Our first real go at a snatch recovery

All this discussion is realy healthy, I've learnt a few other ways to skin the same rabbit. Keep it coming......

Risk assesing and working out what is the best & safest approach to the recovery with the gear you have is what we have allways done.

Just bought a reciever hitch, where would the weak points be in a snatching?

All I can think of is;
The rated shackle fail, not likely
Pull the shackle out of the billet steel, dont know
Shear the reciever pin in the towbar, dont know
Pull the tow bar off, not likely

Also we have used the tree trunk protector ar a bridle to halve the load on recovery points, there is a problem with that?

Once saw a TTP looped through a snatcum but the snatchum only was connected to the recovery point, the other end of the TTP was connected to another recovery point. If the 1st recovery point let go the TTP would stop it flying. They might have been using those tie down points and were adding some insurance, I guess you have to use what you have got.

Macca

The rear hook on the rear bar is obviously not a recovery point but I just found this attachment below.

I thought that the hook is no good because it is not bolted into the chassis properly so why are people manufacturing these?

Or is it just the actual hook itself that is not rated???

http://i9.photobucket.com/albums/a69...onBushHook.jpg

Quote:

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Originally Posted by AB

The rear hook on the rear bar is obviously not a recovery point but I just found this attachment below.

I thought that the hook is no good because it is not bolted into the chassis properly so why are people manufacturing these?

Or is it just the actual hook itself that is not rated???

http://i9.photobucket.com/albums/a69...onBushHook.jpg

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The Nissan GQ factory manual on this site shows the loop above the rear step as for emergency use for towing out of mud etc - have a look for the exact wording. That said, I don't know if snatch straps over 4000kg were in common use in the late eighties????

My MQ had the same bolt pattern in the same spot, but from memory the only metalwork was the bumper - and as the old girl now lives in retirement (!!!) on Fraser Island, I can't go and look.

Quote:

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Originally Posted by macca

All this discussion is realy healthy, I've learnt a few other ways to skin the same rabbit. Keep it coming......

Risk assesing and working out what is the best & safest approach to the recovery with the gear you have is what we have allways done.

Just bought a reciever hitch, where would the weak points be in a snatching?

All I can think of is;
The rated shackle fail, not likely
Pull the shackle out of the billet steel, dont know
Shear the reciever pin in the towbar, dont know
Pull the tow bar off, not likely

Also we have used the tree trunk protector ar a bridle to halve the load on recovery points, there is a problem with that?

Once saw a TTP looped through a snatcum but the snatchum only was connected to the recovery point, the other end of the TTP was connected to another recovery point. If the 1st recovery point let go the TTP would stop it flying. They might have been using those tie down points and were adding some insurance, I guess you have to use what you have got.

Macca

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Hi Macca,

Great post about the TTP thru the Snatch to act as a restraint. Works a treat if you don't have a suitable damper. A short length of rope etc will also do the job

Quote:

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Originally Posted by AB

The rear hook on the rear bar is obviously not a recovery point but I just found this attachment below.

I thought that the hook is no good because it is not bolted into the chassis properly so why are people manufacturing these?

Or is it just the actual hook itself that is not rated???

http://i9.photobucket.com/albums/a69...onBushHook.jpg

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Nissan assign no rating to the factory rear recovery point and many people do not like the idea that the U piece is butt welded to the face plate. The mounting point itself is pretty bl00dy strong IMHO and as the Hook in your pic is rated to 4 tonnes then I see no reason why they are not suitable alternative to the Billet Hitch as the Towbar is is of a similar or lesser rating anyway.

Hi all,

Just as an FYI as we get more deeper into stress and load ratings. Bridles do not 1/2 the load on the recovery points. There is what is known as a "Sling Angle Loading". 90% of the time it is of no concern but is something to keep in the back of your mind if it is necessary to use a very short bridle or you are pulling at an angle.

