What happens if you back off a shackle by 1/2 a turn?
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- Опубліковано 3 жов 2024
- Should you back off a shackle by 1/4 or 1/2 a turn, and if so, what effect does that have on strength? And what's important to focus on?
@FireballTool is where you can find the "Twist" video I referenced.
Error at • What happens if you ba... , the two figures are transposed.
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Notes before you comment:
1 At ua-cam.com/video/9mYzflG28uw/v-deo.html there is an error, transposed the 1/4 and 1/2 turns, sorry.
2 "Hi Robert. I'm a metallurgical engineer and do a lot of work in fastener metallurgy. Those three tensile tests are all within expected scatter for wrought steel parts (both for breaking strength and elongation percentage). If they had run ten samples of each condition, I would predict that the range of the tight, 1/4 turn, and 1/2 turn groups would overlap almost completely. I would also recommend anti-seize grease on the threads. This will prevent binding when removing the pin after use and prevent thread corrosion while not in use." - elektro3000
3 "The quarter turn was taught to sailors in ships anchor gear. There number one concern is corrosion and the ability to slip an anchor. Shipboard shackles are always moused closed so being able to break a shackle free of its pin when it has been siting in salt water for years is more beneficial then a three percent working load loss." @petercaires9276
1 hour ago
4 Sample size - I draw attention to the fact it's only three shackles. That's not as conclusive as 30. However, it's proving a negative; if backing off made a dramatic difference, then it'd show up for sure even in that small sample - consider a shackle with a cut halfway through its pin, you'd wouldn't need a big sample to show that's weak. Not trying to prove that for example "all shackles break above X kg in which case if we took only 3 the 4th could be weaker. I've also broken other shackles before, and they all had consistent results, and they are built to standards. This gives me confidence that the sample size could be small and still useful. ua-cam.com/video/AVqYkgaaKAY/v-deo.html Also, these shackles are made to a standard which gives you confidence they will all perform identically. Soft shackles are not, so you need a larger sample size.
5. The pro riggers and doggers disagree:
"I was in the heavy rigging industry for 50 years. We generally back off the pin just a fraction, not a 1/4 or an 1/8th. Fully tightened you’d have to get a wrench to get it loose if you didn’t. I understand you could weaken the capacity by doing so but we never put a shackle anywhere near its maximum. All equipment and rigging has a built in safety capacity. When rigging gives way it was either damaged or overloaded."
"I m so used to snugging the pin to the shackle it is foreign to do it any other way. This coming from heavy rescue in the fire service and also dabbling in heavy recovery with a local towing service including working off of a 50 ton rotator wrecker and pulling and lifting some monstrous loads. Their company policy is that all shackles are seated to the shoulder of the pin. I would indeed love to see the research that has been done to prove that the pins could become unscrewed in certain situations. Perhaps heavy vibration or extreme/ excessive movement of the rigging. Thank you once again Robert, keep it up man!! Cheers from the US"
There are definitely varying views even amongst the professionals!
- Thanks Robert -
Collating all the opinions of the various warriors in the thread is great.
- NB. (Never trying to undermine - clarification is for us all - open and free), the 3 references I posted demonstrated that difference in opinion (likely "use dependent") between 2 Authorities and a manufacturer.
Any real (significant) variation will be in fatigue life, not in single pull or other short term uses.- so significant reliability engineering outcomes will be seen long term, mostly in running or other semi-permanent rigging.
Next - demonstrate that HT bolts only work as intended when under "designed strain" - If there is no strain, the shear strength is little better than many other "non high-alloy steels".
Onwards, always understanding a little more about what we like to do.
Never broken a shackle in thousands of lifting/rigging evolutions. Refineries, chemical plants, offshore rigs, barges, heavy equipment, etc.
I have had several fully tightened shackles that could not be readily detached. It was quicker to re-rig than to fight the frozen shackle.
@@bodabdan Have broken some but they were Chinese and they were outlawed.
Maybe transposed but the conversion factor is 2.2 on two of them and 2.17 on the third one......
Hi Robert. I'm a metallurgical engineer and do a lot of work in fastener metallurgy. Those three tensile tests are all within expected scatter for wrought steel parts (both for breaking strength and elongation percentage). If they had run ten samples of each condition, I would predict that the range of the tight, 1/4 turn, and 1/2 turn groups would overlap almost completely. I would also recommend anti-seize grease on the threads. This will prevent binding when removing the pin after use and prevent thread corrosion while not in use.
Fantastic comment, thank you! Yes should have said these tests are typically 1-3% or so margin of error. Good tip re anti-seize as well. Added that to the pinned comment!
As another mech engineer, fully agree
As a rigger and not an engineer anti-seize will attract dust and dirt into the threads. In my years of experience I have found the risk of corrosion is minimal. Shackles left in a crane chain box exposed to moisture and dirt for months without use and very little corrosion or binding. Also there’s a difference between cranking a shackle tight and just seating it by hand. In most cases you should still be able to loosen by hand as long as you aren’t cranking the shackle tight. Even though in most 4wd recoveries you may not exceed the breaking strength of a 4.5t shackle I do think it is possible that the WLL could be exceeded regularly due to the dynamic shock loading forces that may be applied during some 4wd recovery techniques.
Great comment, The concept that backing it off weakens the link doesn't make any sense at all. I'm open to proof, but this doesn't provide any.
Well if it was engaged by half a thread would be weaker?
The quarter turn was taught to sailors in ships anchor gear. There number one concern is corrosion and the ability to slip an anchor. Shipboard shackles are always moused closed so being able to break a shackle free of its pin when it has been siting in salt water for years is more beneficial then a three percent working load loss.
Thank you didn't know that, very useful!
Moused as in loosely fastened?
No, "moused" is closing the loop parallel to the pin with string or something so when the pin is removed the shackle doesn't fall out. In marine applications that could mean losing the shackle...in 4x4, it's just on the ground and you pick it up so it doesn't matter and we don't bother mouse. This is again where best practice in one industry does not necessarily apply to another.
