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AUSTRALIAN 4WD MONTHLY TECH TALK Part 1 - Bow Shackles


We sent out our engineer, John Cadogan, to smash some shackles – in the interest of your safety. When a 4WD recovery shackle breaks, it goes off like a shot from grandad’s Lee Enfield .303 rifle. Beaver Sales Logistics Manager Peter Cooch has broken hundreds. He still flinches every time one goes off, standing at the helm of a calibrated, 100-tonne vertical test tower, behind a shrapnel shield. Me? I’m thinking about waiting some place more appropriate – like the next parish – while he gets on with it.


Behind that scattershield is a machine straight from the dungeons of the Marquis De Sade. In its jaws is an Australian Standards-compliant 4.7-tonne Black Rat bow shackle. And I’m standing here gobsmacked because the extremely accurate needle on the load meter has just inched past the 30-tonne mark. The shackle is bent like a pretzel, but it’s still hanging in there.


Next thing I’m thinking (apart from how far away I can slink without trashing my credibility) is how in the blue bejeezus you’d ever manage to generate that kind of load using two 4WDs, conventional recovery gear and the Aussie bush.


Waiting for it to break is by far the worst bit. I’m overjoyed that I’m standing up when it finally lets go with a bang at a staggering 33.7 tonnes’ load. Had I been sitting, I suspect my arse may have over-puckered itself to the chair – and only that damned machine behind the shield would’ve been capable of extracting it.


What did we prove? Apart from my own limitless capacity for cowardice, we proved a randomly selected Black Rat 4.7- tonne bow shackle broke at an impressive 33.7 tonnes’ load. We then performed the same test on a likewise randomly selected 3.2-tonne Black Rat bow shackle which, in turn, broke at a no less impressive load of 27.2 tonnes.


Then we took an unrated 16mm hardware store D-shackle – purchased from Hardwarehouse that morning for $6.81 – and destroyed it for comparison. It’s the same nominal size as a 3.2-tonne rated shackle (16mm) and it was cactus at a comparatively paltry 11.9 tonnes’ load.


After that, we took a brand-spanking 3.2-tonne Black Rat bow shackle and nudged it hard and repeatedly with the grinder to simulate being dragged behind the vehicle, because plenty of shackles drag firewood behind 4WDs.


They also get dragged over rocks for years under winching loads. Gung-ho fools throw them to 100 per cent Rambo types across the span of a winching operation, and they hit rocks hard in the process. In deference to this last act of stupidity, we belted our new shackle hard with hammer and cold chisel, three times around the pin holes and twice on the loop of the bow. These two 4.7-tonne WLL shackles comply with the AS2741 for shackles. It took an incredible 33.7- tonne load to break the one on the right.


Ten years of abuse in 10 minutes – very therapeutic. Then we broke it – which still required a not insignificant heave totalling 26.3 tonnes. Robust little suckers, these bow shackles. We’re not advising you to go out and exceed the WLL stamped on your recovery shackles based on these figures, in the belief that it might be safe to so. It’s not. The WLL stamped on shackle bodies (3.2 tonnes in the case of 16mm S-grade shackles and 4.7 tonnes in the case of 19mm S-grade shackles, according to Australian Standard AS2741 – Shackles) is there primarily because rated shackles are used in lifting applications, where steel and/or concrete is lifted by cranes over peoples’ heads. In these situations, a huge, bulletproof margin of safety is required.


Although no standard demands it, my personal belief is that 4WD recovery is another undertaking in which such extensive margins for safety are entirely appropriate. So let’s look at how a shackle behaves on the way to breaking. Under moderate loads – certainly under the rated load, but also what AS2741 calls the ‘production proof test’ load – the shackle will be ‘elastic’. This means it will stretch a small amount (invisible to the naked eye), and then return to its normal shape without any deformation when the load is removed. (The AS2741 ‘production proof test’ loads for 3.2- and 4.7-tonne S-grade shackles are 6.4 and 9.4 tonnes respectively.)


Some way down the track from there, after more load is applied, the shackle becomes what engineers refer to as ‘plastic’. It bends and, once the load is removed, it stays bent. Apply more load; it bends more, permanently. A requirement of AS2741 is that the 3.2-tonne shackle must endure at least 16.0 tonnes’ load before breaking (23.6 tonnes for 4.7-tonne shackles). It can (and will) bend at that load, but it mustn’t break. As the load increases, the shackle continues to deform until its weakest link, structurally, throws in the towel and breaks.


