Cornering...

[Strangely Brown]

Well, this thread has shown me just how complex steering is!

My method has always been to:
Step 1: Gauge severity of corner, and slow down to an appropriate speed.

And how are you managing the first part of that?

And could you also elaborate on Step 2? How do you determine what steering action will or will not allow you to remain on the tarmac?

[StressedDave]

OK, talking about this whole 'start to steer' or 'hinting' business.

<techie bit, feel free to let your eyes glaze over until the close tag>
Cars corner because the tyres generate a cornering force. A handy way of describing how that force is developed is by the concept of a slip angle. This is the difference between where the tyre is pointing and where it is actually moving. If you like doing vectors and algebra is your bestest friend then you can work out a way of determining the slip angle from the component parts of what the car is doing at any given point in time. It's a fun exercise, but you don't need to know about it. All you do need to know is that you can generate a slip angle at the front wheels by turning the approximately round thing in front of you. You can only generate a slip angle at the rear once the car has deviated from the straightahead.</techie bit>

To get around a corner, you have to satisfy a couple of criteria:

1. You need to generate enough force to take you on the desired path. Too little and you disappear either into shrubbery on right hand bends, or oncoming traffic on left hand bends. Neither is good.
2. You've got to develop the right balance between tyre loads so that the you end up pointing in the final direction of travel.

Now, you don't generate a cornering force at the rear until you're actually turning. So there's a period of time when the nose of the car turns quicker than you need it to - basically you start the car turning, but until you balance out the forces front to back, the rate at which it turns is too high.

The faster you initially turn the wheel, the worse this effect is. If you turn the wheel slowly then the difference between what you want and what you actually got is minimised.

Most (including those with the l33t skills developed by the IAM/RoSPA) drivers will go deeper into the corner than they need to and then whang on a load of steering. Because you haven't got everything in balance you tend to get the turning OK but not the 'going round the corner' bit. It feels like you've got a lot of understeer. Car manufacturers recognise this and give a car more grip than is necessary (at least at the sporty end. Now consider what the motoring press mean when they talk about turn-in) to stop it feeling like terminal understeer.

So, back to 'start to steer' and 'hinting'. They're the same side of a coin - the description may not help particularly because it's far better seen in the flesh.

'start to steer' needs the next bit 'and keep adding to the steering until you're on the line you need' and an understanding that the rate at which you steer can change. If you're doing it right, the rate of steering is never negative, unless you want to play at being Tiff Needell with the helium elbows.
'hinting' is described by Don as asking nicely before you do something or as he puts it 'Darling, please'. It's not necessarily a case of a small step steer before a bigger one.

and a final note THIS NEEDS TO BE DEMONSTRATED BY SOMEONE WHO KNOWS WHAT THEY'RE DOING. You cannot learn this shit from a forum.

[Horse]

So, back to 'start to steer' and 'hinting' . . . It's not necessarily a case of a small step steer before a bigger one

And that's the confusion I had after reading about it, that it meant 'little steer' followed by 'big steer' (sounds like a cattle drive), instead of (as shown to me by Gareth and JC), little steer, followed by drive.

[Mr Cholmondeley-Warner]

Dave, could you graph steering input v. time? That may help to explain the concept... perhaps with and without hinting / start to steer? How the steering input affects cornering line would also be useful. I don't know if you have data logs that might help, or whether it's just a fag-packet drawing that's required. Thinking aloud here ...

(obviously the bend profile comes into play but if we just consider a simple fixed radius, maybe?)

[StressedDave]

It'll be a few days... but yes. I haven't got time to trawl through a couple of hundred hours of datalogs, but then again I think a proper diagram would be better than a noisy line.

[Revian]

Thank you...

<techie bit, feel free to let your eyes glaze over

actually I found that helpful. Some grasp of theory always helps me.

Now, you don't generate a cornering force at the rear until you're actually turning. So there's a period of time when the nose of the car turns quicker than you need it to - basically you start the car turning, but until you balance out the forces front to back, the rate at which it turns is too high.

This puzzles me a bit. My instinct was that as the rear wasn't turning the front would be inhibited from doing so, or at least not added to. And that as soon as the rear began to turn then the whole turning effect would increase. The car would be 'happier' because the stress front/rear (I nearly said on the chassis!) would be reduced.

So, back to 'start to steer' and 'hinting'....'hinting' is described by Don as asking nicely before you do something or as he puts it 'Darling, please'. It's not necessarily a case of a small step steer before a bigger one.

I'd imagined it as putting some stress on the tyre wall. Enough to tension it but not enough to actually create a slip angle.. And feeling this through the steering. I'm wrong there...

.and a final note THIS NEEDS TO BE DEMONSTRATED BY SOMEONE WHO KNOWS WHAT THEY'RE DOING. You cannot learn this shit from a forum.

Sadly, it's unlikely to be learned then...

Thanks again Dave.

Ian

[kfae8959]

THIS NEEDS TO BE DEMONSTRATED BY SOMEONE WHO KNOWS WHAT THEY'RE DOING. You cannot learn this shit from a forum.

Sadly, it's unlikely to be learned then...

You'd be welcome to come for a drive with me if you would like. I can't claim to know what I'm doing, but I have hung around with some of these people for a bit, so I might be of some use.

David

[Revian]

Pmd... I don't claim to be teachable either...

[TheInsanity1234]

Well, this thread has shown me just how complex steering is!

My method has always been to:
Step 1: Gauge severity of corner, and slow down to an appropriate speed.

And how are you managing the first part of that?

I'm not sure if I'm doing the limit point thing, but all I know is I simply drive at a speed which enables me to stop in the distance I can see to be clear.

Therefore, I see a bend, and start slowing down on the straight section (I used to do a bit of go-karting when I was younger, and I think some habits have stuck with me) until the distance I can see 'around' the bend stops reducing, and I'm travelling at a suitable speed to get around the corner.

Rewording that: On approach to the bend, I adjust my speed so I can stop at the point I can't see beyond the bend, then when the point I can stop at starts to move, I'm at a suitable speed to go around the bend.
Does that make sense?

Step 2: Turn the steering wheel in such a manner that I remain on the tarmac.

And could you also elaborate on Step 2? How do you determine what steering action will or will not allow you to remain on the tarmac?

Simple?

If the road curves to the left, I turn the steering wheel in the appropriate direction to get the car to follow the road.

I do try to be smooth with the steering, rather than jerking the wheel around.

I have to admit, I'm not quite sure what you're asking me

[Adamxck]

I think the idea was to make you really think about the different things that are happening and what you are doing/feeling. Its a method coaches use. They ask you a seemingly silly question, but once you start to think about it, there is more going on than first appears.

Maybe. Could be totally wrong.