Why Things Fall Off Cranes
ฝัง
- เผยแพร่เมื่อ 6 ก.ย. 2021
- Things can and still go wrong with heavy lifts even when the crane is perfectly safe and sound.
The bundle deal with Curiosity Stream has ended, but you can still get a great discount on Nebula and support Practical Engineering here: go.nebula.tv/practical-engine...
“Rigging” is the term used to describe all the steps we go through to attach a load to a crane so it can be suspended and moved. And, like all human endeavors, rigging is prone to error. Some of the most serious crane failures in history had nothing to do with the crane itself but were actually a result of poor rigging. There’s a lot that can go wrong below the hook, so in this video, we’re going to take a look at a few of the fundamentals in attaching and securing a load and some of the hidden hazards that can pop up if not done properly and carefully.
Practical Engineering is a TH-cam channel about infrastructure and the human-made world around us. It is hosted, written, and produced by Grady Hillhouse. We have new videos posted regularly, so please subscribe for updates. If you enjoyed the video, hit that ‘like’ button, give us a comment, or watch another of our videos!
CONNECT WITH ME
____________________________________
Website: practical.engineering
Twitter: / hillhousegrady
Instagram: / practicalengineering
Reddit: / practicalengineering
Facebook: / practicalengineergrady
Patreon: / practicalengineering
SPONSORSHIP INQUIRIES
____________________________________
Please email my agent at practicalengineering@standard.tv
DISCLAIMER
____________________________________
This is not engineering advice. Everything here is for informational and entertainment purposes only. Contact an engineer licensed to practice in your area if you need professional advice or services. All non-licensed clips are used for fair use commentary, criticism, and educational purposes.
SPECIAL THANKS
____________________________________
This video is sponsored by Nebula.
Stock video and imagery provided by Getty Images, Shutterstock, and Videoblocks.
Tonic and Energy by Elexive is licensed under a Creative Commons Attribution License
Source: • Elexive - Tonic and En...
Producer/Writer/Host: Grady Hillhouse
Assistant Producer: Wesley Crump
Script Editor: Ralph Crewe
🏗 New to the channel? Check out a playlist to see more videos like this one: th-cam.com/users/PracticalEngineeringChannelplaylists
📺 Get a year of CuriosityStream AND Nebula for 26% off, just $15! www.curiositystream.com/practicalengineering
📝Sign up for my newsletter to keep track of everything I'm working on here: practical.engineering/email-list
Yooooo
Man u reminded of a tragedy happened Abt 6 or 7 years ago, the loud of a Cran fell down on a ... Kid
Awsome vid once again.
I work in a place that uses a gantry-crane to lift big bins of product that’s just been sprayed out of a furnace onto a floor, then pushed into the steel bins.
The bin is lifted via a roughly 50mm diameter steel pipe about 3-4 mm thick.
But it HOT! Probably between 200 - 500 degrees centigrade depending on how long the product was left to cool for.
I’ve been interested in trying to figure out how much tension resistance steel would loose due to different rises in temperatures but I haven’t the smarts for it.
The product weighs approximately a tonne.
Where is the link for Crane failures???
How's this published three days before the vid was published!
“A rigger learning the ropes” wasn’t prepared for Practical Dad Jokes
There was no way to avoid that one.
How does Grady not have this as a second channel?
"How do you know when a joke is a 'dad joke'?
When the punchline is apparent.."
Said Ave cleaning a clogged toilet
@ScottfromTexas Sounds like someone needs to watch the German Forklift Safety video! :)
@@nedj10 ... is it German or Dutch? I have seen it and it's a stitch and a half. I also sent it to a guy who does forklift training and he agrees.
Funny how you always introduce things I didn’t know I wanted to learn
I enjoy the thought the the world is so complex that there are endless topics you could dive into, and spend a lifetime on each one.
I absolutely love it
@@DyslexicMitochondria your username made me click on your profile. Your channel is a hidden gem bro
Let's hope he does a video on punctuation someday.
He is wildly entertaining oin this regard, this we do know 💯
Another important thing: making sure everything is tight before applying the full load force. Sometimes straps get hung up or stuck in a crevace of the load, then once it's high up in the air, the strap slips free, potentially gets cut by a sharp edge, the load shifts into a drastically different orientation which makes it topple over another attachment point, and the straps get a big shock, potentially ripping them or overloading other things. Things relax especially when the load swings, oscillates or bumps into something. Classic case: you lift an I-beam with two basket straps, then they slide together, the beam shifts, slips out of balance or the straps get cut.
or just yolo it
If you are picking up an i beam in a basket configuration you are already failing. No more than 10° of tilt on a basket configuration is typically ok.
You also shouldnt use synthetics directly on square edges.
But you are right things can slip which is why positive rigging techniques are very important. Especially if you operator is rough or your signalman sucks
@@kylevanwinkle2081 Tilt? Are you sure you don't mean bend? Tilt refers to the angle of the load.
@@anteshell no i mean tilt. Less than 10° if angle is generalky accepted as having enough friction to hold the load steady this changes load to load especially when you have any sling angle at all. Basket hitch configuration is pretty much vertical pull. You can sometimes increase the friction by wrapping the sling around the load then putting both eyes into the connector as that acts similarly to a double wrapped choke but not as secure. But you can add more sling angle then.
Its alot of situational judgement calls. But a basket hitch done correctly us okay with some degree of tilt.
When manually installing a exchanger bundle it is not uncommon to have the leading edge sling in a basket with 5° if sling angle the rear sling at 60° and the load floating leading edge heavy. As you lower the leading edge sling by chain hoist it transfers the load to the rear sling and the sling angles work towards reversing. This is a really easy way of putting pipe in the rack with a crane as well granted you would usually choke pipe where as choking an exchanger bundle could damage it. And in either cases the leading edge if the loads needs supporting. Either by the exchanger shell for the bundle or a catch chainfall. Field experience makes this childs play
baskets always scare me
Enjoy your channel. I spent over 20 years working on cranes and rigging signs to be hoisted. I have also worked with construction helicopters who lifted heavy loads to the top of an 800’ building. I loved the challenge my job presented and I was blessed to never have an accident or lose one of my guys.
Maybe you could do a show on construction helicopters.
Thanks for the knowledge.
Sounds super interesting! Hopefully Grady makes a video on it!
That's a team that keeps to the rules
That would be fascinating!
One of the risks that are not stated in the video is jerk forces - if the slack isn't taken up gradually, then the jerk (mathematically: The rate of change of acceleration with time multiplied by the weight of the load) can be enough to damage the sling - even though it has enough strength for a static pull. With helicopter lifts, it's much harder to control that jerk effect...so I think that's a major consideration here.
I had no idea construction helicopters even existed! That’s so cool
using the spring scale to demonstrate the increased force on a load suspended out of vertical was simply brilliant! I don't know why I haven't seen that done elsewhere, I had to learn it as a more abstract concept.
