Correct use of shackles

Assume the following; you are going to do a snatch recovery, you have no winch, the vehicle to be recovered has only one recovery point which is a closed recovery point with a large oval hole installed by a well known 4WD establishment, and you are going to connect your rated snatch strap to this recovery point with a rated bow shackle and lastly, like most recoveries the pull will not be dead straight but have some small angle.
Do you;
1. Put the bow shackle through the recovery point and then the pin through the snatch strap eye?
2. Put the bow shackle through the eye of the snatch strap and then the pin through the recovery point?

This is another camp fire topic.
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Reply By: CraigB - Tuesday, Mar 12, 2013 at 14:12

Tuesday, Mar 12, 2013 at 14:12
Put the bow shackle through the recovery point and then the pin through the snatch strap eye?
AnswerID: 506640

Follow Up By: Idler Chris - Tuesday, Mar 12, 2013 at 14:16

Tuesday, Mar 12, 2013 at 14:16
Do you have any reasons for this answer?
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Follow Up By: Notso - Tuesday, Mar 12, 2013 at 14:44

Tuesday, Mar 12, 2013 at 14:44
I would say that it would be better for the snatch strap to have a straight surface to bear on rather than be bunched up around the curve of a shackle. That way the load is evenly distributed across the full width of the snatch strap eye.
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Follow Up By: Dust-Devil - Tuesday, Mar 12, 2013 at 14:52

Tuesday, Mar 12, 2013 at 14:52
Spot on Craig B

Your half way there Notso

And it doesn't take a rocket scientist to work out the other half.

DD
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Follow Up By: Sand Man (SA) - Tuesday, Mar 12, 2013 at 18:54

Tuesday, Mar 12, 2013 at 18:54
Consider the method of using the tow hitch receiver to connect the snatch strap.
You remove the pin and tow hitch, then pass the loop end of the snatch strap into the hitch receiver, then secure with the original pin.

In this case, the loop of the snatch strap is bearing against the pin.
Still a safe practice.

Bill


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Follow Up By: Idler Chris - Tuesday, Mar 12, 2013 at 20:22

Tuesday, Mar 12, 2013 at 20:22
Most trucks do not have a tow hitch on the front hence the question. Doing as Sand Man suggest is common but the forces on the pin a different between a snatch strap and a steel hitch receiver. I have seen the pin bend under the force and then become a big problem in getting it out. Don't believe anyone who says the pin will not bend.
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Follow Up By: Ozrover - Wednesday, Mar 13, 2013 at 11:28

Wednesday, Mar 13, 2013 at 11:28
Chris,

If you've bent a "Rated" bow shackle pin of the correct rating i.e. 4.7 tonne then I would be very surprised, I would understand a bent pin it the shackle was unrated or of a rating below that of the snatch forces being used.

We've done quite a few snatch recoveries & have broken many snatch straps, but have never bent a rated bow shackle.

BTW, We put the bow through the loop of the strap & the pin through the eye of the recovery point.

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Follow Up By: Member - Scott M (NSW) - Wednesday, Mar 13, 2013 at 15:00

Wednesday, Mar 13, 2013 at 15:00
I'm with Jeff on this one.....

The rear recovery point for my 40 is a rated snatch block that is slid & pinned into the tow bar mount (the type that replaces the towbar). In this case the shackle pin HAS to go through the block as the the hole is large enough for the PIN only.

The snatch strap goes on the bow of the shackle.... see photo

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Follow Up By: Idler Chris - Wednesday, Mar 13, 2013 at 18:14