On the three AS2741-compliant Black Rat shackles we destroyed, the weakest link seems to be the root of the thread on the pin. Its V-notch is likely to be a stress concentrator, and the pin shearing through in this region is evidence of that. Even the one we intentionally damaged elsewhere broke here. In the bush, of course, one seldom has a load meter and an occupational health and safety officer to monitor the recovery operation. You have to do that. But you can use the manner in which shackles behave under load to protect yourself. If you ever see a shackle bend, even a little, stop applying the load immediately. Even a small permanent bend means you’ve taken the shackle well beyond its designed operating range. If a shackle pin ever jams tight in the thread and can’t be released, chances are it’s bent. Throw the whole thing away.


Generating the loads required to bend a shackle would be very difficult. Driving away at high speed with a strong, rigid connection between two vehicles, one of them a bogged D9 ’dozer, might do it. (Did someone just say ‘moron’?) But, realistically, the recovery point on the bullbar or chassis, and the strap or chain between the vehicles, wouldn’t survive the forces any of the rated shackles we tested demonstrated they could withstand. In other words, something else would probably bend and break first. Even if, by some miracle, the chain of elements in the recovery operation were infinitely strong, few if any 4WD chassis would withstand 20-tonne-plus loads without bending permanently.


Age and cyclic loading have an unquantifiable effect on shackles. For this reason, AS2741 specifies a ‘production proof test’ load (above) for each shackle. The theory is, you can take your shackle(s) to an approved testing facility like Beaver Sales’ and have the proof load applied. If the shackles survive that with no appreciable damage, they’re good to use up to their WLL. In practice, however, this process will cost you at least $30 per shackle. And with replacement cost in the marketplace running between $8–$20 depending on brand and WLL, you’re better off merely replacing old and/or suspect units. You should also be aware that not all 4WD recovery shackles comply with AS2741. The Black Rat ones we tested do, but it’s not compulsory.


The standard does require shackles to bear their WLL, along with their stress grade, L to T. A manufacturer’s identification that correlates the shackle to a test certificate is also required. In addition to that, the AS2741-compliant Black Rat shackle pictured also displays its build date, though this is not required. This enables you to determine the age of any Black Rat bow shackle before you use it. The standard also specifies six critical dimensions that must be met for each nominal shackle size. Even having all those elements is no guarantee that the shackle complies with AS2741. Several reputable manufacturers and suppliers of 4WD shackles told us that they had tested their shackles to the standard’s requirements but preferred not to state explicitly that they complied.


In our view, explicit AS2741 compliance is an ironclad guarantee of quality and performance. If you don’t get that, at least buy from a reputable manufacturer prepared to provide evidence of the shackle’s performance under controlled test conditions. If any supplier is not prepared to do that, take your money elsewhere. Hardware-store shackles? Forget ’em. As our tests show, they’re ultimately much less than half as strong as a comparative AS2741-compliant shackle. The one we tested displayed an appreciable bend at just six tonnes’ load (less than the proof load for the Black Rat 3.2 tonne shackle). And it could’ve been a strong one. And it cost almost $7.00, whereas a stamped (but not necessarily AS2741 compliant) 3.2-tonne shackle retails for between $9.00 and $15.00 at most reputable outlets. That’s a lot of added protection for a few extra gold coins.


As we said, there are no standards for 4WD recovery. Instead, the industry’s key recovery-equipment providers have evolved a more or less standardised set of equipment. Straps with a minimum destructive load of 8000kg are common. Tree protectors ranging from 10,000–12,000kg minimum destructive load, likewise. Quality 3.2- and 4.7- tonne shackles hardly, if ever, break, except in the hands of the unfailingly stupid. Still, you’d rather have the strap break first, wouldn’t you? Shrapnel often offends...


