TorqueTalk

NZ4WD - - CONTENTS -

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.

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