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Technical: The story behind the W05's success

12 December 2014 – The 2014 season saw Mercedes clinch both world titles with its F1 W05 Hybrid. But how did the team move into such a dominant position? GPUpdate.net technical guru Matt Somerfield overviews the journey.

Forward Planning

Let's not think of this as an overnight success. An increase in performance of this level takes careful planning over a considerable length of time, whilst also requiring the team to endure a certain level of pain in the process. Mercedes has not only invested heavily over the last few years, luring top personnel from their rivals, but also created an environment in which they can flourish. The team's change from 50-60 per cent scale modelling and wind tunnel testing in late 2012 was pivotal, not only in terms of timing but also in releasing performance. 10 per cent may not seem like a great deal but when we are dealing with fractions of a second, that 10 per cent is significant. It can be the difference between taking something to a Grand Prix and knowing it will improve the car or taking something that potentially loses performance.

Unification

2014 provided something much needed for Mercedes; a clean slate. The regulatory changes imposed by the FIA were the largest ever seen in Formula 1 and meant that a performance disparity between the teams was almost inevitable. The level of performance that Mercedes were able to achieve, however, was shocking. Not only did the team have to heed the aerodynamic changes afoot, they also had to be fully aware of the implications of the new power units. The regulations require that the power unit manufacturers, Mercedes High Performance Powertrains in this instance, supply the FIA with a sample unit for which they must provide to all of their purchasing teams. Having Mercedes AMG F1 as its 'works' team meant that the two started to work in harmony on the 2014 project at its genesis.

This crossover of engineering minds helped to shape the way in which the chassis and power unit seamlessly integrated. This even gave it the edge over the teams that Mercedes HPP would supply; McLaren, Force India and Williams. Lest we forget, these other Mercedes-powered teams had the same power unit as the 'works' team. In terms of ancillary components, however, all four Mercedes-powered machines look very different, with the 'works' team the only one opting for an air-liquid-air cooler.

Power Up

The W05's air-liquid-air cooler was sandwiched between the fuel tank and the engines front face, which meant an extremely short boost tract, not only providing uplift in performance (reduction in turbo lag) in its own right, but also allowing the team to run a conventional radiator arrangement in the sidepods, balancing aero performance.

Much was made about the turbocharger layout of the Mercedes engine early in the season, especially as most simply saw it as a way of isolating the hot side (turbine) on one side of the engine, whilst the cold side (compressor) lay on the other. This decision was also fuelled by being able to place the MGU-H in between the engine's 'V', saving space when considering the other option was mounting the turbo & MGU-H at the back of the engine, increasing the PU's length.

Following the same 'shortest distance to the goal' approach was the log style manifold used by Mercedes HPP in 2014, whilst its rivals still toyed with tuned length manifolds. The log design also freed up internal sidepod space, not only allowing more room to package ancillary components, but also to tighten external bodywork where possible.

Ultimately, the tuned length manifolds may give up a little more performance, but unlike the ones used in the previous V8 era their design won't contribute to significant gains. That's because over time the teams had refined their setup to create a very narrow power band, much higher up the rpm chain, tuning the exhausts not only to cater for the power requirement but also in order to use exhaust blowing aero tactics. Contrary to this these, lower revving 1600cc turbocharged engines make the bulk of their power below 10,000rpm and, with a singular exhaust now placed along the car's centreline, it made exhaust blowing a much trickier endeavour.

Old Tricks

Having said that, F1 engineers don't easily forget, they simply adapt, taking old ideas and making them relative to the constraints they currently work within. The change from two exhausts to one and its centreline placement is one such challenge, and was not only born out of the FIA's insistence on a singular turbo but also in order to prevent the teams from blowing the diffusers edges. The energy expended by the exhaust is not something the teams can afford to forget and all the teams have made effort to exploit its potential throughout the season. The energy expended when compared to the V8s will be lessened, especially with the turbo and MGU-H dampening it, but nevertheless it remains.

The question is raised: How can they blow the diffuser from the exhausts new home?

They aren't, instead they're creating flow structures to marginalise its loss. It's rare to look at an F1 car and say with any certainty 'X, Y or Z' is creating aerodynamic performance; you need to look at the car as a whole to understand why certain areas work. Pre-2014 the teams had the beam wing which helped to create an aerodynamic link between the diffuser and rear wing (upwash). These three surfaces were designed to interact with one another in order to create the most downforce for the least amount of drag. With the beam wing eradicated for 2014 onward it was hoped that the teams would simply lose performance. They of course had other ideas.

In the case of Mercedes, the team has a set of rear wing endplates designed differently to the rest of the field, shaped with an upsweep that is purposely designed to 'upwash' the surrounding airflow, influencing the airflow structure below to assimilate.

Like the other teams, Mercedes utilises a Y100 Winglet or Monkey Seat that surrounds the exhaust, with the intention to control the exhaust plume and further enhance the 'upwash' from below, creating a connection with the lower surfaces of the rear wing's mainplane and top flap. This means it can run with a more aggressive rear wing angle of attack, increasing the peak downforce achievable The team has made several changes to the winglet's design throughout the season, as it looks to exploit the exhaust plume energy in differing way.

Boxing Clever

Much of the performance that the W05's predecessor had was left unlocked owing to issues with how quickly it used its tyres. The team introduced a twin case gearbox for the W04 to remedy some of these issues but this was only a halfway solution when compared to the W05's gearbox. The twin gearbox case solution is not new to F1, with a similar design used on the Ferrari F2004, the brainchild of Aldo Costa, who of course is now in Mercedes employment. The principle idea is that a gearbox must last 5 events. Suspending a self-contained gearbox cartridge within the carbon fibre case/crash structure means that the team can make changes to the outer carbon fibre casing at each event if they see fit. This means that should new suspension geometry offer a performance gain, the team can use a new outer case with differing pick up points without incurring a penalty.