I''m not a rigger per'se but pioneering merit badge (quite a few years ago haha) was probably my favorite, and rope behaves the same way as straps. fun fact, even the most well executed knot will reduce a rope's strength by 30% and a bad knot can reduce it a lot more.
AFIK in most ropes, to get full strength the smallest bend radius must be at least 4x the ropes diameter.
@@cameronwebster6866 that sounds about right, unfortunately, I don't know of any knot that can do that. Well, unless you count the crown knot at the start of a splice haha
@@cameronwebster6866
I have a Thimble right in front of me for a 3/8" steel cable, and it's inside bend diameter is: 1". So that's a 2.5x bend diameter
Fishermen know all about knot strength. Start fly fishing and you will be a knot-jedi after your first summer.
@@dscrive That is why you don't use ropes to lift anything so heavy you need a machine to do the lifting.
I love how much you connect the theoretical engineering to the actual work and construction process. Maybe it's just chemical engineering, but as one in training, I often feel like I'm taught that the people doing that manual work are beneath me somehow. Not only is that just plain wrong, but it's essential to listen to the people on the ground because they have familiarity and experience with the tools and equipment that I won't ever develop. All of my equations and models can be made meaningless by a simple defect, and it's up to their expertise to identify and fix it before it becomes a safety hazard. Learning how to listen and communicate with others is a critical, and I would say undervalued, part of engineering training.
It's probably just your teachers/colleagues. In my EE program, we didn't touch on the actual work that often, but when we did it was always "make sure people can actually do what you're asking of them". In my professional life, I've worked with enough technicians to always keep the execution in mind. I've heard too many stories of engineers designing installations or planning repairs that were stupidly dangerous or even impossible to execute as stated, because they didn't take into account how a technician would actually have to do the thing they were asking.
So yeah, keep that in mind when working with the site guys. They'll appreciate it, work will be done as intended, the bosses will be happy (less mad?), and you'll get yourself a better reputation.
You are going to be a great engineer if you keep that mentality 👍🏻 respect
Indeed. Those lowly manual laborers implementing your design often know it MUCH better than you do, especially with the abstraction that CAD tools can impart. Years ago I had a temp job at a custom conveyor manufacturer. It quickly became obvious that the process and mechanical engineers designing the system had never worked in the shop assembling their designs. Pre-punched holes often needed to be welded shut and re-drilled a half-diameter over, chain guards needed to be modified to fit around motor mounts, etc. If they'd have spent even a half-day per month in the shop actually trying to bolt their creations together, they'd have made much better designs.
In chemical engineering, a process mocked up with glassware on a table can't just be scaled up to the size of an oil refinery. The people actually building the industrial-scale apparatus will often have keen insights into possible problems, or process efficiency gains, whether they can name five elements or not.
As a tech I have long thought that any designer should First work a year in maintenance / repair (or possibly at least assembly) before design...
I love you for saying that. I was a foreman for an ironworking company and on every single job I would have to inform my boss on everything that the engineers/architects f*cked up and they were always defiant and told me I was wrong. 99% of the time I was right, but they would always belittle me for pointing out that an H beam junction was wrong in the CAD files, or various other things that looked good on CAD but don't work in the real world. I had a long, very choppy relationship with my direct boss because I would point out impossibilities on the CAD files before I even got on site and he would call me an idiot...and then get mad when I was right. Eventually I left the company after fighting long and hard to get a company-wide standard put in place so that engineers/architects would have to have a mandatory time spent in the field on jobsites before they were allowed to write up prints. I still don't understand why mandatory field-time isn't a requirement for them, it would save so much time, money, and arguments between foreman and designers. To this day I absolutely HATE architects that have never been onsite, they are stuck up, snobby, feminine man-childs that refuse to accept responsibility when they are wrong, especially when "the useless ground guys" tell them they are wrong and their $500,000 degree was a complete waste.
Saw a rigging accident where they were doing a 50 meter lift inside a power plant. The riggers didn't have long enough cables so they WELDED two wire ropes together. Fortunately no one was under the load and there were no injuries.
There were some people fired though.
Damn, that's stupid. A good splice would have worked a lot better, but beyond their skills and comprehension.
Sounds like they royally deserved it!
WOW, welding ...? Took me a second to figure out how they'd even have done that, because I just couldn't replicate the magnitude of stupid required to think of it.
Of all the ways to possibly join cables... welding directly on the cable should never be the one that's chosen. That's insane.
That’s why YOU use UNION IRONWORKERS to do all rigging.
The only incident of rigging failure I've witnessed was when a large change machine from an arcade fell approx.6 meters after one of its feet snapped off, causing the strap to slip. We later found that the failure was caused by shoddy welding. The feet of these machines are designed to bolt them to the floor, they shouldn't have failed and were marked as anchor points by the manufacturer.
I've seen accidents cuz of shoddy welding too. Some instances, you can't even tell cuz it looks solid outside but the insides are botched. And angle the anchors are used also matter.
@@joshanonline In my experience, welding in general is the worst way to connect things, it is the cause of the majority of failures basically in every area it is used (except for very strictly controlled conditions).
@@joshanonline that is why they have to xray and ultrasound welds in the aerospace business.
@@tatianaes3354 Welding can be done poorly and it can be used in places where it shouldn't. However it still one of the best connection methods especially with large loads as a properly done weld can often be stronger than the two materials being connected together.
Bolts, rivets, joints all have there own failure mods and design oversights. I mean just look at how many accidents have happened because improperly tightened bolts did not share the load evenly.
"...marked as anchor points by the manufacturer" - there's a significant difference between an 'anchor point' and a 'lifting point'. I wonder if this was the reason the foot failed when it was used to lift the machine?
I was an ironworker for 32 years, and I love your videos. We use steel chokers on rebar, and slings on epoxy coated rebar, and fiberglass rebar. Slings bother me, because of their tendencies to slip. When unloading a truckload of steel you can't always achieve the optimum picking points, and some operators refuse to wait for you to set the load down and readjust. It's not always the riggers fault.
In the UK , most if not all rebar deliveries come with slings already attached from the factory. So the slinger can just hook the chains and go. I'm assuming you're in the US, but I've noticed that the UK tends to be a bit stricter on matters of health and safety.
Get new operators or refuse to rig...going along with something makes it the riggers fault.
The rigger can always say no
when you say the operator won't wait, do you mean the crane operator?
@@inund8 Yes.
Great info. We had an accident once on a heavy lift (~140T). I wasn't involved directly, but we all had a safety-standdown and training on it. It was a heavy machine casing that was to be lifted about 6 inches to work on footings. Was supposed to be combination of crane (using wire-rope slings) and hydraulic jacks. When hydraulics developed a slow leak and pressure slowly dropped, it was 'decided' to not lower the hook and just let it take up the weight (hook was rated for 150T after all). Unfortunately, the wire ropes were NOT and they failed spectacularly. Dropped the load those 6 inches and even at that short height, damaged footings and led to a lot more work. Fortunately, only one injury, arm laceration from splaying rope.
