The 2005 Technical Review

After a prolonged period of Ferrari dominance Formula One had been in the doldrums, while the teams expected to rival the Italian marquee were tying themselves in knots trying to find a technical advantage. It was when the FIA stepped in with new, far reaching rule changes that this pattern was able to change. New rules for aerodynamics, tyres and engines provided new opportunities to get an advantage.

Another factor for the other teams competitiveness this year has been their financial state. Many teams have been on extremely limited budgets, facing closure during the winter of 2004. Also some teams were up for sale, creating uncertainty. As the season progressed over a grueling nineteen races, it has been the teams quickest and best to adapt to the new rules that have succeeded, while other teams perhaps not earmarked for success made a breakthrough and stepped up the order.

In being able to do this, the teams have had to really work at what has been the by-word in Formula One in the new millennium, integration. With rule changes affecting the three critical elements in the car, teams needed the ability to make each one work in unison to provide a balance between speed, tyre wear and engine reliability. Curiously Renault and McLaren are teams with a multi-site approach to chassis and engine design; how this has been possible when the perceived wisdom of an "under one roof" as being best shows how teamwork and communication are at the core of a modern Formula One teams requirements.

Rule changes

As mentioned the FIA brought in three sets of rules changes: two to contain speeds (aero and tyre) and one for cost reduction, as well as some speed containment (engine). Firstly the cars were robbed of about 25% of their downforce by raising the front wing, lowering the diffuse tunnel height and moving the rear wing forwards.

This reduction in downforce was married to the demand that a set of tyres last for both qualifying and the race; the effect of these two changes were aggregated as tyre life demands good aerodynamic grip, something the teams were now short of. Engines were also restricted along similar lines to the 2004 one engine per race rule; the engines were now required at the next Grand Prix and raced for another 750 kilometres.

Aerodynamics

Recouping the lost downforce and maintaining a balance, aero development at the front of the cars was as much about recreating the lost downforce as it was managing quality flow to the rear of the cars in order not to upset the rear wing/diffuser or the aero balance front to rear.

Front wing design

With the outer section of the front wing now raised again by 5 centimetres the teams had less interaction with the ground and more disruption to the rear of the car to content with. The teams had two directions requirements to aim for: downforce and sensitivity. A larger, more complex wing would make more downforce, but at the expense of being sensitive to set up and attitude changes, while the teams with simpler, flatter wings had an inherently more benign design, at the cost of grip.

Of course, with careful design both aims could be achieved, and each team started the season with a different idea of what downforce could be generated for a given amount of drag and sensitivity. Wings with a low centre section have a problem with sensitivity, but diligent work mapping the downforce changes with pitch, yaw and steer directed the designs in the right direction. This central section has some effect on the flow at the rear, but most of its flow heads into, or easily around, the sidepods.

With the outer sections now being higher they had to be worked hard. This was not easy, as they lacked the ground effect of last years lower wings, and the steeper flaps created more drag. With a limited amount of space in which to work the outer sections of the front wing, teams had to either make the wing steeper or longer.

The steeper but shorter option was attractive, as they have less drag and are less sensitive, but the downside is the interference to the rear aerodynamics. Longer flaps had their own problems of more inherent drag and being prone to separation, while splitting one large flap into two smaller flaps increases the number of slot gaps to reduce the separation. These three element wings were only adopted by Ferrari and McLaren initially, although Williams joined them mid season.

The end of season flourish of copycat canards on the endplates gave the teams a third option; the canard acts as an extra wing working in a cascade (like a biplane) with the main wing; this produces more downforce at the cost of some efficiency, but critically gives less interference to the rear of the car. I expect these will be a more common adoption next year.

As the limited dimensions on flap height and length affect only the outer portion of the wing, the relatively free reign for the middle 50cm span of the front wing allowed some teams to exploit some new solutions. A lot of teams with a low central wing shape extended the leading edge forward to form a beak; this simply gave the middle section of the wing more chord length for the same benefits described above. Ferrari, and latterly Sauber, used a chin wing; this acts like a slat on an aircraft wing, and creates a different onset flow at the front wing's centre section.

As the teams' primary aim has been to manage the location of the centre of pressure (front to rear downforce distribution) the work the bargeboards/turning vanes play has been the subject of a lot of attention. There has been yet another merging of solutions away from large, rear placed or smaller forward placed boards, to a mix of medium sized rear boards mated to complex forward arrays of vanes.