Mousing is using wire or cordage to prevent the pin from unscrewing there's usually a hole in it for this purpose. @@erictyrrell3560
@@L2SFBC Sailors are taught to use mousing wire, locking wire, and sometimes referring to as sizing wire. This locks the screw pin to the Shackle in a figure eight fashion. This prevents the screw pin from backing out on ground tackle. The ships swivel shot is held together with massive shackle that holds the anchor. All shackles are screwed all the in and the backed off a quarter turn then moused in a figure eight fashion to prevent the pin from backing out. The anchor does not actually hold the ship to the bottom the weight of the chain does that. So as the chain moved around the shackles are getting pounded in every direction. This is why each shackles is locked after it’s quarter turn. The quarter turn allows movement to break rust free so you can remove the screw pin after you cut the mousing wire off. This allows you to slip a fowled anchor. I will try to find it in my old manuals for you.
Professional heavy recovery wrecker operator of 41 years experience here. I completely concur with your assessment. I work daily with equipment and loads fully capable of destroying that screw pin shackle, and I have ruined several over the years. I have never pulled one to complete failure but deformation comes well before failure. I train to normally back off 1/4 turn but for an important reason you didn't cover. When we go to remove the pin after a recovery that was set at 1/4 turn and find we can't loosen it by hand we know the shackle was exposed to plastic deformation. In other words we know the shackle was damaged and needs to be removed from use. We then screw the pin in from the opposite side to mark it as damaged, then back at the barn we destroy it by cutting it apart.
The only exception to the 1/4 turn back rule is a situation where we fear it could become loosened. Such as rigging that will be used over and over to lift items or pallets of cargo onto a trailer. In this case we tighten with a tool and put a zip tie through the hole to insure it can't back out. The zip tie also serves as a visual flag that can be inspected at distance showing the pin hasn't backed out because to do so would bust the zip tie.
Fantastic thank you and a great example of varying the technique according to the use case 👍👍👍
In the case of repeated use a bolt type shackle is better.
24 year crane op here, we do the same, 1/4 turn loose. The testing is kind of pointless, as the shackles are so grossly overloaded, if you've gone that far you've already screwed the pooch! What I got out of this elaborate test, was for a proper shackle used in the right place and time, even 1/2 turn makes no difference.
I’ve done a lot of rigging over the yrs. 1/4 turn is a must and normal with no worry of failure. Having to wrench lose shackle is ridiculous when a slight turn stops this especially if one is flying loads all day or even for 30 minutes. Small or large shackles makes no difference. Never had one fail ever. Knowing how to rig properly will make the difference while keeping you /crew bystanders and your load safe.
I'm not a Crain operator but we do use shackles from time to time and I have told the kids to back it off a little but noooo they use them then ask me to torch them because they can't loosen them and they are afraid they will get burnt if they cut with the torch. I tell them if you cut with a torch it's not you get might hurt if you get burnt it will hurt!
One major component that was left out, is that the screw pin shackles are rated for opposing angle pulls on the bow side of the shackle. In that type of pull you will start to spread the legs of the bow LONG before what was shown in the straight line pulls of this video.
So yes, in all reality it doesn’t really matter in a straight line pull. But if you have opposing pulls on the bow of the shackle, like when a tree saver is connected with a shackle, or a shackle being used as the center point of a bridal, the screw pin should absolutely be shouldered against the bow.
Thanks Casey. What sort of force do you think would it take to damage a shackle in that configuration? And what would be the percentage strength loss in that configuration?
@@L2SFBC it’s not absolute break strength on that pull that is the concern, it’s repeated flexing of the steel. Although not much, allowing the bow to spread open and closed over and over again is the same thing as bending a paper clip back and forth. Eventually that load rating isn’t going to be nearly as strong as what’s listed. I fully agree that those bow shackles are so ridiculously over built for off road recovery that it will never get to breaking strength regardless, but who’s to say that off road recovery is the only thing that shackle is ever going to be used for??
For someone like me it’s not out of the ordinary at all for a piece of gear to be used for off road recovery, then be used with my heavy wrecker on the end of a multi part line pulling a loaded semi truck out of the ditch.
It would also be good to note that those shackles have reference marks on them showing you how far of an angle you can pull on them while still maintaining their rating.
@@L2SFBC and yes, I also fully agree that you don’t have to have everything perfect every single time. Like the twist in the strap, most everything in off road recovery is usually so far under the load rating of the gear being used that you have quite a bit of leeway and forgiveness.
Just like the bend radius of synthetic rope that you listed is what is “required” at peak load. But what most people don’t realize is that peak load on a 3/8” synthetic winch line is up in the mid to high (depending on manufacturer) 20k’s, and since a 12k winch will never be able to put even half of peak load into that line, the requirement for the bend radius is reduced as well.
The farther you are under the limits, the less important all those type of details get.
I think the most important thing to consider in rigging is also the one that is the most overlooked, and that is what you’re hooking too. All the rigging and safe WLL calculations in the world won’t keep you safe if you’re hooked to a bumper or suspension component that can’t hold up to it.
Understood. I'm dealing with recreational 4x4 work here with vehicles usually 4t and under, not competition, not professional recovery. I haven't tested very old shackles, that'd be an interesting one, or shackles that have been used for a LOT of hoisting. I dealt with side loading of shackles in the other video, a common thing taught in Australia is "never side load a shackle" but in fact bow shackles are built for it as you'd know.
The whole purpose of this video is not really about shackles, despite the name. It's to get people thinking about what's truly important in 4x4 recovery, which typically isn't tiny details, it's the bigger picture. I wouldn't want someone stressing about a twist in a strap, a 1/4 or 1/2 turn thinking if they get that right they're safe, when they've not noticed their diff is hung up on a rock, or their fleet angle is way off. That's the conversation I want to have here. Already we've got people coming in from engineering, military, marine...all have inputs and it's interesting to see how their use cases apply, and do not apply. I appreciate your heavy-wrecker experience into the mix too!
Yes, planning to do "forces on a multi-line rig" soon. This is very true "The farther you are under the limits, the less important all those type of details get." For me the most important factor is knowing why you're stuck and then reducing load, not just adding force. The closest I've come to being killed is because I kept winching and snapped a double-line pull in competition. I could feel the winch straining the car not moving. But, comps, right?
