本帖最后由 anordinaryman 于 11-5-31 12:25 编辑 ray9394 发表于 11-5-30 18:12 看过了,对翻车的原因作出了很好的分析(虽然好像是冲着Ford而来), 文中所说摩擦力是用来给车子转向(不然车子便会滑了出去),并强调这不是(留意作者把NOT写成大草)构成翻车的原因: Our (horizontal) force in the previous drawing can therefore be thought of as a combination of two separate component forces. One of the component forces is directly toward the tread of the tire, as shown here. This component is actually the portion of the force that actually acts to give the vehicle sideways force (through the tires' friction with the road) to make it turn. More to the point here, this component does NOT act to try to rotate/twist the vehicle. 抓地力不是翻车的决定因素这里应该说得很清楚了。 看到这里令我想到(只是想,不知是否实情)何以车手会有 ‘抓’ 翻的误解,由于现在很多车使用头直轴,很容易出现转向不足(推头)情况,不从设定上改善的话,车手就只好在打方向时惯性过度转向来增加轮胎的滑移角来弥补(令车轮转向角度大于实际转向轨迹),一旦遇到更高抓地力的场地,车手没有把这个习惯改变/适应过来,照样过度打方向,这时由于轮胎循迹能力增加,车子有更多转向,弯心半径(r)减少了,自然增加了翻车机会,便归咎于场地 ‘太’ 抓了。其实在这个情况下,车手只需要在操控上减少转向动作就可以避免了,当然,更彻底的解决方案是透过设定改善推头情况。 |
本帖最后由 ray9394 于 11-5-31 13:05 编辑 其实,我还没有全部看完。 但这篇文章的发表时间是在Ford Explorer (加Firestone轮胎)的意外后。 但是在文章开始时,已经提到: First, whenever a vehicle turns, Newton's First Law indicates that it wants to go straight, so the tires must therefore create a lateral "centripetal force". This is entirely due to friction between the tires and the roadway. If the road is icy and slick, there is generally not a high enough "static frictional coefficient" to cause the force described here. The vehicle would then not roll over but slide straight, possibly having DIFFERENT problems! A rollover situation can only occur if there is enough friction between the tires and road to create sufficient centripetal force. 就是说没有足够的摩擦力,反车是不会出现的。 |
本帖最后由 anordinaryman 于 11-5-31 14:17 编辑 回复 ray9394 的帖子 完全正确,但请留意所说是需要有“足够”(enough)的抓地力来达到所需翻车的车速(来提供“足够”向心力(sufficient centripetal force)),抓地力是车速条件而不是翻车决定因素(翻车决定因素在车速 (v) 及其他三个变数),因为若公式的值<1,任抓地力怎样无限的增加下去也不能构成翻车(因为抓地力并不参与翻车所需的向上力量把车抬起),抓地力对于翻车只是一个necessary but not sufficient condition。 |
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