But consider this: you’re using a 9000lb winch around a snatch block. The cable is on the bottom layer of the drum. The battery is fresh; the winch motor, cold. You’re categorically stuck – in rapid-set concrete. The shackle holding the snatch block to the tree is an AS2741-compliant 4.7-tonner. The one holding the winch hook to the vehicle’s front recovery point is a similarly compliant 3.2-tonner. You hit the controller. The winch pulls as hard as it can – 9000lb (4091kg). That tension is sent via cable to the snatch block, where (say) 15 per cent is lost to friction around the block. The section of cable between the hook and the block carries 3500kg tension. Total load on the block is therefore in the order of 7.6 tonnes. Load on the shackle holding the hook is 3.5 tonnes. Both these loads exceed the AS2741-specified WLL for the shackles we just described. That’s something for all you OH&S types in industry to think about. Imagine the load it takes to bend the shackle into a pretzel, then rip the pin segment out of its thread – how are you ever going to generate those kinds of loads in the scrub? Understanding the fine print: ‘WLL 3.2T’ is the working load limit of the shackle in tonnes, in this case, 3.2 tonnes. The ‘S’ identifies the unit as an S-grade shackle (shackles are graded L to T according to AS2741), and it is the commonest grade for 4WD recovery. ‘1/98’ is the build date for the shackle, in this case, January 1998. (Having the build date embossed into the shackle isn’t a requirement of AS2741, whereas all the other information is.) ‘BH05’ is a number relating to the manufacturer’s test certificate on this batch of shackles.


WORDS AND PHOTOGRAPHY BY JOHN CADOGAN AUSTRALIAN 4WD MONTHLY.

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AUSTRALIAN 4WD MONTHLY - SNATCH STRAP COMPARO
PHOTOGRAPHY BY JOHN CADOGAN

BREAKING POINT

When push comes to shove, will your snatch strap throw in the towel before it ought to? John Cadogan put 16 different snatch straps through their paces in the testing lab – the results will shock you.

Does your snatch strap measure up? How would you know? Buying a snatch strap is easy. Go to any 4WD specialist or auto accessories outlet, fork over less than $100 and you’ll be the proud owner of one. It’s that simple – and it’s one of the first purchases a new 4WD user is likely to make. Unfortunately, unless you happen to own several hundreds of thousands of dollars worth of testing equipment, you will have no way of knowing whether it will perform as well as its manufacturer claims.

In the transport industry, the industrial lifting game or any job in which you have to wear a webbing harness to protect yourself from a fall, there is a compulsory set of standards to which your specialist webbing gear must conform. That means it has to pass specific tests at a NATA-registered testing laboratory before it can be used on the job. And the reason for that is simple: because people’s safety is at stake.

No such standards exist for 4WD recovery, even though people’s safety is very much at stake during this activity as well. There is no independent label affixed to recovery gear that guarantees its suitability for the job at hand. None is required by any regulatory authority. Instead, an arbitrary assortment of gear has become the accepted standard for recovery. Nobody really checks up on the claims manufacturers make about this stuff, and you certainly can’t tell by looking. If our tests told us anything, it’s that dud snatch straps look much the same as top performers.

In most cases, the brand on your snatch strap bears little relationship to the company that actually manufactured the product. If you imagined, for example, a section of ARB’s or TJM’s premises in which snatch straps are meticulously sewn together, you would be mistaken. Like most webbing products, snatch straps are often made to Company A’s order by a third party and delivered by the truckload. You have no way of knowing if the actual manufacturer is just up the street or somewhere in northern Manchuria.

The reason for this story? We reckon you need to know how that snatch strap you just bought stacks up against its competition.

HOW SNATCH STRAPS WORK
Imagine yourself bungy jumping. You jump off a bridge and plummet 30 metres. Basic physics says you will accelerate to 87km/h in that distance. Imagine what would happen if the bungy operator accidentally replaced the nice, springy bungy cord with one with no spring at all. The impact of stopping dead in no distance would rip you to pieces. Snatch straps operate in exactly the same way as a bungy cord. Because of the short, sharp jerk at the end, an inelastic strap will likely damage the vehicles it is connected to, while a soft, springy strap allows the pull to be applied progressively and smoothly, without damage. A nine-metre snatch strap with 8000kg minimum breaking load and 20 per cent stretch is the accepted minimum standard for most recreational 4WD recovery. If a load of 4000kg is applied to it, such a snatch strap should stretch 20 per cent (the stretch is rated at half the minimum break load). And 20 per cent of nine metres is 1.8 metres – about six feet in the ‘old’ money. So even though snatch straps don’t feel particularly elastic in your hand, they are when significant loads are applied. Their ability to stretch is what prevents them from ripping bits off vehicles – provided you operate the recovering vehicle in a sane fashion: keeping speed to a fast jog (around 10km/h). The rule of thumb is second gear, low range and take it steady. If that doesn’t work, dig a trench (or trenches) and/or indulge in sweaty manual track building until it does.