I was taught the half turn back off... purely so it makes it easier to undo the shackle. Under load it tends to tighten up so if already snug, it will be tightened beyond what you can undo by hand. Backing off half a turn gives the pin some wriggle room but you can still undo it by hand. This was in the Royal Australian Engineers and the thinking was you have to undo the thing under fire or hanging onto something with one hand and don't want to have to faff about or scrabble for a marlin spike or shifter. Great video as always.
Interesting, I was expecting Army people to come on and tell me it must always be done up with a three-metre lever!
@@L2SFBC As well as recovering vehicles, I've also used shackles when sailing. When we used shackles for sheer legs, flying foxes and lifting cranes I was taught never to have the cable run over the pin as it will either tighten it to the point it will never come undone or completely unscrew and drop the load. Your thoughts?
Well, I don't work in those industries so can't really say. However, I can say that I have actually used a shackle as a pulley (see previous video)...and was able to undo it afterwards, albeit with some effort.
@@fatmanfaffing4116 The rule-of-thumb for riggers has always been that the pin goes up or towards the hook. That’s not always possible, depending on what’s being rigged, so the fall-back is that, the pin goes towards the end with the least potential movement. So if you were using a shackle as a makeshift pulley, the pin would go towards the stationary side of the “pulley”.
i was a Chain and Rigging Certificating Tech for 9 1/2 years (also an ex RNZAC Tankie 12 1/2) the reason the pin tightens when you have backed it off is you a very slightly stretching your shackle, after repeated use the pin will not reach the outside edge when screwed in as it is supposed to under specifications for use because the bow has stretched too much. if you want to be safer and still be able to undo the shackles quick use Safety Bow Shackles which are the type with a bolt pin and nut and swap out the safety split pin for an "R" Clip or a locking retainer clip and you can leave the nut very slightly loose on this type without compromising the shackle as much. P.S. ANZAC's Brothers in Arms Forever.
I had always assumed the advice to back off the pin thread more about being able to get the shackle undone after loading it rather than making it stronger.
It is to get it undone, the question is, how much strength do you lose?
Not enough to lose sleep over @@L2SFBC
@@L2SFBC Like we all saw, they lost nothing.
Not this time, no. But I've gone through a tool room where this has been standard practice, and you can clearly see the older shackles have been permanently deformed. The bow is allowed to flex outward, if only slightly, and may not return fully. Do this a hundred times, and suddenly you no longer have full thread engagement on your pin.@@dubious6718
Sure but then during inspect you notice that and you throw them away.
I’ve been involved in hoisting and rigging for 30+ years, working with iron workers , crane operators, millwrights and I’ve never seen anyone back off a shackle. They were designed and manufactured a certain way for a reason. Seat the shackle bolt all the way.If it is tight , use a wrench or drift to undo it, that is why it is flat and has a hole in it.but agrees that in 4x4 recovery the point is mute.
Yeah they were designed to be backed off.😂
100% this "back it off" thing is a new one for me
I m so used to snugging the pin to the shackle it is foreign to do it any other way. This coming from heavy rescue in the fire service and also dabbling in heavy recovery with a local towing service including working off of a 50 ton rotator wrecker and pulling and lifting some monstrous loads. Their company policy is that all shackles are seated to the shoulder of the pin. I would indeed love to see the research that has been done to prove that the pins could become unscrewed in certain situations. Perhaps heavy vibration or extreme/ excessive movement of the rigging. Thank you once again Robert, keep it up man!! Cheers from the US
Then keep snugging. It's not wrong, and if I was writing the rules for the fire service or whatever I would always go for the least-risk approach just in case as they would have additional rules around fatigue, time etc, and usually plenty of people to work things, often fit people appropriate for fieldwork. But, if it's me talking to recreational 4x4 people who can make their own minds up, and may be working solo, I'll say sure if you need a quick winch when the shackle will be under load for maybe one minute with no vibration, you can back off 1/4 turn.
Yes I was more concerned that it might vibrate loose if not tight.
Th eonly way the pin can come unscrewed is if there is no load on the shackle. Any significant tensile load will lock the pin in place due to the side loading of the threads, resulting in friction that prevents the pin un-screwing. An unloaded shackle can indeed come undone and they should not be used without supplementary locking (ie lock wire etc) in a long term application where they are either substantially unloaded or experience load reversals ie tensile load fallig to zero repetitively. In short term, monitored, applications then clearly it is up to the operator to monitor, check and if necessary retighten as required, for example during a load winching event where the cable load is not continuous
- also in the case there may be a sliding line - a loose pin "could"- unlikely but as demonstrated in climbing "experiments" not zero risk - unwind.. (??mouse the pin with a ziptie - nylon is fine?? - it reduces any risk to closer than zero - of course using sling eyes reduces this risk - endless slings may slide settling into place - of course >3 complete revolutions, exceedingly unlikely in a quick lift and move..)
Yes.
If I'm doing a single pull (stumps, recovery, etc) I'll leave the pin "loose" BUT if I'm doing extended pulling (dragging logs, etc) I safety wire the pin because darned if they don't come loose.
So long as you have a shackle rated appropriately this will not be an issue.
Best response yet!
Dig with a shovel,I thought everyone was allergic! I thought that’s why everyone spends thousands on winches and recovery gear, so they don’t have to buy a shovel? Great information,but I’m pretty sure most people still did not hear you say dig! Thanks from all of us who own a shovel
The moral of the story, never listen to internet "experts" hiding behind their keyboards, claiming you're doing it wrong 😂
When I was in the Navy as a boatswain mate we were required to tighten the shackle tight and add more force with a marlin spike to bury the threads.
In the US, a lot of folks drive around with shackles hanging from the vehicle. In those cases I always recommend turn them till tight or turn them then back off 1/4 turn but put a zip tie through the pin hole and the shackle so the pin can’t work itself loose and fall out.
It's common in Australia too, same thing and we have awful corrguations!
