Late last year a local 4WD Club had a “Bust It Night” that was billed as ‘carnage and mayhem.’ With a description like that it was intriguing and therefore I had to ensure I filled one of the limited places available. The night consisted of meeting at the work premises of one of the members which just happened to be the SGS Laboratory where tests are carried out on various products. In the case of this evening it would be the testing of various bolts, recovery hooks, the mounting of recovery hooks, and shackles as well as synthetic winch rope. The premises are equipped with a 60 tonne test rig which is used to test the strength of items. In the first few tests it was the shear strength of various 12mm bolts from normal grade 4.6 and 8.8 through to the 12.9 high tensile. Firstly they were just tightened up and the second sequence was with the bolts correctly torqued up. For the normal grade 4.6 torqueing didn’t seem to make any difference but on the 8.8 there was as much as 20 percent higher rating before it sheared. Moving on to bow shackles and all shackles tested were new items purchased specifically for the testing. The tests started with several of the smaller shackles normally used for say, safety chains on trailers. These bent the pins and fractured at 1.5 tonne. But it was the various 3.2 tonne rated shackles that provided some interesting differences. All the shackles came away bent and stretched but at different ratings. Starting with a yellow pin shackle purchased from Repco it reached 15.9 tonne before breaking. A couple of other shackles were tested and these managed 20 and 21.1 tonne before moving onto a couple of shackles from Bridons. The first one was a yellow pin type which is understood to be manufactured in China and this managed 20.7 tonne while the second one was a 3.2 tonne rated green pin shackle believed to be from Holland and this reached 28 tonne. A used snatch block, believed to be originally rated at 10,000lbs was next, and this stretched the eye before finally breaking it at 12.4 tonne. Next up was recovery hooks all supposedly rated at 10,000lb. Apart from one used hook, these were brand new from wellknown suppliers. The used hook tested first straightened out at 4.8 tonne while one of the new hooks also straightened or opened out at 5.4 tonne. One of the other new hooks took just over 10 tonne but broke the hook off for it to become a missile. Several tests were also completed on recovery hooks mounted to sections of chassis. For this test an actual section of a Suzuki SJ413 chassis was used for lighter vehicles and for heavier ones like Nissans some box section was used as an equivalent when the organisers were unable to find someone who would allow a section to be cut out of their chassis! Just bolting the recovery hook to the chassis showed that it would rip through ( the chassis) with ease at 6.2 tonne. Using plates either side of the chassis increased this to 6.4 tonne before pulling through. The highest rating came with the double plates either side of the equivalent of the Nissan chassis with the plate welded on one side with 15.4T but while the mounting seemed to survive, the ‘chassis’ fractured where it was restrained in the test rig. The real entertaining part of the evening was when it came to test 9.0mm synthetic winch rope. The small section of test rope initially stretched beyond the reaches of the test rig so it was shortened up. This highlighted the point that very few people know how to tie synthetic rope. A standard bowline slipped undone at 1.9t and again at 2.3t. A ‘ figure 8’ knot and a ‘ double figure 8’ knot lasted 3.7 and 4.1 respectively. Proving the point that knotting synthetic winch rope is not always best was what was termed ‘Pete’s Special Knot.’ This lasted to 5.1t before breaking at the knot. The evening was informative and educational as well as entertainment all rolled into one and certainly did meet the billing of carnage and mayhem. All testing was done at a gradual load and didn’t take into account the shock loading that is sometimes applied when using incorrect ropes or straps. But it also really did show that the equipment we use with our four-wheeldrives not only needs to up to a high standard but that mounting and correct use is just as important if not more so. When purchasing vehicle equipment and recovery gear, it is best to pay that lit tle bit more and buy direct from a reputable retailer, even when it comes down to the mounting bolts for recovery points. Stay safe out there.
Shackles on the test rig.