Double declutching
Discussion
Slowly Slowly said:
Walter Rohl is a driving God! 
This is one of my favourite videos of him driving:
http://video.google.co.uk/videoplay?docid=36194436...
911 in the snow at the ring - doesn't get more scary does it?
RobM77 said:
Slowly Slowly said:
Walter Rohl is a driving God! This is one of my favourite videos of him driving:
http://video.google.co.uk/videoplay?docid=36194436...
911 in the snow at the ring - doesn't get more scary does it?
But, whoever it is, that is steering/throttle finesse to which I aspire. Simply sublime. Must be pretty good tyres too - I never thought the car would make it up ex-Muhle...
WilliBetz said:
But, whoever it is, that is steering/throttle finesse to which I aspire. Simply sublime. Must be pretty good tyres too - I never thought the car would make it up ex-Muhle...
That's a good point - it's very steep. They have an ice rally at the Ring every winter, so it must be possible!RIght, all my serious road bashing has been done on bikes and I'd always, when slowly match engine revs to to the next lower gear before engaging that gear.
Its easy peasy on a bike and I could brake as hard as I want and still go down the box perfectly smoothly without and jerking around if the engine revs were corrected by the bikes road speed.
I've only lately started driving cars seriously and have started doing a similar thing.
When going down the box I can keep the heel of my right foot planted with the left side of that foot braking and right side blipping the throttle as I work the box and go down the gears. I can match engine revs to gears almost perfectly (although I do get in a tangle often as I'm still practicing!!!)
What is the name given to what it is I'm doing?
Its easy peasy on a bike and I could brake as hard as I want and still go down the box perfectly smoothly without and jerking around if the engine revs were corrected by the bikes road speed.
I've only lately started driving cars seriously and have started doing a similar thing.
When going down the box I can keep the heel of my right foot planted with the left side of that foot braking and right side blipping the throttle as I work the box and go down the gears. I can match engine revs to gears almost perfectly (although I do get in a tangle often as I'm still practicing!!!)
What is the name given to what it is I'm doing?
This is what happens when a driver attempts a fast gearchange under pressure.
http://uk.youtube.com/watch?v=eKstcSXKynE
He was trying to mix and match gearchange approaches and got caught between two posts, so to speak. When he first drove me on a track in his own car at speed I noticed that he didn't heel&toe or DD. When he drove the tuition M3 he tried h&t, as he thought he should demonstrate his prowess, but it wasn't his absolute natural gearchange technique and so introduced thought where there shouldn't be conscious thought in a less familiar vehicle.
h&t/dd when applied skilfully doesn't waste time it makes for a quicker, more balanced drive. BUT, it has to be "unconscious competence" type capability when applied in anger. Many people to whom I demonstrate the technique at significant speeds can't believe you are moving the clutch twice or indeed putting the throttle in at the right points: And all the time holding the braking at threshold of grip levels. But over 30 years of application of the technique means that active thought can go to external observations of line, braking points, surrounding vehicles etc. If you are thinking in the car then your thinking outside of the car suffers. You have become a learner again. Which is fine and indeed praiseworthy. Just remember to respect the fact and you will eventually become proficient once again, but with an additional, valuable skill. It's like learning to touch-type after you have typed for a long time with two fingers. Which is probably what some readers are about to raise at this post!
If any PH'ers want a demo and you see us on track - just ask.
MikeC
http://uk.youtube.com/watch?v=eKstcSXKynE
He was trying to mix and match gearchange approaches and got caught between two posts, so to speak. When he first drove me on a track in his own car at speed I noticed that he didn't heel&toe or DD. When he drove the tuition M3 he tried h&t, as he thought he should demonstrate his prowess, but it wasn't his absolute natural gearchange technique and so introduced thought where there shouldn't be conscious thought in a less familiar vehicle.
h&t/dd when applied skilfully doesn't waste time it makes for a quicker, more balanced drive. BUT, it has to be "unconscious competence" type capability when applied in anger. Many people to whom I demonstrate the technique at significant speeds can't believe you are moving the clutch twice or indeed putting the throttle in at the right points: And all the time holding the braking at threshold of grip levels. But over 30 years of application of the technique means that active thought can go to external observations of line, braking points, surrounding vehicles etc. If you are thinking in the car then your thinking outside of the car suffers. You have become a learner again. Which is fine and indeed praiseworthy. Just remember to respect the fact and you will eventually become proficient once again, but with an additional, valuable skill. It's like learning to touch-type after you have typed for a long time with two fingers. Which is probably what some readers are about to raise at this post!
