Smoooth . . . or not?

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Horse
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Smoooth . . . or not?

Postby Horse » Tue Jan 19, 2016 3:41 pm

In the recent long discussion about relative civilian / police standards, one comment was made that a significant, noticeable, difference would be that the civvie driver would be smoother than the trafpol.

OK, it sort of makes sense that someone who's objective is 'getting there' might offer a little smoothness in return for some added progress.

But . . . don't all of the 'racing' experts tell us that "smoothness is the key to going fast" or similar?

Picked at random from Google:
http://www.drivingfast.net/car-control/ ... riving.htm
If you only learn one skill to improve your driving technique it should be the art of smooth driving. On the track, driving smoothly allows you to minimise weight transfers, make the most of every last bit of grip, and maintain control at higher speeds.
Remember, if you're driving at only 50% of the car's potential, you'll be able to get away with changing gear roughly and braking, accelerating and steering aggressively. But when you're driving near your car's limits these actions can lead to loss of traction, poor track times and increased risk of an accident.


So how come the trade-off is acceptable?
Your 'standard' is how you drive alone, not how you drive during a test.

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akirk
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Re: Smoooth . . . or not?

Postby akirk » Tue Jan 19, 2016 5:11 pm

I think it is because to be very smooth at very high speeds requires an extremely high skill level - you can gain speed proportionally faster with less smoothness and less skill level than to gain the skill needed for the smoothness to get the extra bit of speed... on a track it is repeatable and many other factors are neutralised - it is then down to shaving off hundredths of seconds - therefore smoothness starts to play a higher weighting in how the speed is affected - on the road, I think that the difference in speed is negligable, but the difference in skill required is much much higher - therefore a better balance of result is quite a bit less skill, only slightly less speed...

and in saying this I am not denigrating the skills of an advanced police driver - merely observing that their skill in that small aspect of driving may not be as high as is possible to get to, their skills may be more focused on other issues (such as observation) - overall they are undoubtedly still very skilled...

someone else may phrase it better, but hopefully that makes sense?

Alasdair

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Adamxck
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Re: Smoooth . . . or not?

Postby Adamxck » Tue Jan 19, 2016 5:12 pm

Perhaps it's not a lack of smoothness that is the difference, but the amount of force and how it is perceived by the car's occupants.

Take an approach to a 30 limit from an NSL. It was suggested that a police driver would accelerate up to the point where they would need to brake in order to be at 30 by the time the reach the sign. Done correctly,the braking will be smooth but very firm. The car will be right on it's nose and everybody inside the car will be 'pulled' forward by the g-force.

A civilian driver might brake earlier and less firmly, or not at all if they decide they just want to lift and use acceleration sense to get down to 30 by the time they reach the sign. Far less deceleration force at work and therefore less noticeable to the occupants.

I'm not sure that really addresses your point, but I suppose its the same as being driven around a track by somebody who knows what they are doing. It's not jerky, but you still get thrown about.
Adam.

TripleS
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Re: Smoooth . . . or not?

Postby TripleS » Tue Jan 19, 2016 5:30 pm

akirk wrote:....I am not denigrating the skills of an advanced police driver....
Alasdair


No, you don't need to do that: I will already have been seen as doing that in my questioning of the degree of difficulty in producing an emergency response drive, when I ventured to suggest that producing an ERD to a reasonably good standard should be within the capability of any good driver. :mrgreen:

Others will disagree, but that's fine: I might be wrong. :)

But to respond to the question raised by Malcolm, in the context of road driving, for most normal purposes smoothness is the most desirable quality, I would say. I suppose there may be situations in which sacrificing smoothness for the sake of extra speed could be the way to go, but for the most part I suspect it isn't.

Best wishes all,
Dave.

Playtent
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Re: Smoooth . . . or not?

Postby Playtent » Tue Jan 19, 2016 8:31 pm

Horse wrote:In the recent long discussion about relative civilian / police standards, one comment was made that a significant, noticeable, difference would be that the civvie driver would be smoother than the trafpol.

OK, it sort of makes sense that someone who's objective is 'getting there' might offer a little smoothness in return for some added progress.

But . . . don't all of the 'racing' experts tell us that "smoothness is the key to going fast" or similar?

Picked at random from Google:
http://www.drivingfast.net/car-control/ ... riving.htm
If you only learn one skill to improve your driving technique it should be the art of smooth driving. On the track, driving smoothly allows you to minimise weight transfers, make the most of every last bit of grip, and maintain control at higher speeds.


"make the most of every last bit of grip" That quote sums up the racing driver who knows the track and could probably drive it with their eyes shut. They have no cars coming in the opposite direction and don't have the risk of a pedestrian, bus or milk float pulling across in front of them. Hence the reason on the road that you can't make the most of every last bit of grip. Because your not driving at 10/10's then smoothness is not as important as it would be on a track when your driving at 10/10's.

Horse wrote:
Remember, if you're driving at only 50% of the car's potential, you'll be able to get away with changing gear roughly and braking, accelerating and steering aggressively. But when you're driving near your car's limits these actions can lead to loss of traction, poor track times and increased risk of an accident.


The civilian advanced driver would spend a lot of time driving the car at 50% of it's potential whilst the Police driver would be far nearer to the limits of the vehicles potential. Hence as described above the risk involved is greater so the skill level required is higher. In order of priority for a Police drive it would be safety, progress, smoothness, whilst the civilian would be safety, smoothness and progress.

We're not talking about split seconds saved or maximum progress, we're talking about the balance between progress and safety whilst being as smooth as possible. Drive a track at 50% of its maximum speed and you could be as smooth as silk, the same on the road. Start pushing to 80% and it's more difficult to achieve that smoothness and requires a higher skill level. Do it hour after hour and that skill level becomes even higher.

