Standard recovery points

Submitted: Monday, Oct 20, 2003 at 19:05
ThreadID: 7952 Views:1407 Replies:6 FollowUps:10
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Does anyone actually know whether the standard recovery hook on the front of my Maverick is rated? I haven't had to use it yet ;-) but am naturally interested in its suitability. Also, does anyone have any comments about using the locator pin in the towbar assy for anchoring a snatch-strap when recovering another vehicle?
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Reply By: Brian - Monday, Oct 20, 2003 at 19:19

Monday, Oct 20, 2003 at 19:19
Hi there SupaMav
The recovery hook you refer to... is it a hook or the "eyelet" style tie-downs that hang below the front end? If its the eyelet, then only use these as a very last resort. They are meant to tie the truck down on the ship, not recover with. A rated hook from ARB will cost around $15, and it almost bolts in place on the chassis, although I had to drill a hole for one of the bolts on mine. I also uprated the nuts and bolts to the highest grade high-tensile that I could find.
There has been and will always be much comment about using the locator pin to anchor the snatch strap, I have a friend who has bent the pin and it was a real pain to rectify... not to mention having 9 metres of strap attached to the rear of the truck until he got home...........
better methods...(IMHO)
a) remove the tow ball from the tongue and use a RATED bow shackle to attach the strap
b) Utilise a second tongue and fit a rated hook to it... this is the method I use and it certainly works for me.

Hope this helps.....
Cheers
Brian
AnswerID: 34491

Follow Up By: GaryInOz (Vic) - Monday, Oct 20, 2003 at 21:13

Monday, Oct 20, 2003 at 21:13
I would be hesitant to use a bow shacle with it's bow towards the snatch strap, as the shacles are designed to break at the pin. This would allow thw bow of the shackle to be a projectile under the full load of the snatch strap. I have heard of this happening several years ago, and having the bow go through the tailgate, rear seat (no pax), between the front seats (2 pax), through the dashboard, finally impaling itself in the firewall of a Range Rover. Food for thought.....
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Follow Up By: Rob from Cairns Offroad Training & Tours - Tuesday, Oct 21, 2003 at 08:23

Tuesday, Oct 21, 2003 at 08:23
As my 4wd training includes recovery work and demonstrations I have done literally hundreds of snatch recoveries with my vehicle using the locator pin thru the snatch strap. I personally think this is the safest way. By removing the ball and using a shackle you are still using the pin to locate the tongue. If the pin should then fail you have about 2 kilos of metal fired back at you. Snatching should be done as slowly as possible yet as fast as nesecary. A series of small pulls is safer than trying one huge pull straight off. Thats how things get broken and ppl get hurt.Cairns Offroad Training & Tours
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Follow Up By: Truckster (Vic) - Tuesday, Oct 21, 2003 at 09:26

Tuesday, Oct 21, 2003 at 09:26
Why would you remove the tounge and then use a shackle? Talk about Huston we have a problem!

Just remove the tounge, and put the strap in the hole, and then the pin back in to hold the strap... Works for me.

also the front hook, I have used a few dozen times with no ill effects... I would rather hooks on the front, so the show is on this weekend might grab a pair.
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FollowupID: 24925

Follow Up By: cookie - Tuesday, Oct 21, 2003 at 13:08

Tuesday, Oct 21, 2003 at 13:08
When considering the strength/failure of the locating pin there are 2 separate criteria to consider, the shear strength and the bending strength. When the tongue is in place the pin is almost in pure shear. The pin is designed to withstand a certain shear load. When you place the pin through the snatch strap you introduce a bending load as well because the load is now acting more towards the midspan of the pin, which the pin is not designed for. The pin is most likely well overdesigned so for moderate snatching loads it will be able to cope with this combined bending and shear load. But if you really give it some it is going to probably fail by bending as experienced by brian’s mate. This isn’t so bad cause it most likely won’t be a catastrophic failure and send the pin flying, it will deform before it fails and hopefully you notice this.
With the tongue in place you will have greater strength and this is how the pin has been designed to be loaded. 4WD outlets carry “snatching tongues” for just this purpose.
I think maybe a small pin flying through the air is more dangerous than the whole tongue as the pin will probably pierce metal where as the larger tongue may just cause a big dent. In any case either is very dangerous and any non-essential people should be well clear and out of the vehicle, your talking massive loads and high velocity if something gives way when snatching. Ideally your snatch strap should be the weakest link, not your terminal tackle at each end.