WHO MAKES ’EM?
Most retailers don’t publicise the actual manufacturer of their straps, but some strap manufacturers label their products clearly. You’ll note that both Kaymar and Super Cheap Auto have an 8000kg strap made and labelled by Spanset (Sydney) while all the Megastraps are clearly labelled by their manufacturer, Just Straps.

WHAT WE DID
Editor Callinan scoured the market for snatch straps – or at least he sent the troops out with strict instructions. Sixteen off-the-shelf snatch straps were the result, and they were bought over the counter for a reason. We wanted a truly random market sample, not one seeded with products supplied by the companies in response to our requests through media channels. (If you received such a request, you might be motivated to test the current batch, and supply only the best of the bunch. We didn’t want such skulduggery skewing the results.) We bought exactly the same straps you would.

It then fell to me to figure out a rational test procedure. The two things that seemed most important to know were the load at which the strap breaks, and the amount by which the strap stretches. These are, after all, the most important aspects of snatch straps in operation. Stretch prevents mechanical damage to the vehicle, and a high breaking load means the whole process is unlikely to come tragically unglued – provided you use the product sensibly.

The next thing I did was approach the NATA-registered testing lab at Beaver Sales about the test. These blokes are, after all, in the business of testing industrial webbing to Australian standards on an almost daily basis. They have both the tools and the expertise. (In fact, the three Beaver staff devoted to our day-and-a-bit of controlled snatch strap destruction had amassed between them well over 20 years of experience at the pointy end of accredited mechanical testing. Not surprisingly, they offered some pretty helpful suggestions).

Beaver Sales’s John Armstrong advised us to use methodology based on Australian Standard AS1353.1. “That’s the standard applicable to lifting slings,” he said. “We can base the testing on that, even though, strictly speaking, the standard doesn’t apply to 4WD recovery.” Beaver’s Peter Cooch advised us to test the straps wet as well as dry, because water can have a marked effect on the breaking point of nylon. “In industry, factors of safety jump almost 20 per cent, from 8.0 to 9.4, if you use a nylon sling,” he said. “That’s specifically to accommodate the reduction in strength of nylon when it gets wet.”

In the end, three tests were performed on each strap. First, we stretched it to 50 per cent of the manufacturer’s claimed minimum breaking load, then measured the amount of stretch. (In other words, we stretched an 8000kg snatch strap to 4000kg and measured its elongation at that load – half the minimum breaking load is the industry-standard way to specify stretch in a strap.) We backed off the load to zero and then heaved again on each strap until it broke, measuring the load continuously right up to the breaking point. Finally, we took a sample that had been soaked in water for at least 24 hours and stretched that until it broke to determine the effect, if any, of water on the breaking load.

HOW WE DID IT
First, each strap was cut in half. That gave us a wet half and a dry half. The machine we used was Beaver Sales’s Hung-Ta 200- tonne horizontal test bed, which is NATA-registered and calibrated. (Accurate, in other words.) It applies precise tensile (pulling) loads to samples, and measures both position and load, which is recorded in real time by a computer. The cut end of each strap was held fast by Beaver’s custom-designed webbing bollard, a massive fabricated steel device that holds a cut webbing end by locking it onto itself using the friction over a pair of large, round pins. The eye end was held fast by a 17-tonne shackle, and a 25-tonne shackle held the 17-tonner to the machine. For the eye end of the strap, it was all very similar to the way it would be rigged in the bush, only the shackle was larger. Two shackles were needed to eliminate the 90-degree twist from the straps as we stretched them. The 17-tonne shackle’s 43mm-diameter pin kept the angle where the eye converges into the strap to well under 20 degrees, the maximum allowed by AS1353.1. (A fatter angle than that could have the effect of unravelling the stitching in the eye during testing – that’s bad.)

The test machine’s computer records continuously as the test happens, but after that the results are not editable, which removes any possibility of post-test number ‘fiddling’. We were given a test certificate to authenticate each test on each strap, and Beaver kept a copy for its records as well.

