Double declutching

[R_U_LOCAL]

Right, as there seems to be some confusion over the subject, here is...

Reg Local's guide to double de-clutching and rev matching and stuff

Firstly, lets start with whether you need to double de-clutch or not. In a modern manual car with a gearbox that is in perfect working order, it's not really necessary at all. Even back in the 1930s, manufacturers were making sychro gearboxes in which double de-clutching wasn't necessary.

In fact, thinking back, I've only ever driven a dozen or so vehicles where DDC was actually essential to changing gear. One was a 1922 3-litre Bentley and one was a 1992 Sherpa van.

However, assuming that you've decided that DDC is either necessary, or that you want to have a go (it won't cause any damage in a synchro box, so feel free to try it), then remember this one simple rule - it's simply the hokey-kokey on the clutch pedal...

In-out-in-out.

If you're changing up through the gearbox, press the clutch, gear lever into neutral, release the clutch, press the clutch, gear lever into gear, release the clutch.

If you're changing down, it's virtually the same, except that, after releasing the clutch the first time, whilst it's in neutral, you should raise the engine revs to match the road speed in the lower gear.

The roadcraft system makes it easier to match the revs, as it seperates the braking and gearchanging. i.e, you'll bring your speed down on the brakes first, giving yourself enough time to change gear and raise the revs with your right foot fully on the accelerator.

Heel-and-toeing is a way of overlapping the braking and gearchange, whilst still raising the engine revs. it involves pressing the brake with one portion of your right foot, whilst pressing the accelerator with another part of the same foot. I've seen various permutations - some people with smaller feet are able to press the brake with the ball of their foot and the accelerator with their heel. I'm (predictably, before anyone points it out), a size 10 in the foot department, so I favour keeping my heel on the floor, pressing the brake with the ball of my foot and rolling the outside edge of my foot onto the accelerator.

Now, Heel-and-toe and double-de-clutching are seperate skills and are not mutually exclusive to each other. You can H-A-T either with or without DDC, and you can DDC either with or without H-A-T.

Hope that clears up any confusion.

[Slowly Slowly]

http://www.tcsracing.org/heelandtoe.htm

http://www.torquecars.com/articles/double-de-clutc...


According to the third paragraph at Torquecars.com doing a single declutch is the first stage then you move on to the full H+T double declutch like a racing driver.
Someone who shall remain nameless said on here all racing drivers only do single declutch H+T.

Another quote from this articles goes as follows.

"On modern cars with syncomesh some people argue that the DDC is no longer of value and others say that it is WHAT PROPER DRIVERS ON THE TRACK DO some maintain that it is only of value on down changes in the heel and toe method but as with most driving techniques it depends on driver preference car type and driving conditions".

Sounds to me like DDC H+T is better than SDC H+T.

[ph123]

Just to throw something in for consideration, 20 years of my competition driving was in single seaters or sports racers which had Hewland race boxes, which of course do not have synchro.
So back in the 60's I got into the habit of DDC and T&H, something I can't shake even now. It was useful to have something like a heel bar across the floor and a serious clutch foot rest to steady your feet during this very quick footwork. (The violence of the stiffly sprung racecar across a surface, G forces etc not to be overlooked either)
It was either that or replace your gear ratios and selectors regularly and risk missed shifts; something meagre winnings wouldn't cover ... !

[GreenV8S]

Slowly Slowly said:

Sounds to me like DDC H+T is better than SDC H+T.

Seems to me you have read that some people use DDC H+T and are jumping to conclusions without really understanding why you would use DDC - despite the fact that several people have summed it up on this thread quite clearly imo.

[Slowly Slowly]

GreenV8S said:

Slowly Slowly said:

Sounds to me like DDC H+T is better than SDC H+T.

Seems to me you have read that some people use DDC H+T and are jumping to conclusions without really understanding why you would use DDC - despite the fact that several people have summed it up on this thread quite clearly imo.

