Cogging down into tight bends - motorsport Question
Discussion
GreenV8S said:
Obviously you'll want to match the engine revs during the gearchange so I guess you're looking for some way to operate the throttle and brake pedals at the same time as the clutch. If only there was some way to do that ... 
HahahaI was just wondering what the best way to cog down would be without locking up
I think you've thankfully given me that information dear sir
jagdpanther said:
GreenV8S said:
Obviously you'll want to match the engine revs during the gearchange so I guess you're looking for some way to operate the throttle and brake pedals at the same time as the clutch. If only there was some way to do that ...
HahahaI was just wondering what the best way to cog down would be without locking up
I think you've thankfully given me that information dear sir
I'm no track driving expert, but I know a couple of tips that are particularly useful for track driving - particularly when entering tight bends.
Firstly, if you remain on the brakes up to and just past the point of turn-in, then the weight transfer forwards will aid your front-end grip, and give you a sharper, more responsive initial turn into the corner. The downside is that, conversly, there will be less grip towards the rear of the car, which can be dealt with through my second tip...
Be smooth coming off the brakes as well as going on to them. Jumping off the brakes suddenly redistributes the cars weight at a time when you're alsoe redistributing it laterally through cornering. Taking half a second longer to come off the brakes makes for a much smoother transition and keeps the car settled into the first part of the corner as you start to reapply the accelerator.
As for locking the wheels under braking, this is the reason why many competition drivers change down sequentially when entering a tight corner. Block changing from, say, fifth down to second, gives you more scope for getting your timing wrong on the heel-toe downchange, and locking your driven wheels up via the driveline. If you change sequentially, 5-4-3-2 whilst braking, this is less likely to happen.
Firstly, if you remain on the brakes up to and just past the point of turn-in, then the weight transfer forwards will aid your front-end grip, and give you a sharper, more responsive initial turn into the corner. The downside is that, conversly, there will be less grip towards the rear of the car, which can be dealt with through my second tip...
Be smooth coming off the brakes as well as going on to them. Jumping off the brakes suddenly redistributes the cars weight at a time when you're alsoe redistributing it laterally through cornering. Taking half a second longer to come off the brakes makes for a much smoother transition and keeps the car settled into the first part of the corner as you start to reapply the accelerator.
As for locking the wheels under braking, this is the reason why many competition drivers change down sequentially when entering a tight corner. Block changing from, say, fifth down to second, gives you more scope for getting your timing wrong on the heel-toe downchange, and locking your driven wheels up via the driveline. If you change sequentially, 5-4-3-2 whilst braking, this is less likely to happen.
R_U_LOCAL said:
As for locking the wheels under braking, this is the reason why many competition drivers change down sequentially when entering a tight corner. Block changing from, say, fifth down to second, gives you more scope for getting your timing wrong on the heel-toe downchange, and locking your driven wheels up via the driveline. If you change sequentially, 5-4-3-2 whilst braking, this is less likely to happen.
Not to detract from the reason you give, but changing down sequentially also enables the (we presume driven) rear wheels to contribute more to slowing the car.On the other hand, it can be hard to find time for all the downchanges, and the driver may prefer to have both hands on the wheel for more of the braking distance.
WilliBetz
Firstly, braking:
The accepted way to slow a racing car with maximum retardation is a technique called threshold braking. This takes more skill than road techniques like cadence braking etc, but is much more effective at stopping the car. If you can find a copy, Andy Walsh's Lotus instructional DVD gives a good demonstration of all the methods of braking, including ABS, which clearly shows this with a demo on an airfield. The idea with threshold braking is to bring the wheels to the point of locking and hold them there by modulating the braking pressure. The key is to be gentle - it's quite an art! Be gentle coming on the brakes (don't stamp on them like a cockroach), and be measured with your modulations as well.
Obviously you only have one pedal controlling brakes on all four wheels, so to threshold brake efffectively you'll need to set up the front/rear brake bias - many competition cars have a bias adjuster in the car for doing this (also useful in the wet as you're braking less so there's less weight transfer and you can get away with more braking at the rear). The other thing that will be of great benefit is to get the car corner weighted. This is where you sit in it on scales and the ride height is adjusted at each corner to even out the weight around the car (most importantly left/right, although front/rear is also done to within practical means). A car that hasn't been corner weighted will tend to lock up one side of the car before the other, so you're missing out on braking ability. Plenty of places will do this for you and it's quite cheap to have it done.
