Rear recovery hook

Quote:

---

Originally Posted by AndyRevill

I'm sure I've seen this discussed several times before, probably on other forums and from memory the issue was always that if you could "guarantee" that the strap pulled across the full width of the pin then you wouldn't bend it as you were still utilising the shear strength of the pin. However, if the pull ended up being more concentrated towards the middle of the pin then there is a risk you could bend it. Personally I would have thought for $50 it was worth having a proper hitch receiver/shackle set-up rather than having to deal with all the crap that might get up inside the hitch receiver?

I'm interested in this comment:



Does the orientation really matter? I would have thought that there's more chance of being able to pull in a straight line but height difference is less controlable, so having the shackle pin horizontal might be better? Either way, I suspect nothing is perfect but using a bow shackle would allow the strap eye to move?

cheers, Andy

---

If the shackle pin is horizontal and the pull is off centre then there will be sideways forces pulling the shackle body against the pin. Shackles are designed to take loads in a direct line, pulling sideways against the shackle places undue forces on the pin which can bend the pin or distort the shackle body, which will be evident when you have great difficulty undoing the shackle pin.

Quote:"Does the orientation really matter? I would have thought that there's more chance of being able to pull in a straight line but height difference is less controlable, so having the shackle pin horizontal might be better?"

What height difference are you talking about, are you trying to snatch up a vertical cliff face. The correct alignment of the shackle is crucial if you dont want to break or damage the shackle.

Dougal using a thin plate, as you describe, will concentrate the load over a very small area which at worst will bend the pin and cause it to fail, or gouge a groove in the pin which renders it unsafe.
I Have been a Rigger (Class1 Ticket), Crane driver (3 tickets), a Dogman and a Scaffolder in Mining, Construction and Shipbuilding on and off for over 40 years and I have never broken or seen a broken shackle. EXCEPT in 4WD recovery operations, does that tell you something, SHACKLES are designed and built to lift things, they are not designed to be pulled sideways, jammed in a hole with the pin pulling on a thin plate, they are designed for slings to be placed in the "D" or "BOW" and the pin to go over a crane hook or appropriate lifting lug/eye.
Abuse them and they WILL break, wherever possible have the pin vertical so the pull can centre the shackle, Regards Frank.

Quote:

---

Originally Posted by Tank

Dougal using a thin plate, as you describe, will concentrate the load over a very small area which at worst will bend the pin and cause it to fail, or gouge a groove in the pin which renders it unsafe..

---

I agree that it will give point loading on the pin and wear both the pin and plate, but I consider this a lesser evil than the scenario below.

https://www.aulro.com/afvb/images/im...009/06/787.jpg

Using a rotating shackle mount would get around this problem and be the best solution. But I haven't seen any for sale as recovery items.

So it may be better to redrill the section that goes into the drawbar reciever at 90 degrees so the shackle sits vertical thus allowing for more severe sideway pull and less angle for the horizontal pull.
cheers
blaze

Quote:

---

Originally Posted by Tank

What height difference are you talking about, are you trying to snatch up a vertical cliff face. The correct alignment of the shackle is crucial if you dont want to break or damage the shackle.

---

I wasn't talking about anything specifically and certainly not a cliff face, merely suggesting that it seemed more likely you could control the alignment of the two vehicles horizontally but that was harder to do vertically - say on a beach where someone has tried to get off, gets bogged and someone on hard sand pulls them out, there could be a reasonable height difference - but when does this become significant? or does this only become an issue at greater angles? just interested to know if I should re-drill mine. It seems a lot of these are sold with the shackle pin horizontal?

Andy

I see merit in drilling another hole for when the other location is a better fit.

My receiver pin had significant wear and the holes were elongated from a previous owner towing a horse float, so I have re-drilled the holes to 3/4" and use a quality 3/4" tractor pin. I would imagine that this pin would be plenty strong enough for recovery operations. Opinions?

Hey Dougal - thanks for all the interesting info. Much appreciated, especially your full colour stress pictures.

Back on snatching via a pin, what if you put a good sized sleeve over the pin, so the diameter went up from 16mm to (say) 20mm or something.

All you'd have to carry would be a small 2" length of tube, and then insert it in the strap loop before you put the pin through.

Whould that change most of the forces to shear, instead of trying to bend the pin?

Thanks
David

Quote:

---

Originally Posted by POD

My receiver pin had significant wear and the holes were elongated from a previous owner towing a horse float, so I have re-drilled the holes to 3/4" and use a quality 3/4" tractor pin. I would imagine that this pin would be plenty strong enough for recovery operations. Opinions?

---

19mm is 67% stronger than 16mm (1.67x as strong). If the material is the same.
I still wouldn't snatch from it, but it's certainly better.

Quote:

---

Originally Posted by spudboy

Hey Dougal - thanks for all the interesting info. Much appreciated, especially your full colour stress pictures.

Back on snatching via a pin, what if you put a good sized sleeve over the pin, so the diameter went up from 16mm to (say) 20mm or something.

All you'd have to carry would be a small 2" length of tube, and then insert it in the strap loop before you put the pin through.

Whould that change most of the forces to shear, instead of trying to bend the pin?

Thanks
David

---

Everyone loves pictures.:cool:

Yes, that would do a similar job to the receiver in spreading to load to the pin edges in shear, but will be a lot more fiddly to get in place. I guess the risk of chaffing the strap on the tube corners remains as well as the strap pulling right to one side.

I haven't got time to crunch all the numbers now, but considering it's got a 16mm hole through it, your sleeve would want to be bigger than 30mm, which doesn't leave much room to get a strap around it.

No need to crunch the numbers - I was just wondering, and being a farmer that is how I would solve the issue (unlike most farmer's solutions, no fencing wire involved in this situation!).

30mm + the thickness of the strap would make it a very tight fit :p