If any PH'ers want a demo and you see us on track - just ask.
MikeC
Edited by instructormike on Thursday 16th August 00:39
Edited by instructormike on Thursday 16th August 00:39
You can take any car or lorry gearbox out of gear without using the clutch, as long as there is no load going through the gearbox, either in the direction of the wheels or the engine.
So if you're accellerating hard, you ease up a bit and knock the gearstick out. At the same instant you push the go pedal, and before the clutch is disengaged the engine revs are rising.
Whilst the engine revs are rising you disengage the clutch and the clutch side of the gearbox is spinning. By this time the next gear is selected the engine revs are falling as the clutch re engages.
That's what I do, and it can be done surprisingly fast. In fact I always find it's the key. I have a feeling it would work on a crash box just as well as a synchro box. Sometimes, I cut it just a bit too fine, and miss, that is to say, that the clutch is already re-engaged at the point where the gear is trying to go in.
I think most competent drivers would do it this way, the synchromesh merely provides a small ammount of room for error on the first phase of the change, where you have to get the timing of releasing the throttle and knocking the gearbox out. Obviously, if you make that mistake, you don't actualy know until the point where you are trying to push the next gear in, and gearbox baulks or crunches.
To give an idea how close it is in time, you'll probably be pushing the clutch at the point where you knock the gear out, but it won't be released yet. The human brain is a fantastic thing. The machine or car becomes like your arms. You know how long they are, without having to look at them. The same is true for the insides of the gearbox and clutch. Most never see them, but most also can jude the moment of engagement within a couple of milimeters, in an instant of a second, all with barely a thought.
Double declutching, does have a place but it is often much slower (at least if it's worth doing), so much so that most would find it uncomfortable. The best examples of an appropriate place is on an uphill incline with a heavy load, or with a very big engine that has lots of internal friction on a downhill incline. In both circumstances, the load on the transmission is such that it is not possible to keep the engine and roadsides of the gearbox reasonably matched. With a crash box, the speed of change is no longer enough. With synchromesh, one will probably get away with it.
The most significant thing that double declutching cannot do is make a crash box engage easily at a standstill. A similar technique can be used to good effect, and most competent people do it normally anyway, without realising. The additional clutch operation in double declutching is about releasing the gear, and it's more often than not completely superflous. If it weren't your synchro rings wouln't last in excess of 100K miles.
So if you're accellerating hard, you ease up a bit and knock the gearstick out. At the same instant you push the go pedal, and before the clutch is disengaged the engine revs are rising.
Whilst the engine revs are rising you disengage the clutch and the clutch side of the gearbox is spinning. By this time the next gear is selected the engine revs are falling as the clutch re engages.
That's what I do, and it can be done surprisingly fast. In fact I always find it's the key. I have a feeling it would work on a crash box just as well as a synchro box. Sometimes, I cut it just a bit too fine, and miss, that is to say, that the clutch is already re-engaged at the point where the gear is trying to go in.
I think most competent drivers would do it this way, the synchromesh merely provides a small ammount of room for error on the first phase of the change, where you have to get the timing of releasing the throttle and knocking the gearbox out. Obviously, if you make that mistake, you don't actualy know until the point where you are trying to push the next gear in, and gearbox baulks or crunches.
To give an idea how close it is in time, you'll probably be pushing the clutch at the point where you knock the gear out, but it won't be released yet. The human brain is a fantastic thing. The machine or car becomes like your arms. You know how long they are, without having to look at them. The same is true for the insides of the gearbox and clutch. Most never see them, but most also can jude the moment of engagement within a couple of milimeters, in an instant of a second, all with barely a thought.
Double declutching, does have a place but it is often much slower (at least if it's worth doing), so much so that most would find it uncomfortable. The best examples of an appropriate place is on an uphill incline with a heavy load, or with a very big engine that has lots of internal friction on a downhill incline. In both circumstances, the load on the transmission is such that it is not possible to keep the engine and roadsides of the gearbox reasonably matched. With a crash box, the speed of change is no longer enough. With synchromesh, one will probably get away with it.
