DDC - Heel &Toes

[Matt Prior]

DDC? A bit. H&T? All the time. LFB? Only mid-corner on my favourite roundabout to provoke lunatic oversteer. teeth.gif

[Paul Ranson]

I sometimes DDC Land Rovers and the like. I see no point with a proper gearbox on a sporty car. I sometimes HT, but I think this is not usually necessary unless you're going properly fast, and then it depends on the circumstances, how many gears you're dropping etc.

 

FWIW you cannot DDC a sequential, so anybody planning bike engined fun or Quaife upgrades can safe themselves the effort of the practicing.

 

If you don't bother declutching at all the issue becomes moot. By definition if you can DDC properly then you can also clutchless downshift. This allows you to LFB (not necessarily against power) which will safe significant amounts of time, perhaps going into the Molehill at Curborough.

 

Paul

[Rory McLeod]

OK time to show my hignorance (again!), why cant you DDC a sequential box? (and yes I dont really know the diff tween straight cut and sequential boxes). To me, engine rotation is transferred to propshaft rotation via a gearbox, so on a downshift you spin up the engine to ease the wear on the clutch due to the rotation difference tween g.box and engine. Are the ratios on a sequential box close enough not to have to do this?

 

Edited by - Rory McLeod on 17 Jan 2001 19:51:13

[Number Six]

My hignorance too but don't bikes have slipper (sp?) clutches?

 

Where's Mr. Carmichael?

 

Andy

[Paul Ranson]

OK time to show my hignorance (again!), why cant you DDC a sequential box?

 

There is no neutral inbetween the gears. Or at least not one you can shake your left leg at.

 

(and yes I dont really know the diff tween straight cut and sequential boxes).

 

Three independent gearbox characteristics,

 

straight cut/helical

 

This refers to the way the gears are cut. 'Straight cut', or 'spur'. Maximum noise, maximum power transfer, cheapest to make. I think you get a higher torque capacity for a given gear size too. Helical is quiet, which I think is its only advantage.

 

Synchromesh/dog

 

Refers to how a gear is temporarily locked to the output shaft. Synchromesh as a baulk mechanism that magically allows the gears to be engaged without crunches or bangs. I think it also extends the life of the gearbox. I think I need a picture to show how this stuff works. I don't have one to hand. The Quaife catalog helps.

 

H pattern/sequential.

 

H pattern, like almost every car. You move the stick from position to position to shift, the position you leave the lever in determines which gear. Sequential, like almost every motorbike, you tug (or kick....) it forwards or backwards to shift down or up. The shifter returns to a central position each time. Sequential makes every gear shift equivalent, going 'across' the box is no longer an issue. OTOH you cannot skip from 5th to 2nd and have to pass through every intermediate. Knowing what gear you're in can be tricky.

 

So you could have a helical/synchromesh/sequential, or a straight cut/dog/H pattern

 

etc....

 

Paul

[elie boone]

Rory, a sequential box is mostly with a dog drive this means that there is no syncromesh.With a dogdrive box you do not need to use the clutch

exept to engage first gear,sequential is a system of changing gear straight cut gears are the type of "teeth" on the gears.

Number Six, another good trick when somebody is close on your bumper

Use your windscreenwashers and make sure they spray rather high on the windscreen.thumbsup.gif teeth.gif

 

 

[Number Six]

Elie - teeth.gif, another favourite is actually **speeding up** when I get to some bends that I know (whilst LFBraking at the same time of course) and leaving the bugger for dead. Then poodle along again at the speed limit and repeat at next series of bends, heh hehteeth.gif

 

Andy

[elie boone]

Number Six, I whas talking about my tin top (slow car & driver)but with a seven there is no problem exept mine is still not finished sad.gifmaybe i wont even get it finished before Stoneleigh.(sorry Nich H)

 

 

[Rory McLeod]

Thanks all, this has been a very informative thread for me!

 

[Number Six]

Marius - if you cannot reach the accelerator pedal whilst braking with the right foot what you need to do is weld or bold on a length of aluminium/titanium (make sure it will not bend) to the accelerator (on the left side) - you can also further adjust the accelerator up ordown to get it just right when the brakes are biting on average full lockup...

 

John Lyon showed me this on his old white race 7...

 

I don't need to do this on a 7 as my feet are big enough!

 

I did have to do it on my 911 in Amerika, you can buy a fully adjustable device to do just that for about 100 dollars...

 

later,

 

Andy

[Peter Carmichael]

I think www.leftfootbraking.com is a bit cheeky in its advertising. It says M Schumacher left foot brakes, which appears to be a bit of marketing bollocks from people trying to sell a product.

 

M. Schumacher left foot brakes because he doesn't have a clutch pedal and he practised all his young life in karts. He may overlap the release of the throttle with the application of the brakes to reduce the time of transition and to smooth the transition but I bet he doesn't do anything significant to balance the handling of the car.