Good lesson in, 'when things change, don't make up procedures on the fly'.
reminds me of:
a cop spots a guy dragging a chain up the middle of Main St. . . . being a cop, he stops him and asks "why are you dragging that chain up the street?" . . . guy answers "you ever try to push one?"
Pretty good video. Exceeding the 30 degree angle is the biggest issue I see on job sites. The ticketed crane operator is almost always the most knowledgeable rigger on site. People think we just sit in cab and lift stuff but most started out rigging and still have to do quite a bit of it. Bottom line if not sure how to lift something ask crane operator.
This is good advice right here. I’m an ironworker and when I’m rigging something out of the ordinary, I always explain to my operator how I’m rigging it and ask for his opinion. Even if I’m sure that it’s gonna be fine, it never hurts to get another point of view, especially for something that can affect people’s lives.
Makes sense, losing a load is not good for anyone.
Similar to Newly enlisted officers being advised to listen to some of the more experienced men under their command as their accrued knowledge will save you a lot of time. Even though on paper they should do what you say.
Offshore, we keep it to 60 degree from horizontal or larger 80% of the time. 50+ degree if we do have to (e.g. limited hook height), with special approvals.
Absolutely. I've refused picks on multiple occasions because the rigging wasn't done right, until the rigging was corrected. Fortunately our guys know that I don't do something like that for no reason, and have only had any actual pushback on it once or twice.
My father worked at a General Electric locomotive manufacturing plant. The diesel locomotives were shipped overseas from the United States in large cargo vessels. One day a crane operator was unloading a locomotive and the ship started to tilt - and tilt some more - and even more - and the crane operator had to drop the choo-choo train into the ocean to prevent the ship from capsizing.
I guess that was before TH-cam, otherwise you would post a link...
So the crane was attached to the ship and the shifting load from lifting out the train moved the center of gravity out overboard?
I don't think a land-based crane would have the same issue, someone clearly missed that when planning the unloading operation.
@@Kr0noZ There is quite a spectacular video where they tried to unload a river barge with an on-board crane, and the whole lot capsized.
it must have been spectacular... even more with the paperwork...
I have to point out that only steam trains are choo choo trains. Diesel trains are just trains
Rigging is used extensively in the AV production world. Any arena show you go to will have chain hoists supporting the PA and lighting trusses. Where the hoists attach to the structural steel of the building changes with each show, so riggers will walk out on the beams to create the rig points and attach the chains. The stage hands will usually have multiple riggers dedicated to the task.
I was about to comment about how this knowledge is used extensively in AV, but I see there’s someone else in the know!
Exactly, I did the same thing when I built the courses for Ninja Warrior and various Adventure parks. The only difference between the permanent, semi-permanant, and temporary structures I built was sometimes I would use the hoists to attain a certain height and then use steel braided cable with copper crimps. Every time I see those aluminum trusses somewhere I always find myself picking apart it's integrity and shitting on the small-brains that built it, and then I inform someone of how unsafe or out of code it is lol
@@thehodgi1 ... it's not just the AV world. Any major production company will have riggers for "flying" their gear. Decades ago it was just sound and lighting, but now there's lots of video and special effects up there as well.
Have some AV / Lighting friends who fly trusses and do rigging. I don't know about all the structural aspects of it but this helped me understand it more. Certainly a lot of variables to factor in.
Rigging, spreader bars, learning the ropes... those themes are really going somewhere :p
I expect an upcoming video giving an educational look at shibari :D
@@GuzziHeroV50 I mean it actually has a long history involved with the feudal system of Japan and the class structure of warring shogun states.
owo
Look for upcoming content on Nebula
@@GuzziHeroV50 shibari uses ropes exclusively, so spreader bars would be outside its domain. not all bondage is shibari
As a rock climber, this was fun to watch. Shout out for rope access too. Everything has a load rating, all the same stuff matters but the force are often dynamic as well. Can't think of a good engineering example of dynamic loading off the top of my head. I'm sure you could come up with some excuse! A deep dive on multi-point load equalisation for shifting force vectors on anchors would be interesting too! Must be some suspension bridge examples there?
A swinging load will always exceed the force of gravity (depending on the width of the arc). Otherwise cranes are mostly static, compared to safety ropes for climbers.
engineer's favourite dynamic loads are people (not applicable) and... wind!
What about rain? Water is pretty heavy stuff - as anyone who has ever hand mixed concrete will tell you! If the load (including the case, ropes, etc) is absorbent, it's going to get a lot heavier during a lift in rain. Also, when using multiple slings/ropes, I would be a lot happier if I knew that the load safety limit for each rope included the possibility of load transfer if one or more of the other ropes fails - and an allowance for the sudden increase in load as this happens. That huge telescope in South/Central America (can't remember it's name or location!) that failed recently might still be repairable if this principle had been followed.
@@paulhaynes8045 If you are thinking of the Arecibo radio telescope in Puerto Rico (famous from James Bond and "Contact" movies), that was more about corrosion and (lack of) maintenance, I believe.....
You’d think, as a rock climber, you wouldn’t want to think about things falling, no?
As a fresh CE graduate, even finishing COSH, this kind of very specific topics aren't really given point during my study. That's why this kinds of videos are really helpful for a novice like me. Thanks for always giving us these very educational and easy to understand videos.
Just started my 1.5th year (long story...) and I agree! It's really something that I look forward to learning more about.
As a trades person I can confirm that new engineers don’t know anything about rigging.
I'm a mech and it should have come up in your statics class. or if not mentioned directly given you enough info to figure it out.
@@nick4506 yup it did. What I'm specifically saying was, it was never taught what's so special with the sling they use or what are the different methods for rigging. I guess a person need to be specialized in the field for these types of info to matter, is what my uni prolly thought.
@@kuyaforce6103 yea im a mechanical and this stuff came up for me, Its actually core for all of the disciplines at my uni. it seems like something right up civs alley. wired that your uni didn't cover it.
when slings are slanted, they put extra, sideways tension to bolts and load hooks. failure can occur there as well, by forces working lateral and nοt longitudinal. classic failure hazard in rock climbing, when carabiners get loaded sideways.
Agree.. all shackles and hooks normally are de-rated to a certain % when they are loaded sideways, and not at the same plane of the slings
This content has me "hooked"
I'll see myself out
I was upset that he didn't say "pun intended" after 9:52 "learning the ropes" of rigging.
_Giving you enthusiastic applause while insistently showing you the door_
We're not letting you off the hook for this! Sling around him tight!
One thing that affects the load a crane can carry is management caterwauling that the sling or chain is just fine, keep using it, a little cut won't hurt it. This is more common in steel shops that have a bridge crane.
Whenever I found a damaged sling I cut the eye open so nobody else could use it.
@@brianveroba9059 Absolutely, I started doing the same when I came across stuff like that.