Cookie
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Follow Up By: Truckster (Vic) - Tuesday, Oct 21, 2003 at 21:50

Tuesday, Oct 21, 2003 at 21:50
4wding Association in NSW and Vic train people to use the pin in this way... Both the accreddited courses I did with the clubs showed and in their manuals show the same thing. use the pin which I have numerous times, inc diamond getting excited up Mt Skene the other day.
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Follow Up By: cookie - Wednesday, Oct 22, 2003 at 14:36

Wednesday, Oct 22, 2003 at 14:36
Basic engineering calculations will show that the pin will definitely take more load being loaded with the tongue in place. My calculation show almost 4 times more. This is not to say that putting the pin directly through the strap is unsafe. Peoples experience has shown that generally it works fine. This only means that the loads generated from snatching hasn’t exceeded the breaking strength of the pin. I don’t really know but I am guessing the load generated during a snatch isn’t really close to the breaking strength of the strap, it shouldn’t be. Most straps are rated to around 8 tonnes, the equivalent of hanging 3or 4 4wd’s from your strap in mid air. A recent magazine article gave exact values. Snatching is dynamic and it depends how hard you pull but you may be only generating a couple of tonnes of force. However some quick calcs I did showed that the safe working load putting the pin through the strap was only in the order of a few tonnes. Not much margin for error. With a tongue in you have approximately 4 times this, say ~12 tonnes. Then you need to consider the safe working load of your shackles or hooks. The only way to know accurately would be to connect a load cell to your strap when snatching and measure the forces. I assume strap manufacturers or someone have done the calcs. I don’t know if 4wd associations have done the numbers or just know that is OK from experience. I would love to see some info on this, a very grey area.

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FollowupID: 25064

Reply By: SupaMav - Monday, Oct 20, 2003 at 19:27

Monday, Oct 20, 2003 at 19:27
Howdy, Brian. The hook that I am talking about is literally a hook. It has a funky bit on the end which looks like something designed to actually stop a snatch strap from falling off too easily (the hook faces downwards).
I hear what you are saying about the towbar's anchor pin . . . good advice. I hadn't thought about what would happen if it bent!
AnswerID: 34493

Follow Up By: Truckster (Vic) - Tuesday, Oct 21, 2003 at 10:09

Tuesday, Oct 21, 2003 at 10:09
Ive used that one with large flat plate on the end dozens of times... still use it now, but 2 hooks on the bar and an "A"frame are the best option.
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FollowupID: 24927

Reply By: Brian - Tuesday, Oct 21, 2003 at 16:21

Tuesday, Oct 21, 2003 at 16:21
Whew... I started something here didn't I???... :-) I said there will be much comment!!! :-)
GaryInOz..we only use Rated Shackles... rated higher than we need... if the Range Rover incident is the same one I had heard about, the shackle was not a rated one but a very cheap imitation.Not much consolation after the damage was done I realise... but if rated gear was used maybe....just maybe the accident wouldn't have happened.
Truckster... Houston here in my place doesn't have a problem....honest!! :-)
I don't take the tongue out and then use a shackle... I had been taught to remove the tow ball from the tongue and then use a rated shackle on the tongue... but I found that the best way (for me anyway) was to utilise a spare tongue that has a rated recovery hook attached via highest grade high tensile bolts, with Nyloc nuts. As far as the tiedowns.... those welds could give way in an instant! I fitted the front hook first!
Cookie has got my point about the pin bending in the tow bar, and also points out that when a recovery is in progress, keep all bystanders well away. I was taught one and a half times the snatch strap length is the closest any bystander should be, but I make sure my family and any kids etc and anyone else that will listen are well past that!
Finally... the above is only my opinion....nothing more... nothing less... Anyone can recover any way they like, just make sure it's done safely!!!!!!
Always ask yourself "what can go wrong???"There's plenty that can go wrong!!!
Cheers people
Brian
AnswerID: 34621

