Could you increase steering feedback?
Discussion
It's a quite complicated equation - because by increasing steering feedback, you will almost certainly make something else worse - but, yes, there are lots of things you can do.
Essentially, they will fall in to 2 categories:
1) Compliance; look at harder suspension bushes (or rose joints in place of bushes), solid steering rack mounts or subframe mounts (if applicable), lower profile tyres, etc.
2) Geometry; the main factors that effect steering feedback are castor, kingpin offset and the gearing of the steering rack.
Essentially, they will fall in to 2 categories:
1) Compliance; look at harder suspension bushes (or rose joints in place of bushes), solid steering rack mounts or subframe mounts (if applicable), lower profile tyres, etc.
2) Geometry; the main factors that effect steering feedback are castor, kingpin offset and the gearing of the steering rack.
Agree with Sam_68 on this one - you're likely to make something else worse. Certainly without power steering, the low-speed effort required will be higher.
I'd be inclined to do one of two things before making changes:
1) Check that there's nothing stiff in the steering that's reducing feedback (eg. seized rubber bush, etc.)
2) Develop more sensitive hands
I'd be inclined to do one of two things before making changes:
1) Check that there's nothing stiff in the steering that's reducing feedback (eg. seized rubber bush, etc.)
2) Develop more sensitive hands
dilbert said:
Smaller steering wheel.
That can be a mixed blessing.The smaller (diameter) wheel will reduce the leverage and thus increase the resistance, but resistance in itself can easily overwhelm the other sensations.
Ayrton Senna used to have the engineers put into his race cars the biggest diameter wheel that would work space-wise. This gave him more incremental control over his inputs.
If you're going to make any changes to the wheel itself, I would rather start with a wheel that is thinner in section (assuming that it is not already thin). This makes the wheel better suited to steering with one's fingertips. A fat wheel tends to force one to use the palms of one's hands, which is awful for steering feel.
If the car in the OP does not have PAS anyway, it is more likely that feedback, as opposed to simple resistance, will be improved by the geometry and compliance changes suggested.
I also would not omit trying different front pressures, which can be a quick and costless means of getting a sense of what one is looking for.
Cheers.
flemke said:
dilbert said:
Smaller steering wheel.
That can be a mixed blessing.The smaller (diameter) wheel will reduce the leverage and thus increase the resistance, but resistance in itself can easily overwhelm the other sensations.
Ayrton Senna used to have the engineers put into his race cars the biggest diameter wheel that would work space-wise. This gave him more incremental control over his inputs.
If you're going to make any changes to the wheel itself, I would rather start with a wheel that is thinner in section (assuming that it is not already thin). This makes the wheel better suited to steering with one's fingertips. A fat wheel tends to force one to use the palms of one's hands, which is awful for steering feel.
If the car in the OP does not have PAS anyway, it is more likely that feedback, as opposed to simple resistance, will be improved by the geometry and compliance changes suggested.
I also would not omit trying different front pressures, which can be a quick and costless means of getting a sense of what one is looking for.
Cheers.
As you will know, if you lift the front wheels off the ground, you can turn the steering wheel easily. I would imagine that in this condition, you could turn the steering column, without using a steering wheel (that is to say, with it removed).
Changing the steering wheel in these conditions has no measureable effect on the steering system. There is no change in the resistance of the system as a result of changing the wheel diameter.
Changing the size of the wheel merely changes the steering rate, which is equivalent to changing the level of mechanical advantage.
If you have a big mechanical advantage, you can barely feel the road, but you have to turn the wheel a long way to get a significant stering input. The wheel is not very sensitive.
Equally if you have a small mechanical advantage, you can really feel the road. You don't have to turn the wheel very far to get a big steering input.
Adding power steering increases the mechanical advantage at the wheel and makes the steering less sensitive. Removing it has the opposite effect.
Using a big steering wheel gives big greater mechanical advantage, and less feel, and a smaller one, less mechanical advantage and more feel. Adding power steering is equivalent to using a bigger wheel.
