Correct winching techniques & load ratings

[Mick G]

1. What are your thoughts on using a drag chain in a winching situation? As far as I can see my ARB drag chain has no rating on it but I have read and heard of drag chains being used to connect hand winches to tree protectors plus to spread load between two recovery points and the hook being attached in the middle of the chain.

2. Also when using a snatch block, surely i need to double the strength of shackles etc as I will be exerting double the load?

Thoughts and experiences appreciated.

[Charlie]

Probably the chain would be this stuff,
www.pwbanchor.com.au/transport.html#features.
Twenty year ago most people used 6 mm chain without problem,nowdays 8mm is pretty standard.I'm guessing it would have a swl of arround 2 ton.
Regards Charlie

[Bush65]

When using a chain etc to spread the load between 2 recovery points, the angle between the legs has a great influence on the loads in the chain and at the recovery points.

When using a snatch block, the load on the shackle attaching the snatch block to a tree protector can be double the load in the winch rope. But it wont necessarily be greater than a single line pull in the same situation, only greater if the winch is stalled out on a single line pull. In other words if it requires 1000 kg to pull the truck out, the load on the anchor is still 1000 kg, whether using a single line or a snatch block.

[Mick G]

When using a chain etc to spread the load between 2 recovery points, the angle between the legs has a great influence on the loads in the chain and at the recovery points.

Is it a safe operating procedure - assuming you are not trying to pull a rig out at an angle against an opposing force like a tree stump for example. Let's assume we have a 360 degree mud bog, will the drag chain & recovery points be up to the job with the extra laod created by the angle?

[bazzle]

In practice " as long as the chain is not damaged" ie, used for dragging logs along the road etc, Yes.

Bazzle

[Major60]

Your drag chain from ARB will be rated. Every 8th link or so will have a rating code on it. Look up the code on the BillaVista Recovery Bible or one of the numerous lifting and hoisting WWW sites.

Double the shackle rating??? Think about the physics of it the weight of the car is't changing.....

[Bush65]

When using a chain etc to spread the load between 2 recovery points, the angle between the legs has a great influence on the loads in the chain and at the recovery points.

Is it a safe operating procedure - assuming you are not trying to pull a rig out at an angle against an opposing force like a tree stump for example. Let's assume we have a 360 degree mud bog, will the drag chain & recovery points be up to the job with the extra laod created by the angle?

Lets say we have 1000 kg load in a winch cable attached to 2 equal length legs of chain from 2 recovery points.

Now if the included angle between the chain legs is 120 deg, the load in each leg is 1000 kg and the side load on each recovery point is 866 kg.

If the included angle is 90 deg, the load in each leg is 707 kg and the side load on each recovery point is 500 kg.

If the included angle is 60 deg, the load in each leg is 577 kg and the side load on each recovery point is 250 kg.

So if the included angle between the legs is small (by using suitably long chain) the load on the recovery points will be less than when attaching to a single recovery point.

[blackhj]

Double the shackle rating??? Think about the physics of it the weight of the car is't changing.....

Years ago when I was in the army reserve doing driver training, they taught us a whole heap of formuleas for this. They covered the weight of the vehicle and how it changed with 1 , 2, 3, or even up to 8 wheels unable to turn. You had to do the calculations before you attempted the recovery, alot more fun to just suck it and see, but interesting none the less. Anyway I have forgotten all of it and lost the notes I had, has anyone else heard of this kind of stuff?

[Major60]

Yes there are calculations for mire etc that allow you to work out how "heavy" the vehicle is based on how stuck it is. However using a block or 2 or 3 etc doesn't change that basic weight so adding a block doesn't mean that you also need to double the ratign of everything else like shackles in the set up.

IF you use 4.7T shackles on heavy vehicles as standard and keep the 3.2T ones for the smaller vehilces then you shoudn't have a shackle problem.

[Bush65]

Yes there are calculations for mire etc that allow you to work out how "heavy" the vehicle is based on how stuck it is. However using a block or 2 or 3 etc doesn't change that basic weight so adding a block doesn't mean that you also need to double the ratign of everything else like shackles in the set up.

IF you use 4.7T shackles on heavy vehicles as standard and keep the 3.2T ones for the smaller vehilces then you shoudn't have a shackle problem.

I use the heavier shackles because they are larger, which is more suitable for the eyes of tree protectors.