![]() The front impacts 0.5 m (slow down distance) as above. The same car as above falls from height 14.2 m and crashes on the crumple zone with the front down on a massive concrete tarmac. S = m a g h / F avg (5c) Example - a Falling Car The deformation slow-down distance can be expressed as If the dynamic energy from the fall is converted to impact work - equation 2 and 4 can be combined to The dynamic energy in a falling object at the impact moment when it hits the ground can be calculated asį weight = force due to gravity - or weight (N, lb f )Ī g = acceleration of gravity (9.81 m/s 2, 32.17405 ft/s 2 ) For a car crash with 90 km/h (25 m/s) the de-acceleration will be 64 times gravity (same parameters as above). Note that the National Highway Traffic Safety Administration (NHTSA) states that "the maximum chest acceleration shall not exceed 60 times gravity for time periods longer than 3 milliseconds ". The impact creates a force 28 times gravity!!Ī person sitting inside the car with seat belts on will de-accelerate with a force 28 times gravity. Note that the gravitation force (weight) acting on the car is only The front of the car impacts 0.5 m (the deformation distance).į max = 1/2 (2000 kg) (16.7 m/s) 2 / (0.5 m) Example - Car CrashĪ car with a mass of 2000 kg drives with speed 60 km/h (16.7 m/s) before it crashes into a massive concrete wall. Note! - The deformation slow-down distance is very important and the key to limit the forces acting on passengers in a car crash. The deformation slow-down distance can be calculated as The average impact force can be calculated as In a car crash the dynamic energy is converted to work and equation 1 and 2 can be combined to In an impact where the object is not deformed - the work made by the impact force slowing down the moving object equals to the work done by a spring force - and can be expressed asį max = maximum force at the end of the deformation (N, lb f ) When a crumple zone deforms in a car crash the average impact force is designed to be as constant as possible. S = deformation distance, crumple zone (m, ft) In an impact - like a car crash - the work made by the impact force slowing down an moving object over a distance by deforming the crumple zone can be expressed asį avg = average impact force during deformation (N, lb f ) F1 cars at least get the luxury of sitting in a custom-molded cocoon to withstand the G forces, karters get a little flap of fiberglass.The dynamic kinetic energy of a moving object, like a falling ball or a driving car, can be expressed as 1.5 G is a shitload whether people realize it or not, that's 1.5x your body weight pressed up against a cafeteria lunchroom seat, that's nothing to scoff at. ![]() The problem is people just want to say what sounds cool rather than what an honest number really is. I've been in a rental kart with so much grip it would go up on two wheels in a hairpin, but to be fair that was because it had oil soaked into the tires and that acts like a tire prep. Then again, higher track use with more rubber laid down would make a big difference as well, both with the Rotax and rental kart. I should also note that there are softer tires out there than what I was running, MG Greens would probably add a little bit more G force. Likewise, the rental kart G's are probably like 1.2-1.3 sustained with peaks of 1.5+ G. When one of the car magazines subjected a shifter kart to a standard lateral G test (Motor Trend? Road and Track? Car and Driver? One of those.) they got 1.5 G sustained, which is about what my video would support since jolts above 2 are more from the rocking of the kart and bumps than true handling G's. ![]() There is one 3G peak somewhere in that lap for all of 1 frame, but it's not a sustained grip.
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