 

Alex,

 

Buddy Fey's book "Data power" shows how logging systems can draw the friction circle on a polar graph of the lateral and longitudinal G. On my Stack system, the system calculates up the combined G using pythag'. This line shows how well you sustain the use of the friction circles throughout the transition from braking to turn in. - turn in uses lateral g, quickly building up to the peak of grip available.

 

As usual, words are an awkward tool to describe what most track drivers (including Alex) do with varying degrees of success.

 

Turn-in requires full use of the grip circle, as does the apex. There is nothing special about the apex apart from that you clip the kerbing. Whenever the car is just sliding, you are by definition using the full grip circle.

[Peter Carmichael]

Marius,

 

The shape of the footwell may be subtley different with a LHD configured Caterham. I have certainly met LHD tin tops where the central console has prevented H&T. It is worth taking the time to set up the pedals to be in exactly the right place for H&T so that it isn't too long a reach.

 

I find that a small adjustment to the throttle pedal position is required for track use where you are using H&T when you are hard on the brakes and the brake pedal sinks a bit further than when you are on the road.

[Paul Ranson]

He may overlap the release of the throttle with the application of the brakes to reduce the time of transition and to smooth the transition but I bet he doesn't do anything significant to balance the handling of the car.

 

I think some F1 drivers do brake against power, I suppose it's possible this is for handling reasons, I can't convince myself one way or the other about over/understeer.

 

One thing it does give you is instant go when you get back off the brakes, maybe it can take a significant time to get the throttle open, the air flowing and the power back up.

 

It would be interesting to see some real datalogs.

 

Paul

[mark.hall]

I thought the F1 practice of braking under power was to warm the brakes. I seem to recall Martin Brundle saying something like this during his year at McLaren when Mika was able to make significant ground up on him due to this very technique. The warmed brakes allowed Mika to brake "for real" a bit later than Brundle, who used an almost traditional 2 footed approach to braking.

[Number Six]

"I find that a small adjustment to the throttle pedal position is required for track use where you are using H&T when you are hard on the brakes and the brake pedal sinks a bit further than when you are on the road."

 

I thought that's what I said... teeth.gif ... must be an echo...

 

Jim Clark and Stirling Moss did not have data logs.

 

Driving is not a science, it is an art.

 

It is intuitive, it is tactile, it involves the emotions, memory, pecuniary state, age; it involves one's sexual reproductive bits (what a load of bollocks) [Cojones!] and many other things besides, including the time of the month if you are Anna Rexia!

 

I'll take Jim Clark or Ayrton against Schumacher any day.

 

 

 

 

Andy

[Pierre Gillet]

I have found on my LHD the almost perfect settings of the pedals, and I really enjoy braking hard on the road before some corners H&T/DDCing cool.gif

Those who do not do it should absolutely try it, including Mr Osello if he wants to be a senior Officer of our two-member Vernolitan area!! wink.gif

Cheers,

 

Pierre

[old captain slow]

Left foot braking under power in a kart is an effective and sensitive way of balancing the kart round long corners right on the limit. I haven't tried it in a 7, but it should work too I would have thought.

 

Just a comment.

[Peter Carmichael]

Jim Clark and Stirling Moss did not have data logs.

 

Driving is not a science, it is an art.

---

 

Bollocks.

 

Even the most artistic of drivers are just engaging the laws of physics on their behalf. You don't need much track driving experience to discover that the laps that *feel* fast are not necessarily the fastest laps. So I refute the assertion that race driving is intuitive. From the point at which you start wondering whether you have the right tyre pressure you are engaged in an exercise in objectivity. Try a change, measure the effectiveness with a stopwatch; from this I claim that the principle of objective scrutiny is won. Datalogging just extends the scope of this scrutiny.

 

Dave W's comment:

Left foot braking under power in a kart is an effective and sensitive way of balancing the kart round long corners right on the limit. I haven't tried it in a 7, but it should work too I would have thought.

---

 

This interests me, but leads me to ask questions. What sort of kart? 4 wheel brakes or rear axle brake? If the latter, then the observation won't translate to Caterham driving. My instinct is to believe that such left foot braking is a useablity issue, it being easier to modulate the power delivery with a light application of the brakes than to back off the throttle slightly.

[Number Six]

"Jim Clark and Stirling Moss did not have data logs."

 

I take back what I said. They did, in fact, have the same data logs we all have - their brains.

 

They also had/have highly developed senses and their intuitive "feel" for driving *any* type of car was predicated upon using these senses to maximum effect. they could do things with cars the the "theorists" would not be able to explain...

 

As an Engineer Peter, you have a thorough understanding of mechanics and how a car should behave - you intially said that LFBraking was academic in a RWD car such as the 7:-

 

Quote:

 

"As for Number 6's question, left foot braking can only be used with RWD to promote understeer in a trail-braking situation. Under most circumstances, more control is achieved by relaxing the steering input. In FWD left foot braking can be used to reduce understeer (tuck in the nose) under acceleration through fast corners - its applicability to RWD is academic."