The thing about all of this is that the range of practical wheel sizes is quite narrow. Below a given arbitrary size there can be more feedback than an average person can maintain control over. The only way to get more feedback is to be stronger. Equally the cabin is only so big, so the wheel wont get much bigger or less sensitive.
I suspect that Mr Senna suffered the same as anybody would given a powerful car with big tyres, and a tiny steering wheel. His sensitive, delicate arms, coudl not feel the grip, on those occasions where his muscles were struggling to fight too much steering feedback. The forces were so great, that he could not achieve any degree of precision.
Using a bigger wheel that was less sensitive did not matter because his arms were sensitive enough to detect the smaller signals from the road, but by comparison, he did not have to fight the wheel, and was less tired, and more effective in the long run.
Senna, assuming he actually used a bigger wheel, used a wheel that gave him less feedback, but a more comfortable experience. His skill, and not his brawn, was what won him races.
The steering reate can be changed in a number of places, but the easiest place to change iut a little bit, is at the steering wheel. If you want more adjustment, then you have to change the rate of the rack, or the lengths of the control arms.
Changing other geometries of the suspension may have an effect on the steering, although in an absolute sense, it can only directly affect the linearity of the steering system. Such effects (bounce steer) are small, and it must be debatable if they are noticed by the normal person.
Changing other suspension geometries, and weight distribution, may affect the feel of the steering, but any such effects are indirect. Such things affect the stability and grip of the vehicle, which is then experienced as a loss, or increase in grip. Such experiences will all be felt as a multiple of the mechanical advantage available at the steering wheel, brought about by the length of the control arm, the steering rack rate, and the size of the steering wheel.
(Still better watch out for those nutters like me in their £200 bangers though Flemke!)
Edited by dilbert on Sunday 10th February 00:07
dilbert said:
But surely there isn't any resistance in the steering system.
Yes, of course there is!Apart from the frictional resistance, there is the geometrically induced resistance I mentioned above.
The bigger the steering wheel, the more leverage the driver is able to exert to overcome this resistance.
A big steering wheel requires more physical movement to achieve the same steering rotation (circumference=pi x diameter so for example, 1 full turn of a 10" steering wheel relates to 31.4" of movement at the rim, wheras a 15" wheel requires 47.1"
.... but what Flemke is saying (correct me if I'm wrong, Flemke?) is that the corollory of this means that feedback through a bigger steering wheel gives a bigger movement at the rim, which is easier to detect.
For example, lets say the front wheels start running out of grip and the slip angle increases fairly suddenly by, say, 2 degrees:
With a 10" steering wheel, 2 degrees = 31.4"/180 = 0.17" (4mm) movement at the rim.
With a 15" steering wheel, 2 degrees = 47.1"/180 = 0.26" (6.6mm)movement at the rim.
Clearly, the driver is sensing a combination of weight (effort) and physical movement, but what you gain in the 'weight' element of the feeback by using a smaller wheel, you lose in the 'movement' signal.
Does that make sense?
Edited by Sam_68 on Sunday 10th February 01:36
Sam_68 said:
dilbert said:
But surely there isn't any resistance in the steering system.
Apart from the frictional resistance, there is the geometrically induced resistance I mentioned above.As I said...
With the wheels off the ground, there is no resistance. (At least you seem to be reasonable the negligable frictional losses in the rack, and various bearings).
I would agree that there is a resistance to a turning force once the wheels are on the ground.
The point is that the steering system is the same irrespective of the wheels being on the ground. The ground is not a part of the steering system since it never moves or changes. Equally I would say (although I suspect you wouldnt) that the steering works even if the wheels are not on the ground. The reason this must be true, is that if you become airbourne, and turn the wheel, when you land, you will start to turn in the direction you indicated whilst you were airbourne.
Without the presence of the ground, which is not (even) a (necassary) part of the system, there is no (o.k. negligable) resistance. There are only reaction forces.
If you are airbourne there is nothing for the steering system to push against, so there is no reaction of forces (is that your resistance?).