I was a Chain and Rigging Certification Technician for 9 1/2 years and what I got all the time from riggers is they were taught it so it was easier to undo afterwards. I would show them that as soon as you back the pin off slightly the whole pin can rock in the thread left and right and tell them that it is the same as using Eye Bolts and that the flange of the pin shank is supposed to make contact with the mating surface. I would also ask them "when you have backed it off a 1/4 turn is the pin still tight after your lift?" and they will say "yes" and I tell them it is because the shackle has stretched very slightly and every time they back it off it will stretch very slightly each time until the pin does not reach the outside edge of the shank in the threaded hole as required under specs of the shackle for use. I have seen shackles get a lateral force sideways on the pin and spit the pin out partly due to bad rigging of load. it is definitely the repeated cycle though that did the main damage of them stretching it slightly more each time. (and that was with staying withing the lift rating also). our visual inspection on them would start with checking all parts for wear and damage and include seeing the pin when screwed all the way in reaches the outside. other dangerous thing I would find all the time is mismatched pins and bows and some had even fitted imperial pins into metric shackles and vice versa. (the thread being metric or imperial I mean) and they may fit and do up but it leave the pin more prone to being spat out. with the pins on shackles the original reason for having a hole in the pin was riggers could put their marlin spike into it to undo them, a lot would carry one as they used them for aligning parts when craning in. I would train engineering students a few times a year at a local Tech Institute and deliberately break a chain in my mobile testbed to show them how fast stuff moves when it breaks. my testbed could do up to a 30 Metric Ton pull so I could test up to 20mm G80 chain anywhere in the country.
worst thing i would see with recovery winches in industrial use is people trying to use them on a single strait pull instead or using a snatch block and double purchase and overloading the winch because they were being cheap and brought one too small. the cables would be absolutely ruined. i used to do a lot of Certifications for a power company and ended up saying to them ring the local 4WD Club and get them to teach your guys recovery and they will show them the right way and save yourself more money that what it will cost to do some training and the club may even do it for a BBQ and some beers and a donation to the club.
Overloading the equipment is what causes binding plain and simple.
@@Tom-og7fi you can deform a shackle and have it bind without overloading it if not used correctly. have thrown away a shackle that was an hour old when the customer run me to go back and check it and it was bowed out of shape as they had rigged it badly and pin was not done up properly. load was not over the rating of the shackle.
@Weetbix1969 if you say so. I've been in the rigging arena for 30 plus years I've also seen a very small handful of shackles that were somehow damaged but only the threads. If a shackle bows or fails it is either bad to begin with or overloaded.
@@Tom-og7fi to be fair the biggest problem ones were NOT with riggers who most i found always looked after their gear and respected it which is probably why you never saw many bad ones. it was people rigging stuff that "thought" they knew what they were doing that had only basic training for rigging loads on their Gantry operators or Dogman course that were the dangerous people. i have helped with investigations on injuries and also sadly a death caused by shackles that let go so i have seen the worst of it and have thrown so many away that were not up to spec for certifications so think i know what i am talking about. i was also a wire rope and height safety specialist for 15 years on top of doing chain and rigging certifications.
It's pretty wild to see that thick shackle deform like clay!
Thanks for the very informative video! I appreciate you putting this in perspective to help us better understand the things that are important!
I was taught that backing a shackle a quarter turn is to help mitigate the occurrence of the threads being warped under load to the point of binding. that way if you're up on a lift and have to for some reason undo the pin you are less likely to need a tool to do it. In the case that you can't undo it by hand you have bigger problems that need addressing before anything else is even considered. I don't know how true that is but I always followed it because I had never seen anything to the contrary.
The threaded pin is what sheared off and failed, right where the threads begin, all three times
The shackle bent but didn’t break
Yes, there is a big stress riser right there. The pin transitions from plain to threaded, and it goes into the shackle ear. Thus that is the weakest link most of the time. Some manufacturers counterbore the ear so that the plain pin portion extends into the ear. I haven't seen any tests to see if this helps but it doesn't matter. Just need 5:1 safety factor (or whatever they are aiming for).
Great video. I've never actually needed a shifter to loosen a bow shackle and I do them up finger tight.
Great video as always. On rigging courses I have done they always say seat the pin fully, this is normally company policy for liability reasons but also they talk about repeated use of equipment. Having it backed off a bit allows the shackle to expand slightly under a side load, this process repeated over time expands the shackle and weakens it according to to courses I have taken. Now obviously there is a lot of health and saftey regulations in the rigging world but it's nice to see actual test that backs up that it's still safe enough to back off a pin in light 4wd recovery.
Yes this is recreational rigging for a winch on occasion. Not constant hoisting. Different use case.
What exactly is the definition/interpretation of, light 4WD recovery?
Vehicles weighing around 4000kg or less, and occasional, infrequent recoveries where time is not a critical factor. So, not competition, and no pro every-day work either.
Good video, thanks for the info! As I suspected, backing off the shackle makes no practical difference to its strenth for recovery purposes. It would have been cool to see some quantifiable data as to how much of a benefit it is to back it off, ie. How much easier is it to open the shackle after use if you do. Cheers!
Well, for that we need experience...and the reason it's been in 4x4 training manuals since forever is because it is possible, mostly, to undo it after a recovery.
Hello Robert, again outstanding results and justifiable conclusion, especially with in line pulls. Be interesting to see what would happen at side pulls, which is where I think many vehicle recovery scenarios are concerned. Even in side pulls the screw pin bow shackle will probably be the last thing you have to worry about breaking. Well done Sir and thank you for your outstanding education.
Thanks Chris, means a lot coming from you. More tests in the future...
A few seconds thought by anyone with some metalurgical or mech eng experience clearly should indicate that the "snuggness" of the pin in the loop of the shacke is no going to make any appreciable (ie statisically valid!) difference to the UTS because of the failure mechanism caused by where the shackle actually yields!
It's clear that at the point of ultimate failure, ie where the minor diameter part of the pin thread transitions to plastic deformation, necks and hence experiences a run-away failure, the pin is ALREADY very bent as mentioned, ie even a loose pin at this point is not actually loose anymore! In order for the pin to fail in tension, then it MUST be hard up against the shackle loop. In all theses tests, far far before UTS failure the shackle pin will not be removable because deformation of the pin irreversably locks that pin into the shackle loop so it cannot be removed as it can no longer be unscrewed. I suspect that a test with a grossely un-mated pin would actually not be that far behind in terms of UTS, although the failure here would not be overal plastic deformation but localised bending moment stress concentration at the base of the thread leading to crack propogation.