Being a professional driver interested in classic cars I fully understand DDC with H+T, when I drive my truck I sometimes change gear without using the clutch, I drove from J1 M6 to Nine elms lane in Wandsworth without a clutch once, admittedly it was 10.30pm when I got to Staples corner but it's still not bad 27 sets of lights, I only had to stop twice.
When SDC with H+T was mentioned on here I just couldn't see it, the 2 web sites I highlighted support DDC with H+T, It takes all sorts, but if you can do them both(not at the same time of course) then IMO the more difficult one is better.

[BertBert]

Slowly Slowly said:

http://www.tcsracing.org/heelandtoe.htm

http://www.torquecars.com/articles/double-de-clutc...


According to the third paragraph at Torquecars.com doing a single declutch is the first stage then you move on to the full H+T double declutch like a racing driver.
Someone who shall remain nameless said on here all racing drivers only do single declutch H+T.

Another quote from this articles goes as follows.

"On modern cars with syncomesh some people argue that the DDC is no longer of value and others say that it is WHAT PROPER DRIVERS ON THE TRACK DO some maintain that it is only of value on down changes in the heel and toe method but as with most driving techniques it depends on driver preference car type and driving conditions".

Sounds to me like DDC H+T is better than SDC H+T.

So as we are into trying to prove a point...I have found 2 vids on youtube that show racing drivers doing HnT without DDC. Over to you to find the ones double-declutching...

if you find this one... http://www.youtube.com/watch?v=WD5zq0Jkpoo nah, not racing, just pootling

Bert

[GreenV8S]

Slowly Slowly said:

Being a professional driver interested in classic cars I fully understand DDC with H+T

That's not the impression I got when you had to go and lie down after having H&T without DDC explained to you.

Slowly Slowly said:

When SDC with H+T was mentioned on here I just couldn't see it, the 2 web sites I highlighted support DDC with H+T, It takes all sorts, but if you can do them both(not at the same time of course) then IMO the more difficult one is better.

Rather than just apply the most complicated techniques you can find, it's better IMO to understand the purpose behind them and apply them WHEN APPROPRIATE.

To reiterate: DDC used unnecessarily wastes time and attention that can often be spent on better things. For example, I often use both techniques together on the track because I know that on the V8S the synchros need the help when they're hot. If the gearbox is coping OK without it I won't bother, and this means the gear change will be quicker and require less driver input, freeing me up to concentrate on going faster. DDC just for the sake of it seems the antithesis of advanced driving to me.

[Chris71]

So, changing the subject a little, if you have normal size 10 or 11 shoes and pendant pedals, what would be the normal way to heel and toe?

I've tried it with my toes on the brake pedal, trying to bring my heel round to blip the throttle, but found it very difficult to maintain a steady pressure on the brake. The brakes on the car in uqestion were very well servoed and I found it impossible to do without accidentally jabbing the brake a little harder at the same time and sending myself flying forward

Needless to say this was done slowly on a very quiet road...

[Slowly Slowly]

GreenV8S said:

Slowly Slowly said:

Being a professional driver interested in classic cars I fully understand DDC with H+T

That's not the impression I got when you had to go and lie down after having H&T without DDC explained to you.

Slowly Slowly said:

When SDC with H+T was mentioned on here I just couldn't see it, the 2 web sites I highlighted support DDC with H+T, IT TAKES ALL SORTS, but if you can do them both(not at the same time of course) then IMO the more difficult one is better.

Rather than just apply the most complicated techniques you can find, it's better IMO to understand the purpose behind them and apply them WHEN APPROPRIATE.

The reason why I had to go for a lie down was I was shocked, I was shocked that enthusiasts should be doing a short cut to a classic driving technique, I now understand why you do it. I think we have deviated slightly from what the OP originally asked, he mentioned DDC not DDC with H+T.
IMO (as I've already said) DDCHT is more difficult to get right than SDCHT so as I take pride in my driving, (not that you don't)and if you can master DDC then you can also change gear without the clutch it's got to be a more rewarding driving task, It might take more time but I don't think the OP was bothered about speed, you use SDCHT because it suite your application so thats fine.