In the dynamic system, the best place to use the word resistance, is for when the wheels are sliding. The word 'resistance' in this context implies that the energy you put in to the steering wheel is turned to heat. The only time this can happen is when the vehicle is stationary, or when the wheels are sliding, and then only when the steering wheel is actually moving. (Which oddly is when the wheel feels lightest). Technically resistance to steering force is very small indeed.
Much more pronounced, in order are gyroscopic reaction effects in the road wheel, the spring forces of the tyre sidewall and the centrifugal/centripetal reaction forces of the vehicle mass as a whole.
Not a lot of point in considering the stationary feedback, and the sliding feedback is something Mr Senna would have been trying to avoid.
If you're interested in the dynamic feedback, then the thing which will change the "feel" of the steering most is tyres.
The springyness in the tyre sidewall, gives information about the steering forces being applied to the tyres, particularly on the limit of grip. This is known as the slip angle. A stiff sidewall will have more grip, but won't give much feedback. A soft sidewall will gove lots of feedback but not have much grip.
This only holds for smooth surfaces, because a stiff sidewall is grippier due to it not deforming under the steering forces, and being a more optimal shape for grip. Rough surfaces with soft walled tyres can give better grip, because the tyres are more likey to conform to an irregular surface profile.
Edited by dilbert on Sunday 10th February 02:28
dilbert said:
...Changing other geometries of the suspension may have an effect on the steering, although in an absolute sense, it can only directly affect the linearity of the steering system. Such effects (bounce steer) are small, and it must be debatable if they are noticed by the normal person.
Changing other suspension geometries, and weight distribution, may affect the feel of the steering, but any such effects are indirect. Such things affect the stability and grip of the vehicle, which is then experienced as a loss, or increase in grip. Such experiences will all be felt as a multiple of the mechanical advantage available at the steering wheel, brought about by the length of the control arm, the steering rack rate, and the size of the steering wheel.
I cannot understand why you would think that linearity is not part of "feedback". I'd say that is an important part of steering feedback.Changing other suspension geometries, and weight distribution, may affect the feel of the steering, but any such effects are indirect. Such things affect the stability and grip of the vehicle, which is then experienced as a loss, or increase in grip. Such experiences will all be felt as a multiple of the mechanical advantage available at the steering wheel, brought about by the length of the control arm, the steering rack rate, and the size of the steering wheel.
As you said (I took out most of your post for graphic simplicity), the practical range of wheel diameters is not that wide. I don't know whether you have experimented with different diameter steering wheels on a car. I have done so on a number of vehicles, and the difference in effort required is surprisingly big.
You seem to think that the word "resistance" can relate only to the friction in an unladen steering system. I think of the word differently, but no matter. Your point was that a smaller steering wheel is harder to turn than a big one, and my point was that "harder to turn" is not synonymous with "feedback".
If you've ever tried to steer a PAS car after it has stalled, you will know that the effort required is great. In fact, your hands, arms and shoulders are working so hard just to rotate the wheel that their inherent sensitivity, which has not evolved to be optimal in such conditions as those, is dominated by the effort of the bigger muscles and their demand for increased oxygen. Feedback, that is, richness and clarity of information received, does not automatically go up with effort required.
Mario Andretti once made a driving instruction video in which he advised one to do the majority of the steering control with the "inside" arm because, he said, the muscles in use are more sensitive than those of the "outside" arm. There are other factors that bear on this advice, such as how much lock is on, how much the car is rolling, and how well fixed in the seat the driver is. If you do a bit of steering whilst thinking about this advice, I think you will find that, although the outside arm/shoulder want to do more of the work because they are the stronger, the inside arm/wrist/fingers are receiving a great deal of information - despite the fact that the outside arm is doing the bulk of the effort to keep the lock on.
Cheers.
dilbert said:
With the wheels off the ground, there is no resistance. (At least you seem to be reasonable the negligable frictional losses in the rack, and various bearings).
