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Not an expert here by a long shot but makes good sense. If the chain is threaded through the snatch strap and the chain breaks I can assume that the only missile would be the strap as the two halves of chain would still be attached.Quote:
Originally Posted by garrycol
Feel free to debunk this if it is flawed as I too are looking for the best and safest way to snatch.
Dave.
For what it's worth, I've seen in a Land-Rover manual somewhere that the front spring hangers on leaf-sprung models should only be used for recovery in an emergency, and the chassis should be checked for alignment afterwards.
Of course, I can't remember where I read it, but it was from a factory publication.
If you use spring hangers ,you must use both, like I described
Doing a snatch recovery on one hanger or one recovery hook mounted on one side of the chassis can twist the chassis.
A light framed U channelled chassis vehicle like a War time jeep will twist the chassis easily if pulled without a bridle.
It is all common sense again and looking at the job in hand , the equiptment advailible and the possible loads required with vehicle design strong and weak points.
Putting on hook on the inside of each front spring hanger. Metal there is very thick and in a box section - will mount up near the chassis - crush tubes will not be required in this position (by the way - there are crush tubes in the front and rear X member fittings but I have not found any in fittings mounted to the chassis - the winch chassis pulley mountings do not have crush tubes).Quote:
Originally Posted by 101 Ron
The individual recovery hooks do not have a suitable rating (4500kg) to be used individually in a heavy snatch - hence the need for a bridle able to handle up to 10t - will never happen but that is what the snatch strap is rated to.
Rated chain would seem to give more options, particularly for the rear.
Garry
Chain should never be used for snatching. Just don't do it.
Those little cast hooks also don't have the geometry needed to resist an angled pull, you're likely to rip the bolts out of the chassis.
Which is my next point. Without crush tubes they're not anchored well enough for recovery and will eventually slog the chassis holes.
Suitable crush tubes are around 30mm solid with a 13mm through hole. This is what's needed to take the clamping force of a grade 8.8 bolt torqued as it should be.
I think you're better fitting recovery eyes and using shackles than using those $20 hooks. The rating on those hooks is not to any standard I know of, I ran a FEA study on one and they're past yield with the stated load.
Compare that to shackles tested to BS3032 which have a minimum breaking load of 6 times their rated capacity.
Why should rated chain (exceeding the strength of the snatch strap) not be used as a bridle when snatching with a snatch strap?Quote:
Originally Posted by Dougal
Garry
Because there are better things to use with safer failure modes. Chain is best used for slow movements with known loads. Snatching isn't either of these.Quote:
Originally Posted by garrycol
Not to mention the idiots who see you using chain and copy your methods using not rated chain.
I think the minute snatch straps were made available there was going to be trouble.
"Hey - how about we use this giant stretchy thing between two multi-ton loads, and attach it to steel things of an unknown strength, and then one of us drives off at speed? What could possibly go wrong?"
They are one of those things that have to be done just right or suddenly the dangers become very bad very quickly.
Apparently they were first invented for bogged tanks, but that's a bit different to everyday domestic use. This is why I prefer winches because they (usually!) involve a nice steady load.
Dougal, can you explain that a bit more? I was going to use a couple of those hooks as well, but since I made my own bullbar I've been toying with the idea of just making recovery points from heavy plate as well.Quote:
The rating on those hooks is not to any standard I know of, I ran a FEA study on one and they're past yield with the stated load.
Here's a nice picture showing the stress in my recovery hook with a 4.5 T load applied to the inside of the hook. It's fixed at both bolt holes.Quote:
Originally Posted by Davo
Basically unless these are made of kryptonite (they're not) they will start to bend and open up long before the load stamped in the side of them.
Basically they're very weak and should be treated as such. Capable of nowhere near the load that's stamped on them.
I have one of these on my vehicle and I'm okay with that. I know the limitations of it and use it appropriately.
The main thing is, that people know what they're dealing with.
https://www.aulro.com/afvb/images/im...009/10/449.jpg
Like all our recovery equipment we have to know how to use these things correctly - dig out vehicle as much as possible - the snatch vehicle move slowly to slowly load up the snatch strap. The purpose of the tow vehicle is NOT to pull the vehicle out but to load up the strap and act as an anchor as the strap pulls the vehicle out. Any pulling my vehicle will be closely supervised to minimise stupidity.Quote:
Originally Posted by Davo
Where do we draw the line - most equipment we use does not specify the standard used - the hooks I have, have a rating of 10,000lb and are the items sold by ARB. I am the first to be critical of ARB but I do not believe that would falsify the rating on these hooks. It would just be nice to know whether that is swl or total max load.Quote:
Originally Posted by Davo
People have responded to this thread that they have found them great if used within their design capabilities - ie use two with a bridle to share the load. One will be strong enough for most snatches but to be safe and to be sure the chassis is not damaged (applies to any recovery point) the installation of one on each chassis rail should be used.
Garry