Some of you will doubtless be asking yourselves if cutting the straps in half doesn’t blow the results out of the water. That’s a fair question, but the answer is a resounding ‘no’. The results, and the methods employed, are valid. People test straps like that all the time. We used the eye plus a bit over a metre of plain strap on each test. Stretch was measured by marking a 1.0m gauge length on each strap at no load, then measuring the distance between the gauge marks at half the rated load. If that one metre grew to 123cm under load, for example, we knew the stretch was 23 per cent. If it was 115cm under load, 15 per cent.

As for breaking each half, we were able to test a segment comprising both the eye and a representative sample of the plain strap. The thing about tension is that it’s the same at every point on the strap, which makes having a long length more or less redundant. So you could use one, two or 50 metres of the stuff and it would still break at the same load.

If the machine is pulling with 5000kg of load, each point in the strap is experiencing 5000kg tension. It wouldn’t have mattered how long we had the strap – once the breaking load is reached, the strap simply breaks. The important thing was to test both the strap and the eye – because it’s no good if the webbing is super-strong and the stitching of the eye is second-rate, or vice-versa. The construction of the eye is just as important as the quality of the webbing.

Last, did Beaver’s tricky webbing bollard, which held the cut end, affect the results? No, thankfully. None of the samples tested broke anywhere near the bollard. They all broke near the eye, as you’d expect. We experienced around a 50:50 mix of stitching and webbing failures – all near the eyes. Either the stitching failed first, or minute damage done to the webbing by the needle while sewing the eye together meant the webbing in that region was the weakest link.

RELATING REALITY
How does what we did relate to the real world? First, in the real world, the load is applied a lot quicker than we could apply it with the test machine. The trusty Tung-Ha is flat out at a smidge over 200mm per minute, but your average 4WD is travelling more like, say, 10km/h during snatching. That’s around 800 times faster. It was generally felt by the testers that our slower testing procedure made the samples break at their ‘best case’ result. In other words, when stretched faster, the straps would tend to break at a lower load. But by how much? Nobody can rightly say.

Our results are divided into two broad categories: straps that passed and straps that failed. Simply stated, ‘passing’ means the dry break result we got in our test exceeded the manufacturer’s claimed rating for the strap. An 8000kg-rated strap that broke (dry) at 8247kg (or 8001kg, whatever) passed. If a 10,000kg-rated strap broke at 9866kg, it failed the test.

Having said that, any load in the eight-tonne ballpark is a great deal of vehicle recovery force – more than double the working load limit of many shackles, and more than most winches will ever crank out. So is 7689kg. In this context, ‘pass’ or ‘fail’ doesn’t necessarily equate to ‘suitable’ or ‘unsuitable’ for 4WD recovery. It relates only to whether our test sample broke either above or below the manufacturer’s claimed rating in our tests. Slings, cable, shackles, chains – all that stuff – are never meant to be used even remotely near the point at which they will break. Significant factors of safety are always employed. Straps are no different.

Straps taken close to their breaking point are unlikely to last very long or be acceptably safe. It’s not desirable to operate them at anything like those loads. If there were a standard for 4WD recovery, which there isn’t, it would likely adopt a factor of safety of around eight for snatch strap use. In this way, an 8000kg strap that passed a series of prescribed standard tests would be issued a working load limit of 1000kg.

Our tests are merely a means of comparing the performance of each strap to that of its competitors in a series of controlled, repeatable tests, so that you can make an informed choice while you’re out there in the marketplace with a wad of cash burning a hole in your pocket.

THE RESULTS
As you can clearly see from the table, this story will generate a fair whack of hate-mail from the industry. Incredibly, only half of the straps we tested managed to withstand their manufacturers’ claimed load ratings. And some of the biggest names in the business have come away with a huge shortfall between the rating and the actual performance in our test.

There is one absolute Barry Crocker among the results – Super Cheap Auto’s 9000kg snatch strap failed at less than half its rated load, so we can’t even tell you how well or badly it stretches. It popped its cork at a mere 3798kg. Not a good result at all. At least it made the rest of the field look like champions.

Both of ARB’s snatch straps also failed to inspire, compared with the competition. The company’s 11,000kg strap would have proved itself among the top performers – had its rating been 8000kg. However, with an 11,000kg rating it under-performed to the tune of more than 2.5 tonnes. Mean Green, Kaymar, Megastrap and Bushranger all offered 8000kg straps that out-performed ARB’s 11,000kg strap. ARB’s 8000kg strap? Also off the pace compared with its rating to the tune of almost 1.2 tonnes. Both ARB straps failed through the stitching, which just ripped apart.

