Thanks for the rule of thumb on belt power, Adam. I checked my own source and found a slightly more conservative value, but not enough to warrant a discussion. One of the Youtube comments reckons the engine recorded a torque of 3554 ft lb, but that was presumably somewhat before the belt loss, certainly 3554 ft lb on a pulley approximately the same diameter as the engine flywheel at an estimated 190 rpm (using a musical tempo meter) gives 125 horsepower - quite a lot!
Looking back at the video from the flywheel side again; Shortly before the incident, the belt is oscillating at the same frequency as the chuffs. That to me suggests a resonance between the belt natural frequency and engine running speed. The brake is then wound further down and the engine starts to lose the battle with revs. dropping dramatically, I think the video also shows that the belt is slipping by that stage. Then the inevitable happens.
If the engine revs are dropping and the belt is slipping you are clearly way past the optimum point for transmitting useable power from the engine. Does that not tell you something?
Martin
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