Looking the video and the stress strain curve, id suggest this happens at around 50 to 65% of UTS, ie a long way before the shackle actually fails. In a real recovery situation, if you've bent the pin, the shackle is scrap, well before you were in any risk of breaking it. Obviously, this is done on purpose by the specific design of the shackle to make it safer, ie to indicate to the user they were getting close to a failure before it actually fails.
This means it's basically irrelevant how much you back off the pin after fitting it (within reason obvs 🙂 )
Well, had to show video and a test to prove it. I have bent other shackles when I tried rated vs unrated and as you say, the shackles were deformed well before actually breaking. ua-cam.com/video/AVqYkgaaKAY/v-deo.html
The biggest thing about the measured standards that are on the shackles is, they were done with the 1/4 turn clocked off the bolt in the first place. The greatest thing about these shackles is they were designed to be utilized without wrenches. There is a greater chance of binding if you were clamped in tight. If I'm doing a long distance tow with a shackle, I'd tie the bolt off so that it won't 'go anywhere'.
14:10 this is where a high lift jack is useful - jack it up, fill the hole then tip it over. Anyone running high lift jack hasn't discovered other options unless they need to move the vehicle from one side to another.
As a Machinist I learned using shackles for lifting using chains or straps, you hand fasten the shackle .
If you’re breaking shackles, you’re using an underrated shackle for the operation or grossly improperly rigging.
Steel Iron worker structural fabricator here...
If you don't back off at least the 1/4 turn it will be impossible to undo without tools. That means it will wear out quickly.
The idea of baking it off is to stop it from binding after the lift. so you don't have to get a pin or a wrench to off load.
SWL 4 3/4T
They are meant to pick dead loads not shock loads.
The main reason for backing off a 1/4 turn is when the crane starts picking the load and the chocker or load being picked will actually turn the pin and chinch it super tight.
When the load is landed you need a tool to break the shackle pin loose.
In construction you only use 80% SWL
3% could be metallurgical differences. Tests of this type should be done with equipment from the same batch.
If you're using a shackle that would break due to the pin being backed out any amount you're using the wrong shackle. I thought it was hilarious when you said "you'll be in space or hospital". 😅
I was in the heavy rigging industry for 50 years. We generally back off the pin just a fraction, not a 1/4 or an 1/8th. Fully tightened you’d have to get a wrench to get it loose if you didn’t. I understand you could weaken the capacity by doing so but we never put a shackle anywhere near its maximum. All equipment and rigging has a built in safety capacity. When rigging gives way it was either damaged or overloaded.
Interesting! Many others with similar situations are saying "never back it off"! No wrong answers in my view.
@@L2SFBC just remember that all shackles aren’t screw pin. Some just have the pin and a cotter key through it.
@williamscondra3811 you are describing a clevis, which is not a shackle. A clevis will fail far far sooner than a properly rated shackle.
@@duncanwatson7297 Clevis is just another name for a shackle. They’re all shackles. They all have a capacity and if used properly they will lift what they’re rated for. Like I said, I was in the heavy rigging industry my whole life. I don’t deal in semantics. There are screw pin shackles, pin and cotter key shackles and shackles with a pin that is threaded on the end with a nut and a cotter key. If used as intended one is no safer than another.
Just don’t back them off. They’re designed to seat in. Don’t be lazy just use a tool to release the shackle is required after loading. 😎👊👍🇦🇺
To get a riggers ticket in Australia you have to know that when you do up a shackle you always back it off bit, no matter how big the shackle or load, or you don’t get the ticket.
5:29 Nit picking here but someone can't use a calculator...... It's quite surprising that the bow remained intact in all 3 cases, even though the two eyes are thinner than the main body. Also surprising is the fact that the pin broke in all cases, even though it's the thickest piece and a harder steel. Shows how cutting a thread weakens the pin/bolt at the point where the thread ends. Finally 3% variation in maximum is well within tolerances for such a shackle, I imagine. And yes, I am 100% comfortable using them in recovery with 1/4 turn loose. Nothing worse than having to find a shifter to undo the pin in the middle of a steep slope recovery :)
That's incredible the amount of load it took !!
there's an argument to be made for fully tightening and using a witness mark on the threaded end. in the event the shackle fails in a situation that would be highly unlikely to exceed the working limit, you'd have a better case for a product failure claim.
I prefer to finger tighten and not back off… the issue is more about vibration over long periods which may undo the pin. But, not an issue for a quick recovery. In a long term situation I would normally tie the pin to the bow with a wire.
had the safety guru asking me for shackles to rig up a large bottom of the mine pit warer pump. told him we dont have the correct gear, you need the ones with a split pin through tge shank. Oh no was his reply the crane operater said tge ones you have will di the job. I replied , tge crane operater is not a dogman. If they eent unbeknownsed to me, tge shackle shanks vibrated loose, the $80000 water pump went cnunt up down the decline, the safety guru went out the gate and down the road.
@@darryllspalding9680 - nb. ?edit for clarity - phone typos..
If you are using the correct shackle for the load you will never ever have a problem or issue with backing off a quarter of a turn.
Interesting results. I know they state they performed QC on the shackles, but I wonder what that QC process actually was. Just the position of the shackle in the bin after forging can affect the exact strength of the shackle itself as it cools and that cannot easily be determined with QC. Clearly we are not seeing a large difference in the results, and more samples would not likely change the overall opinion, however it would indicate the average variance in the manufacturing process of the shackle itself. Which could indicate the gap is actually even smaller based on the variance in the shackle itself.
It was also curious to see the shackle that was flipped reverse of the other two tests (the quarter turn test) such that the blue ring was in contact with the pin instead of the yellow ring. From a process standpoint this is an uncontrolled factor in the test and adds a potentially unknown variable. I would also be curious to see what prep was done for the shackles prior to testing.
Largely it seems to come down to the fact it doesn't matter from a strength perspective. Only a compliance standpoint (liability based on if you are, or are not following manufacturer directions as an example) or for other use case specific reasons such as corrosion affecting the ability to undo the shackle.
The good thing about those shackles is that they do have QC standards so you can be sure they will break above a consistent level...and even the 1/2 turn one managed that.
I've noticed heavy recovery operators use a nut on the other side of the shackle.
This proves that it doesn't matter as they all broke after what they are rated for.