Their aim is to collect the flow off the front wing, then route it in the most efficient manner around and under the car. The forward arrays work with the suspension arms and try to flatten the rising wake of the flow to prevent too much air passing over the car to the rear wing.

It is this interaction with the wishbones that has been one of the year's most interesting variations. McLaren found in their pre-season aero testing that the lower wishbones placement was critical in managing the flow off the front wing: as the front wing was now re-sited 5cm higher up, the team also rushed a re-sited lower wishbone onto the car.

The resulting "no keel" set up provides a very clean shape to the nose of the monocoque; the other teams remained with what were effectively single keels, although Renault had a small variation on that design.

Equally the lower edges of both the front and rear bargeboards were trying to straighten the flow under the car to improve the diffusers efficiency and also to flick up some air that would otherwise pass under the car and trail it along the flanks of the sidepods. This flow also acts to seal the underfloor from the higher pressure above the car, upsetting the diffuser.

To this end the omnipresent "axe heads" act as flat bottomed flip ups, working in conjunction with the undercut to the sidepods. Now present on most cars on the grid, the sidepods undercut streamlines the flow under the car's nose and over the splitter.

Sidepods

Sidepod design followed on from the themes of the past few years, with the teams forever repackaging the internals into smaller spaces to allow the aerodynamicists freedom to wrap the bodywork tighter around the rear end, to improve the flow to both the rear wing, lower beam and over the diffuser. To make the sidepods shape fit what the aerodynamicists need teams have designed novel shaped radiators, either by folding them into a V shape or making a flat profile with a complex outline.

Cooling designs are again gelling into a common standard, which is long low flip ups kicking up high and around the rear wheels, above which are cooling chimneys and louvered engine covers. Tuning the amount of cooling the cars needed was done either by resizing the chimney or the removal of the louvre panels.

Renault had permanent louvres molded into the engine cover; this preventing them being replaced by smooth panels, and instead there were blanking plates added to the inside of the engine cover. This was a curious solution as, even when closed off, the louvres would have an adverse effect on the aerodynamics.

Chimneys remained a primary cooling option, and the teams have found them also to be extremely useful in shaping the flow along the rear of the car. Angled chimneys start to the split in the flow between the rear wing and around the rear wheels. Even when the cars cooling requirements rendered the chimney redundant they were still installed, but closed-off or replaced with specially shaped blind ducts. As the rear of the car is now often packaged so tightly teams have resorted to a lot of small outlets and scoops to vent or cool parts around the rear of the car.

Downforce creation at the rear of the car often started as far forwards as the sidepod leading edge. The shoulder wings run by several teams acted along the same flow-conditioning theory as the chimneys, sending the flow in the right direction aided by the spiraling vortex created by the wing shape. While they added their own downforce, their main aim was to improve the overall downforce of the car. As these were only really using the outer tip to do the work most teams discarded the inner section adjacent to the chassis, as it added little benefit.

Diffuser

All the work down at the front of the car and along the sidepods has been aimed at making the three rear aero devices work to their best effect.

The whole cycle of rear downforce starts with the diffuser: this year the outer tunnels of the diffuser were capped at a height around half that allowed previously (125mm) and, with no undercuts allowed, effectively the whole diffuser must be visible from below. Up to 2004 the side tunnels were worked hardest to create the downforce; now the teams have had to make them even more aggressive and made the function of the centre tunnel more of a primary concern.

Flow passes under the floor in a relatively straight line, as the flow reaches the end of the flat bottom (in line with the front of the rear tyres) before getting kicked up with a step running the width of the floor. This helps the flow to attach cleanly to the sudden ramp of the diffuser roof. As the flow exits the side diffuser tunnel there are gurneys attached to the upper side to drag the flow out of the tunnel as hard as possible.

From here the flow rises rapidly, aided by the shape of the rear wishbones and the lower wing beam, while the outer sides the flow are shaped by the bulbous brake ducts and fences around the floor's edge. The centre tunnel of the diffuser now has a very steep initial ramp, and the flow's exit is managed by the shape of the lower beam around the rear lamp. This year some teams have installed mini wings above the lamp to aid the sudden rise of the flow out of the tail of the car.

