Joining Snatch Straps, to do or not to do

[the evil twin]

Some good info but a few missed the point of the thread. It is not about how to join the straps but what are the implications of the operation and effect on ratings etc if you do.

Remember some Manuf state you shouldn't join two Snatch Straps at all... sooooo, assuming the eye thru the eye method is used... some questions that immediately leap to mind are;

What effect will the join have on the "rating" assuming the straps are identical IE will the eyes working against the straps lower the breaking strain ?
What effect will the double length have on the energy imparted IE if you use say 2 metres of slack and the same vehicle speed for a single strap and a doubled will the kinetic energy be double, the same or half of that using a single strap ?
What will be the effect of two different rated straps ?

[hekarewe]

I have had to on occassion join straps together for either reach or to INCREASE the stretch ergo increase build up of energy in the strap. with out telling you all how to suck eggs we all know that they work like a rubber band and excelerate the energy created by the towing vehicle. eg 2 straps will stretch twice as far and generate twice as much energy/force.

joining straps of different wieght ratings but same lenth the only risk i would see is the week link syndrom. that strapjoined would only be rated as strong as the weekest strap used eg 9tonne joined to a 6 tonne then over that combined strap would only be rated at 6 tonne.

joining straps of different lenths i would advise agianst unless it was the only option left and be very careful. the shorter strap will reach its maxium stretch befor the longer one and would not have as much energy as the longer strap this could cause a catastrophic failure in the strap and we all know what that could to both by standers and vehicles

REMEMBER NEVER EVER UNDER NO CIRCUMSTANCES EVER JOIN STRAPS TOGETHER USING D SHACKLES!!!!!

hope this helps clear a bit of this of this up for you.

[the evil twin]

Twice as much force?... are you sure?...
The same fixed amount of energy is being imparted by the vehicle so wouldn't each identical strap convert 1/2 the available energy? If the "first strap" converts 100% of the energy, surely then there is no energy left for the second strap?

Different lengths and same rating - the shorter strap reaches its limit before the longer one?... are you sure?...
The manufacturers produce the straps rated to a particular value but in varying lengths so if you had a 9 metre 8,000 Kg and a 12 metre 8,000 KG would they not stretch an equal percentage under the same load and both max out at the same time?. Sure the the 12 metre will stretch further in actual length but why will the shorter one reach its max stretch before the longer one under the same load?

I'm not trying to be a smartrrse also I am not saying I am correct, being the Devils Advocate is a lot of fun actually... I am trying to educate people in the use of recovery gear and "thinking" about the forces involved and the effect on ratings of various components

Here is a direct quote from the 4WD council of Australia safety notes on Snatch Recovery Straps (not winches SNATCH STRAPS) ...
Only connect to correctly rated recovery points on the vehicles, with only
‘Load Rated’ shackles. Load ratings are marked on shackles as WLL (Working Load Limit). Bow
Shackles are suitable for this purpose and should be rated at least 3.25t.

So if indeed the force was double and now potentially 16,000 KG, hows the poor old 3,250 Bow Shackle looking

[snicko]

We are doing Driver Training through the FWDSA and in their reference Manual they show you how to join two snatch straps together but nothing has been mentioned about ratings, lengths etc.

From the (lack of) information supplied I would asume (as you should'nt) that its OK.

Any help????

[molongmick]

As far as I see it, the weakest factor would be the weakest snatch strap. If two a joined together, I feel that the stretch would increase, (strap one plus strap two stretch) before the snatching effect would come into play. I don't know if it would double the pulling force, maybe just double the distance needed to drive before snatching happens. Keeping in mind that the snatching effect will be like putting two rubber bands together, you strech further before it pulls back. Just a thought (If you put two snatch straps in pearalell, then this would probably double the jerking force).

[the evil twin]

Hiya Snicko,

Yeah, its an area that has been overlooked IMHO. I am a Trainer/Assessor with a certain Gov dept over here in W.A. and everyone goes away from the courses knowing 'how' to join the straps but not what the effect of doing so will be. Unfortunatrely I/we cannot instruct anything that is not in the approved manuals or course notes.

Again from the National Council

CONNECTING THE RECOVERY STRAP
Carefully inspect the Recovery Strap to determine that it is in good condition. If the strap is wet, dirty,
cut or chaffed, it will not perform properly. A wet strap may be 20% under strength, a damaged strap
may break. Do not allow the strap to contact hot surfaces or sharp edges.
Roll the strap out between the vehicles, and make sure there are no twists and leave about 2-3 metres
slack between the vehicles. The joining of straps should be avoided wherever possible (Retailers carry
varying lengths of strap). NEVER USE A METAL OBJECT to join straps – if the strap breaks it can
become a missile and cause damage or injury.

In fairness to all I put the bold face type to highlight one of the points not the Council (the upper case wording is theirs tho).

I have my views on what some of the effects may be but I tell students to exhaust every other option before resorting to joining two recovery straps. The upshot becomes this tho... IF they have explored all other options and they HAVE to join them then think long and hard about what effect will that have on other equipment in the procedure.

[AussieRoadHammer]

Ok I've given this some thort...
A Snatch strap is designed to have some stretch so as to allow a progressive load onto the recovery vehicle, this stretch allows the recovery vehicle to gain momentum to "snatch" the stuck vehicle from its entrapment.
By adding more snatch straps to the recovery gear you would be increasing the amount of stretch and therefore the recovery vehicle will have to travel further soaking up this stretch and taking on the dead load of the stuck vehicle which will reduce the effect of the momentum.
To better explain this... if someone was stupid enough to use, say 100 metres of Snatch straps then once the slack was taken up during the Snatch the next say 10 metres of travel would be stretching the straps - slowly loading up the pull on the recovery vehicle. This load will have a slowing effect on that vehicle and if it didn't stall or break traction its snatch effect would be seriously diminished.
IMHO the shorter the snatch strap the better the snatch-ability and only use a winch extender strap if absolutely necessary.
I'm no expert.
Just my 2 cents worth

[molongmick]

Thanks for that, that is what I was trying to say in my waffle, you just put is alot better than me.