I don't back off a half turn, but I don't tighten the pin all the way either. If you put it on tight it won't come off by hand.
Good thought exercise, thanks. Take away? Shackles are way stronger than needed for basic offroad recovery use. Don't let them get overly corroded and don't lose the original pin and you should be good.
Im a tank commander in the canadian army. We always turn back 1/4 turn when doing recoveries. Our shackles are rated for well over what we are usually going to put them through. Being able to remove the shackle is very important! Ive had inexperienced guys hand tighten shackels and after a recovery we had ro wait to get maintenance to cut it off witha torch.
Thanks! What sort of forces are you putting on which size shackles?
@L2SFBC well I'm not a scientist by any means. On full sized tanks we use cables with Ballard hooks. These tanks weigh 70 tons on their own. I believe the cables are rated at 150 tons. When shackles are used (often from the recovery tank leopard ARV) you can expect winches to be used that are rated at 100 000kg. On smaller armored vehicles (LAV) we have 60ton shackles, well over double the vehicle weight. Yes I've broken them and when they go it can be very dangerous! Cables can swing and cut someone in half so safety during recovery is always important.
steady pulls are not where most failures accrue, it is shock loads that cause most failures as there is a multiple of the force being applied.
I never heard of backing off the pin? Just finger tight is good enough.. unless my friend Todd decides to use it as a snatch block and demonstrates the power of his winch while his jeep flips off the side of the mountain.🤦
backing off the shackle a quarter of a turn isn't about failure of the part. as you said, you'll most likely never see that kind of load in 4-wheeling. it's more about being able to turn the shackle pin without having to resort to a crescent wrench to loosen it.
Interesting as usual. In the different situation of travelling with a load ie using shackles with a trailer - I always do them up tight because I am concerned that the vibrations will loosen them esp. if they are already loose.
Yes, I agree there - it'll need to remain done up for a long while, and there is vibration. A typical 4x4 recovery is transient, and has no vibration. I solve the safety chain problem by ensuring my shackles have the pin handle upwards.
Our shackles are under constant load. We screw them all the way in, but not tight. All shackles that will be in place without a load will be moused.
It was taught to Off Roaders so they could remove the pin 📌 by hand after an extraction
If you’re using tools that are so close to their failure point that a 3% difference is important; use a bigger tool.
The simple fact that you are loading up a shackle to it's breaking point in any recovery or lifting scenario would be the real issue not the arguing over whether 2% or 3% difference in strength makes one iota of difference.
Always left my shackles loose for 40yrs, saves so much time .
So much stuff is overtightened by folk who don't understand the laws of physics
Everyone seems to be focused on undoing it by hand. That little hole in the pin is specifically sized (I assume anyway) for a screwdriver. You can tighten it all the way every time. Just grab a screwdriver to loosen it. No compromise in safety, and it’s not inconvenient to do.
Safety applies to the whole job and everything we do. The argument is that making a job more difficult by wrench-tight shackle pins may not be worth it. With vehicle recovery it doesn't matter so much because they don't use a lot of rigging and it is easily accessible. I would say though, recovery rigging is probably more likely to be overloaded, impacted and abused. Lifting loads can easily be a different story. Working with more tools at height means an increase in the potential of dropped objects and fallen workers. This is a big reason why certain trades are more likely to back off shackle pins. The risks change for every job. In all cases though, shackles don't fail because the pin was not cranked tight. If shackle pins are coming loose, you are using the wrong type of shackle.
Right. The application matters. A shackle that will be attached to something and left there, exposed to weather and vibration, or driven down the road, could possibly work its way loose. A simple recovery effort that will only see the shackle in service for a short period of time is a completely different situation. One method has the benefit of not working its way loose, the other has the benefit of easy removal by hand. Either way, a quick insertion of a number two Phillips screwdriver is not that hard. Since neither seems to change the working load, I suppose it’s just personal preference at that point. 🤷🏻♂️
Thank you for understanding!
If you back off from snug, that’s less tools carried through the mud especially if you’re the guy that uses a screwdriver in the hole. Nothing like getting yourself unstuck only to fall onto a screwdriver carrying your gear back to your rig.
You get it! 👍👍👍
I’m a 70’s kid, dad was a forestry instructor, foresters carried a spike and dad instructed to tighten the shackles fully and nip up with the spike, especially if the rigging was going overhead, think forestry winch or yarder etc
Mate, you’re talking about using a shackle well beyond its practical limit. There’s times when you need to back it off, and times when you don’t want to. If I’m doing a single lift, say, a motor onto a pump frame, it’s 500kg and I’m using a 3.2T bow shackle, backing it off a bees-dick won’t make a difference (except to make the job a lot easier and more efficient)… but if I’m towing a piece of heavy equipment through harsh conditions, say, with a bulldozer, then I’m gonna tighten it up and also use a tie-wire… people need to stop trying to prove how smart they are and just get out and do some work.
I'd rather have the full capability of the shackle you never know
so.....backing off 1/4 or 1/2 turn, shackle still performed well beyond rating. seems like if you are worried about backing off 1/2 turn, you need a bigger shackle ???? Good riggers never lift loads so close to WLL......
Agree.
Thanks for that. I'm sick and tired of being told to tighten it or loosen it👍 and while people are watching fireball tools check out the file dragging. Ha ha now the cats amongst the pigeons.
Another great video. It's really helpful that you provide evidence to support the conclusions, but especially good that you encourage us to focus on what matters more, rather than fussing over things that hardly matter at all.
Thanks!
Thanks for the Super Thanks!
Love your work Robert ! Thanks. I'll always 1/4 turn back off
Hi Rob I commented a while ago but this time we agree, am liking ur line of thinking which I utilise every day at work......if it ain't gonna come into play doesn't matter if ya back it off or not
..
Nor if the slings have a twist .... as long as the person rigging load or setting up the recovery gear has a mech mind and knows of potential failures in his set up. He and rerig if red flags pop up during recovery.