Horse wrote:So how come the trade-off is acceptable?


There is no trade off. Put the civilian driver at the same speed as the Police driver and their smoothness would suffer far more than the Police driver.

I struggle to see how driving down a road at 60-70mph using acceleration sense/mild braking to set yourself for a corner some 50m away can compare to the Police driver on the same stretch of road at 120mph using very firm progressive braking to shave off more speed than the civilian driver is actually travelling and setting for the same corner 200m away. Which would feel smoother to your passenger? I'm sure the driver shaving 20mph off their speed would feel smoother than the Police driver shaving 75-80mph off in a similar distance.

Rest assured, if your doing a 3 car overtake at 120 you need to be smooth. If your driving on the motorway at 150, you need to be smooth and its far harder to be smooth at 70 than it is at 30.

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Horse
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Re: Smoooth . . . or not?

Postby Horse » Tue Jan 19, 2016 9:27 pm

Just to clarify : it wasn't me who suggested that would be an observable difference. But I did say that I'd expect a trade-off!
Your 'standard' is how you drive alone, not how you drive during a test.

Astraist
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Re: Smoooth . . . or not?

Postby Astraist » Tue Jan 19, 2016 9:50 pm

Horse wrote:OK, it sort of makes sense that someone who's objective is 'getting there' might offer a little smoothness in return for some added progress. But . . . don't all of the 'racing' experts tell us that "smoothness is the key to going fast" or similar? [...] So how come the trade-off is acceptable?


Smoothness is the key to going fast on the track, because if you can drive the car in a none-smooth fashion and not meet the wall, than you weren't driving it fast enough to begin with, and - if you have a moment and need to react unsmoothly - chances are it's too late already...

That's all good and well for a closed circuit, where you ride much closer to the absolute limit, even though you don't actually drive 10/10s most of the time, even at the high-end of racing.

When you look into racing on closed roads (rallying) which is probably closer to police driving, than it becomes humanly impossible to be that accurate in driving consistently at such proximity to the limit, so any driver, based on his or her style, would choose one of two:

Drive signifcantly below the limit, in a smooth fashion.
Drive a bit faster in a destabilised fashion.

The latter involves taking "V" lines through corners which in racing pace tends to result in gently sliding the car into the corner. The added advantage is a better view through the corner and you tend to get a decent exit in expense of mid-corner speed which is generally immaterial.

The difference between the two driving styles is that the latter can unlock a bit more performance, but for a given precentage of the car's performance envelope being used (and a percentage of safety margin being maintained) - the former is faster.

On a road open the public, the safe limit for progress is lower so the added performance from driving in a destabilised fashion isn't tangible, so the smooth driving style is the only safe solution.

That is in no way to suggest that a smooth input is ramped up slowly. Particularly with braking and acceleration, but sometimes (albeit rarely, to me) even with steering.

Playtent
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Re: Smoooth . . . or not?

Postby Playtent » Tue Jan 19, 2016 10:21 pm

Horse wrote:Just to clarify : it wasn't me who suggested that would be an observable difference. But I did say that I'd expect a trade-off!


I actually think it was me! :D

waremark
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Re: Smoooth . . . or not?

Postby waremark » Tue Jan 19, 2016 10:43 pm

I would be surprised if police drivers corner anywhere near the limit of grip, at which smoothness might be an issue. Swift road drivers probably corner at 0.3 or 0.4 g compared with a limit of grip of around 1 g.

I wonder what is meant by smoothness in the racing driver context. When I see video of racing drivers they are generally working the steering wheel as they corner, whereas most of us smoothly wind the steering on, hold it constant for a bit, and then smoothly wind it off. Is the working at the wheel, or I could call it sawing at the wheel, which the best racing drivers do, smooth?

michael769
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Re: Smoooth . . . or not?

Postby michael769 » Wed Jan 20, 2016 8:52 am

I'd be wary of comparing the hand movements of a road driver with that of a race driver. The steering setup is very different in race cars to road cars and the manner in which you have to operate the steering control has to change as a result.

Smoothness also means something different on the racetrack than on the road. With road driving a major aspect of smoothness is the perceptions that any passenger would have of the drive - this is not a concern on the track, if you do have a co driver, they expect to be chucked about the inside (as much as the harness will allow). On the road not chucking your passenger (or driver) about imposes a degree of restraint in how you use the controls that generally exceeds that needed to keep the car on the road.

On the track smoothness is about dialing in very fast adjustments in position and speed, but without destabilizing the car. This requires very fast hand movements but without so much abruptness that you mess up the vehicles stability. At high speeds the boundary between stable and not stable is razor thin, and consistently achieving the highest speeds requires the driver to always place their control inputs right on the razor edge, so to speak. When this is achieved it will, to an observer outside the car still look like somewhat violent control inputs - our eye's and brains are not quick enough to pick up the differences (unless the driver's getting it really badly wrong) - the difference is only seen in terms of the outcome - ie in lap times or the car going off.

In racing terms the smooth drivers are the ones who have the strongest natural aptitude to find the razor's edge time after time - fundamentally this is what separates drivers in identical vehicles. This who lack that ability either find themselves in the gravel traps, or have to slow down their inputs (and thus their speeds) to maintain stability. Anyone can drive fast - doing it faster than everyone else whilst staying on the track is the skilled bit.

In reality even the Senna/Shumacher/Hamiltons of the world do not manage perfect smoothness all the time, they just get a bit closer more often than the rest of the field. Much of what you see them doing is correcting for their "failure" to find the razor's edge.


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