The frictional resistance in rack and bearings (and inertia, remember) is not negligible, in terms of steering feel. Most race teams go to great pains to minimise it, particularly since the initial 'stiction' does a lot to deaden the small signals that are so valuable to driver perception of what is going on at the contact patch.The whole point of striving for good steering feedback is to be able to detect really quite fine levels of information about tarmac quality and slip angles.
dilbert said:
The ground is not a part of the steering system since it never moves or changes.
Eh? Which planet do you live on? I can only assume it isn't this one, because down here we tend to use a strange blend of crushed rock and tar as a road surface, whereas they obviously use mirror-smooth, perfectly flat, continuous sheets of some other material where you live? And your road surface must have a perfectly constant coeffiecient of friction and no rain, presumably? And you've found a way to stop all vehicles leaking oil and spilling diesel? And there are no changes in camber or vertical alignment? Gee.... it must be boring driving there, though?
dilbert said:
In the dynamic system, the best place to use the word resistance, is for when the wheels are sliding. The word 'resistance' in this context implies that the energy you put in to the steering wheel is turned to heat. The only time this can happen is when the vehicle is stationary, or when the wheels are sliding, and then only when the steering wheel is actually moving. (Which oddly is when the wheel feels lightest). Technically resistance to steering force is very small indeed.
No!! We are talking about feedback. The tyres are sliding and moving continuously except when the car is stationary. Here on our planet, imperfections in the 'tarmac' (as we call it) mean that there are small vertical and scrub displacements of the tyres even when the car is running in a straight line, and of course when cornering they are always operating at some slip angle.You're thinking in reverse... it's not about the energy you are putting into the steering, it's about the energy the steering is delivering to you...and most importantly how well it enables you to detect very small changes in the amount of that energy!
Incidentally, the wheels are always either stationary or sliding... even in a straight line, on your planet's perfect roads, there is some longitudinal slip at the tyre contact patch, not to mention the effects of toe, camber and other geometry factors. So by saying 'the only time that resistance can occur is when the tyre is stationary or sliding', you are basically saying 'the only time that resistance can occur is all the time'!
...the exception being when a car becomes airborne, when I would agree that steering feedback is usually pretty limited.
Dilbert said:
Much more pronounced, in order are gyroscopic reaction effects in the road wheel, the spring forces of the tyre sidewall and the centrifugal/centripetal reaction forces of the vehicle mass as a whole.
I agree. Which is why you've got to take such great car to ensure that the relatively small signals of feedback being fed up from the tyre contact patches via the steering system are not masked out by other factors.Dilbert said:
Not a lot of point in considering the stationary feedback, and the sliding feedback is something Mr Senna would have been trying to avoid.
That's about as wrong as it's possible to get! Sliding feedback is exactly what Mr Senna would have been trying to assess, since it told him how far into the tyre's slip/grip curve he was operating.Dilbert said:
If you're interested in the dynamic feedback, then the thing which will change the "feel" of the steering most is tyres.
Agreed. Tyres are very important, both in the way they feed back information from the contact patch (compliance) and in the way they generate (or more actuately, react to) forces in cornering, braking, acceleration and even steady state, straight line running on real-life tarmac.But the main consideration when designing/selecting tyres has got to be grip; quality of feedback is very much a secondary consideration. So you need to tune the rest of the system to make sure you are making the best of whatever feedback information the tyre happens to be giving you.
dilbert said:
The springyness in the tyre sidewall, gives information about the steering forces being applied to the tyres, particularly on the limit of grip. This is known as the slip angle. A stiff sidewall will have more grip, but won't give much feedback. A soft sidewall will gove lots of feedback but not have much grip.
Tyres are not that simple; sidewall stiffness is only one of the factors that governs slip angle and it isn't a straightforward case of stiffer=grippier, either... though as you say yourself, this only holds for smooth surfaces and there is no such thing, here on our planet, as a perfectly smooth road surface.If we lived on your planet, we could dispense with pneumatic tyres altogether and just apply a thin coating of rubber to the rim of the wheel itself, couldn't we?
I agree with your comment that sidewall stiffness is one of the factors that governs feedback, though; it falls under the 'compliance' category in my original post.