 

End Quote:

 

Now it seems that many folks on this thread, including myself, would beg to differ. It seems that many of us have discovered that LFBraking can be very useful indeed in an RWD car, and can be used in many different ways to induce different effects.

 

Good drivers are capable of thinking laterally - so what you initially said was obviously wrong, and a load of bollocks.

 

But hey, that doesn't fit with the "theory" does it?

 

That is the difference between science and art. The artist does not let science dictate to him - rather, it is the other way around.

 

 

 

 

 

Andy

[Number Six]

One other thing Peter.

 

Quote:-

 

"Try a change, measure the effectiveness with a stopwatch; from this I claim that the principle of objective scrutiny is won. Datalogging just extends the scope of this scrutiny."

 

End Quote.

 

Try doing the above in the middle of a race!

 

The "driver as artist" will be able to cope as his car/tyres may degrade during the course of a race. Because he/she is intuitive, he/she will be in sympathy with the car, and will get the most from it as opposed to the "driver as scientist" who will be by default completely at sea without his beloved datalogs and measurements!

 

(oops, forgot about telemetry - but I hope you get my point)

 

 

 

Andy

[Peter Carmichael]

Andy,

 

You seem to believe that a race is won by the driver. I contend that the driver is just one player in a team.

 

Science is not a matter of labcoats. Science is the art of knowing. Cartesian principles regarding the accumulation of knowledge do not exclude that unstructured experimentation can yield a result (your artistic driver). In order for the greatest knowledge to be extracted from the experiment the observations need to be placed within the context of what is already known and a model of the behaviour needs to be formed. Only then can the potential of that knowledge be unleashed on a repeatable basis, winning races.

 

There are no formula one teams (or other top racing formulae) who do not apply this principle.

[Peter Carmichael]

Now it seems that many folks on this thread, including myself, would beg to differ. It seems that many of us have discovered that LFBraking can be very useful indeed in an RWD car, and can be used in many different ways to induce different effects.

---

 

"Many" have not begged to differ.

 

Are all the folks going to believe you on the basis of your say so? That isn't even the beginnings of a level playing field that you are setting up here. If LFB works there is a reason. If you can explain the reason or if you can knock holes in my argument (yes, I bothered to phrase an entire structured argument) then maybe we will get somewhere and then I will be happy to back down and I will learn something along with everyone else. The reason I am still typing is because you are mucking around with other peoples' knowledge and you aren't stepping up to the mark.

 

Warming brakes and transitions back onto the power are pretty good reasons. Your own observations on handling along with Graeme Finlayson's are ones that I would like to understand better. The only way I can do that is by questioning them.

 

I followed the reference to http://www.DrivingTechniques.co.uk and found this, which appears to agree with me and my science, depending on how you understand the phrase "aid stability in corners":

 

LEFT-FOOT BRAKING

 

Left foot braking in a rear wheel drive car is quite unusual. It's first use is to aid stability in corners, and help keep turbos spinning by holding the car at the correct speed with the brake and keeping your foot on the gas. Apart from this, it has recently been adopted by some drivers as disaster recovery.

 

If you are tanking into a corner, particularly in the wet and the car goes into massive oversteer you may wind on the opposite lock. If it has gone too far it may be possible to floor the accelerator and hit the brake with the left foot.

 

The idea is that you will keep the rear wheels turning due to the power of the engine, but will lock up the front wheels. This puts more grip to the rear wheels and less to the front, hopefully bringing the car straight.

 

This is really only a last attempt technique for recovering previously irrecoverable situations. If you were to use it as a general driving technique you will be one of the slowest drivers on the road... I mean track!

---

[Jason Plato]

Yawn !!

 

 

[Blatman]

Whilst I am not qualified enough to debate at any length with Peter the various merits of his science, I have one observation.

His contention that

"I refute the assertion that race driving is intuitive. From the point at which you start wondering whether you have the right tyre pressure you are engaged in an exercise in objectivity."

While I would agree with the hard scinece part, the fact is that you are still relying on what the driver feels through the steering, suspension and his bum. Science provides a structure for measurements of change, but the change is what the driver feels , (he doesn't get in and know changes have been made until he feels them, surely?) and then decides, based on how the car feels , if he likes or dislikes the changes. The science then determines which change to make next, and by how much. The science, by it's very definition is objective, but surely driving feel is subjective.

The only other way I can think to illustrate my point goes back to F1 analogy. Schumacher seems to like a pointy, twitchy feel to his car. There appear to be very few other drivers in F1 who set up their car similarly, but if science (ie Schumachers engineers) say that this is "right", shouldn't they all have their cars set up the same wayquestion.gif

[Number Six]

My apologies to Dave J.

 

Andy