Features - Technical
FEBRUARY 23, 1995
Preview of 1995 Formula1 Cars. How the Technical Regulations have influenced design.
BY PETER WRIGHT
In the aftermath of Imola and fuelled by Wendlinger's accident at Monaco it was obvious to most that in spite of the superb safety record over the preceding years, there were areas that could be improved. If Formula 1 was to retain its credibility, measures to improve primary and secondary safety would have to be introduced. Unfortunately safety is not yet a precise science, depending largely on statistics and experiment, and it took until last September before the 1995 Technical Regulations became firm enough for real design work to start, leaving just six months from blank CAD screens to first race.
The FIA's clear safety objective, in so far as the cars are concerned, is to reduce cornering speeds, without increasing top speeds, in order to reduce the kinetic energy involved in any accident, and to minimise the injuries to the driver in all types of accident. The first steps towards this objective are embodied in the regulation changes for 1995 that set out to:-
· Reduce downforce
· Reduce power
· Increase energy absorption by the car's structure
· Reduce injuries to the driver by his restraint system, and by impact with the structure, barriers or detached parts of the car
The Technical Regulations are drafted in such a way that they are not only as unambiguous as possible (a difficult task in the face of the ingenuity of Formula1 designers) but also as policeable as possible. The Constructors requested that all checks to confirm compliance with the Regulations, from 1995 onwards, should be achievable within two hours of the finish of the race so that a firm result could be published. However it is not until a dozen design teams have sat down and worked their way through the small print that the full possibilities and implications of the changes become apparent. So, what did they find, what did they make of it, and who made the best of the inevitable compromises?
By far the easiest regulation change to draft was the striking out of "3500cc" and the substitution of "3000cc" in the section that stipulates the maximum swept volume of the engine. This, combined with the rigorous definition of the physical properties of permitted fuel and the tidying up of last year's regulation to prevent pressurisation of the engine intakes via the airbox, should achieve an approximately 100 bhp power reduction, or around 14%. That was the easy bit! The engine designers have been faced with the choice of reducing the capacity of their existing engine and re-optimising for 3-litres, or an all-new design. The former carries less risk, but is burdened with non-optimal size and weight - everything is a bit too big. The latter route permits full optimisation and integration with a new chassis - especially if a new team is involved, as is the case with McLaren and Mercedes - but limits time for development in the period available. The dilemma is even greater if the designer decides that the old engine has too many cylinders for the reduced capacity, and wants to remove two cylinders from his V12 or V10. These sort of decisions tend to win or lose Championships!
The chassis and engine designers must work closely together during the early stages of the design process, as the concept of the engine and its development objectives, bear greatly on the layout and detail of the car. The torsional stiffness of an engine depends primarily on its length, its cross-section and the details of the joints between the load bearing components. The chassis designer will prefer a V8 structurally, as it is inherently the shortest engine and has the largest cross-section. It also has its CofG furthest forward (more of which later), but a higher CofG compared to a V10 or a V12, due to a longer stroke. The Benetton benefited from these characteristics in the Ford Zetec-R V8 in 1994 and this configuration must be being studied very closely for new 3-litre engines.
The higher RPM practicable with the shorter stroke and lighter reciprocating parts, tends to result in a peakier power curve. Jordan have opted for 7 speeds in their new gearbox to be mated to the Peugeot engine, in anticipation of this. It is interesting that Ferrari, who experimented with 7 speeds in their early semi-automatic gearboxes (the semi-automatic gearchange makes the extra changes feasible for the driver), abandoned it in favour of 6 speeds, even though their V12 has always suffered from a peaky power curve. Drive-by-wire throttles provide a simplified means of building in progression as the driver feeds in power on exiting a corner.
The changes in the regulations that affect aerodynamics complete a process that will have reduced downforce by around 30-40% over the highest figures attained with the flat bottom. The 50mm step, apart from raising radiators and exhaust systems, means that the expansion ratios (ratio of cross-sectional areas under the car at the leading edge and trailing edge of the flat bottom) that used to be attainable are no longer possible. It is still feasible to get very close to the ground with the centre section of the car, under the monocoque, but its aspect ratio (width/length) is terribly small - around 0.2. Separating the airflows under the centre section from the two raised sides, and inducing the maximum flow of air under the car will be the objective of the aerodynamicist. Hence the outbreak of paranoia about the secret details of turning vanes, fences and all manner of gizmos.
New dimensions for the exclusion zones relating to anything with an aerodynamic influence (around and behind the front wheels; above and forward of the rear wheels) explain the small wings tucked into some unlikely and aerodynamically inefficient places, in the quest to extract the last ounce of downforce from the air flowing past the car.
There is always much talk of total downforce, how cars compare in this respect, and how much has been lost, and yet this is misleading. There are few circuits where maximum downforce is carried - eg:Monaco and Hungary. On other circuits what matters is the magnitude of the downforce for a given top speed. The parameter that determines the aerodynamic performance of the cars is the Lift/Drag Ratio. Because so much downforce has been lost from the underside of the cars, where it was generated relatively efficiently compared to wings, the L/D has fallen by 40-50%. With the reduction in power, cars will not be able to carry even the new lower maximum available downforce, at many circuits.
