Close Call: Rigging Point Failure

[Mick Dempsey]

Ben after doing a bit more reading especially of arrozdoce link I don't think it does I'm just talking bollocks ! Like I said I'm no expert on physics but it looks like it just side loads the stem so on a defective stem that's the last thing you want..

would be nice to have some more opinions?

 

I think you're right (this time) now I think about it:crazy:

[MattyF]

See I was always thought the stem going to the rigging device always needs to be the higher and more substantial one to what I would call the secondary crane point which can be weaker but takes the first bit of load and puts it either away from the groundy or targets , I can't find any thing for forces but on the link it's very clear that it is the stem going to the bollard that needs to be more substantial and takes most of the load looking at the photos ..if you are to have two pulleys in a tree and the one that will take the more force.

[daltontrees]

Ben after doing a bit more reading especially of arrozdoce link I don't think it does I'm just talking bollocks ! Like I said I'm no expert on physics but it looks like it just side loads the stem so on a defective stem that's the last thing you want..

would be nice to have some more opinions?

 

I reckon it would have just about been OK if the spar that broke had not been in poor condition. As you look down you can see it was rotten on the side that had to take tension, and when its butt hits the ground the butt end shatters.

 

You were requiring it to act alomost purely in tensional sideways pull with a long lever arm. On the other hand the other spar that you cut was acting almost like a strut, mostly taking just compression down its length.

 

The breakage of the failed spar would have absorbed a bit of energy. When the 'goofd' top hit teh ground head first, it was stopped form carrying on by teh failed spar acting as a counterweight. At this point the remaining good spar was taking the weight of both and absorbing the kinetic energy of both. It might have taken the whole top without the second pulley attachment. The only good the failed spar did was the amoutn of energy its breakage would have absorbed.

 

You were right not to climb. A bigger lift would have been the answer, but that's in a perfect world. Lucky in the end, but I suspect subconsciously you had taken precautions by being on the right side. If that flying spar had taken out the lift with you in it, you would have had a short journey to your funeral.

[Stephen Blair]

I took a deep breath before the camera showed the top of the tree.

Just too big, simples.

Glad everyone was ok

[toxicity2182]

I'm not saying I never make mistakes but that oak section on mattyf's video was a schoolboy error. It was always going to fail.

[Thesnarlingbadger]

Thanks for sharing the video, if not for anything else it should make people think twice about what they are rigging.

Your right in saying if you had climbed you wouldn't have taken such a risk but there may have been other risks involve in doing that. It's better a headstone was knocked than yourself at risk. Once again cheers for the share. :-)

 

 

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[MattyF]

yeah no doubt about it !as the ground crew where out the way and it broke out over the dz as I hoped if it did .. still surprised me it lasted as long as it did ! That's being under pressure though , this was the second tree of the day.. I was told the first only needed a branch off to get it to commit with the winch ..more like a good third ! Not a day I will forget any way

[Riggerbear]

I took a deep breath before the camera showed the top of the tree.

Just too big, simples.

Glad everyone was ok

 

 

Same thoughts here

[TIMON]

Can't get the videos to play, the app keeps crashing and won't send the crash reports.... grrr.

Looking at this video brought it home to me how much stick we give our rigging kit as most of the time the tree is the strongest link in the system.

When I LOLER people's kit I often wonder "how many times has this gear been taken past its SWL?" I can't tell by checking it...

How many of us know the SWL of our weakest link in our rigging kit? or the different configurations (and stay below it?)

Fair play to you for posting this, it's given me a lot to think about.

Thanks [emoji106]

 

 

Timon.

[Mark Bolam]

Timon, hit the 3 dots top right of the screen then select 'Web View'.

Vid then plays on YouTube.

 

 

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