Ahh well.
I'm wrong again then.
Just be clear about it, and let me know that the steering has failed when the wheels are off the ground, so I can dismiss what you're saying as rubbish without reading it.
I'm not thinking about steering in reverse. In your world, it seems you ask the car where it's going.
In my world, I apply a steering input. If the car can't do what I ask I have to revise my strategy. It's a great idea because I have control over where I go. I have to have some idea of what the car will be capable of in the conditions, because if I exceed that capability, by a significan margin, nothin I can do will correct it.
By contast, you seem to let the car do what it wants, so that you can listen to it. My nly advide would be to make sure that you don't get too many trees in the window at the front. Clearly the closer they are to the front window, the worse it is.
I'm wrong again then.
Just be clear about it, and let me know that the steering has failed when the wheels are off the ground, so I can dismiss what you're saying as rubbish without reading it.
I'm not thinking about steering in reverse. In your world, it seems you ask the car where it's going.
In my world, I apply a steering input. If the car can't do what I ask I have to revise my strategy. It's a great idea because I have control over where I go. I have to have some idea of what the car will be capable of in the conditions, because if I exceed that capability, by a significan margin, nothin I can do will correct it.
By contast, you seem to let the car do what it wants, so that you can listen to it. My nly advide would be to make sure that you don't get too many trees in the window at the front. Clearly the closer they are to the front window, the worse it is.
Edited by dilbert on Sunday 10th February 10:57
dilbert said:
In your world, it seems you ask the car where it's going.
In my world, I apply a steering input. If the car can't do what I ask I have to revise my strategy.
This is really quite a scary discussion, if you are telling me you drive high performance cars? And you're telling me you take no notice whatever of the information being fed back to you from your tyres?In my world, I apply a steering input. If the car can't do what I ask I have to revise my strategy.
I don't let the car do what it wants at random, but yes, I do listen to what it tells me in response when I apply a control input. That's why it's called feedback, see?
Even before I 'apply a steering input', I'm listening to what the steering is telling me about the condition of the tarmac, and I judge my inputs accordingly.
If you don't take any notice of feedback, at what point do you 'revise your strategy'? If you drive a 911, I assume it's around the time you plough backwards through the bus shelter full of schoolkids?
edited to add:
I think I've worked out where you come from , though... it's Planet Playstation, isn't it??Edited by Sam_68 on Sunday 10th February 11:48
Sam_68 said:
dilbert said:
In your world, it seems you ask the car where it's going.
In my world, I apply a steering input. If the car can't do what I ask I have to revise my strategy.
This is really quite a scary discussion, if you are telling me you drive high performance cars? And you're telling me you take no notice whatever of the information being fed back to you from your tyres?In my world, I apply a steering input. If the car can't do what I ask I have to revise my strategy.
I don't let the car do what it wants at random, but yes, I do listen to what it tells me in response when I apply a control input. That's why it's called feedback, see?
Even before I 'apply a steering input', I'm listening to what the steering is telling me about the condition of the tarmac, and I judge my inputs accordingly.
If you don't take any notice of feedback, at what point do you 'revise your strategy'? If you drive a 911, I assume it's around the time you plough backwards through the bus shelter full of schoolkids?
Edited by Sam_68 on Sunday 10th February 11:44
dilbert said:
I'm not telling you anything.... (I wouldn't presume)
My apologies... your profile says you own a Porsche 911, albeit a non-functioning one. I shouldn't jump to conclusions... I can only hope that here in the real world, you don't drive anything fast that isn't operated by a little plastic hand controller.
Edited by Sam_68 on Sunday 10th February 11:58
Sam_68 said:
dilbert said:
I'm not telling you anything.... (I wouldn't presume)
My apologies... your profile says you own a Porsche 911, albeit a non-functioning one. I shouldn't jump to conclusions... I can only hope you don't drive anything that isn't operated by a little plastic hand controller.
Gassing Station | Suspension, Brakes & Tyres | Top of Page | What's New | My Stuff