Wednesday, August 20, 2008

Steering Timing

Ok, I haven't written anything for a long~~ time, mostly because there's no more activities (since Ryosuke is gone) and because I got tonnes of work piled on me... X-p

But I guess I can't run away from slacking off, whether by writing this blog post or taking a nap on the toilet bowl... X-p work has just got to wait.. :-p

Well, this post is not about any activity, more like an information supply.. X-p

Just wanted to talk about steering correction, the thing that we failed that led to the massive accident damage on 'Shiro Suisei' :-p Paul Brand, a Star Tribune journalist got this to say about skiding and steering correction :-)

"A car oversteers because of the "yaw" generated by the rear tires sliding while the front tires are still gripping the pavement. The vehicle is effectively a pendulum pivoting around a vertical axis through the center of the front axle. There are only two key issues to saving a slide like this -- steer the same direction as the back end is sliding, and make the steering correction right now!

Little actual correction of the wheel is optimal, but only if the steering is corrected virtually instantly. The key to this is the eyes -- look where you need the car to go, not where it's going. Because the hands naturally follow the eyes, by looking in the direction the car is sliding, the hands tend to make the right correction.

Sadly, inattention, distraction, lack of understanding, inexperience and panic tend to delay the driver's recognition, processing and response to the slide. This allows the slide to increase in angle, meaning the front tires are no longer pointed where the car is headed, and once the correction is begun, more steering input is necessary (because of the increase in the angle of the car).

Now, if the steering correction is properly dialed in, the pendulum effect begins to slow. If there's enough traction available from the pavement, the rear tires will finally stop sliding, and the vehicle is at the limit of the yaw/slide and ready to snap back in the opposite direction. In performance driving vernacular, the energy built up in the rear springs unloads as the tires regain grip, initiating the "second reaction" hook slide. This occurs because the driver does not recognize the pause of the pendulum and the impending second reaction, and the back end snaps back in the opposite direction while the steering is still corrected in the direction of the initial slide. The instant the rear of the vehicle begins to swing back in the opposite direction, the front tires are no longer pointed where the vehicle needs to go -- thus the start of the back-and-forth "fishtailing," or, in the racing world, "death wiggle."

To prevent this, the three steps necessary to save a rear-end slide are 'correct, pause, recover' -- or C-P-R in the motoring world. Steer into the slide just enough instantly, anticipate the pause as the back end rotation begins to slow, and continue to look where you need the vehicle to go. Prepare to steer back in the other direction at the same moment the back end begins to snap back. Timed correctly, C-P-R keeps the vehicle traveling in the same direction it originally was before the back-end sliding.

Thus, there's really no such thing as "overcorrecting." It's more of a delay in initial steering input, then a delay or lack of recovery -- turning the steering back toward the center/neutral position as the back end snaps back. It gives the appearance of overcorrecting because the front wheels, as the car snaps back, are still turned in the original direction of the skid. But it's because of the delay in recognizing and responding to the second reaction, not because the wheel was turned too much initially.

One final key point. In terms of how much steering correction to input, this is entirely dependent upon two things: How quickly the correction occurs, and how rapidly the pendulum or back end is rotating around. There are wimpy little slides on dry pavement that require only small corrections, but then there is the "mother of all slides" at higher speeds or on wet pavement that requires every bit of available steering wheel input/angle to keep the front wheels pointed where the vehicle is sliding. This is why the "shuffle steering" technique is so important. It doesn't matter how quickly the steering correction is done -- if the steering isn't turned far enough to keep the front wheels pointed where the vehicle is sliding, the back end is never going to pause, giving the driver a chance to recover.

The last words on this issue: What if you don't "catch" the slide? In racing terms, "if you spin, both feet in," meaning lock the brakes hard instantly and keep them locked until the vehicle comes to a complete stop, and if it's a manual transmission, push the clutch in to keep the engine running. This slows the vehicle as rapidly as possible and keeps the vehicle traveling in a straight line, hopefully right down the middle of the road, as it spins." --Paul Brand--

Apparently, what occured to us was the "mother-of-all" slides plus the "second reaction" hook slide X-p a deadly combination... Zid was able to correct the intial slide, but failed to anticipate the 'second reaction' and the force the rear throws back at us that sent us spinning like a drunken bumble-bee... X-p

Well, hope we've learnt a lesson from that, and improve on our pathetic skills X-p haha...
(I'll be posting more tips on advanced driving whenever I feel like slacking off again.. X-p or when I'm not sneaking away to the toilet for a nap... X-p hoho...)

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