Also bear in mind the frictional characteristics of the tyre/tarmac interface. The maximum grip for most modern racing tyres against most tarmac surfaces is at about 4% slip, although obviously this varies greatly. This means that the optimum situation is to have the wheels slipping very slightly - you'll see F1 drivers doing this under braking quite a bit (Lewis is especially good at it!). Do bear in mind also the difference between static and dynamic friction - i.e. once you breach this 4% (or whatever it is) and lock a wheel (i.e. dynamic friction, the tyre is sliding), the car doesn't stop quite as quick as the friction isn't as high, but what's far more important is you'll need to back off more than you'd think to unlock it (and get back to static friction) and prevent damage to the tyre. The difference between static and dynamic friction is smaller in the wet, meaning it'll be easier to lock a wheel, which is why braking is harder in the wet. Incidentally, note that all of the above advice also applies to cornering and what happens when the car starts to gently slide and then let go.
Secondly, gear changing:
This has been explained well already on this thread. You've got two options here - going down through the box (i.e. 6, 5, 4, 3) and block changing (6, 3). Both have advantages and disadvantages, and it depends on your strengths and weaknesses as a driver as to which is quicker. i.e: block changing allows you to concentrate on the braking, but step changing one gear at a time makes for easier heel and toe and you're less likely to mess it up and lock the rear wheels (remember you'll be threshold braking, so the rear wheels will be teetering on the edge of lock up!). I spoke to Dave Minter about this last year (ex ride and handling engineer from Lotus, now freelance), and he said that of all the people he's taught (he did, and I think still does, teach Lotus driver training at Hethel), most find block changing better as it allows them to concentrate on what most people find more difficult - threshold braking. Find what suits you best though.
Hope that helps.
The accepted way to slow a racing car with maximum retardation is a technique called threshold braking. This takes more skill than road techniques like cadence braking etc, but is much more effective at stopping the car. If you can find a copy, Andy Walsh's Lotus instructional DVD gives a good demonstration of all the methods of braking, including ABS, which clearly shows this with a demo on an airfield. The idea with threshold braking is to bring the wheels to the point of locking and hold them there by modulating the braking pressure. The key is to be gentle - it's quite an art! Be gentle coming on the brakes (don't stamp on them like a cockroach), and be measured with your modulations as well.
Obviously you only have one pedal controlling brakes on all four wheels, so to threshold brake efffectively you'll need to set up the front/rear brake bias - many competition cars have a bias adjuster in the car for doing this (also useful in the wet as you're braking less so there's less weight transfer and you can get away with more braking at the rear). The other thing that will be of great benefit is to get the car corner weighted. This is where you sit in it on scales and the ride height is adjusted at each corner to even out the weight around the car (most importantly left/right, although front/rear is also done to within practical means). A car that hasn't been corner weighted will tend to lock up one side of the car before the other, so you're missing out on braking ability. Plenty of places will do this for you and it's quite cheap to have it done.
Also bear in mind the frictional characteristics of the tyre/tarmac interface. The maximum grip for most modern racing tyres against most tarmac surfaces is at about 4% slip, although obviously this varies greatly. This means that the optimum situation is to have the wheels slipping very slightly - you'll see F1 drivers doing this under braking quite a bit (Lewis is especially good at it!). Do bear in mind also the difference between static and dynamic friction - i.e. once you breach this 4% (or whatever it is) and lock a wheel (i.e. dynamic friction, the tyre is sliding), the car doesn't stop quite as quick as the friction isn't as high, but what's far more important is you'll need to back off more than you'd think to unlock it (and get back to static friction) and prevent damage to the tyre. The difference between static and dynamic friction is smaller in the wet, meaning it'll be easier to lock a wheel, which is why braking is harder in the wet. Incidentally, note that all of the above advice also applies to cornering and what happens when the car starts to gently slide and then let go.
Secondly, gear changing:
This has been explained well already on this thread. You've got two options here - going down through the box (i.e. 6, 5, 4, 3) and block changing (6, 3). Both have advantages and disadvantages, and it depends on your strengths and weaknesses as a driver as to which is quicker. i.e: block changing allows you to concentrate on the braking, but step changing one gear at a time makes for easier heel and toe and you're less likely to mess it up and lock the rear wheels (remember you'll be threshold braking, so the rear wheels will be teetering on the edge of lock up!). I spoke to Dave Minter about this last year (ex ride and handling engineer from Lotus, now freelance), and he said that of all the people he's taught (he did, and I think still does, teach Lotus driver training at Hethel), most find block changing better as it allows them to concentrate on what most people find more difficult - threshold braking. Find what suits you best though.
Hope that helps.
Interesting stuff. A few thoughts:
I think the difference between coefficients of static and dynamic friction is greater for wet tarmac than dry tarmac. So, to stop quickly, assuming you don't need to steer simultaneously, it's less disasterous to lock the wheels in the dry.
Threshold braking is a pretty complicated skill to develop (well, that's my experience!) which requires the driver to be very attuned to the feedback through the steering wheel. The need for sensitivity to steering feedback might influence the driver to block change.
http://www.egr.msu.edu/~olsonbr1/research/traction... gives a lot more information on this. Much of it practically incomprehensible.