Rear wing

The rear wing itself is made of two elements (a main plane and one flap), and has been moved forwards; as a result it does not work in such close conjunction with the diffuser. The horizontal aerofoil elements, such as the mid wing and shelf wings, collect the flow as it is upset by the cockpit opening and roll structure, turning it into a smoother, downwards flow towards the rear wing.

The wing itself has had to be worked harder this year, partly as a result of the downforce lost from under the car and by its less ideal placement further forwards; this comes at the cost of drag created at the wing tip and, by mid season, every team had slots on the front of the endplate to bleed high pressure from within the wing to offset the low pressure at the outside of the wing and reduce the strength of the vortex created.

Tyre management

This year the rules were changed to force teams into using a single set of tyres for qualifying and the race; whereas previously the teams worried about degradation and waning performance but not wear, as they only had to last a single stint before being replaced. This year the tyres wear rates were an overriding concern, and degradation was partially eliminated by the harder compounds adopted to fight wear.

Tyre wear comes from two factors; tyres working in traction (that is accelerating and braking) and in slip (which comes from cornering); each issue has its own solutions. Traction wear is related to the lower speed range where the cars acceleration is greatest. Formula One cars are currently traction limited, and they have too much power to put it all on the ground. As a result the search for traction starts with the mechanics of the car, the suspension geometry spring and damper rates, and weight distribution.

A softer set up inherently works better for traction, but this does affect the cars higher speed behavior, which tends to require stiffer settings. Traction control makes the most of the available traction (and not vice versa) as it works to prevent wheel slip above a certain slip ratio (differential between front and rear wheel speed). Previously the teams would have been near to the edge of the slip ratio to get the most traction, now the ratio (albeit driver adjustable in the race) of slip is lower to preserve the tyres.

As the second form of wear, slip wear is more difficult to control as it occurs at both low and high speed, with the low speed problem the more damaging. In slow corners mechanical grip controls how much the tyre slips, which is the angle between the tyres path and the cars direction. Suspension geometry, weight distribution and, to a lesser degree, lack of downforce combine to create very high slip angles; this wrecked front tyres or induced graining.

Graining is where the slip angles damage the edge of the groove, with bits of rubber breaking away and then sticking to the tread of the tyre. The effect is like running on ball bearings, as the tyres main tread is separated from the track by the grains of rubber. A grained tyre can be recovered, with careful driving, to full grip within a few laps. Running hard on heavy fuel or with low downforce are key ingredients to graining.

High speed slip wear is also a function of suspension geometry and downforce. As the slip ratios tend to be smaller the risk of graining is not as marked, but it is harder for the driver to mitigate; aero balance changes at the next stop are the key to relieve high speed slip.

Whatever the cause, once the tyre has started to wear the effect accelerates, leaving the driver with the option of purposely running slower, running out of grip as the tyre wears, or changing the tyre; with the rules disallowing the latter it has been down to the drivers to manage their tyres.

One high profile factor associated with tyre wear is the risk of flat spotting the tyre under braking or in a spin: either produces a high wear rate on a small part on the circumference of the tyres contact patch. The tyre works like a cam and vibrates. Minor flat spots can be managed by careful driving, but more serious ones lead to severe vibration, making the drivers vision blurred and inflicting damage to the chassis.

Kimi Raikkonen's flat spot problem was clear to see, but the team were unsure if a tyre change would be allowed and believed the chassis could take the visible amount of vibration being metered out by the tyre. Eventually the wheel bearing cried enough and collapsed, taking the front suspension with it. Fortunately the FIA clarified what constituted a dangerous tyre, even if self inflicted, and allowed tyres to be changed if in this condition.

As with all things on a Formula One car, compromise is the critical factor in making a set of tyres work for the whole race and also in qualifying. A car's balance is made up of two factors: the weight distribution (front to rear) and the car's aerodynamic centre of pressure (where the front and rear downforce are equal). The general rule is the weight is biased to the rear (around 52-58%) with the weight distribution being just ahead of it, to induce understeer rather oversteer.

The specifics of these settings vary with each team and each race track: teams that have struggled to put weight or downforce where they want end up with unbalanced handling, which may prove faster over a single lap but handicap them in the race, as the car is harder to drive. An alternative is to have a better balance and forego some speed advantage to preserve the tyres.

