exploding choker's

[elicokiz]

Has anyone else used choker chains for winching out small diameter stumps? (<7cm dia dbh) having serious doubts about safety???

regards

Dave:thumbup:

[openspaceman]

Has anyone else used choker chains for winching out small diameter stumps? (<7cm dia dbh) having serious doubts about safety???

regards

Dave:thumbup:

 

I would expect the bigger danger to be from any elastic energy built up in what the choker is attached to. The choker will have a proof load which is about half the expected breaking strain. The choker proof load should exceed the winch bare drum pull. Good 7mm choker chain has a breaking strain of ~6tonnes.

 

Yes we frequently winched trees of all sizes over before 360 excavators became common.

[Big Bolt]

all the time cable normally snaps first !!

[elicokiz]

all the time cable normally snaps first !!

 

We had two break explosively luckily the guys were well out of the way of the cable as it rebounded...scary stuff and was realiy surprised they seemed to break so easily?.

[Big Bolt]

are they a good make and proper chain ?

[oldwoodcutter]

When i was a young man i had a steel hawser miss my head by about a foot.Talk about making the hairs on your neck stand on end.

One end was on an oak stump and the other on a cat d7

[Stephen Blair]

I prefer strops for roots and hang a jacket on the cable incase it goes twang

[Mike Hill]

As far as I remember I Chain does not store Energy like a Wire Rope or Strop does.So if a tensioned Chain breaks,it will just fall to the ground.

 

However when a Chain Breaks it can fragment,sending peices of sharp Steel flying.

[elicokiz]

As far as I remember I Chain does not store Energy like a Wire Rope or Strop does.So if a tensioned Chain breaks,it will just fall to the ground.

 

However when a Chain Breaks it can fragment,sending peices of sharp Steel flying.

The chain must have shot a fair distance in the air as it seemed like several seconds before it hit the ground a good 30 ft from the stump.begining to think a keyhole slider may be damaged as there are four on the cable, will check it out on Monday

 

Regards

Dave:thumbup:

[openspaceman]

As far as I remember I Chain does not store Energy like a Wire Rope or Strop does.So if a tensioned Chain breaks,it will just fall to the ground.

 

When you strain a wire rope it deforms by elongating and squeezing its core, this is energy stored and it is not much IMO. It must give this energy up as unwinding and heat in the core. Older wire ropes used in trawlers were apparently more springy and hence caused much damage when they let go. Breaking wire rope whilst skidding is unspectacular but if it lets go when winching a tree it can be spectacular because the energy is stored in the bowing of the stem. It follows that the danger is in the bit that breaks attached to the tree rather than the winch but in my minds eye I don't recall an incident of this.

 

I was never on site when serious accidents happened and there were only two with guys I worked with because their firms hauled timber for us, both with fordsons and cooks or boughton winches which worked directly off the PTO controlled by the foot clutch, essentially no dead man's handle as required now. I think the spades lost anchor in both incidents. In one the driver got off and the tractor winched its way up the beech stem to the attachment and broke, writing off the tractor. In the other I never found the detail, even though we all met up in the pub on a Friday evening it became taboo because the driver was killed when the tractor crushed him. After that I think only the owner of the firm drove that tractor.

 

When you strain a chain it's stored as deformation of the link, as chains have more shock absorbing capability than wire rope it stores more energy, as it gives up this deformation I suspect it all ends up as movement at the broken bit.

 

Nylon strops are the worst because they store lots of energy as they deform and if they are attached to something that can break off they catapult that broken bit with all the energy. This is why using KERR to debog a vehicle can be dangerous.

 

Polyester strops have little shock absorbing and hence break suddenly without releasing much energy. All above my comment and opinion and open to disagreement.