WilliBetz
I think the difference between coefficients of static and dynamic friction is greater for wet tarmac than dry tarmac. So, to stop quickly, assuming you don't need to steer simultaneously, it's less disasterous to lock the wheels in the dry.
Threshold braking is a pretty complicated skill to develop (well, that's my experience!) which requires the driver to be very attuned to the feedback through the steering wheel. The need for sensitivity to steering feedback might influence the driver to block change.
http://www.egr.msu.edu/~olsonbr1/research/traction... gives a lot more information on this. Much of it practically incomprehensible.
WilliBetz
GreenV8S said:
jagdpanther said:
I think you've thankfully given me that information dear sir
Obviously I was being facetious (who, me?). However, if you're serious about this I'd suggest that threshold braking is well down the list of things you should be concerned about.
RobM77 said:
Why would that be? I presume you're suggesting (quite rightly) that it is more important at first to concentrate on driving smoothly, understanding the correct lines and getting used to the idea of driving for competition rather than on the road. Once those are dispatched with, threshold braking is essential to be competitive.
It's very hard to win a sprint, but very easy to lose it. Also very easy to damage self and car in the process. The key to success IMO is not driving fast. The critical skill is to be able to find the limits of the performance envelope as quickly as possible and then exploit them. The learning is actually far more important than the exploiting, because you have so few chances to get it right at a sprint. But for me, and I think for most people, doing well is not actually that high on the list of priorities. My list is:Bring me and car home undamaged.
Have fun.
Feel that I have done as well as I could have hoped to.
Feel that my driving skills are improving.
Be competitive against the people in my class.
Win.
It's hard to sum up how to do this in a few words so I won't. But what I will say is that pushing the limits under braking is one of the easiest ways to lose, and also to hurt yourself. You stand to gain perhaps tenths or hundredths of a second, you risk throwing seconds or tens of seconds away. Once you have perfected everything else then you need to ensure that you are using every scrap of the grip circle there is, and that will mean threshold braking and trail braking and the perfect line and the right choice of tyre pressures and all that other stuff. But that's the sort of thing you worry about in your tenth season not your first. For a novice I suggest the priorities should be to identify and understand the hazards, and to learn how to learn to drive fast on an unfamiliar course.
ETA:
On reading, that all sounds a bit Zen even to me. Maybe one day I'll try to come up with something more tangible. But it's too late for that tonight. Anyway, figuring out how to do it for yourself is half the fun!
Edited by GreenV8S on Wednesday 18th July 22:54
GreenV8S said:
Bring me and car home undamaged.
Have fun.
Feel that I have done as well as I could have hoped to.
Feel that my driving skills are improving.
Be competitive against the people in my class.
Win.
Thats pretty much the list I will be working from Have fun.
Feel that I have done as well as I could have hoped to.
Feel that my driving skills are improving.
Be competitive against the people in my class.
Win.
More so number two over number one
...I mean, the car bit 
Edited by jagdpanther on Wednesday 18th July 22:44
GreenV8S said:
RobM77 said:
Why would that be? I presume you're suggesting (quite rightly) that it is more important at first to concentrate on driving smoothly, understanding the correct lines and getting used to the idea of driving for competition rather than on the road. Once those are dispatched with, threshold braking is essential to be competitive.
It's very hard to win a sprint, but very easy to lose it. Also very easy to damage self and car in the process. The key to success IMO is not driving fast. The critical skill is to be able to find the limits of the performance envelope as quickly as possible and then exploit them. The learning is actually far more important than the exploiting, because you have so few chances to get it right at a sprint. But for me, and I think for most people, doing well is not actually that high on the list of priorities. My list is:Bring me and car home undamaged.
Have fun.
Feel that I have done as well as I could have hoped to.
Feel that my driving skills are improving.
Be competitive against the people in my class.
Win.
It's hard to sum up how to do this in a few words so I won't. But what I will say is that pushing the limits under braking is one of the easiest ways to lose, and also to hurt yourself. You stand to gain perhaps tenths or hundredths of a second, you risk throwing seconds or tens of seconds away. Once you have perfected everything else then you need to ensure that you are using every scrap of the grip circle there is, and that will mean threshold braking and trail braking and the perfect line and the right choice of tyre pressures and all that other stuff. But that's the sort of thing you worry about in your tenth season not your first. For a novice I suggest the priorities should be to identify and understand the hazards, and to learn how to learn to drive fast on an unfamiliar course.
ETA:
On reading, that all sounds a bit Zen even to me. Maybe one day I'll try to come up with something more tangible. But it's too late for that tonight. Anyway, figuring out how to do it for yourself is half the fun!