This year the struggle for front downforce pushed teams into rearwards weight shift to balance the aero; this then upsets the tyres from lack of grip in both and low speed. Bizarrely the quest for more front downforce can come at the expense of rear downforce, as the flow to the rear end is upset, thus a balanced set up for front end grip can bring rear tyre wear from high speed slip in the race.

Teams tend to err on the side of front end grip, as this dictates braking and corner entry, at the cost of traction out of corners. Top speed isn't affected, but on some tracks a lack of traction out of a slow corner onto a straight can leave the car vulnerable to overtaking from a car with better traction.

Tyres

Despite Ferrari's dominance in recent years there has been a true tyre battle, with Michelin gaining wins from Bridgestone on the basis of a better tyre on the day. This year Bridgestone lacked in their response to the rule change, and their sole reliance on Ferrari (and vice versa) left Michelin with a tyre advantage. The result was clear; Ferrari were left to trail most of the Michelin runners despite a car that was perhaps better than some of the Michelin shod cars. While the reasons for Bridgestone's initial lack of response to the new rules can be understood, the lack of progress through the year despite immense testing mileage was surprising.

Tyres cannot be measured and designed to a specific brief like perhaps an aerodynamic part can be; the black art of tyre design calls for experience and intuition. Michelin's dominance in long distance racing and their recent philosophy in Formula One tyre design have conspired to give them an advantage this year. The simplistic understanding of the difference between Michelin and Bridgestone lies within their emphasis on different parts of the tyre to create grip.

Bridgestone have a more flexible construction; their tyre literally drapes over the track to create the full contact patch for grip, and this greater deflection and flexibility creates heat inside the tyre, making the compound run hotter. Michelin have a squarer, stiffer shouldered tyre which keeps the tread more aligned with the wheel, placing reliance on the chemical grip of the compound to give the adhesive-like grip. This more rigid set up produces less heat, which is kinder to the compound.

Gearboxes

A quiet revolution has gone on in gearbox design this year. While the primary goals of less weight and shorter cases remained, the internals and the shift mechanism have been transformed for some teams. Shift speed is a critical aim with the current generation of sequential semi auto gearboxes. The shift itself is made up from the drivers demand for a new gear from the steering wheel, then the engine throttling off, while the old gear is disengaged and the new gear engaged, then lastly the engine returning to the throttle.

Limiting this process is the speed the engine can lose revs at, and the speed of the disengage/engage process. The former issue is hard to improve upon, as the engine already has no real flywheel and the torsional impact of a slowing engine affects reliability. Thus it is down to the mechanical shift element, and a new engagement method has been adopted by up to three teams where the conventional dog tooth engagement method is revised to use two (upshift and downshift) dogs in a ratchet like manner. Accurate details are scarce on which of the teams have used this technology and how it works in detail.

The externals of the gearbox and, in particular, the case have progressed little this year; McLaren have joined BAR by adopting a carbon fibre case, while Ferrari and to a lesser extent Jordan use carbon fibre to reinforce their metal (Ferrari titanium, Jordan aluminum) to provide strength to localized areas. Elsewhere titanium or magnesium is in use. Most teams adopted the seven plus reverse format, leaving Renault with a six speed unit.

Engines

With the change to two race engines, the engine suppliers have for the large part produced a batch of reliable engines, yet the power output and rotational speeds (revs) have increased despite these new demands. As the season closed off Formula One saw the most powerful normally aspirated engines (i.e. not turbo or super charged) it's ever seen, with the three litre format and 19,000 rpm giving power of over 900 hp and perhaps nearer to 950hp.

Notwithstanding the high output and engine speeds, the engines are able to make power from down near 4-6,000 rpm aided by variable inlet trumpets and sophisticated electronics. All of this is crammed into a package 23 inches long, 21 inches tall and 17 inches high, which in plan view is the area of about fours pieces of A4 paper!

In order to maximize the engine life available teams were required to restrict the engine to a quota of laps over the opening days of a race weekend. This preserved engine life in order to provide the power required by the team, such as for qualifying and in certain parts of the race. Turning the engine up in the race can be done from various mappings set from the steering wheel, and each setting trades fuel economy with power, and hence reliability. Additionally the driver gets an overtake button; this a momentary switch to allow for higher revs and power for short bursts, but it is not used for whole stints.

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- The Autosport.com Team

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