The most significant thing that double declutching cannot do is make a crash box engage easily at a standstill. A similar technique can be used to good effect, and most competent people do it normally anyway, without realising. The additional clutch operation in double declutching is about releasing the gear, and it's more often than not completely superflous. If it weren't your synchro rings wouln't last in excess of 100K miles.
Edited by dilbert on Wednesday 22 August 20:15
WilliBetz said:
It isn't Rohrl driving in the snow, though, is it?
But, whoever it is, that is steering/throttle finesse to which I aspire. Simply sublime. Must be pretty good tyres too - I never thought the car would make it up ex-Muhle...
You're correct it isn't Rohrl, its Tim Schrick. (German racer/tester for Auto Motor und Sport, and a bl00dy good driver)But, whoever it is, that is steering/throttle finesse to which I aspire. Simply sublime. Must be pretty good tyres too - I never thought the car would make it up ex-Muhle...
This is him in a Carrera GT
Nice car control, but just listen to it 
http://www.youtube.com/watch?v=j9ne380EagI
GravelBen said:
WilliBetz said:
It isn't Rohrl driving in the snow, though, is it?
But, whoever it is, that is steering/throttle finesse to which I aspire. Simply sublime. Must be pretty good tyres too - I never thought the car would make it up ex-Muhle...
You're correct it isn't Rohrl, its Tim Schrick. (German racer/tester for Auto Motor und Sport, and a bl00dy good driver)But, whoever it is, that is steering/throttle finesse to which I aspire. Simply sublime. Must be pretty good tyres too - I never thought the car would make it up ex-Muhle...
This is him in a Carrera GT
Nice car control, but just listen to it http://www.youtube.com/watch?v=j9ne380EagI
I'm watching the Carrera GT one now MarcusL said:
In relation to the above discussions and the difficuty of H+T has anyone tried left foot braking (rally style) - now theres a recipe for disaster...
Yes, a while back, and I nearly ate my steering wheel......As for DDC, I'm practising that now as part of my Ride Drive training. Certainly makes the downshifts smoother when you hit it right.
i always always use heel and toe. even when im driving a transit.... but, also double declutch when using the box to slow me down.......I think anyone thats ever driven a crash box will be expert in the art !!!!
Try a ERF Tripple splitter crash box.......18 gears and no clutch required !
Try a ERF Tripple splitter crash box.......18 gears and no clutch required !
RobM77 said:
I still don't understand the 'difficulty' of heel and toe. For me it was one of the easiest bits about learning to drive. I'm beginning to wonder if my feet are abnormal!
I've started H+Ting and, after a few jerky practice attempts ,it's becoming pretty much second nature. I have to admit I don't always do it but if I'm braking quite heavily into a corner and I know I'm going to need a lower gear then a quick H+T makes for a much better controlled entry speed and a much more planted car in the corner. It's also a nice feeling to go to a lower gear without even feeling the transition. Maybe it's just me but I find it easier to H+T between certain gears especially 4th to 3rd. 3rd to 2nd is a lot more difficult for me for some reason. I also struggle to H+T all the way down the box quickly, but I am getting better at it. It makes for a smoother drive and it makes for less wear and tear on the gear box.MilnerR said:
RobM77 said:
I still don't understand the 'difficulty' of heel and toe. For me it was one of the easiest bits about learning to drive. I'm beginning to wonder if my feet are abnormal!
I've started H+Ting and, after a few jerky practice attempts ,it's becoming pretty much second nature. I have to admit I don't always do it but if I'm braking quite heavily into a corner and I know I'm going to need a lower gear then a quick H+T makes for a much better controlled entry speed and a much more planted car in the corner. It's also a nice feeling to go to a lower gear without even feeling the transition. Maybe it's just me but I find it easier to H+T between certain gears especially 4th to 3rd. 3rd to 2nd is a lot more difficult for me for some reason. I also struggle to H+T all the way down the box quickly, but I am getting better at it. It makes for a smoother drive and it makes for less wear and tear on the gear box.Gassing Station | Advanced Driving | Top of Page | What's New | My Stuff