Edited by GreenV8S on Wednesday 18th July 22:54
I said it was too late, and it is, but my closing thought for this evening: the first thing you need to learn in this sport, as in most, is how to avoid getting hurt. Once you have got the hang of that, you can worry about everything else. But if you keep hurting yourself you're unlikely to get very far. To a driver, this means thinking about how and where things might go wrong, what is likely to happen as a result, and what defensive measures you should take to mitigate these risks. The result will be a defensive driving strategy which keeps the risks within acceptable levels. This isn't hard to do if you approach it rationally, but you should have solved this problem before you ever set a wheel on the track. (Incidentally, the solution to this problem in the context of a race track is extremely valuable on public roads as well. It's one of the few 'track' skills which imo applies to normal driving on public roads.)
Edited by GreenV8S on Wednesday 18th July 23:31
GreenV8S said:
I said it was too late, and it is, but my closing thought for this evening: the first thing you need to learn in this sport, as in most, is how to avoid getting hurt. Once you have got the hang of that, you can worry about everything else. But if you keep hurting yourself you're unlikely to get very far. To a driver, this means thinking about how and where things might go wrong, what is likely to happen as a result, and what defensive measures you should take to mitigate these risks. The result will be a defensive driving strategy which keeps the risks within acceptable levels. This isn't hard to do if you approach it rationally, but you should have solved this problem before you ever set a wheel on the track. (Incidentally, the solution to this problem in the context of a race track is extremely valuable on public roads as well. It's one of the few 'track' skills which imo applies to normal driving on public roads.)
Again, wise words. However, I would say that learning to drive truly quickly on track requires a smooth hand and an excellent understanding of the balance of a car. If you can exercise restraint on the public road, then these facets make for a much safer road driving experience.Edited by GreenV8S on Wednesday 18th July 23:31
Absolutely no disrespect, but I would guess there’s more than enough namby-pamby lardy-dah theoretical ‘smooth driving/line conscious’ ‘nice’ myth-prolonging guff above to send you to sleep.
Re your question: couple of things to practice:
Committed Car control
Raw naked aggression in terms of speed
You must learn to:
1 brake on the limit of adhesion (and not overbrake)
2 toe & heeling, changing down on the limit of adhesion whist maintaining every bit of momentum, controlling understeer and oversteer.
3 ensure your exit speeds are optimized (over your entry speeds)
Changing gear when the car is slipping/sliding without losing time and fumbling the whole deal, is an art in itself, an extremely rare commodity.
An FTD/Qualifying lap though, may not be a pretty sight.
Watchwords would be
Aggression, car control, momentum, efficiency, and PRACTISE.
All of which has as much to do with ‘attitude’ as ‘technique’.
Tongue-firmly-in-cheek IMHO.
Re your question: couple of things to practice:
Committed Car control
Raw naked aggression in terms of speed
You must learn to:
1 brake on the limit of adhesion (and not overbrake)
2 toe & heeling, changing down on the limit of adhesion whist maintaining every bit of momentum, controlling understeer and oversteer.
3 ensure your exit speeds are optimized (over your entry speeds)
Changing gear when the car is slipping/sliding without losing time and fumbling the whole deal, is an art in itself, an extremely rare commodity.
An FTD/Qualifying lap though, may not be a pretty sight.
Watchwords would be
Aggression, car control, momentum, efficiency, and PRACTISE.
All of which has as much to do with ‘attitude’ as ‘technique’.
Tongue-firmly-in-cheek IMHO.
I'd like to say that the vast majority of quick racing drivers are neither risk takers or aggressive in any way at all. I take an interest in the psychology of racing and this is overwhelmingly the case. There are some exceptions to this rule (Senna and Hunt being the first two that spring to mind), but most good racing drivers are cool, calm, calculated and smooth (like fighter pilots).
I know from my own experience of racing that as soon as I get a bit excited or aggressive, my lap times start suffering - this is the case for the overwhelming majority of racers, from club level up to F1.
If you look at champions from across the whole spectrum of motor racing, there are many more like Clark, Hamilton, Moss, Schumacher, Stewart, Fangio, Hill, Prost, Hakkinen, Surtees, Loeb, Sainz, Rohl, Bell, Brundle etc than there are like Senna and Hunt.
I know from my own experience of racing that as soon as I get a bit excited or aggressive, my lap times start suffering - this is the case for the overwhelming majority of racers, from club level up to F1.
If you look at champions from across the whole spectrum of motor racing, there are many more like Clark, Hamilton, Moss, Schumacher, Stewart, Fangio, Hill, Prost, Hakkinen, Surtees, Loeb, Sainz, Rohl, Bell, Brundle etc than there are like Senna and Hunt.
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