Back in the late 80's I was in IE at a major manf. plant. Our bridge crane was huge and when the siren was wailing, I'd move some where it wasn't. I never EVER felt safe under the load. It's like being claustrophobic. I didn't mind heights on a good structure, but I never could trust loaded slings, chains or hooks. Especially if I didn't rig it. I still don't get under stuff unless it has stands or blocking under it.
@@stxrynn I now work for a concrete precasting plant, and it is a no-questions instant termination for anyone who walks under a suspended load. Some of our pieces weigh 60,000 pounds.
Makes me glad for my boss and foreman. One of our chain slings got dropped when taken off the hook and landed on its steel tag hard enough that it broke.
We still had the parts and it was still legible. The foreman insisted the chain be retired until it could be retested.
As an iron worker for over 20 years this is a pretty good beginner video. Biggest three problems I've ever seen with rigging failures are people not checking their rigging regular enough for wear. Using slings in a basket with a spread which allows them to slip and cut. I almost never use a basket or allow it to be used around me. Also using synthetic slings on Sharp edges without softeners.
I like your example of how the angle affects the load. It's amazing how many people in rigging don't understand how much this affects the load. Pulling on shackles at Angles also affects its load rating.
I always think that the best way to explain this is to hold two weights, with your arms hanging vertical. Now raise your arms to the horizontal (or even 45 degrees). You can feel how the weight increases
@@gcunn1 good idea
With the straps also chemicals and ultraviolet . stay strong and carry on . Bless ya'll.
I have designed a fair amount of lifting yokes/spreader bars and there are a lot of things to keep in mind to ensure the safety of the workers.
Hmm, googling 'spreader bar' shows multiple possible meanings...
@@HavokTheorem I can design any spreader bar you want, i don't judge.
@@HavokTheorem equalizer beam
Thanks for “codifying” something I’ve always felt I have an almost “intuitive” feel for. While watching crane segments being added to the huge crane at SpaceX Boca Chica, I thought that getting that crane from horizontal on the ground where the segments were being added, up to the near vertical working position was going to put some incredible strain on the wire ropes. I was curious as to whether they would have used another crane to help start the lift. . .
Great stuff!
PS. . . as a former “small aircraft” pilot, part of the training involved doing “weight and balance” calculations to ensure that the airplane remained controllable under a wide variety of conditions. That training has transferred nicely to loading up a vehicle for long trips. . . even though I’m not the driver. . .
It's kind of cool how we have that intuitive sense about what's going to slip, without always knowing why. I think it's because of childhood play, things like building with LEGO or building forts. Loading up my truck for a long-distance move and then having a bad roll-over accident where nothing in the back of the truck was broken except the bins that held my stuff ... pretty good proof that I knew how to tie stuff in properly.
This was quite fascinating!
As someone who just recently completed a lifting manager course this video is so useful! The key basic principles condensed into a short period of time well done, much better than a 16 hour powerpoint presentation
I once saw a 3/4" diameter steel sling fail in a straight pull configuration. I was an apprentice millwright working with two journeymen to extract 1-1/4" diameter epoxy anchors where the epoxy hadn't set up. We were instructed, under much protest from us, to use the 35 ton bridge crane in the building to pull the anchors. It was like a bomb going off when the sling broke and it shot the crane block about 10ft up. The anchors never did come out.
I used to be a live sound engineer, and I did a *lot* of rigging of loads above stages/audiences.
There's a lot of folk who are convinced that if you put a burlap sack around the beam you may be setting up as a load point, the sling will be protected from the i-beam. But if you're rigging a tonne from that basket, that's a lot of contact pressure on the sling regardless of 4 layers of burlap or not! More often than not we come to de-rig the stage to find that the sack has been cut through and the sling is no longer fit for service! This is especially so when there's an amount of dynamic load on the point, say from a beam of 30 moving lights all moving in concert. It doesn't create the most motion, but it's enough combined with the load to saw right through the sack over time!
We keep pieces of cut up 1/4" wall, 5" diameter rubber hose to layer between edges and slings, and that works really well. I don't think we've ever had anything actually cut through the rubber since we started doing that.
But we've got scrap sections of that hose left over from other parts of our shop, and not everyone has that advantage.
As a helper, crane operator/rigger, then trainer at a nuclear power plant, I first hand found out the importance of rigging inspection. There were rudimentary procedures during construction prior to reactor loading. We were testing engagement of alignment of control rod drives into the reactor penetrations. I reached to grab a sling holding a suspended one, and the swedge collar slid upward in my hand! It had never been swedged. I immediately set the load down and reported it. Huge monetary and engineering problems if it had dropped. Consequently, a complete rigging inspection and tracking procedure was implemented immediately. I will never forget that and I am now 71, seems like yesterday.
"A rigger learning the ropes." I wonder if that pun was intended.
that my friend is a carefully engineered joke, just funny enough to hold its own weight;)
@@beartastic-ftw haha...that's a good one.
That's a good one x2
Tip for the part at 7:00 put a piece (2 pieces) of colored tape on the measure, that makes the difference MUCH easier to see!
"A little learning is a dangerous thing; drink deep, or taste not the Pierian spring: there shallow draughts intoxicate the brain, and drinking largely sobers us again." -Alexander Pope.
I'd say this just scratches the surface of rigging. But I'd also quote Pareto's 80/20 rule, this might cover most of the problems of rigging failures. The rest could be specifics to each case. Then again, I don't know anything about rigging so I might be completely wrong. Who knows.
th-cam.com/video/hjh2JPy-3IMh/w-d-xo.htmlttps://th-cam.com/video/hjh2JPy-3IMh/w-d-xo.htmlttps://th-cam.com/video/hjh2JPy-3IM/w-d-xo.html
Speaking as "just some random dude with a chain hoist and a couple slings in his garage lifting things out his his truck bed," this was rather informative, even if not for training purposes. Just shows me I need to get out and learn a thing or two before I try and pick up something more than a few hundred pounds with my setup. Another fantastic video from Practical Engineering!
I appreciated that little FYI at the end. Many persons, myself included, use youtube videos as a way to quickly understand a topic. I even heard a doctor say once that he googles information when trying to make a decision. It makes sense if he already has an idea of what the answer will be, but I can imagine someone using this video to "train" themselves on rigging. Better safe than sorry.
My wife is an ER/ICU doctor, and uses Google frequently (usually for things like harmful interactions between different medications, or the correct dosages needed for uncommon meds) since the amount of detailed information she needs to remember is IMMENSE and always changing. The key is knowing the sources that can be trusted to keep that information accurate/up-to-date. She will also occasionally use TH-cam to refresh her on the correct steps for performing a specific procedure that she hasn't performed in several years. She wasn't trained by Google and TH-cam, but it would foolish to not use appropriate tools to make sure she does things right the first time rather than rely on her memory all the time.
@@jlhillmann79 Right. That knowledge base is important and also knowing which sources she can trust is also important.
Taking me back to my Air Assault school days in the Army. Whole lotta time spent learning very specific ways of rigging up all sorts of gear for transport by sling load.
