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Old 29th Aug 2006, 08:06
  #214 (permalink)  
Loose rivets
Psychophysiological entity
 
Join Date: Jun 2001
Location: Tweet Rob_Benham Famous author. Well, slightly famous.
Age: 80
Posts: 4,706
I put quite a lot of thought into my original post p3 #45 and can not really better it, except for going over the technicalities in a little more detail. I did make comment about the higher attainable speeds in modern cars, but I didn't really spell out the physics.

When the police Volvo passed me on that narrow road, he was AT LEAST two and a half times the speed limit. As I implied, probably for fun.

Most ppruners will know that doubling the speed, gives the mass 4 times the energy, but not all are clear just what this can mean for the modern car. It is my argument that these new high speeds are unacceptable on modern roads in a car that is really just an improved saloon.

The very nature of these new levels of energy is difficult to put into perspective. The old ‘stop in nnnn feet' really is meaningless, since most people wouldn't have the faintest idea what these distances look like while traveling at 159 mph., or even a modest hundred. A whole new set of physical rules apply.

Firstly, the gyroscopic effect on the wheels becomes very significant and as some may remember, the forces are precessed through 90 degrees before effecting a force on the suspension. At these speeds the suspension will be coping with forces way outside its design parameters, and the way it copes, is in reality, testament to the overall good design, but it simply can not be relied on to function correctly under these complex loads.

The traction, at any moment just a few square inches of very hot rubber, will have to cope with these new energies. At these speeds the equations are so complex that designer and driver alike will be unaware of the exact processes taking place. Remember, this is a car made to drive sportily at the most, not one to compete with F1 technology, that has millions spent analyzing telemetry. Even with that incredible expenditure, some of the feedback is totally unexpected.

As the speed rises, so reliance on luck will play a greater and greater part in the progress, and no amount of training will turn this modest vehicle into a race car.

This complex string of variables is continuously having its datums altered, by weather and changes in driving techniques for example. The calculations become impossible to process, so progress is made with a certain skill...and a lot of luck. It is the reliance on luck that is unacceptable.
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