My mechanical sympathy won't let me rev an engine with the clutch down, maybe I should change my name to Mr Awkward.


Don't say it............

[ph123]

Chris71 said:

So, changing the subject a little, if you have normal size 10 or 11 shoes and pendant pedals, what would be the normal way to heel and toe?

I've tried it with my toes on the brake pedal, trying to bring my heel round to blip the throttle, but found it very difficult to maintain a steady pressure on the brake. The brakes on the car in uqestion were very well servoed and I found it impossible to do without accidentally jabbing the brake a little harder at the same time and sending myself flying forward

Needless to say this was done slowly on a very quiet road...

Chris. Just use the ball of your foot to brake and maybe the side of your shoe to blip the throttle; just roll your foot over. It's not an exact science when you're learning.
And it's much easier to practice at speed. Driving slowly and it doesn't come together until you're well practised. The raison d'etre is also much clearer when pressing on.

[BertBert]

ph123 said:

Chris71 said:

So, changing the subject a little, if you have normal size 10 or 11 shoes and pendant pedals, what would be the normal way to heel and toe?

I've tried it with my toes on the brake pedal, trying to bring my heel round to blip the throttle, but found it very difficult to maintain a steady pressure on the brake. The brakes on the car in uqestion were very well servoed and I found it impossible to do without accidentally jabbing the brake a little harder at the same time and sending myself flying forward

Needless to say this was done slowly on a very quiet road...

Chris. Just use the ball of your foot to brake and maybe the side of your shoe to blip the throttle; just roll your foot over. It's not an exact science when you're learning.
And it's much easier to practice at speed. Driving slowly and it doesn't come together until you're well practised. The raison d'etre is also much clearer when pressing on.

So to add to this, I am rubbish at using the side of my foot at the top to the right of the ball of my foot IYSWIM. I twist my ankle round a bit and use the side of my right foot a little lower down. Porsche, TVR and Radical pedals are good for this being hinged at the bottom. I had my Caterham pedal lengthened so I could get to it lower down on the side of my foot.

Bert

[BertBert]

Slowly Slowly said:

My mechanical sympathy won't let me rev an engine with the clutch down

I am interested in the mechanical reason for this. I can't work out what is unsympathetic about a blip with the clutch down.

Bert

[ph123]

... increased heat on the clutch release bearing.

[R_U_LOCAL]

BertBert said:

Slowly Slowly said:

My mechanical sympathy won't let me rev an engine with the clutch down

I am interested in the mechanical reason for this. I can't work out what is unsympathetic about a blip with the clutch down.

Bert

ph123 said:

... increased heat on the clutch release bearing.

The small amount of time that it takes to rev-match with the clutch down makes such an increase negligible to the point of almost non-existence.

I'd argue that the effects of rev-matching on reducing wear on other parts of a cars transmission and engine far outweigh any problems that could be encountered in revving the engine with the clutch down.

I've been using the method for over 20 years now, and I've never had a release bearing failure in any of my cars or my works cars.

[Slowly Slowly]

R_U_LOCAL said:

BertBert said:

Slowly Slowly said:

My mechanical sympathy won't let me rev an engine with the clutch down

I am interested in the mechanical reason for this. I can't work out what is unsympathetic about a blip with the clutch down.

Bert

ph123 said:

... increased heat on the clutch release bearing.

I'd argue that the effects of rev-matching on reducing wear on other parts of a cars transmission and engine far outweigh any problems that could be encountered in revving the engine with the clutch down.

But if you can Rev-match without the clutch being down then it has to be better, even though the difference is very small.

[R_U_LOCAL]

Slowly Slowly said:

But if you can Rev-match without the clutch being down then it has to be better, even though the difference is very small.

If it makes you happy, then carry on.

My point is that it's unecessary in a modern car, and DDC was never designed to save wear on the release bearing anyway - it was designed to make gearchanging in non-synchro gearboxes easier (or actually possible).