Love the channel keep up the quality sharing of knowledge! Chur
ive worked as an electrician for industry, in plants.
building the plants themselves.
every time we lift something with a crane, the shackle bolts are just-before-tight, or a quarter turn.
but usually we are using 8 inch shackles, up to 20 inch
A Crosby 7/8 screw pin shackle is load rated at 13,000lbs, both of these tested shackles failed at 5 times that load. tight or lose pin is irrelevant for off road use on vehicles up to 1 ton pickups. Even a 15k winch will only pull that line load on the first drum wrap.
its breaking the pin not the shackle i a person and just their hand cant tighten it enough to make a difference. you could have used all 3 tight and they would still be different most likely the same outcome. i use to move barges and that hole in the shackle was used to tie it where it wouldn't not back out and we would leave it at least 1/2 turn off. because if you got it tight you would have to use a torch to get it off. the same way when i was in the Navy. we always backed them off and used wire to tie it where it wouldn't back off.
Another here for backing off to make removal easier...I always thought this was just what you did.... 🤷🏻♂️
I am an instructor for a steamfitter apprenticeship program and I believe that the issue with the “backed off” shackle pin is the possibility of the pin coming out from vibration. The likelihood is I agree low but it is even lower if the pin is jammed tightly.
Reducing the risk of failure is the chief important issue when engaging in overhead rigging.
Surely though everyone works to a safety factor of at least 2:1 if not more so if you’re planning on loading within 50% of the rated load you’re going to use a higher rated shackle 🤷🏻♂️
In the real world it typically won't matter. Ten guys do it one way, ten the other, and their results will be the same. There can always be exceptions -- but they're exceptional. :) It is true you may need a tool to loosen a shackle that was seated pre-load. Not an issue, unless of course you don't have a tool handy. I tighten. Have an adjustable wrench next to my seat. I leave them on the bumper so have to tighten them anyway vs losing them. Not uncommon for my friends to lose one on the trail...or maybe in a parking lot.
In reality tightening or/1/4 loosening of these Bow or D shackles for just this application is marginal, its only in medium to heavy lift configuration you do not tighten the shank due to the possibility of the shackle bolt over tightening during the lift , most professional operators use a shackle with a pin shank with threaded nut and split pin or wired if it's a permanent lift arrangement It comes downs to if it's a critical lift you use the correct gear and technique.
I'm really curious as to the breaking strength of the 5/8 hitch pin we all use. Both in single shear and double shear.
This was tested and from memory, around 9t and that was a bend not a break, in double-shear.
I tend to prefer rated lifting slings for tree trunk protectors or bridles because you know what they actually rated at. Interesting video.
yes, lifting equipment actually is rated!
@@L2SFBC But people don't understand how the ratings work.
- yes WLL, not MBS (MBS is negligent advertising - ie. totally unsuited to any lifting...) MBS should only be used as a guide, in non life critical applications.
you also forgot "there might be leeches or crocs in the water" for reasons to rush.
well, i always have and always will release a d shackle at least a 1/4 turn when im using one. that break difference is honestly not even worth the ink they use to put it on the recovery instructions. as you said, noone is going to meet that force on a recreational recovery.
The debate on if you back off a shackle half a turn or not in four wheel drive recovery is less so about shackle failure and more about it not becoming a projectile if the pin works loose and comes out. I’ve seen a pin in do itself half way through repetitive snatching.
Great factual info as usual. When you mentioned twisted straps I immediately thought of the Fireball Tool video! For excellent technical recovery videos, I watch "Florida Off Road Recovery". Matt regularly recovers vehicles much larger than his with a winch and multiple snatch blocks - he is a master. He, like you is very factual and knowledgeable. Love your videos.👍
Matt has been on this channel commenting!
@@L2SFBC Like minded people. Facts, experience, and great knowledge. 👍
Just an unrelated but related fact about twisted straps. In the USA semi drivers are allowed to put a twist in their flat straps (keeps them from vibrating and making noise); however in Canada that is not allowed. SuperTruckerDan is a flat bed hauler and did make a YT video about this.
@@funnyfarm5555Fireball Tool did a video about if twisting straps weakens them, check it out, cool results.
From an experienced heavy lift rigger (designing the rigging for very large crane lifts such as bridge beams, HVAC equipment etc) we design the rigging so that the MAX load on any part of the rigging including shackles does not exceed the rated value ( which is much less than deformation or even failure). The reason to back off a shackle pin is not to increase strength, its to prevent the shackle pin from rotating and getting super tight under load to the point it can not be removed by hand. IF you stay withing rated limits of the manufacture, you should not have a failure just because you backed it off a 1/4 turn.
Slinger here.
Its not about letting it be strong to the its rating, because if you need it THAT strong, you're doing it wrong anyway.
It's about being unable to undo it after a lift, and often you can't be in a position to whack it with a hammer to loosing it again.
I have never backed off my shackle and I have never had an issue. However I use shackle that is rated for 4 times my usual pull weight.
I don't think the 3% is statistically significant, and - more importantly - when the breaking strength is 10 times the rated strength... who cares? If you are yanking a 2 ton vehicle with a 1/4" shackle then you get what you deserve, and the 3% wouldn't help you. Use the appropriately rated shackle and you don't have to worry about this stuff. If you don't, then you will suffer. Play stupid games and win stupid prizes. I am trained in rigging (I went to school for that) and I always back off the pin on the shackle (when threaded) because I don't want to have to get tools to undo it after a lift. The guy below who suggests anti-seize has a good point for a shackle used for recovery. Mine are kept indoors and used for rigging, so rust isn't an issue, but if you're keeping it in your trunk then I'm all for that.
Obviously if you are well within your weight limit I’m definitely backing it out a quarter turn. Say your weight is 300lbs and your shackle is rated to 2000lbs, then it’s a no brainer. This test is well over the shackles limit.
- and the Australian Riggers Guides have (at least the version I have access to) the "back off" routine - without noting the potential for siezing/mousing the shackle (edit; it does - I reread the sections to check, my bad)... For trailer securing type of use - a "loose bolt" is liable to vibrate loose after 1000km jostling down the road. The concept of "tool-less" release of threaded fittings is a little idiotic, if easy disassembly is mandatory, use a softie, or safety hook - carabiner is a tool-less "clevis" - spring hook (German origins) other styles exist.
As with HT bolts - the higher the tension the less the potential for fatigue (over a long life)- loads/stress up in the high mid elastic range. A deformed/bent pin results in a useless "temporary securing device." (Carry a small podger/"shackle release spike" in the vehicle in case needed).
