andrew forgot to remove after pre-tensioning. The wraps also have a tendancy to bind up together while pre-tensioning, adding to the situation.

I’d expected to see it swing out once and then watch it land on the return…..but his mind was elsewhere, as clearly was mine for being so assuming. But its something he’s done a million times with consummate ease, which is why it seemed worthy of a thread! Thanks

Tree&Surf, the rope routing of the Hobbs makes it real easy to take off the additional wraps with out losing the necessary tension. Its never once been brought to my attention as an issue.

sorry guys if Ive missed anyone elses queries only I have to rush out for the moment.

Phased1 thanks, and I'll pm you later

newguy18

More rigging errors,groundies pay attention.

__________________
Have your say join us today.


old schooler

rbtree

Each device has its own peculiarities...as does the choice of line.

for this delicate and common rigging scenario, we've found that using two guys to work the GRCS is better. One guy to hold the rope tightly, and one to crank. If the self tailer is used, it may require more wraps to be undone, thus taking more time. With skill and maybe a bit of luck, the rope holder can apply enough tension to not have to remove a wrap when the time to let the load go has come. That's tough to do, and rare. Good guys can get that wrap off pretty quickly though.

However, said maneuvers are a bit dicey if the LD is right under the work. It's never a good feeling to be directly under the load when cranking. If possible, locating the LD on another tree can be great....it just requires a couple more blocks for redirecting the line.

Glad the boys are OK, Reg

Did I hear you're being deported?

rbtree

My comments in bold[/B]

rbtree

Years ago, I did geet hurt. We were removing a largish hemlock over a roof. Ziplined brush and logs out and over. When speedlining wood, it's best to butt hitch it onto a slack speedline, stop it, then tension the speedline. But, as you get lower down, the room to work decreases. So, the load must be snubbed and stopped in a short distance, which Ian, one of the best rope men, was doing smoothly. Well, I forgot to be 180 degrees behind the load, and it clipped my ankle. Being as it weighed 300-450 lb, the pain was intense. Luckily, I was able to finish the job, and was no worse for wear the next day.

Also, when zipping after lowering, we always want to stop the load in a relatively short distance, to limit the distance that the load has to be cranked back up onto the speedline (or the speedline tensioned-whichever method is best for the situation.) So, rapid slack removal is key in approximately halving the amount of freedrop before braking is quickly applied, so it is possible to snub off the load with only a bit of line let out...and keep rigging forces to a reasonable multiple....of course the climber will get shaken around somewhat....but, at least, typically, the stem will be quite wolfy by the time said jerky operations are in use....so the movement won't be too scary...just keep yer teeth away from the stem!!!

rbtree

Hey college boy, didn't they teach ya to speel.....or did the Southern Cal sun, surf and blondies waylay yer ambition...


there a play on woids there..

and a quiz (that I dunno the answer) what bimbo played the part?

RC1

Thanks Roger

And just to clarify once more what seems to have been mis-understood: The first log had not been cranked up tight on the Hobbs. It had 2 wraps to allow for gradual decelaration of the load. But as I'd explained in my initial post about notch/hinge cuts inducing slack into the line, it didn't seem unreasonable or particularly challenging to remove the slack by pulling on the line as the log folded and then releasing i.e. normal fall-arrest operations....you can here the ratchet take up the slack but then Andrew fell thereafter and instinctively gripped the rope and so locked up the load....

As well as, there were much bigger logs to deal with later on, so I'd hope to use the opportunity to get him primed up for them.

While one persons reaction to having an object thrown at his head might be to parry it away, another might duck instead. With no time to think, people just react....but you cant always predict in what way!

dannyboysfc

I say you went too easy on that groundie, that mistake was ethier a lack of focus or a lack of experience. Coulda been serious!!!

Tim Craig

I know Reg mentioned the uptake of slack is important in certain situations especially when the stem is getting very low over a roof etc and there is less margin for error, but surely all that is needed is just a manual pull by hand without the use of the cranking device in the Hobbs/GRCS. I can see what Ekka is saying with the catapult effect, it seems as though this would be the case if the device was cranked up way beyond a sensible force.

I assumed all that is trying to be achieved by cranking the device is the removal of excessive stretch and some minor slack created by the whole set up following the rope from the lowering device to the main knot/choked sling of the piece of timber being removed

I've got by 12 years of treework rigging down some very big wood off vertical sections only using a portawrap, where it is almost impossible to remove the slack Reg is discussing unless you incorporate a block and tackle Z-Rig into the system above the Porty.

I have some video footage of the Porty and the elusive slack in this rigging situation Reg is referring to I will try and post soon, its a very interesting watch. Many people dont understand why the slack is created especially when the set up can seem so tight prior to the piece being cut.

I dont think anyone has made a serious attempt to deconstruct this particular rigging operation, although some guys in Germany recently made an attempt using digital locators and computer animation to follow the trajectory of the log as it fell. It was in a recent edition of ISA Arborist News and was pretty incomprehensable.

Maybe we could come up with a serious deconstruction/analyses of this important part of our work with diagrams/footage etc.