Ever seen piccy's of dudes on sailing boats tensioning the sail halyards etc. They initially pull directly down on the line to get the most tension. Then they grab the line between the sail and the anchor point and pull at 90 degrees. This is because any tension at 90 degrees on a line between two anchors actually becomes a mechanical advantage. So the snatch or winch attachement point being at 90 degreees (usually) to the bridle attachments actuall allows a mechanical advantage so instead of say 1000 lbs tension now being distributed 500 lbs to each point it will be between 500 and 1,000 as the angle increases.

Rule of thumb... allow for the full stress being applied to the recovery points even with a bridle. This gives you plenty of leeway as the actual load is a trig relationship to the angle of the sling so if the sling was straight then the full 1000 lbs will go to each point, at 45 degrees the load on the points will be 700 Lbs and at 30 degrees the load will be down to 500 ish... as most bridles will give you 45 degrees or better Sling Angle Loading calling the load as 1000 lbs on the Bridle connection point is heaps of leeway but only IF IT IS A STRAIGHT PULL.

So why worry about it anyway... because IF it is not a straight pull then heaps of force is applied to the short side of the sling up to close to 100% (or 1,000 lbs in our example) to the attachment point and remember these are torsional loads not direct IE the sling is pulling to the side

OK , cool just use a long sling that gives you 30 degrees or less Sling Angle eh... well that then introduces another problem. The force only has to be slightly off centre IE teh other vehicle pulling at an angle to now get you back up to 100% of teh force on one point

Here is an excellent diagram to illustrate http://www.slingchoker.com/sling2/crosby/ix/ix249.htm

Hehehehe... anyone had a brain explosion yet?

Its no biggee really, but it shows the reason why so much gear has to be of a higher rating than would appear logical at first thought

Yes I just did thanks for the mess

Quote:

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Originally Posted by AB

I'm in need of some recovery points next week for the new beast so i'm assuming to start fresh and do it right would a tow hitch hook be the way to go for the rear?

What about the front?

What is the best / safest system for the front?

Just an example pic below of what system I'm talking about


http://www.nissanpatrol.com.au/forums/

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Hi

I just went to an A.R.B sale and picked up a BushRanger "Tow hook with keeper" (http://www.bushranger.com.au/tow_hook_with_keeper.php) for the front and "Recovery hitch" (http://www.bushranger.com.au/recovery_hitch.php).

Recently found that trying to insert the snatch strap in to the slot where the tow ball has been removed from was not possible.
I was looking for a tow point that allowed shackle attachment (solid circle/hole type) so i could attach the shackle through the eye of snatch strap. After reading this thread i am rethinking?

I was taught that you applied gentle pressure to snatch strap when recovering a vehicle, or you 'take up the slack' in strap and 'let the strap do the work'. The rocket start to jerk the bogged vehicle introduces extreme conditions to the situation, increases chance of snapping strap. Stored energy in the cable plus slow momentum of towing vehicle assists towed vehicle to drive out. There is a video here of a pommy (no offense) land-rover drive who aggressively snaps winch cable and snatch strap in recovery of bogged Jeep, shackle flies in that video also.

Just two queries
What are peoples opinion (dare I ask) on the shackle point in this "Recovery hitch" setup? (note says only tow to capacity of tow bar)
The rocket approach seems like fun but does the hare bet the tortoise on occasions (ie slow and steady)?

That is what I call a Billet Hitch and is perfect for any towing, winching, anchoring etc. The rating of the Hitch and Shackle is usually well in excess of the Tow Bar rating which is why they say "don't exceed the towing rating".

The Hare method is why Snatchies were invented to be used. I suggest a 1 metre S to start to all my friends but the WA Police Manual which is what I am required to use when training says you start with 2 metres of Strap in the S and both vehicles in low 1st at 5 to 10 KPH for your first attempt.

The object of a Snatch Strap is as a "damped multiplier" to progressively increase the recovery force past that which a single vehicle can exert by harnessing the momentum of the front moving vehicle. You can do the same technique with a rope but one dude gets whiplash and the other dude eats the steering wheel.

Starting with a taught snatch strap doesn't really utilise the principles fully and means you are in two stationary vehicles immediately loaded up so may get mired yourself