Shearing and twisting of metal components (frames, driveshafts, diffy halfshafts) is a result of the torsional stress limit of that component being exceeded.The typical culprit here is torque...too much force being exerted on the component in too short a span of time. Here's an analogue: Your body can withstand going zero to 100 mph in 6 seconds...think sportbike. Your body cannot withstand the same change in velocity (100 to zero) in one tenth of a second...think sportbike into concrete barrier. The killer here is time...or more specifically, it's effect on the magnitude of acceleration. Import cars, even the ones that are built to the nines, don't generate a whole lot of low-end torque. If you were to look at a plot of their dyno sheet against time, you'd see that they don't put down a shitload of increase in a small timespan. And while they may be pushing 800+ HP, they do it in the upper RPMs with significantly less torque. They build a lot of power, and some of them even put down a lot of torque...but... At no point do they produce enough torque in a short space of time to exceed the structural limits of their frames. Big tractor-trailer engines, however, can go from zero to 2000 ft-lbs in the blink of an eye...so they're designed with this in consideration and placed into big-ass frames. That's why our halfshafts shear off under wheelhop during hard launches...as the rear wheels bounce on the ground, the shafts rapidly oscillate from a condition of extreme torsional stress to almost none...the metal cannot withstand such changes of force in such a narrow timeframe and twists itself apart.
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13:26:04 12/31/02
