Claude Rouelle is an ebullient Belgian raconteur. In his three day seminar he
tells slightly risqué jokes, shows lots of fun video snippets from his lap-top,
and at times expounds on his version of his meaning of life and death. Oh yes,
and gives some of the very best grounding in race car suspension dynamics that
you’ll buy at any price.
Running from 8 am to damn-near 7 pm, the three-day seminar is a
roller-coaster grind of brain work, or, as Claude would put it, ‘mental
masturbation’. Even with the breaks every 90 minutes or so, the rapid-fire
bellows of “Yes or no!”, Claude-isms (“Air is invisible therefore it is more
difficult to see”) and complex concepts presented in a thick French accent (“I
dearly speaking, you actually ‘ave a very able spring of the suspension which is
not affected by eye-ro-dymics”) makes for very long days.
Add to that the fact that any beginning teacher would be appalled by his
habit of standing in front of the whiteboard as he draws on it, losing his place
in his lap-top files as he tries to find the right picture to show on the LCD
projector, and a lousy approach to answering questions and well, if it wasn’t
for the brilliant information, you’d be tempted to give it all a miss.
Especially at US$950.
Claude Rouelle has worked in Europe, Japan, the US and Australia as a race
car engineer and consultant. He has a masters degree in engineering and has been
involved in cars as diverse as NASCAR, Formula 1 and touring cars. His company,
Optimum G, is based in the US but his seminars annually span the globe from
Australia to France, the UK, Italy, Germany and the US. His laptop PC is a
resource flush with data-log records and photos of a huge range of race cars and
he uses these extensively. However, the course itself is based around animated
PowerPoint slides, paper copies of which are given to the course
participants.
The Australian seminar, organised by MoTeC and run at that company’s
Melbourne facility, was held in June.
The Participants
The course blurb suggests that a huge variety of people should attend the
seminar: race engineers, race drivers, team owners, students who want to find
jobs in racing, and so on. The reality is that participants need to have a quite
extensive knowledge before they attend: concepts like roll centres, weight
transfer, motion ratios and aerodynamic coefficients should all have been past
grist for the mill.
At the seminar I attended were young graduate mechanical engineers (often
those who had been involved with Formula SAE), a Holden suspension engineer, a
longstanding V8 Supercar team manager, two V8 Supercar drivers, three V8
Supercar race engineers, a MoTeC support engineer, an advanced amateur racer, a
production car racer, a sports sedan builder, a TAFE teacher and several retired
racecar technicians looking at making a return. Oh yes, and another journalist
who had also got a free ticket courtesy of MoTeC.
The depth of experience in the room was made clear in the first hour, when
Rouelle encouraged each participant to speak briefly about their backgrounds.
However, it’s unfortunate that this experience was seldom used in the seminar –
although there were many opportunities where the subject could have come alive
if particular handling problems had been highlighted with experiences from those
gathered. (One time when this occurred was when discussion turned to tyre
slip-angle versus grip. Is it better to have more slip angle for a given grip,
or less? The answer is less, because reduced drag occurs on the car – and the
participant answering the question used an example of his own low-powered car
that slowed greatly when passing through a long, full-throttle corner.)
Day 1
After some preliminaries, the first topic was tyres.
The most interesting concepts related to the internal behaviour of the tyre –
that in four ways a tyre acts as if it has internal springing. These are
vertical, longitudinal, lateral and in torsion (ie when viewed from above as it
is steered). Should any of these ‘springs’ (or elasticities) reach a
‘coil-bound’ state (ie the limit of their elasticity) then grip will be reduced.
The concept of a tyre having a vertical springiness (it acts as part of the
suspension) is common, but less thought about are the other directions of
elasticity. For example, the longitudinal tyre deformation causes the centre of
the contact patch to sometimes be ahead or behind the centre of the wheel. A
front-wheel drive car under strong acceleration will have a contact patch that
can move sufficiently for the steering geometry to change.
Another interesting point is that the self-aligning torque (felt by the
driver as the weight of the steering) doesn’t necessarily increase with grip.
Instead, the steering may be going light even though to provide more grip, the
wheel can be turned a little more (ie increasing the slip angle). Talking about
slip ratios, the concept that a tyre develops most grip (whether in braking,
acceleration or cornering) when having a slip ratio of 5-8 per cent was also
covered. This is the approach used in traction control and ABS (and probably
also in well set up stability control systems).
Especially important for later sessions was the concept that as vertical load
on a tyre increases, so does contact path area and resulting grip.
(Not mentioned was the argument between those who believe that for a given
vertical load and tyre pressure, the footprint area of a tyre doesn’t change
with tyre width – the contact patch changes in length versus width but the area
remains the same. I privately brought this up with Rouelle, but other than
saying “I don’t buy it” and then moving smoothly into an irrelevant discourse on
how Michelin store the tyres in their truck, he didn’t have an argument either
way.)