So what does it say re back off?
@@L2SFBC/ NSW Workcover - I have a freely available "old version" - 1995 ?? current or not:?? (NB,, I was incorrect in another comment re mousing - they do mention mousing... in the "shackle", as well as the "lifting" /"sheave" sections.)
EDIT:The critical line went missing-repasted, look it up if want to verify... "Rigging Guide".
P70: Do not use a shackle or pin which is bent, strained, deformed or damaged. Tiny microscopic cracks
may have developed during deformation. These can extend under quite small loads and lead to
complete failure.
Screw shackle pins should be tightened then loosened very slightly, so that the shackle pin can be
unscrewed when the weight is released. If the pins are tightened and the strain is taken on the shackle
the pin often jams and is difficult to unscrew.
Where shackles are subject to vibration such as on luffing bridle pendants, mouse the shackle pin to
prevent the pin from unscrewing.
Shackles are designed to take vertical forces only. Diagonal forces will strain the shackle and lead to
eventual failure.
NB: P32 - in sheave block section: The screw pins of ‘D’ or bow shackles should be moused where used on standing rigging, and running
rigging where the pin can become unscrewed, causing a serious accident.
Bullivants guidelines: (p155)
Ensure the pin screws down flush and is bedded
evenly on the surface of the shackle eye. Do not over
tighten and mouse pin for security if vibration may be
an issue.
• For safety pin shackles ensure that the nuts and split
pins are fitted and in good order.
Canadian guidelines.. no mention of backing off:
Shackles
• Available in various types (Figure 49).
• For hoisting, should be manufactured of forged alloy steel.
• Do not replace shackle pins with bolts (Figure 50). Pins are designed and manufactured to
match shackle capacity.
• Check for wear, distortion, and opening up (Figure 51). Check crown regularly for wear. Discard
shackles noticeably worn at the crown.
• Do not use a shackle where it will be pulled or loaded at an angle. This severely reduces its
capacity and opens up the legs (Figure 52).
• Do not use screw pin shackles if the pin can roll under load and unscrew (Figure 53).
Humans are terrible at risk analysis. We tend to ignore the actual highest risks (in this the case, the gear with lower or ambiguous load ratings like soft shackles or wrapping a strap around a sharp edge) and focus on dumb things with extremely unlikely failure modes (like a steel shackle with the pin backed off 1/4 turn).
Exactly. We like to focus on small things which are easy to understand.
Loads far in excess of rated values .
In proper ratings it really isn’t an issue.
If loaded well beyond test strength it is the fault of the rigger.
Finger tight =! Full tight, where is the shackle key? Done all the way is still loose and shy of torqued.
Nah
I use shackles with a two inch pins
I cut that lug of and wed a big nut on and use an inch drive air tool for doing up and undoing. Easy
Many hours of 4x4 recovery and im staying with my 1/4 turn back. Nubs who tighten it all the way and then cant undo it when we have cold wet fingers.
Yep!
1:37.....Oh yeah.....The PIN gave up(sheered)....eventhough it was a bit beefier....
Just shows the threads are the weak point at the area of the end of the thread but also where the shackle is pulling at it at that exact point. Threads are the weak point.
00:20 KITTTY!!!
ive used shackles for decades in trucking and would never back off a shackle. never heard of that in Canada or Australia.
Ha...just had an Australia rigger say that the test involved backing them off! Can't verify that for sure though.
Splitting hairs, eh? One would think that the manufacturing tolerances would be of a possibly larger effect.
Yes, two engineers have made this point, and suggest that if lots of tests were run, there would still be a difference but the scatter would encompass 3%. See pinned post.
I argue that you should not be using any steel shackles in a recovery. Because they are dangerous missiles in a failure. We should be working towards vehicle hard points that are designed to use soft shackles.
I agree with that too, but for the moment, we use them.
Another great and technically informative video. Invaluable information 👌
Here's an interesting fact. I can only speak for Crosby as I do not have tolerance specs for other manufacturers. Crosby publishes acceptable shackle pin shoulder clearance which is acceptable even after the pin is wrench-tight. This is hard for many riggers to accept as they are usually taught the shackle is no good if the pins do not shoulder out. It is sad that Crosby shackle quality is not what it used to be and I see many companies switching over the Van Beest Green Pin shackles. Their castings are much smoother and they do not use raised lettering. The later is important because raised lettering is tough on synthetic slings. Another point is Van Beest and some others counterbore the shackle ear to allow a full diameter pin to engage the ear. Crosby, CM, Campbell, Chicago...they use a fully threaded ear and so you have a good pin stress riser right at the shackle ear (where the pin thread starts).
I've swapped over to buying Green Pin or even Skookum shackles for the projects I do for Bechtel. Green Pins are half the cost of Crosby. Last time I checked, Skookum shackles were cheaper than Crosby alloy shackles. The use of Dyneema or Spectra synthetic rigging has made the use of alloy shackles more necessary so that the shackle isn't the weakest link.
Fantastic information, thank you so much! Interesting point re the raised lettering too.
Well now we can say with confidence that it doesn't much matter and leaving it loose if probably best practice.
Well not quite loose!
@@L2SFBC If I put the lug nuts on my truck on finger tight and backed them off a 1/4 turn how would you describe that situation?
@@michaeldose2041 Don't treat your lug nuts like shackle pins. Bad things will happen.
@@boomupengineering Did you watch the video? Did you look at what the content creator wrote? When you back off your shackle 1/4 turn you could describe it as loose. The CC appeared to take exception to that. So if I backed off my lug nuts a 1/4 turn they would CERTAINLY be described as loose. You comment then is pedantic. I know you're an engineer and I never met one yet who knows as much as he thinks he does. Maybe a diagram would help? Some reading comprehension classes?
Do you want your lug nuts done up to the same torque as say towbar bolts? You'd know what happens if you over-torque lug nuts. So, it's almost like there's different torques for different situations, wouldn't you say?
If you want a "real life" answer , as an American Union Ironworker. We fly big deal steel.... heavy structural with Crosby shackles all day every day. We back it out a 1/4 turn so the conector doesn't have to "un-stuck" the pin. Big bridges and skyscrapers_ we have NEVER had a failure from this
Thank you!!!