Some of the most interesting rigging Ive seen has been Ron Pratt on youtube. He's a heavy equipment tow truck operator with a rotator truck, so its pretty much just a crane with wheel lift on the back. But the rigging having to all be off-the-cuff, with an approximate weight, best judgement on CG, limited lifting points, and other constraints such as overhead powerlines, traffic lanes still operating nearby, the need to drag stuff either forwards and backwards, or sideway on a variety of surfaces is super impressive to see done.
There's some interesting principals here for lots of regular practicalities outside of cranes, particularly 6:10 to 7:30. Things like securing loads to your car, boat rigging, various other boat ropes, fastening things in the garage, moving furniture, etc.
having worked as a machinist for years, this was fun, I've used a lot of slings and chain fall hoists, and we've absolutely had abraded slings break, because someone failed to examine the sling before working with it. It's certainly not a 20 ton beam, but we did lose a piece that weighed about a tone off one.
The other part of physics... what happens when someone doesn't secure a work piece into the machine well enough, and doesn't get it balanced well between the chuck and fixtures, definitely seen someone lose a 600 pound part turning at over 100 rpm.
anytime the weights big, or high rpm in high power machines, dangerous things happen, But you can only make things so fool proof, because they'll go on and make a better fool.
I had a dismantled and stripped car body hanging from a synthetic sling when i was lifting it from customer's yard onto my truck. The sling went under the front door frames, which did not have door seals installed anymore. On that day i learned that even painted sheet edges can cut a sling. Ever since having a body fell on ground half a meter in front of me, i have used a lifting chain to lift scrap cars.
6:10 I think each sling would be experiencing 1/cos(30deg) = 115% of the load, not 1/cos(60deg) = 200%. It's so easy to get this backwards. Great content!
No, he's correct because the angle is from horizontal. see 7:48 for the formula
So if vertically his load on the sling is 100 Ton, with 30 deg from horizontal he'll have 100/sin(30deg) = 200 Ton of sling load. If his sling is 60deg from horizontal then the load on the sling is 100/sin(60deg) = 115 Ton.
Remember you're comparing the 'vertical' part of the triangle to the 'diagonal'. so it's sin
@@adityac3239 Oh, you know what? You're right! I didn't even see the little "30deg" label in the diagram. I only noticed that the diagram shows an angle of about 60 degrees from horizontal. I went back and measured the diagram and found that the angle labeled "30" is actually 53 degrees. So that's what confused me. But, if you read the label, then absolutely, the sling experiences 1/sin(30deg) = 200%.
Holy cow, in my statics class, we just hit chpt4 and my first hw problem dealt with determining the load on a single cable ran through a pulley. The issue was that the cables are spread apart as they contact the steel Beam for stability. I had trouble convincing myself that the load was greater on the cable as the angle of spread increases. This darn x-components of the force vector will alluded me for the last time haha 😄
This video was published the exact day I needed it. Thank you for making these high quality videos Grady; what you do matters. I'm happy to help support people like you who make good educational content like this.
Your sketches of the center of gravity jarred something in me. The CoG of a suspended load is always directly under the hook.
only after its off the ground and not slung in a manner to compensate. its easy to chain uneven weights up level but sticking out weird. i do it all the time with roof trusses/ partially built roofs.
@@bocaks but stil the CoG is directly under the hook.
I witnessed a chain sling failure on a small crane lifting roofing materials to the top of a building. This was in the summer of 2009 at Arizona State University. Fortunately the workers had kept the area under the hoist clear so no one was hurt. Besides, it was summer, so there were hardly any students on campus anyway.
Thanks to Practical Engineering for doing the heavy lifting involved in making these TH-cam videos.
At eighteen years old I was rigging cut timber for helicopter lifting in the forests of the Pacific Northwest. I moved onto another career path as a heavy construction worker, as a boilermaker. Rigging was a large part of the apprenticeship training program for us. I was onsite multiple times when mistakes were made and cranes or materials were dropped or collapsed. After seeing the tension guy wires slice a full-size Chevy pickup when the crane attached to them collapsed, I was convinced that there’s no room for mistakes in construction.
As a side note, I still have the Rigging book that I was given back when I first started in construction back in 1979. It fits in a pocket and has vast amount of useful information.
The biggest failure I’ve seen always has to do with the connection point of riggings. Whether the hook is missing its safety latch or the sling angle is too acute and they should’ve used a cross arm or if they used a choke and the choke slides. Another thing is when the load leaves the ground and rigger with the tag line and the load starts to spin from wind.
th-cam.com/video/hjh2JPy-3IMh/w-d-xo.htmlttps://th-cam.com/video/hjh2JPy-3IMh/w-d-xo.htmlttps://th-cam.com/video/hjh2JPy-3IM/w-d-xo.html
Safety latches have only one purpose, to keep unloaded slings from from being flung from hook while traveling.
I have been a crane operator for 42 years and I would never make a lift unless I was satisfied with the rigging used.
Good to hear! Keep up the good work
I worked as a rigger driver and am trying to become a crane operator. You manage to explain so much clearly and concisely, thank your for your excellent work. Love the content keep it up!
Very interesting, I remember reading something about hammocks that use a kind of really wide vertical sling. The forces at the tree are loads more than just half the body weight of someone sitting in it.
Another possibility of failure in lifting with angle in slings is... a failure of the lifted object itself!
Because doing so, you also add significant compression stress within the object. And if you have a slender thin tube* it might break by bending (from its self weight) and then eventually fail by buckling...
* And if you are wondering: yes this is a mistake I saw once. Please use my experience to not replicate this error on your construction site! 😉
Thanks for the interesting example. I raised this hypothetical scenario earlier: When the sling angle approaches 90 degrees, the load will be crushed by the lifting force. Good reason to use a spreader bar.
I really appreciate your models you make to demonstrate the topic you're presenting. They make your points more tangible and easier to understand, thank you.
Thar turbine being lifted at 9:10 is a cool example of how the riggers chose to sustain the weight near the middle of the load, having a vertical strap (instead of going from the hook to the outsides of the load)
Never have been a rigger, and probably never will be, but securing a lot of stuff to a trailer, and lifting engines etc. with a engine crane was has given enough experience with similar concepts and materials for this video to really make sense and resonate!
All construction workers working around or with cranes should be shown this video
"You don't use ratchet straps..."
**nervous laughter**
From a crane operators point of view Grady has explained this perfectly, brilliant video
I operate a 75-ton crane on at least a once per week basis, and these fundamentals are drilled into us. We primarily rely on synthetic rigging, and at times we have to employ shallow angles due to clearance concerns. We're not allowed to hook up anything unfamiliar without checking total weight, CG and strap angle.
The thought of using shallow angles is entirely scary to me; even though chains are rated far below breaking point, I still can't see myself willingly subjecting a chain to twice the actual vertical load!