Also touched upon in this section, and repeatedly addressed later, is one of
the most important points of the seminar. When a car is cornering and weight
transfer occurs from the inside tyres to the outside, the outside tyres gain in
cornering grip because of their increased load. At the same time, the inside
tyres lose in their grip because of their reduced loading. However, the reduced grip from the inside tyres is a
greater loss than the increased grip from the outside tyres. This is a
critical point because it means any lateral weight transfer is going to reduce
the overall grip of the car. (It’s also why, all other things being equal, the
fitting of a sway bar reduces grip at that end.)
Other fascinating snippets tossed in by Rouelle include the idea that front
tyres shed rubber that is picked up by the rear tyres, and tyre companies try to
use compounds that won’t adhere to other manufacturers’ tyres, so as not to
benefit them on the track!
From the most to the least expert participant, Day 1 was an eye-opener –
there was plenty to learn, even if you picked-up on only one-third of the
points. But Day 2 started disappointingly.
Day 2
This session began with aerodynamics. I don’t know if it is because this is a
particular interest of mine – or despite of it – but there was little to learn.
Although we spent several hours on the topic, all that was really covered were
the basic drag and lift formulae and the idea that rake (the angle that the
underside of the car makes with the ground) causes major changes in lift and
drag. Clearly, this isn’t Claude Rouelle’s area. In fact, it was only when he
was addressing the suspension set-up used to order to obtain the optimum rake
angles in different corners that the seminar came alive at all.
In fact, the most interesting aerodynamic point was made the previous day.
That is, because the centre of pressure is higher than the centre of gravity,
lateral and longitudinal aero loadings (ie side winds and drag) cause moments on
the car body. For example, the frontal drag causes a pitch moment on the car,
pushing the back of the car down, and sidewinds cause compression of the
suspension on the downwind side of the car.
But there was good stuff to come... very good stuff indeed in the kinematics
sessions. However, I must admit to drowning in the technical detail – before
attending the course, I wish I’d spent an evening revising roll centres, centres
of gravity, moments and couples! The relationship between the instantaneous
centres of rotations, the way that they can move as the car rolls and pitches,
and the changes that suspension geometry can make to them is, to say the least,
complex and involved.
By the time Claude got to lateral weight transfer – suspended, non-suspended,
geometric and elastic – I was lost. And to be honest, I think that if anyone in
the room had been required to succinctly and accurately explain the concepts
they had just (apparently) learnt, they’d have been mostly lost as well.
Certainly, in discussion with me immediately after the session, an engineering
graduate (and current V8 Supercar race engineer) had forgotten one whole
category of weight transference – and I am pretty sure my understanding was far
less than his.
This is one of the glaring weaknesses in Rouelle’s approach – there’s never
any requirement for students to verbalise their conceptual understanding (easily
achievable say in 10 minute group work on a set problem) and so an exultant
Claude sweeps himself along, bellowing “Make Sense?” and “You see I mean?” and
“Yes or no?” while the audience half-heartedly nods.
If audience questions were carefully and effectively addressed, much of the
deficiency would be remedied - but this isn’t so: despite encouraging them,
Rouelle is dreadful at answering questions from the audience. A typical Claude
answer begins: “I am going to answer your question but let’s go backwards...” and
following that are all sorts of entertaining excursions... perhaps half of which
answer any of the questions. At one stage a participant asked a very simple
question (“Is there any information available on the optimum steering effort for
a driver?”) and needed to ask the question three times before it was adequately
answered. Most students don’t have this tenacity. Another problem is that when a
question is asked in the form of a statement, Claude tends to answer “Yes!” –
even when the statement appears wrong in the context of the material that has
just been covered. Certainly, for me, this considerably increased confusion.
Are these comments the pickiness of a teacher of nine years experience?
Possibly, but if you have a lot of hard concepts to communicate in three 11-hour
days, you need to be a very good teacher indeed...
Day 3
While again it covered a lot of ground, the greatest revelation on the last
day was in the tuning of dampers. How dampers work, both in low speed and high
speed damping, and how that influences the car’s behaviour, were all brilliantly
covered.
Even more important is the way in which linear potentiometers can be used on
the suspension to not only show how well the damping bump and rebound settings
are optimised, but also to derive an enormous amount of information about how
the car is behaving. Although the seminar is organised by MoTeC, there was never
a whiff of any paid advertisement for the company’s products – but by the time
the coverage of suspension logging was finished, there wouldn’t have been a
person in the room who didn’t realise the critical nature of this logging... by a
MoTeC system or another.
Despite going longer each day than it was meant to, on the last day the
seminar ran out of time. This was very disappointing, as the final section of
the course notes – Car Set-up – looked the single most critical part of the
course – and it was literally not covered at all. It was in this section that
the theory of the previous days could have been integrated into an action plan
on how to get the best results from a car. This session could also have been
used to quantify the relative importance of the different aspects of the car –
kinematics, dampers, springs, aero and so on. Without such a prioritisation,
where do you start?
Conclusion
Exactly as it stands, this is an indispensable course for anyone who circuit
races any type of car – or even anyone who has a good general knowledge of
suspension but wants to take it to a much higher level. However, with a bit more
direction, instead of it being an 8/10 course, it could be 9 or even 9.5.
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Julian Edgar attended the course courtesy of MoTeC. Claude Rouelle courses
are held around the world – see
www.motec.com.au/rouelle for more
information.
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