Repco’s 7500kg, Megastrap’s 9500kg, Ox’s 8000kg and Terrain Tamer’s 8000kg straps all failed in our tests at around one tonne under the claimed rating.

There was only one ‘technical failure’ in the group. Mean Green’s 10,000kg strap failed by just 241kg – a margin of under 2.5 per cent. It’s hard to find too much fault with that.

Eight straps credibly exceeded the manufacturer’s rating – some by more than one tonne. Those excellent performers were Mean Green’s 8000kg, Kaymar’s 8000kg and Terrain Tamer’s 11,000kg straps.

What about when they’re wet? Well, it’s pretty obvious from the results that water does significantly reduce a snatch strap’s breaking load. (It must be remembered that snatch straps are often used while soaking wet in a creek, in mud or in the rain.) Of the straps that passed, the effect of being soaked with water for more than 24 hours was to reduce the breaking load by an average of 1048kg – more than one tonne. That’s between 9.1 and 12.5 per cent, depending on the rating of the strap.

Megastrap’s 11,000kg and 8000kg straps, Mean Green’s 8000kg strap and Terrain Tamer’s 11,000kg strap all experienced a reduction in breaking load of more than 1.1 tonnes when wet.

Only Kaymar and Bushranger offered straps (both rated 8000kg) that exceeded their minimum breaking load specification when both wet and dry. Super Cheap Auto’s 8000kg, Megastrap’s 8000kg, Mean Green’s 8000kg and Terrain Tamer’s 11,000kg strap came credibly close to their minimum breaking specification when wet, however.

How much did they stretch? That didn’t vary much, with the range being 15 per cent (Mean Green 8000kg, Terrain Tamer 11,000kg and Bushranger 8000kg) to 24 per cent (Megastrap 11,000kg). Among the 8000kg straps that passed the dry minimum breaking load test, Black Rat’s offers the most elongation, at 23 per cent.

CONCLUSION
Based on the relative results, it is extremely difficult to find a good reason to recommend any strap that our testing indicates did not match or exceed the manufacturer’s claimed performance. In comparing the straps, we awarded a winner and a runner-up, then divided the remainder into three categories indicative of the straps’ relative performances.

To fit into the ‘Highly Recommended’ category, a strap had to exceed its manufacturer’s rated load before breaking (dry) and exceed 90 per cent of the manufacturer’s rated load before breaking when wet. To fit the ‘Recommended’ category, a strap had to exceed (or come damn close to exceeding) the manufacturer’s rated load before breaking (dry), and exceed 85 per cent of the manufacturer’s rated load in the wet. ‘Not Recommended’ straps comprise the remainder – that is, the straps that failed to come within a reasonable margin of the manufacturer’s claimed minimum breaking load in our tests, and continued to under-perform in the wet.

WINNER
Kaymar 8000kg For exceeding the manufacturer’s minimum break load by 1288kg during our dry-break test, continuing to exceed that limit by 681kg in the wet-break test, and offering an impressive 20 per cent stretch at 50 per cent of the rated 8000kg load.

RUNNER-UP
Bushranger 8000 For exceeding the manufacturer’s minimum break load by 679kg during our dry-break test, continuing to exceed that limit by 281kg in the wet-break test, and offering 15 per cent stretch at 50 per cent of the rated 8000kg load.

HIGHLY RECOMMENDED
Black Rat 8000kg (Best stretch in the 8000kg class – 23 per cent)
Mean Green 8000kg
Terrain Tamer 11,000kg
Megastrap 8000kg
Super Cheap Auto 8000kg


RECOMMENDED
Megastrap 11,000kg (Best stretch in the 11,000kg class – 24 per cent)
Mean Green 10,000kg

NOT RECOMMENDED
Terrain Tamer 8000kg
Ox 8000kg
Repco Mortorguard 7500kg
Megastrap 9500kg
ARB 8000kg
ARB 11,000kg
Super Cheap Auto 9000kg

THANKS TO
Beaver Sales Height Safety and Confined Space Testing Centre, 142 Magower Rd, Girraween (02) 9896 3088, home of the mighty Hung-Ta tensile test machine. If it can hurt you, chances are the Beaver boys can test it.