@@sissy021 All shallow angle loads are calculated prior to rigging selection and purchase, using the heaviest version of each lifted assembly for assessment. We don't like exceeding 80% of the de-rated WLL, so we have occasions where a single strap could accomplish a straight lift, but with de-rating and safety margins we end up with four of said strap to accomplish the same lift at low angle.
Absolutely brilliant insights for lay people like me. I always like watching building works and this helps me appreciate what their doing even more.
What surprised me the most was that those synthetic slings are rediculously cheap compared to the usual industrial stuff. Yet some keep on using them until they fall apart...
I got told that they are kept cheap in order to remove the reason for not replacing them.
Just be careful buying the cheap synths. We bought a set of cheapos that were rated at 10k vertical but were substantially lighter than other 10k vert synths we'd had before. We did a couple test picks with them, increasing the weight each time, and one broke with a 7.5k load. I cut both into small pieces so they couldn't be garbage picked and now procurement has a hard rule against buying cheap lifting equipment.
I worked in commercial and industrial construction for 20 years as a plumber/gas fitter. Anytime there was a lift near me I stopped what I was doing and paid attention to the lift. I saw many close calls of riggers improperly rigging loads. The worst I saw was a 10 ton air handler drop from about 3' as they lifted it. The crane operator could see from his cab 200' up there that the spreader bar was incorrectly set. As soon as he raised it the bar swung and the straps slipped under the air handler. It happened so quickly. It fell and damaged the under frame of the unit. Many other close calls. But that was the only load I saw fall.
Rigging videos always bring out the worst pedants! These two riggers give this a solid A. From our couch to yours, cheers Grady!
No one wants to be the subject of an all-hands meeting, getting proper rigging equipment is always cheaper than the damage bad rigging can cause. Not to mention the costs of a safety shutdown and a full blown investigation.
Be your brother's keeper.
just recently I have seen a crane lifting steel rods for concrete. lifting is nicely offcenter with worker below it. nothing happened, but it looked like there wasnt much needed for a few rods to slip out and fall
That's the kind of thing I've seen more often than any other. It always made me nervous, and I wouldn't be anywhere near that sort of load. It's bad enough for rebar, where the level of friction between bars is fairly high because of the ridges on the steel. But then when it's Ridgid or EMT? Nothing to keep those center pipes from going flying out!
Same problem when transporting a load of pipes, strapped onto the back of a truck. Come to a sudden stop, and those pipes will go right through the vehicle in front.
@@paintedwings74 especially when they just look like some artisitc mikado game, with some rods sticking out up to a meter on either side. one particular rod was flexing so much, with the angle due to offcenter lifting it hung nearly vertical at the end.
My first summer in the trades when I was still in high school taught me the dangers of improper rigging. We were working in teams of 2 and I was put with a guy who'd been there for about 10 years, and we were picking and moving an approx 3' diameter pipe approx 30' long. I knew nothing (Including the fact that he wasn't the brightest man there), so when he had us hook the hooks of the 2-legged chain sling into each end and hoist away I never questioned it. The pipe got about 5' off the floor before BANG the chains broke, embedding themselves in the walls on either end of the 80' long room and BANG the pipe hit the floor. We were waaaay too close and it rolled towards us. Luckily we were up on a sand pile (sandblasting company) and it stopped short of crushing us.
I still remember that incident vividly decades later; and the lesson it taught me about the importance of proper rigging has served me well in the time since.
As a industrial mechanic/millwright I learned it in school, I enjoy the way you simplify things and make it accessible to everyone
Sometimes I try to explain something I know but it's hard to find the words.
You do it very well !
Keep it up 👏
I used to wear a hoist all the time when I was a warehouse worker and had to use a cherry picker to get to high shelves. And we were required to inspect and sign off on the state of our synthetic hoists for exactly the reason that you covered. They were super vulnerable to abrasion. But thankfully modern-day synthetic hoists have features that make abrasion way more obvious on purpose. Like bright red threads buried in the fabric that become extremely prominent as soon as it reaches a certain abrasion level.
Basically if you see the red threads, you throw out the Hoist and get a new one. Period.
Have you watched any of the TH-cam footage (eg from NASA Space Flight) of the Space X spaceship construction down in Boca Chica? They make extensive uses of cherry pickers, sometimes at ridiculous heights (in a place known for its gusty winds!). I have long wondered how they have never had an accident (as far as we know). Those guys at the top of the cherry pickers, 50m up must be either brave or crazy - or both!
@@paulhaynes8045 oh yeah. I've seen the footage. Thankfully those guys are very much tethered to an anchor point on the Cherry Pickers. Even if they were thrown off the side, they would just end up dangling by the Hoist. That has its own share of Hazards, but at least they didn't go Splat on the pavement lol
"Putting you in the shoes of a rigger, learning the ropes." I see what you did there.
I also appreciate the language and terms you’re using here, pretty simple but not too dumbed down, now I’m going to watch the crane failure one and hope I never experience that
I love your remark about rope from a truck. I grew up on a family run dairy farm and sometimes there are things we had to move that required some form of rigging to lift from hooks on our front end loader and of course we never had anything resembling proper gear. Fortunately it was infrequent and they were very light loads compared to anything you're discussing here, and we're at very low heights. Still, I hated doing it every time we had to.
*"Why Things Fall Off Cranes"*
*Human error, and gravity... Done.*
And Road Runners.
Human error is not the root cause of industrial accidents.
@@Crlarl
Things like metal fatigue wouldn't have an affect, if it weren't for laziness, and complacency in not doing proper safety checks for that sort of things.
Those are called, human errors. It's funny that you mention that it's not the root cause. In the list of causes, human error can encompass the vast majority. Guess what that would then make it... *Teh Rewt Cawze.*
Not to mention... seeing as most things in industry, if not all, are done because of humans, that would kind of make them the root, as well. So...
Yeah 'human error' is just a catchall. What error was made? Why did it happen? This video helps to understand the errors that are made so folks can avoid repeating them.
@@Psyrecx
Human error only happens when the surrounding systems allow it. While human error is factored into failure analysis, there will always be something behind it. Training, safety systems, and corporate pressure are all root causes.
As a theatrical/concert rigger this was a great video to watch! It would be fun to see you do a video on the FOY flying system for actors, which was developed for Peter Pan. I think you'd enjoy it!
Question though, at 7:39 (beam lift), I can't help but notice that both hooks are in the same direction...meaning the one on the left is backwards and has a better potential of falling out if there is a shift in load due to wind or placement on the structure being built...
yes it;s not most ideal. even better would be to use hooks with springy flaps. or shackles locked with pins
One of my favourite channels - Ron Pratt - shows a lot of his rigging for recoveries. I think I've heard nearly every thing said in this video on his as well.
In 2020 I built a big carport and the steel posts and beams were very heavy, posts 145Kg and beams up to 245Kg. I used my 6x4 steel trailer as a mobile crane base. I then created a 4.5m upright post and at the top a T section. One end for the block and tackle and the other end used to stabilize the post. I made and used a spreader bar for the beam lift. It worked perfectly and made the job relatively easy. I used practice lifts to make sure the trailer crane was not overloaded. Love your vids mate. Subscribed.