This operation in rigging has caused the death of many professional treeworkers when the stem has failed beneath them - maybe more to do with tree inspection prior to the work commencing but knowing how the rigging is working and what forces/actions are involved in this operation should be vital reading/understanding for all practising arborists.

Who really knows for sure what exactly is happening when a large piece of timber is dropped into a block?

I know we have safe working loads and use ropes and gear way beyond our actual needs but I still think its critical we know for sure how to rig vertical sections properly.

treevet

I would have been inclined to butt tie the 2nd log (instead of tip tie) to avoid the scenario that happened. That would have put the piece below your feet. Could have been squashed many times by gm's. Would have created more shock load but been mitigated by letting it run. I think you may have said it had a lean towards you tho but didn't appear to.

rbtree

The perspective that a 105 degree angle of view wide angle helmet cam gives is going to be different than reality. Trust Reg when he said it leaned back. That procedure he used is a common one, and works well, as long as the groundie does his job.

Tim, I'm not sure if you got my point (and Reg's) about rapid slack removal. It is employed only when the load is tipping over.... a quick pull while the rope goes slack reduces the freedrop of the load by a fair bit...the amount would depend on the actual center of mass of the log, how far it would fall normally versus with rapid slack removal. Relatively more percentage of reduction in the shock load would result with a shorter log, I think.

Before this maneuver, which requires finesse and perfect timing, it does work to tension the line which can actually open the kerf and help tip the log over, which also effectively reduces the amount of slack in the system. In order to do that properly and safely also requires finesse, as the groundie has to at the device, cranking, then know when to remove the handle, set the proper number of wraps, and move away from the drop zone, ready to do the dynamic stuff.

treesandsurf

Yep, I could see two persons on the GRCS would make it much smoother. Cranking out slack and then letting the piece fly all in one swift motion is an art!

My ambition is hopelessly distracted these days...

jp

treevet

Watched the vid again and it still appears the piece would have better been butt tied as it easily detached with a push from his left hand and fell off to his left, and would have safely tensioned and gone towards the crotch but even safer hung below his feet. Whenever you go without trusting "best scenario" I am gonna put the piece below my feet or bucket. Dumb end of rope could snag a knot/kink or root besides gm error. Been rigging big stuff for 4 decades. This is being way over analyzed.

Grcs are great probably. I do not have one, but effect can be created other ways. My big worry would be smashing one and suffering the repair or the loss cost. That is swearing? You have a very mellow personality Reg.

RC1

Didn't think I needed to on something so staight forward for a groundsman who is normally so smooth!

Ive no reason to say otherwise treevet.

In fact, all the other logs from that stem had been sent towards the camera but by the time I got to that last one, the rigging point was so close that it offered me hardly any line-angle/direction whatsoever....so I sent it the other way to allow the grounds-man more time and travel to let it down safely! The last thing I expected was to see it come swinging all the way back to where we'd started!

The point behind the video was only encourage people to check and check again that everyone is paying attention, thats all

Again, this was a one-man-operation....Andrew simply pulled on his end of the rope which turned the Barrell and took up the slack as the log folded!

Thanks

treevet

thanks for making the videos you make Reg. Still would like to see a drama with hacks and wankers and good arbs, few wives thrown in, some bar time. Soap opera tree hour starring RC1

newguy18

I'd rather see pomie's gone wild.

__________________
Have your say join us today.


old schooler

treesandsurf

Those two lines from where you quoted me Reg were two different responses. The first line was for Rog's advice to use two people to pre-tension the line when using the GRCS (one to hold the line while one pre-tensions, cranks the slack out).

The second line in that quote was for your buddy on the ground, ain't easy but it is possible!

jp

rbtree

no two ways about it, it is awesome!! I'm into my 4th decade of tree work....and we do have a bit of timber out west here.......been around the block a time or two, done a coupla challenging trees......but now that we have the GRCS, for nearly 5 years now, we got it going on!

Chipper winch, chain saw winch, Hobbs, and GRCS are all in our arsenal.....
And the GRCS is far and away the most versatile and best of the bunch. Pretty hard to even come close to duplicating the tasks it is capable of, at least the ease with which it allows them to be pulled off.

When it comes to tough access trees, storm stuff where no crane access is possible, we can pull off work that most tree companies can only dream about.

Do you know Todd Kremer, out of Chicago? They have 3 GRCS's and used them all on one 84 inch back yard elm, when there was no access for their 40 ton crane.....it and many other jobs he posts about at treebuz show that his company and skills are cutting edge...and then some.

We used the GRCS and Milwaukee right angle drill to "reverse speed line" about 10 turns of brush and wood from a wild area today...part of a 5000 plus board foot fir logging job...6 trees 110-160 feet tall. Stand by for some videos....

treevet

You are obviously a very experienced arborist and takedown man RB, but did you ever notice that when you start thinking that other companies can only dream about doing the work you do and you start throwing out higher and higher numbers, presto,.....you stop getting jobs and you drive by and the tree has disappeared.

Looking forward to seeing the vids.

RC1

Don't hold your breath Treevet

Hey Rog, you guys worked out which button to press yet?

treevet

You movin to Canada RC?

Tim Craig

Tree Consult

RC1

We now have a foot in the door but it has taken a long time!