Minggu, 11 Maret 2007

Shifting Technique a great article

I regularly get friends asking me to take them out for a few hours driver training, so they can improve their skills and tell their mates they've been taught "by a proper Police Instructor".

If I get a full day with someone, I can give them a little taster of most aspects of advanced driving. A sort of Chinese buffet, starting with the basics of smooth car control, moving on to improving observations and planning, and then, if I've got some confidence with their ability, doing some higher speed cornering and overtaking. There's no way I could get anywhere near teaching someone everything they'd learn on a full course, but they get a small sample of most aspects, and I've never had anyone who doesn't think they've improved at the end.

Occasionally though, time will be limited, and someone will ask me to take them out "just for an hour or so" and teach them something.

So I always teach them something with which they'll feel a difference immediately, and which they'll go away and practice. It's also something that their regular passengers will notice immediately (a number of wives have already thanked me ) and it's something they can show off to their mates if they are so inclined.

I teach them to change gear.

"Teach them to change gear Reg? Don't be daft - everyone knows how to change ruddy gear. Except for the Americans and they're too fat to use a proper gearstick."

Well, most people do know how to change gear in a manual car, and some people know how to change gear smoothly, but I can teach people to change gear so smoothly they can out-smooth Sean Connery (before he lost his hair and starred in Highlander).

It's a well established fact that you should operate a cars controls smoothly, but why? What difference does it make? To be honest, it doesn't make a great deal of difference at lower speeds - my mum is rougher with the gearstick than Big Daddy used to be with Kendo Nagasaki, but she only trundles round at town speeds, so it's never caused her a problem. The point at which smooth car control does start to matter is when the speed increases. When a car is travelling at high speed, the potential weight transfer either under heavy braking, hard acceleration, or high-G cornering is very high, and it's this transfer of weight across the car which can seriously unsettle it if it's not done smoothly. Changing gear is one way of transferring the vehicles weight backwards and forwards, and so, if you can do it as smoothly as possible, the weight balance of the car moves around in a more stable manner, and your progress will be safer. Plus, your passengers will appreciate it too.

So, what's the secret? Well, it's not one thing, but, as with most things in driving, it's a series of actions which must be coordinated and timed to perfection in order to get it right. I've seen grown men - some of them high ranking Police and Army officers, congratulating themselves, and feeling chuffed to pieces at getting one gearchange correct. Remember, these are people who make life-or-death decisions, and they were impressed enough with their own improvement in a basic driving skill, to say "let's do it again" with a big grin on their faces.

In true driving school style, I'll split the subject into two sections. Predictably enough, they are...

1. Changing up through the box.

2. Changing down through the box.

But before I move on to the more advanced sections 1 and 2, lets start with how you move the gearstick.

Most people simply change from the gear that they are in, to the gear they want to be in. But in reality, it's slightly more complex. What you're doing is taking the car out of the gear it's in, putting it into neutral, taking it out of neutral and then putting it into the next gear. I know they sound the same, but there's a very subtle difference, and if you can get into the habit of pausing for about 1/2 a second whilst in the neutral phase, you will give yourself enough time to operate the most important pedal for smooth gearchanges - the accelerator.

Oh, and a quick note on holding the gearstick. Police driving schools teach the "thumb up and thumb down" method and I quite like it, as it encourages you to place sideways pressure in the correct direction, and helps to avoid selecting the wrong gear. Basically, hold the gearstick with the palm of your hand, and if you're selecting first or second, point your thumb down. If you're selecting third, fourth or fifth (or sixth!), point your thumb upwards. If you place the pressure on the gearstick with your palm, you'll always move the gearstick in the right direction.

Most gearboxes are sprung so that the stick "rests" in neutral between third and fourth gears, so sideways pressure is only ever needed when selecting first, second and fifth (and sixth) gears. Changes to third and fourth just involve a movement either straight forward, or straight back from the neutral plane.

Right - back to 1 and 2.

In explaining how to change up through the 'box, I'm going to assume that you'll move the gearstick correctly, as described above - most importantly, including that essential pause in the neutral phase.

The most important aspect of changing up correctly is what you do with the accelerator pedal. A lot of drivers will press the clutch and completely release the accelerator pedal whilst they change gear. They will then release the clutch prior to re-applying the accelerator. This technique will usually result in the car jerking forward when the clutch is released because the engine speed doesn't match the road speed for that gear. This jerk is more pronounced in lower gears than it is in higher gears.

The way to avoid this jerk is to release pressure on the accelerator before and during the gearchange, but not to release it completely. I'll talk you through it.

Lets assume we're about to change up from 2nd to 3rd in an average car, at about 40MPH. In this imaginary average car, the engine will be doing 5000RPM at 40MPH in 2nd gear, and 3000RPM at the same speed in 3rd.

Before you start to change gear, ease off the accelerator slightly so the rate of acceleration slows. Then press the clutch and change gear as described previously. Whilst you're changing gear, ease the accelerator back until the revs have dropped from 5000 to 3000, and then hold the revs there whilst you release the clutch. Once you've released it, squeeze the accelerator, and continue accelerating. Allowing the revs to drop correctly will remove that jerkiness from the up-change, and you'll notice the difference immediately.

Changing down is very similar, but the process involves raising, rather than lowering the revs. Racing and competition drivers "blip" the throttle on down-changes to match engine speed to road speed, but I'm talking about road driving, which is slightly different. A blip is only suited to very fast gearchanges, which aren't necessary on the road, so in advanced road driving, the revs are raised during the downchange, and not blipped.

As you're changing gear, squeeze the accelerator gently to raise the revs from 3000 to 5000, release the clutch, and then continue accelerating.

It's taken me ages to explain something which can be done in around a second, and it's far easier to teach by demonstration and then trial and error, than it is to write it out, but I think that's my best explanation.

Have a go tomorrow when you get a chance. Don't just change from 2nd to 3rd - I always get students to drive along a straight piece of road at 50MPH, and change randomly through the 'box, without losing road speed. the gearchange will always be heard, but the point is that it shouldn't be felt.

Then, when you've practiced for a bit, see if anyone notices.

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