Mobile crane operator here! 9 Years of experience and i would like to correct one mistake you made early in the video. Not every hoist is done with a hook. I've lifted plenty of stuff in confined space with only the thing at the end of the wire. Ofc this limits your lifting capacity to what ever one line can pull and you need to use correct shackles; But sometimes you indeed lift stuff with the line that's on the cranes winch.
Are you meaning the becket ? Bless ya'll from hooterville, n.c.
Felt like I was back in the Army in Air Assault school. Failing the sling load portion was the single most common reason for people to drop out of the school.
for chinook?
@@PrograError Blackhawk
The unnecessary horizontal tension also explains why suspension bridge towers are so tall. Was wondering about that when I visited the Golden Gate recently.
This may not be a training video, but it does cover a lot of the key concepts and does a much better job of keeping people awake!
For 30 years I never had a problem with rigging failing when using fabric straps. I'll stop an entire project and go out and buy straps before I use a chain. Chain slips way more often than straps. I also way overrated my lifting straps, 4 straps rated 6400 pounds each to lift a 4000-pound piece.
which is sane. As much as possible, a single sling should be able to take the full load, in case of failure of the other ones (or of the anchor points, another source of lifting accidents). at least long enough that you can bring the load on the ground.
Chains have their place, like hooking to a attachment point, but definitely not as a basket on steel, but I do prefer straps for most of the picks I’m associated with.
Chains caused a number of early mining elevator disasters. Because with a chain, one link will just snap instantly without warning, while woven or braided straps will often show visible sign of going weak that can be spotted in advance.
Everything has a weak link / area . Bless ya'll from hooterville, n.c.
PROTIP: If you have to pay a guy biweekly because he disappears for three days every time he gets a check, don't let him sling a load.
What does this mean?
@@Cloud7050 means he's on some type of shit
@@Cloud7050 It means he takes his pay and keeps the brewery in the black ink. 😉
@@Jenny_Digital As a brewer I appreciate his commitment, but I would also give him less critical tasks on the job.
@@andvil01 Quite so. I’m not saying an alcoholic _shouldn’t_ work, only that he shouldn’t be tasked with anything that could have severe consequences. Also, I wouldn’t want to loose money over it but that’s a distant second as most of us have for one reason or other had a bad patch.
As an industralworker who works with cranes on a daly basis, i can tell you that the shown example are just the basics. Much more dangerous is, when you work with loos Atatchmentpoints (like the shifting on 5:06). And there are a lot of them. Magnets, Liftingclaps, suction cups... Also you have to think about the forces when something is stuck (Heavy tools from the machine fir example)
We use at least 500kg (most of the time 1500 - 2000 kg gear to lift things wixh are "Just" a few hundred kg, so we are on the safe side. These components who fall down are all with loos atatchmentpoints. If you have a fix Atatchmentpoint (thread, Holes....) you are quiet safe.
I doubt you had this in mind when you made this but - the info here gave me a lot to think about in regards to a different kind of lifting, that still involves rigging the load just right...
In my case the "load" is actually my husband, who is disabled. Anytime we are getting him in and out of the house, there's a small chance that he might fall. Because of that, we have two different things - a lift belt and a sling - to try to help get him back on his feet. We've never had to use the sling so far - thankfully - but I feel a lot more confident that I can at least know what to look at, and how best to get that sling around and under him. I've never needed to hoist anything (or anybody!) in a basket, never had to so much as haul a bale of hay on a pulley and rope. Your examples here and explanations gave me a lot more helpful insight than any of the other stuff I've read. Again I know you didn't intend that, but I wanted to say thanks anyway, because feeling more confident that I'll be able to help my husband if or when he falls again takes a big load off my shoulders! (pun intended)
Hey grady, could you do a collaboration with ToldInStone to show how the ancient Romans would build their buildings before modern equipment? It could be really cool. Also I love your channel I've watched since forever
Yeah the Temple of Jupiter would be a good one.
oh the impeccable timing.. I'm on site right now with a tower crane in front of me
Step back - a long way!
I really appreciate your videos. I worked on new ship construction projects at the beginning and near the end of my career. The first shipyard at assigned riggers to each crane. Only trained certified riggers and crane operators were allowed to rig, attach, lift, land, and detach loads. The crews were responsible for inspection of all rigging gear and routine maintenance .such as greasing sheaves and wheel bearings.
In the secong shipyard routine crane maintenance was done by a single crew
Continued... The second shipyard did not use assigned riggers. Instead, any worker was allowed to rig a load.
During the construction process in the first yard I can remember only one accident when a padeye failed and a 150 LT unit was dropped during the process of turning the unit over. Luckily no one was injured and damages were limited to bending a spreader into a near perfect U-shaped piece of scrap.
I cannot say the same for the second yard. Load damage was a regular occurrence. Cranes were regularly out of service from lack of routine maintenance. I knew if a crane was lifting something I needed to head in the opposite direction.
Jim Harbaugh, the University of Michigan football coach, made the comment, "...because you're standing on third base does not mean you hit a triple." Lifting a load safely requires not only trained personnel, it requires a strong process that assures safe practices are followed.
Keep up the good work.
Bob
My summer job was as a stevedore, before container ships. I still have nightmares about some of the things we had to rig. The most dangerous were these huge ingots of iron. We used wire cables and hooks. Once out of the ship, they would be placed in box cars, with inches of clearance. Winds would come up and once these got swinging, we got out of way. Saw someone's fingers get crushed once. ugh. However, only saw one rigging failure, put steel rods through the side of a ship.
Thanks for giving me a concrete answer to the question: "But Dad, when am I ever going to need trigonometry?"
"You can't push a rope after all"
Don't tell my wife!
I've been operating crane for over 8 years. Great video! Only thing I would add is that in my experience spreader bars are just for loads that are too tall for straight rigging or you want to avoid the rigging crushing the load. Usually you're using a single bar so on a 4 point pick you will still have sling angles on both sides. Not to say there isn't a scenario that would be the case but extremely rare.
Been putting off watching this because I just didnt have any interest in the topic. Decided to watch it today because I try to watch all of your videos and this has been one of my favorites. The presentation of the information was the best I've ever seen. It's the small things that make the biggest difference like the thermal camera and the spring scale to demonstrate the reality. Great video.
Why things fall off or the cranes hook?
Incompetent riggers, often pulled off the streets with little to no training.
Companies also dont offer training very often, more companies require you to have experience and certifications before hire. This leads to buying certs, or just passing a test without actual experience. Then lying on the job application to just have a chance to learn on the job.
Poor pay means it hard to keep good riggers around. Most big crane companies start pay scale fairly low and by the time those people hired are decently skilled they often leave for higher paying rigging job.
As a rigger by trade with nearly 10years of experience ive seen many bad rigger and even good riggers using bad rigging practices.