Wednesday, Mar 13, 2013 at 18:14
We have a misunderstanding. What the Sand Man was taking about and what I replied to did not have a shackle involved. He was talking about removing the tow hitch, inserting the eye of the snatch strap into the hole in the tow bar where the tow hitch goes, and using the same pin that holds the tow hitch in to go through the eye of the snatch strap. This pin is not rated it is just a piece of shaped steel rod designed to hold a tow hitch. In it normal function it cannot bend as the forces are in two places on either side of the two hitch. To fail it would have to sheer in two places. However if it is holding a snatch strap the force on the pin is in the middle of the pin between the sides of the tow hitch a situation for which it is not designed. This method has one major advantage in that there is no shackle involved so no possibility of a lump of iron flying through the air should the pin fail. A bent or broken pin is a hassle but much safer. It takes a huge force to bend a tow hitch pin let alone break it if you believe that you need these extreme forces to effect the recovery you should not be using a snatch strap but looking at other much safer methods.
Rated bow shackles will, and have broken, but like Jeff I have never seen it because you would have to be an absolute moron to put shackles under that much pressure.
Lastly my understanding is that a rated bow shackle is rated for a straight pull, which is where the two holes where the pin goes are under equal load. In Scott M's photo the other end of the strap could be higher or lower and the forces on the shackle would be equal on each side. However if the other end of the strap was to the side then the force on one side of the shackle will be greater than the other side. And the greater the angle the greater the difference in the forces. As we would normally operate well within the rated capacities, small angles should be of little concern. I have seen rated snatch blocks with two pin holes so that the bow shackle can be horozontal as shown or the receiver turned 90 degrees so that the shackle is vertical, which would then mean it does not matter what the side angle of the pull is the shackle would be evenly loaded albeit a higher load as the angle increased away from a straight line. A thing to remember is that as the angle of the pull increases, and it does not matter if you are snatching or winching, the load on the equipment also increases and I would believe that the load would increase exponentially.
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Follow Up By: Sand Man (SA) - Wednesday, Mar 13, 2013 at 18:44

Wednesday, Mar 13, 2013 at 18:44
Almost correct Chris.

My pin is a hardened, lockable pin and will withstand the force of a snatch.

Actually, I would be surprised if standard pins bent either as we are only looking at something like 50mm between the sides of the square receiver "hole".

Bill


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Reply By: Idler Chris - Tuesday, Mar 12, 2013 at 14:15

Tuesday, Mar 12, 2013 at 14:15
The related article was put there by ExplorOz it does not answer the question.
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AnswerID: 506643

Reply By: Member - Rosco from way back - Tuesday, Mar 12, 2013 at 16:21

Tuesday, Mar 12, 2013 at 16:21
I don't believe it matters either way, as some recovery points are adequate however won't accept more that the bow shackle pin.
Possibly more important is to remember to back off the pin a 1/4 turn after tightening to prevent it jambing.
AnswerID: 506651

Follow Up By: Member - Rick P (NT) - Tuesday, Mar 12, 2013 at 17:52

Tuesday, Mar 12, 2013 at 17:52
And also don't forget the safety factor, have people stand at least 1 1/2 times the length of the snatch strap away from the vehicles and put something like a wet towel over the snatch strap.

Cheers
Rick P
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Reply By: olcoolone - Tuesday, Mar 12, 2013 at 17:58

Tuesday, Mar 12, 2013 at 17:58
It will make no difference as the weakest point on the shackle will be the tread and no matter where the shackle is the load will be the same.

Most people when using a shackle will position it in a way to cause less movement.
AnswerID: 506658

Reply By: Rockape - Tuesday, Mar 12, 2013 at 18:38

Tuesday, Mar 12, 2013 at 18:38
Mate,
if you are doing a lift with flat soft slings that have sewn eyes, one end goes over the hook and the other 95% of the time on to the bow of the shackle unless you are going around the load.

As the Rossco said, most of the time you can't get the bow through the recovery point.
AnswerID: 506663

Reply By: Lachy T - Tuesday, Mar 12, 2013 at 19:53

Tuesday, Mar 12, 2013 at 19:53
If said recovery point is like the one I am thinking off from a well known 4WD establishment then you would place the eye of the snatch strap on the pin of the bow shackle and the arc of the shackle on the recovery point.

This is because if you pull on any angle other than down the centre line of the car (+ or - 10 degrees) you would be placing a side load on the shackle and loading the thread. Where as by having the arc of the shackle against the recovery point this allows the shackle to rotate further from the centre line of the car and therefore only place a side load on the recovery point whilst maintaining a straight line through the strap & shackle.

This assumes that your recovery point is rated for a side load, which I believe a certain 4WD establishments recovery points are.

