Tuesday, Oct 21, 2003 at 13:08
When considering the strength/failure of the locating pin there are 2 separate criteria to consider, the shear strength and the bending strength. When the tongue is in place the pin is almost in pure shear. The pin is designed to withstand a certain shear load. When you place the pin through the snatch strap you introduce a bending load as
well because the load is now acting more towards the midspan of the pin, which the pin is not designed for. The pin is most likely
well overdesigned so for moderate snatching loads it will be able to cope with this combined bending and shear load. But if you really give it some it is going to probably fail by bending as experienced by brian’s mate. This isn’t so bad cause it most likely won’t be a catastrophic failure and send the pin flying, it will deform before it fails and hopefully you notice this.
With the tongue in place you will have greater strength and this is how the pin has been designed to be loaded. 4WD outlets carry “snatching tongues” for just this purpose.
I think maybe a small pin flying through the air is more dangerous than the whole tongue as the pin will probably pierce metal where as the larger tongue may just cause a big dent. In any case either is very dangerous and any non-essential people should be
well clear and out of the vehicle, your talking massive loads and high velocity if something gives way when snatching. Ideally your snatch strap should be the weakest link, not your terminal tackle at each end.
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