Another thing is time frame and site limitations. On paper you can alway do things perfect but reality is sometimes you are forced to do scetchy things.
I was thinking about that too. It's hard to imagine the team just nodding along approvingly as you hold everything up because the sling is a little frayed or the load rating is a little close for comfort or the crates all need to be opened and have their centers of gravity marked. Can't just grab a heftier sling on a quick trip to home depot I'm guessing. But perhaps if the rigger has a certain gravitas like Sam Elliott or Nick Offerman they can pull off the safety first power move just fine.
@@jboogie8369 ive yet to see a company push a truely dangerous situatuon, if the rigger/operator isnt confortable you can typically say no and keep your job. usually its not really damaged rigging that hold things up, its using rigging near 100% capacity on unknown weights, it putting slings at horrible angles because you dont have the head room, using multiple small chain hoist or lever hoist because bigger isnt available, or needing to flex company policy.
Not having the correct length slings. And more often than not its uncontrolled movements.
We have fixed most of those issues at the company i work it with simple things like wide mouth deep throat shackles, d-rings, and having a really good engineering team to help us on calculated weights and find center if gravity on complex structures.
We also pay okay, its towards to bottom of the scale but its not horrible so we get repeat employees. Most if which are handpicked. I cannot afford to hire and train a new guy since we work short time lines and i need to walk away and know that rigger can handle things. I hate that we dont hire helpers to learn. When we do get teaching moments we try and spread the knowledge but hands on experience is the only way to be competent
@@kylevanwinkle2081 Thanks for the color on that one. I've always found workers' attitudes toward safety interesting. Pride often plays a role either way. Some are too proud to admit they can't safely complete a task with their current gear or support, and some take pride in their knowledge of the best practices and failure modes associated with their trade. Naturally, there is far less downside to the pride exhibited by the overly cautious :)
@@JaredCzaia well end of the day the job has to be done. Trick is to know where to stand your ground and where the danger line is. Stepping away from danger is what we want. Figuring out a safe way to do the job is 90% of the job. Its literally risk management and finding out what the acceptable amount of risk is. Something as simple as walking under the load, isnt dangerous 99% of the time but the 1% of the time the load falls or shifts could kill or maim you. So you do the best you can to not get under the load. But there are times where there is no other way to do the job.
Cfr1926.1425 is the osha regulation that says being in the fall zone is okay if you are required to be there except for tilt wall applications because concrete anchors can fail unexpectedly or the concrete could crack and fail.
Honestly i think 3rd party certifications have hurt the industry. Just because you can pass a test doesnt mean you can rig.
Shallow sling angle increases sling force. What provides the necessary opposite force? The load.
For mid-size loads, the sling is often far stronger than the load itself, so if your angle is too shallow you end up unexpectedly snapping/buckling/bending your load.
Good point.
Thanks for the intro to the topic. i ve worked in a couple construction and manufacturing processes (mostly back in the 90s). i ve watched the center of gravity issue bite once or twice. i though of a couple other points of failure based on my very limited experience... crate and hardpoint failure - where the structure that houses the item to be hoisted fails or the ring/hook or loop on the object fails during lift. often seemingly due to non vertical load. in my case the crate holding 84x120 glass broke at the corner due to a knot in the 2x10 board near the top corner mount where the chain at... a REALLY wide angle pulled in to hard. thankfully it only partially failed before the problem was addressed and the crate was set down. rigging is some crazy stuff not to be taken lightly
As a forklift op, I can say from experience that you never truly know where the center of gravity is just from visual inspection. Many a time I’ve lifted just a few inches to see if I’m right or how far off I am. Would highly recommend being on a forklift that is over loaded, that way you can learn what it feels like when the machine is getting tippy, so you can stop whatever you were doing and rethink the lift. It’s your fault if something goes wrong, not the guy who told you “it will work, trust me”
Another common mistake is to divide the lifted object weight by the number of slings. If using 4 chains (or other rigid rigging), the weight will be balanced between two or three lifting points and the other lifting point(s) will balance the load. This is due to small length differences between each sling
With synthetic slings, the stretch help spread the load. With rigid slings, other measures can be taken to limit this phenomenon
You mean like a 4-legged chair always wobbles on an uneven floor, but a 3-legged milk-stool is perfectly stable...
Yes!
I guess a combination of rigid chains, a bad center of gravity, and poor sling angle, can far exceed the rated load.
Hi, Advanced rigger with over 20 years experience here.
You are wrong. Very very wrong. Synthetic fibre slings have a length tolerance in manufacture of up to 3%, unless they're a "matched set" from the same machine, on the same day as part of the same batch, and certified as such.
Wire rope slings, you can use up to 3 legs to take the load (on a multi leg lift).
On everything else, no matter how many legs you have, two must be capable of lifting the entire load.
If just one chain link difference in length can change the load share so greatly in chain slings (and it can), 3% is up to 3 friggin' centimetres (over an inch) PER metre of sling difference, using soft slings.
Please delete or edit your comment to remove a VERY dangerous piece of advice from eyes that may be stupid enough to trust your word on this.
Yup, I can and will provide links to manufacturer info, Australian Standards and rigging guides to prove what I say, if you're stubborn enough to question me on this.
@@gordonrichardson2972 If you're allowed to rotate the chair, it is possible to move it into a stable configuration - th-cam.com/video/OuF-WB7mD6k/w-d-xo.html
Crane Operator here, on your angle of the sling part of the video, not only are the slings a factor to worry about but you can bent the very thing you are picking up if the angle is too small.
One of my favourite things about your videos is the insights into the fundamental principles that underpin the world around me, something I was always obsessed with learning about from a biology perspective but am only really dipping my toes into understanding what people do with engineering. Even something as simple as learning what rigging means is a lever for cracking open the rest of the mystery with research. Thank you
Rigging?!!?!
Dude, it's over. He lost the election.
...Oooh, that kind of rigging.
Sorry. I have PTSD... Post trump stress disorder.
(Awesome video, man! As always a pleasure disposition and packed with information. My only complaint is that it wasn't an hour long!)
First!!!!! Wohooo!!!!
Nobody cares
bababooey
Take this nonsense to TikTok
Great video. I have been rigging for years and everything was right in your video. Inspecting the rigging before use is also important. It might fail at much less then it's rated capacity if it's damaged. I have seen two rigging failures and both were rusted slings.
Great video. I wish I had this 30 years ago when I taught rigging in the Army. The biggest issues we always had, was making quick assumptions. Like lifting a 2&1/2 ton truck, many peoples first thought is it weighs 2&1/2 tons, but that is wrong. It can carry 2&1/2 tons, and empty weighs a heck of a lot more. I always taught the soldiers to stop and try to get the same calculation results by using different sources for the numbers. Look on the item, to see if there is a weight, instead of reading the bill of lading. Then before lifting, look for a failure place, such as a sling that may slip, a chain hooked up wrong, ect. The when in doubt, recheck all the steps, and calculations.