Lachy
AnswerID: 506667

Follow Up By: Idler Chris - Tuesday, Mar 12, 2013 at 20:16

Tuesday, Mar 12, 2013 at 20:16
Close enough Lachy T wins the teddy bear. When you have a side pull you are loading one side of the shackle where the pin is, potentially halving its strength. The lesson is that recovery points with only a round hole should only be used with nearly straight pulls. And even if you have a recovery point with an oval eye you would still need to know what sort of side force it will take.
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Follow Up By: Lachy T - Tuesday, Mar 12, 2013 at 20:20

Tuesday, Mar 12, 2013 at 20:20
YAY. I always wanted a teddy bear. :-)
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Follow Up By: gbc - Tuesday, Mar 12, 2013 at 21:50

Tuesday, Mar 12, 2013 at 21:50
You forgot the bit where the rule book says to NEVER put a sling on a shackle pin, always on the bight of the shackle. I understand what you are saying and why, but the 'lesson' is flawed in that you probably shouldn't be doing the recovery using that method full stop if you follow the book that wrote the lessons. The answer is also ambiguos in that side loading of bow shackles is fine (think twin leg lifts). What is not fine is pin binding of shackles which is what the general gist is about. If you want to get pedantic, the whole shackle pin should also be packed to sit straight as well, but who the hell does that in the 4wd world. Best way out I can think of is to simply add another shackle to the first one.
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Reply By: Member - Royce - Wednesday, Mar 13, 2013 at 06:19

Wednesday, Mar 13, 2013 at 06:19
This is one for the Myth Busters. All the comments above are logical and may be true, but there are so many variables.

This is a 'last resort' situation. An awful lot of the performance of the shackle will depend on the driving and timing of the tow vehicle, which will in turn effect the forces on the shackle.

The thickness of the recovery point will be crucial in whether the pin bends or not. If it is too thin then maybe the pin should not be through it.
AnswerID: 506681

Follow Up By: Idler Chris - Wednesday, Mar 13, 2013 at 07:55

Wednesday, Mar 13, 2013 at 07:55
There are many variables that is why discussions such as this are valuable as it adds to our knowledge so that when things go pear shape we are better prepared to assess the situation with some modicum of safety. There have been deaths and serious injuries from using snatch straps so I certainly agree with Royce that they should be used as "last resort".
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Follow Up By: Rick and Kerrie - Wednesday, Mar 13, 2013 at 07:59

Wednesday, Mar 13, 2013 at 07:59
Fitted ARB front recovery point to the Troopy yesterday, the instructions that came with the unit said to put the shackle through the recovery point and the pin through the eye of the strap and back the pin off 1/2 turn.
That's good enough for me.

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Follow Up By: Lachy T - Wednesday, Mar 13, 2013 at 12:22

Wednesday, Mar 13, 2013 at 12:22
Which is what you should do, weather or not you "should or shouldn't" put the eye of the sling on the pin, if that is the way the manufacturer has designed and tested the system then that is the way it is designed to be used.

Also, where were you told not to put the eye on the pin? In the case of more than 1 eye, then yes, but when only a single eye is being used on the sling or strap it shouldn't matter.
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Reply By: pop2jocem - Wednesday, Mar 13, 2013 at 11:16

Wednesday, Mar 13, 2013 at 11:16
It would appear from your description that the recovery point was correctly designed by having "a large oval hole", therefor the shackle open ends should allow the body of the shackle to inserted into the recovery point and the pin go through the sling.
AnswerID: 506697

Reply By: Shaver - Wednesday, Mar 13, 2013 at 15:06

Wednesday, Mar 13, 2013 at 15:06
In a former life as a Recovery Mechanic (Army) & before the advent of snatch straps a "Bow Shackle" is used where there is the possibility of a side load in a winching or pulling situation. A Plate Shackle is used to join 2 SWR's. A "D" Shackle is used in a straight line pull. The pin on both "A & B" shackles were attached to the recovered vehicle. For the uninitiated there is more to recovery than attaching a winch rope & hoping the shear pin doesn't sheer. For example degrees of slope, turning resistance, frictional losses, type of terrain & the all important 25% safety factor. The Army had formula's for equipment that was bogged in various types of ground . To winch a vehicle you have to know what the final TPR is or you are heading for trouble & possible loss of life, especially when a SWR starts to sing !
AnswerID: 506705

Follow Up By: Shaver - Wednesday, Mar 13, 2013 at 15:22

Wednesday, Mar 13, 2013 at 15:22
Should read "pin on "B & D" shackle's !
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