doubling up your snatch strap

[Wallyd]

I think it will snap in half if you fold in half. The ends are uber strong, and u are putting all the force on the elasticity part of the strap. The strength is along the material, not across it. Big no no.

[AussieCJ7]

Come on guys think about this more clearly

YOU DO NOT DOUBLE the breaking strain safe working load. Yes each leg will have its own strength and because the configuration each leg will see half of the pulled mass assuming the centre point can slide easily to equalise the load but if the load shifts badly or a failure is seen the one leg will suddenly see the full mass and the relevant breaking strain

This is even more likely because a strap is too wide to slide freely in a shackle and is too wide to use in a snatch block

You also do not change the elastic property as that is a factor of the material but the stretch is over a shorter distance as such it appears to stretch less. It has the same rate of stretch over a shorter distance so the total gain in length is less

[warod]

Tim is correct.
Obviously no riggers here ?


Sent from my talking bone
using white fella magic

[SeaComms]

Originally Posted by AussieCJ7

Come on guys think about this more clearly

YOU DO NOT DOUBLE the breaking strain safe working load. Yes each leg will have its own strength and because the configuration each leg will see half of the pulled mass assuming the centre point can slide easily to equalise the load but if the load shifts badly or a failure is seen the one leg will suddenly see the full mass and the relevant breaking strain

This is even more likely because a strap is too wide to slide freely in a shackle and is too wide to use in a snatch block

You also do not change the elastic property as that is a factor of the material but the stretch is over a shorter distance as such it appears to stretch less. It has the same rate of stretch over a shorter distance so the total gain in length is less

I am not convinced of a few few things (not saying anyone is wrong, in fact I could well be totally wrong but it looks like a good discussion point!).

Firstly one leg cant fail and transfer the load to the other leg, as the centre of the strap is simply folded over a shackle. If one side fails the whole thing lets go.

Spreading the load across two layers like this according to all the rigging sites I could find does in fact double the load capacity. Though with the middle folded over a shackle I would still be unsure of the load on the material right at the shackle.

The elastic property will not change, this is true, but since the load is halved in each layer and the length is halved, then I am guessing the amount it stretches will be roughly a quarter what it would be if used as a single length, making it feel a lot stiffer.

[AussieCJ7]

Seacom. The load transfer come if the towed vehicle slides to one side quickly. The friction on the shackle and width of strap means it won't slide to equalise load

Not saying don't double them over. But don't assume it doubles the safe working load is all I am saying.

There is a number of times I have used a tree trunk protector as a bridle sling to push the load on both recovery points and frame rails. Worst cast a snatch strap can do this but don't do it to double the breaking strain

[axiom]

Ummm to do the physics on this Aussie CJ7 is actually correct. It doesn't double the stregth, but it halves the amount of force on each attachment point on the car (with the two connections).

Apart from being at work at the moment, you should be able to jump on google somewhere and type in force/vector diagrams and come up with a decent explanation of it all.

[SeaComms]

I think we are all thinking of a different setup!

The OP was talking about a strap attached to one attachment point at each vehicle (attached to a single shackle at the first vehicle, then through a shackle on the second vehicle, then back to original shackle on the first vehicle again). So if the towed vehicle slides on the track when being pulled the shackle at the back of the towing vehicle will simply rotate to match the direction of pull and will not change the load on either layer of the strap. Since there is only one attachment point on each vehicle the force on the attachment point is the same as if it were a single strap, but half the load is carried on each layer of the strap.