I'd even argue that pressing the clutch twice for a gearchange would create more wear on the bearing than pressing it once and revving the engine.

Like you've said, the difference is small. So small as to be negligable, in fact, so I'll leave it up to your personal choice.

[GreenV8S]

Slowly Slowly said:

But if you can Rev-match without the clutch being down then it has to be better, even though the difference is very small.

That's a rationalisation, not a reason. If you're splitting hairs that finely then you might also be concerned about doubling the number of times the clutch mechanism is actuated. In practical terms the difference is utterly negligible in the scheme of things, and not something that should determine your choice of driving technique.

Being able to change gear smoothly is obviously important, but being able to do this without spending any longer than necessary and without taking any more of the driver's attention than necessary is also important. Changing gear compromises the driver's ability to control the car and anything that extends the duration of a gear change is undesirable. Even supposing that you *can* do clutchless throttleless tripple-declutch H&T gear changes with bells on, doesn't mean that it is sensible or desirable to do it.

[Slowly Slowly]

GreenV8S said:

and anything that extends the duration of a gear change is undesirable. Even supposing that you *can* do clutchless throttleless tripple-declutch H&T gear changes with bells on, doesn't mean that it is sensible or desirable to do it.

I hear what you are saying but as a truck driver I sometimes pull off the motorway and take an alternative route, this way when the motorway is closed or has serious delays I will already know a different route.
I don't see "extending the duration of a gear change as undesirable" at all, if you learn a new skill it makes you a better driver.(like finding an alternative route)
When I drove from J1 M6 to Wandsworth without a clutch it was in a loaded 16 tonner, I went off J1 and back on again stopping on the down on ramp as I came to a stop it stalled, thats when I realised my clutch was knackered, It was now stuck in gear engine not running, I couldn't (at first) get it out of gear.
Normally I would have had to phone for recovery which would take me to the nearest base to tranship, very time consuming I'm sure you'd agree, Instead I used my knowledge and may I say skill to get it to it's destination, about 100 miles, try it sometime in a car, then try it in a loaded 16 tonner.
My point is it If I had'nt spent time learning to clutchless changes I would not have been able to get the truck to Wandsworth.
I would always tell a new young driver to keep learning and practicing different skill because you never know when it might save your life, ie, getting a car off the motorway if the clutch goes.

[BertBert]

Slowly Slowly said:

GreenV8S said:

and anything that extends the duration of a gear change is undesirable. Even supposing that you *can* do clutchless throttleless tripple-declutch H&T gear changes with bells on, doesn't mean that it is sensible or desirable to do it.

I hear what you are saying but as a truck driver I sometimes pull off the motorway and take an alternative route, this way when the motorway is closed or has serious delays I will already know a different route.
I don't see "extending the duration of a gear change as undesirable" at all, if you learn a new skill it makes you a better driver.(like finding an alternative route)
When I drove from J1 M6 to Wandsworth without a clutch it was in a loaded 16 tonner, I went off J1 and back on again stopping on the down on ramp as I came to a stop it stalled, thats when I realised my clutch was knackered, It was now stuck in gear engine not running, I couldn't (at first) get it out of gear.
Normally I would have had to phone for recovery which would take me to the nearest base to tranship, very time consuming I'm sure you'd agree, Instead I used my knowledge and may I say skill to get it to it's destination, about 100 miles, try it sometime in a car, then try it in a loaded 16 tonner.
My point is it If I had'nt spent time learning to clutchless changes I would not have been able to get the truck to Wandsworth.
I would always tell a new young driver to keep learning and practicing different skill because you never know when it might save your life, ie, getting a car off the motorway if the clutch goes.

But surely, despite one's skill, 100 miles without a clutch will put (certainly in comparison to a rev with the clutch depressed) a very undesirable mechanical strain on the gearbox. You will be wearing the baulk rings on the synchros significantly by doing this.

Bert

[Slowly Slowly]

Yeah right.