Follow Up By: Member - Bradley- Wednesday, Oct 22, 2003 at 11:13

Wednesday, Oct 22, 2003 at 11:13
Brian, i too use the tounge with a shackle fitted through it, this allows for freedom of movement in any direction for the strap / chain etc. No sharp edge for the strap to rub on. The shackles i use are 3500 kg lifting shackles with a 5 rating Ie they begin to fail at 5 times the rated load Ie 17500 kg. Me thinks this is a little better than a mild steel pin !!

As usual most people cut corners ( $ 3 hardware store shackles etc) and wonder why they get hurt or things fail. A friend of mine tried to pull out a tree stump in his back yard with a tie down strap, result - new back window new windscreen and a new pair of jocks thanks.......Life is short- but there's always time for a yarda.
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FollowupID: 25050

Reply By: SupaMav - Tuesday, Oct 21, 2003 at 20:25

Tuesday, Oct 21, 2003 at 20:25
Interesting (and dangerous) topic. Thanks for the comments one and all. My friends and I have been happily using our towbar locator pins thru the snatch strap with no ill effects. I was more worried about the one at the front . . . to be sure I guess I'll just replace it with a rated unit.
AnswerID: 34639

Reply By: Macco - Wednesday, Oct 22, 2003 at 19:47

Wednesday, Oct 22, 2003 at 19:47
Hi all,
Just a thought. Personally I dont like the idea of snatching with the pin of the towbar due the the reasons given above in respect to shear and bending forces however if this is 'the approved' method as per the 4WD trainers, I am thinking that maybe a simple improvement could be considered. Maybe if we were to obtain a piece of heavy wall tubing that was cut to the inside dimension of the towbar slot, was a nice fit over the original pin with an outside diameter to allow the strap still to be installed, that this would 'spread' the load on the pin and reduce the bending load back to shear load as the pin was designed for. Therefore the tube in my situation would be 48mm long/16mm inside diameter by 24mm outside diameter. This is a very small piece of tube that could be thrown in without taking up too much room and can be fitted in no time but will still allow for a safe and less damaging recovery.

any thoughts?
AnswerID: 34749

Follow Up By: Member - Bradley- Thursday, Oct 23, 2003 at 09:04

Thursday, Oct 23, 2003 at 09:04
Yeah, spot on macco, the use of the thick wall pipe will place the majority of the stress and strain forces back into 'shear' loads at the end of the pipe. Haven't done the pages of stress/strain calculations (and don't want to!!) but the tube you have sugessted sounds good. I dont like placing the end of the strap inside the towbar tube because it allows the strap to contact a sharp edge if the load is off centre, This is only my personal feeling (don't want to start a forum war). You will probably need to get that size pipe machined from bar stock. Cheers Brad.Life is short- but there's always time for a yarda.
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Reply By: Brian - Wednesday, Oct 22, 2003 at 21:56

Wednesday, Oct 22, 2003 at 21:56
At several of the mining companies I have worked for, all the tie down points on all vehicles were gas axed off!!! As there have been incident reports from WA where miners had been killed when they let go whilst using them for recovery!!!!
Spend the extra $ and get rated ones fitted!!!!
Brian
AnswerID: 34777

Follow Up By: SupaMav - Thursday, Oct 23, 2003 at 07:44

Thursday, Oct 23, 2003 at 07:44
I wasn't actually talking about the eyelets at the front but the actual standard Nissan hook that is attached to the chassis rail (all Patrols have them including my previous MK). But I do agree that the eyelets are not meant to be recovery points. On that note, I have seen a few pilots with their D-shackles attached to them . . . . hopefully only for storage!
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FollowupID: 25130

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