Many mechanical devices are all-or-nothing, although you are right about a hand brake not being one of those (ever seen a sprag clutch?). If you think THAT'S scary, you should see how little material there actually is in items like your wheel spindles, wheel bearing contact surface area, etc. We put a lot of power and weight through just a few small bits of metal that are all there is between our backsides and a grisly death. The materials science involved is a really amazing thing.. The way most vehicles are set up, the actual ignition switch is a mechanical component that physically disengages contacts to cut power to the powertrain control module and controlled systems. So yeah, for most vehicles, you sorta do have a big red button. Also, most folks don't realize that brakes generally have several times the horsepower of the powertrain (typically, I hear the value of 5 times quoted, but I haven't seen that figure substantiated). That's why, at full throttle and with the torque converter at stall on an AT-equipped vehicle, which boosts engine torque output at 2:1 (typical figure), the front brakes still hold. Due to weight bias and brake system type, the rear brakes may or may not hold, but the fronts will. That's where the great majority of your braking power comes from anyway (ever wonder why front brake specs are always higher than rear?). Hauling the vehicle down from 100 or 150 kph to zero dissipates a LOT of energy, but even at full throttle, the brake system should be up to the task if it's been properly maintained. Of course, the way many/most maintain their vehicles, that can get iffy. Barring a mechanical failure in his brake system, this bloke should have been able to stop. The way he was talking about screaming, when he was finally able to stop, the real story is likely that he just panicked.
Sorry, g00ey, that's not how electronic transmissions and abs systems work. I know, I work on them all the time. And while there are a lot of cars that use RFID to start up, I've never seen one of those that's like anything you describe either. ABS works by pulsing the system pressure and bleeding it off. It doesn't fail in a hold-open mode, but hold-close. That's both for mechanical and electronic failures in the actual ABS part of the brake system. And typically, when a transmission controller stops working, most systems (the Ford in question is one of these, trust me, I,ve had LOTS of these units apart on my bench) the electronics are easily overridden by manually downshifting the stick. That's what controls the highest possible gear through a spool valve in the valve body; the shift solenoids just provide for control between 1st and the mechanically selected highest possible gear. Your understanding of TRACS is fairly accurate(but not quite on the money)--they also use retarded ignition timing and transmission upshifts to reduce engine output and wheel torque along with fuel system trim. I wouldn't bet on a system bus overload either. You have to realize that the computers operate at a few megahertz, but they are controlling mechanical events in the hertz to the kilohertz range, typically. They are very much up to the task. For instance, at 3000 rpm, a six-cylinder engine is only experiencing 9000 ignition and injection events per minute, that's 150 events per second per system. Each injector and spark plug is operating at 50 hertz. In computer terms, automotive mechanical systems are ridiculously slow. Fuel injector pulse width, for instance is typically in the 1-10 ms range. The control systems and communication buses COULD be at fault, but as someone else already stated, sounds like a human panic event. Those systems are built to a much higher physical standard than most of the hardware we typically see in a server room or on a desktop. Their operating environment requires it. From an automotive control systems point of view, not likely much to see here...move along.
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Many mechanical devices are all-or-nothing, although you are right about a hand brake not being one of those (ever seen a sprag clutch?). If you think THAT'S scary, you should see how little material there actually is in items like your wheel spindles, wheel bearing contact surface area, etc. We put a lot of power and weight through just a few small bits of metal that are all there is between our backsides and a grisly death. The materials science involved is a really amazing thing.. The way most vehicles are set up, the actual ignition switch is a mechanical component that physically disengages contacts to cut power to the powertrain control module and controlled systems. So yeah, for most vehicles, you sorta do have a big red button. Also, most folks don't realize that brakes generally have several times the horsepower of the powertrain (typically, I hear the value of 5 times quoted, but I haven't seen that figure substantiated). That's why, at full throttle and with the torque converter at stall on an AT-equipped vehicle, which boosts engine torque output at 2:1 (typical figure), the front brakes still hold. Due to weight bias and brake system type, the rear brakes may or may not hold, but the fronts will. That's where the great majority of your braking power comes from anyway (ever wonder why front brake specs are always higher than rear?). Hauling the vehicle down from 100 or 150 kph to zero dissipates a LOT of energy, but even at full throttle, the brake system should be up to the task if it's been properly maintained. Of course, the way many/most maintain their vehicles, that can get iffy. Barring a mechanical failure in his brake system, this bloke should have been able to stop. The way he was talking about screaming, when he was finally able to stop, the real story is likely that he just panicked.
Sorry, g00ey, that's not how electronic transmissions and abs systems work. I know, I work on them all the time. And while there are a lot of cars that use RFID to start up, I've never seen one of those that's like anything you describe either. ABS works by pulsing the system pressure and bleeding it off. It doesn't fail in a hold-open mode, but hold-close. That's both for mechanical and electronic failures in the actual ABS part of the brake system. And typically, when a transmission controller stops working, most systems (the Ford in question is one of these, trust me, I,ve had LOTS of these units apart on my bench) the electronics are easily overridden by manually downshifting the stick. That's what controls the highest possible gear through a spool valve in the valve body; the shift solenoids just provide for control between 1st and the mechanically selected highest possible gear. Your understanding of TRACS is fairly accurate(but not quite on the money)--they also use retarded ignition timing and transmission upshifts to reduce engine output and wheel torque along with fuel system trim. I wouldn't bet on a system bus overload either. You have to realize that the computers operate at a few megahertz, but they are controlling mechanical events in the hertz to the kilohertz range, typically. They are very much up to the task. For instance, at 3000 rpm, a six-cylinder engine is only experiencing 9000 ignition and injection events per minute, that's 150 events per second per system. Each injector and spark plug is operating at 50 hertz. In computer terms, automotive mechanical systems are ridiculously slow. Fuel injector pulse width, for instance is typically in the 1-10 ms range. The control systems and communication buses COULD be at fault, but as someone else already stated, sounds like a human panic event. Those systems are built to a much higher physical standard than most of the hardware we typically see in a server room or on a desktop. Their operating environment requires it. From an automotive control systems point of view, not likely much to see here...move along.