Big Snatch

[codz]

What would have been cool is to have a dynometer (?) or what ever its called to measure the peak loading. At the workshops I've been to, being able to know the peak load on the riggin system teaches us something, far more than a big snatch breaks a rope, makes you realise the forces involved and the importance of using correctly rated kit-knowing, not guessing the forces is an eye opener for those attending the workshop.

Tbh I'd be a bit disappointed going to a workshop, seeing a demo with an obvious outcome and not being able to learn anything-just how much did the rigging system exceed the mbs? That was a 5ton log, but what force did it peak at when it snatched? How far would you have to let a log like that run/be slowed down before it was safe to stop it before it hit the deck?

 

Again hindsight reveals the "obvious outcome" it would have been great to incorporate a load cell in place of the large shackle and if anyone is willing to loan us one we will repeat the test. As for how far you would need to let it run? More than we did!

[josharb87]

As for how far you would need to let it run? More than we did!

 

[scotspine1]

codz, joe,

 

just out of interest, how is the shackle attached to the timber? can't quite make it out from the vid?

 

Also if you look beneath the side stub on the left, what's happening here?

 

cheers

Edited February 16, 2013 by scotspine1

[Stephen Blair]

I think it was over complicated, double the rope up, timber hitch, have it a nats whisker above the cut, put some grooves in the wood to hold it in place, big open faced gob, and cut more to the hinge,

Wouldn't bother with shackles, just hung over the big nug and wrapped down round the stem a few times .

Tim and I are just nipping out to show you, I will send him the pics I take as I can't upload from my phone

[RC0]

 

To me, that comment crosses the line. Not sure how you thought it would be productive. Everyone's entitled to their opinion I guess, and now this thread has been quite thoroughly derailed, so I reckon I'm going to leave this here.

 

It wasn't meant to be productive Joe. I just read his post, his first one ever and thats what came to mind. At least it was honest. I doubt very much it hurt his feelings or anything....same here, water off a ducks back. Moments come and pass, no big thing.

[codz]

codz, joe,

 

just out of interest, how is the shackle attached to the timber? can't quite make it out from the vid?

 

Also if you look beneath the side stub on the left, what's happening here?

 

cheers

 

The shackle is attached to the log vis an eye to eye sling double wraped, just loke you would if you were setting a cambium saver on a straight stem. This method maintains the integrity of the 2 parts of rope with minimal strangth loss through bend ratios. It also meant the sling did not have to be choked.

The dead end of the rope is wrapped around the stub and then wrapped around the log beneath. We were not confident in the structural integrity of the stub so we did this to back it up in case it failed. It was difficult to set the ropes to avopid rope on rope and also not have the ropes lock up.

[High Scale]

Mental Avatar codz!

Edited February 16, 2013 by High Scale

[codz]

I think it was over complicated, double the rope up, timber hitch, have it a nats whisker above the cut, put some grooves in the wood to hold it in place, big open faced gob, and cut more to the hinge,

Wouldn't bother with shackles, just hung over the big nug and wrapped down round the stem a few times .

Tim and I are just nipping out to show you, I will send him the pics I take as I can't upload from my phone

 

It is a common misconception that the attachment to the piece being lowered needs to be close to the scarf cut. It only needs to be somwhere below the midpoint of the log to prevent it doing a 360. No matter where the log is tied on below the midpoint it will fall the same distance.

The scarf cut also would have no bearing on the out come, we could have step cut it for the same result. The hinge is only effective for about 30 degress, probably much less with dead timber. The hinge was completley redundant prior to any load reaching the rope.

Edited February 16, 2013 by codz

[Stephen Blair]

Hi, thanks for replying.

I have never put the rope far up the stem, i would need to try it to see, not doubting you, I just get it when I do it.

I am not convinced in my head

On the video, it took quite a pull to get it over, I can see that by the stem moving.

I have never worked with big gum so I don't know how it reacts hinge wise, I just feel if it went over slower it wouldn't of built up so much force.

I understand it's not nice having your work criticised, especially by folk who weren't there .

I should of considered this when I made my original comments, I never and unfortunately it has put a sour feel to this thread.

Long story short, you guys tried it and it never worked, what would you do next time with the same rope to give it a better chance of success?

 

 

 

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[codz]

Mental Avatar codz!

 

It was 46 degrees on the first day of that removal!, I might have a bit of footage.