Thread: Another injury from an incorrectly used snatch strap

Chain being made of steel is more elastic than any rope or snatch strap. That means that the energy released will be more instantaneous end therefore a more violent reaction. Add to that the extra weight and hardness of steel and you end up with a far more cataclysmic event. That means more damage.
Then there is the sheer inconvenience of carrying the stuff around.

Cheers Billy

for me, if its more than a light to medium tug on a strap, than it's winch time. People, I think, are too quick to rely on a huge yank with a snatch to solve everything. A winch is slower, less stressful on all, and more predictable.

The use of a "flimsy" bag over any strap in a hope to stop it flying is rubbish, over rated and marketed. The use of a bag is fine, but they need to be weighted, and weighted a fair bit. Then be positioned 1/3 in from both vehicles, not at the half way. Of course with a winch being used than the bag is only required on the on the car being winched.

There is enough information out there in magazines and on forums about dumb snatching practices. Young men are 10ft tall, some get it, some don't. The only bit missing in that story is the they were drunk and stolen car. I don't know if it was like that, but would not surprise me.

Originally Posted by cuppabillytea

Chain being made of steel is more elastic than any rope or snatch strap. That means that the energy released will be more instantaneous end therefore a more violent reaction. Add to that the extra weight and hardness of steel and you end up with a far more cataclysmic event. That means more damage.
Then there is the sheer inconvenience of carrying the stuff around.

Cheers Billy

No. Chain (or anything of steel for that matter) is far less elastic than a snatch strap, in the sense that the amount of elongation before failure is very small, so the energy stored per unit length is insignificant compared to a snatch strap. Most of the energy storage in a recovery situation with chain is potential energy by the weight of the chain being lifted off the ground.

In a light four wheel drive recovery situation the length of chain is short enough that negligible energy is stored elastically, and there are no serious repercussions if something breaks. (Other than the vehicle being recovered rolling back down the hill etc)

But because of the lack of elastic energy storage, chain cannot be used for snatch recovery. It can only be used for a steady pull, similar to what you would use for a winch. If you try a 'snatch' recovery, you can just about guarantee something will break.

John

Sad story indeed, hope the fellow pulls though.

Interesting a number of news reports have mentioned the police have set this up as a crime scene - I wonder what charges they are looking at?

For what it is worth I found this list of things not to do as well. Best learn from the mistakes of others, as no-one has the time to make all the mistakes themselves.

20 things you should never do in a 4WD recovery

Originally Posted by cuppabillytea

Thanks for that XDrive. Would you know the best trainer in the Sydney region?

Cue the plug for Tim and Truski who do the training for the Sydney Land Rover Owners Club

Years ago before snatch straps we had less of this sort of thing.
Wire ropes were the danger if they broke during winching.
Snatch straps are dangerous for the reason the forces involved are uncontrolled and not as easily calculated as normal winching or pulling.
I personally lose track of the amount of times I have seen vehicles sitting on the diffs in a mud hole being snatched.
If winching the forces would be calculated something like weight of vehicle over two and then the dragging diffs would be calculated and then any slope in the pull with a 25 % safety factor and it all adds up to a far bit of pull to get the vehicle out.
But the force is known and catered for.
A snatch strap none of the above is known well and there is a extra force of the snatched vehicles acceleration from stop to its speed though the mud over a short period of time.
What I am saying snatch straps are good for light pulls if someone has loss traction and just needs a little bit of help to get moving again.
A snatch strap used for anything more is trouble .
Snatch straps are harder to estimate there condition when old or wet compared to a chain or wire rope.
How many broken snatch straps have you seen ?
Every broken snatch strap is a lack of understanding of forces and should not happen and not acceptable in the world of true vehicle recovery.
Shackels and recovery points have tremendous sudden strain placed on them with snatch straps which is hard to cater for unless there is a great amount of over build in the recovery point etc.
Snatch straps are over used and over promoted as a means of recovery by major retailers and magazines etc.
They are over used in the wrong applications as they are cheap and light weight to carry in the vehicle.

Originally Posted by JDNSW

No. Chain (or anything of steel for that matter) is far less elastic than a snatch strap, in the sense that the amount of elongation before failure is very small, so the energy stored per unit length is insignificant compared to a snatch strap. Most of the energy storage in a recovery situation with chain is potential energy by the weight of the chain being lifted off the ground.

In a light four wheel drive recovery situation the length of chain is short enough that negligible energy is stored elastically, and there are no serious repercussions if something breaks. (Other than the vehicle being recovered rolling back down the hill etc)

But because of the lack of elastic energy storage, chain cannot be used for snatch recovery. It can only be used for a steady pull, similar to what you would use for a winch. If you try a 'snatch' recovery, you can just about guarantee something will break.

John

Go and got a steel ball baring and a plastic ball. Drop them from the same hight on to steel bench or some other unforgiving surface and see which bounces the highest. Steel is far more elastic than any plastic I've ever heard of. Elasticity being the ability of a material to return to its original shape. Don't kid yourself the length of stretch has anything at all to do with it. For the same energy and mass the energy release is much more sudden and therefore faster. I stand by my original post and beg you to do some research for your own sake.
Cheers Billy.

Elasticity is the ability of a material to return to its original shape after it has been deformed.

If you deform a lump of steel - it will not return to its original shape. Steel is virtually NOT elastic at all.

The fact that a steel ball will bounce higher than a plastic ball in the example given above is simply because the steel is more stiff or rigid and does NOT deform as much, and therefore cannot absorb the energy of the impact. The energy has to go somewhere - so the ball will bounce higher (under the right circumstances, such as the material being "bounced off" being of equal stiffness and also not able to absorb the energy of the impact).

In technical terms - the lower the elasticity of a material, the higher the "Young's Modulus" for that material. A stiff material needs more force to deform compared to a soft material. Therefore, the Young's modulus is a measure of the stiffness of a solid material.

The Young's Modulus for steel is about 200 GPa, for rubber about 0.1 GPa and for materials like polypropylene / nylon etc, about 2 GPa.

Why is chain being mentioned here as an alternative to this type of recovery, you can't use steel chain in a snatch recovery, simple as that.

I really hope he recovers and I especially hope his mates that were there helping, learn from this.

Baz.