Since the reduction in 1993 of rear tyre width from 18inch to 15inch, the CofG of the cars has moved forward to give 2-3% more weight on the front axle. This was necessary to maintain the stability margin with the reduction in rear axle cornering capabilities. It was not possible to achieve a change of this magnitude without the use of ballast, as the position of the engine/gearbox relative to the driver, dictated by the length of the fuel tank, precluded it. The solution has been to reduce the weight of the engine/gearbox by as much as possible (the masses behind the CofG) and lighten the remainder of the car until it is 20+kg below the weight limit. The required ballast is then mounted forward of the CofG to adjust its position as desired. Why else would Ferrari make formidably expensive steel gearboxes in 1994, change the material to titanium, and then design a new carbonfibre gearbox for this year, unless they had a CofG problem generated by their long, heavy V12?
The removal of the minimum fuel tank capacity regulation - 200litres- for this year, has eased this situation somewhat, allowing the engine to be mounted further forward. The enforced moving back of the driver to ensure a cockpit long enough to accommodate the tallest specimen, has partially cancelled out the benefits. As an aside, it is amusing to note that just as the designer could stop worrying about who was going to drive his car, and whether he would fit, the weight regulation was changed to include the driver in the minimum weight (from 515kg to 595kg, which includes 10kg for the new side impact structures, leaving 70kg for an average driver). So, back to the Team Manager to find out how much weight has to be saved to compensate for the new heavyweight signing!
The freedom to move the engine forward, into the space vacated by around 100-120litres of fuel, has stimulated a return to longitudinal gearboxes. Their narrowness and the freedom to move the mass of the gears forward, more than outweighs the inconvenience of changing the ratios, which are located between the clutch housing and the final drive, and must be removed forward through the front face of the gearcase. The more cautious teams have retained their tried and tested transverse layouts, in order to have one section of the car (often the section that gives the most trouble in early testing) that is proven.
The shorter fuel tank, deeper, wider cockpit area, side impact test requirements and increased structural and crash test criteria, mean that the structure of the monocoque will be extremely stiff. Instead of struggling to maintain torsional stiffness while slimming the monocoque down, the designers have had the sectional size determined for them, and by the process of building in sufficient strength and impact absorption, there should be adequate stiffness.
The taste of Active Suspension that most teams had in 1993 brought home to the engineers the potential advantages the system offered in a) divorcing ride height from spring stiffness and b) de-coupling suspension stiffness and damping in heave (vertical motion), pitch and roll. With the banning of Active Suspension for 1994, suspension engineers focused on purely mechanical means of achieving some of these advantages. Last year the emphasis was initially on controlling ride height as closely as possible, but without the addition of hydraulic energy it is no longer possible to raise the car as aerodynamic loads compress the springs and tyres. However as the aerodynamic downforce was reduced by progressive regulation changes, there was a shift away from ride height control towards the classic suspension disciplines. Mechanisms began to appear (on the Sauber for example) that allowed a rising rate stiffness in heave, without a coupled raising of the roll stiffness.
With the further reduction in downforce and the smaller influence of the undertray, it is becoming less important to maintain a low ride height at low speeds, at the expense of very stiff suspension at high speed. The trend towards more "normal" wheel rate characteristics will continue; and greater sophistication in separating out the modal characteristics (heave, pitch and roll) of the car on its suspension will be evident. Tyrrell's hydraulic front suspension on their new car would appear to be targeted at achieving independence in heave and roll. The potential advantages are fairly subtle, but small differences are going to count for more and more under the new regulations.
Which brings us to the tyres. Goodyear must have breathed a sigh of relief, for the second year running, not to have to redesign, re-tool and redevelop the tyres for Formula1. They know what it takes having been through the process in the winter of 92/93. Much of their engineering effort is currently focused on the threat from Firestone (Bridgestone) in Indycar racing and they really did not need a big change in Formula1 tyre specifications. Having said that, as one of the unsung heroes of Grand Prix racing, Goodyear will undoubtedly produce a reliable, consistent range of tyres to suit the altered power and downforce characteristics of the 1995 cars, and successfully juggle the teams' requirements for refuelling strategies against tyre life.
There are no new regulations for 1995 that impose any further bans on electronics or their use. However it is in the nature of computers that their use is limited only by the imagination of the software writer. There has been a steady stream of queries from the teams to the FIA and each point has been clarified. Where the answer is, "Yes, you can do that.", no-one but the team involved and the FIA knows what will be tested and maybe raced. The main areas of experimentation centre around the gearchange, the operation of the clutch, drive-by-wire throttles, differentials and brake balance. So long as the techniques do not substitute for the skill of the driver, by taking over or assisting with control of the car, or sending signals to the driver to aid him controlling it, they are likely to be allowed.
Rigorous checks of electronic hardware and software will be carried out by the FIA at teams' premises, and back-to-back checks against approved software, at the track. This has meant some revision of the way software is loaded and read back for both chassis and engine control computers, and has forced all teams to look closely at their software housekeeping. Along with the ability to check fuel against the analysis of approved samples, again at the track, and new, laser-based dimensional checking equipment, these measures should enable the Technical Regulations to be policed in a timely, credible, and hopefully, uncontroversial manner.
One change in the regulations is a direct result of the new approach to dimensional checks: the height of much of the bodywork and aerodynamic devices used to reference to the ground. Now everything is referenced to the Reference Plane - the lowest part of the sprung mass of the car apart from the plank. The job of Race Engineer will be that little bit easier as it will no longer be necessary to check wing and body heights every time ride heights are changed.
If the new regulations have not introduced much added variety into the cars, even though they are all new, I sincerely hope they will bring the performance of the cars much closer together and produce safe, entertaining racing. Which Technical Director has arrived at the best compromise and interpretation of the new Technical Regulations, only consistent results will reveal.