How details made a title winner for Mercedes



Words by Mark Hughes

With Mercedes having secured the 2014 World Constructors’ Championship in Sochi, here through Giogio Piola’s drawings we look at some of technical details responsible for the W05’s on-track performance, aside from the incredible power unit that is shared with Williams, McLaren and Force India. For a direct Piola-illustrated comparison between the Mercedes, Red Bull and Ferrari and their differing power units, see the feature in December’s edition of the print magazine.

Front suspension

A uniquely-shaped lower front wishbone is at the heart of one of the W05’s key aerodynamic advantages over the competition. Rather than the conventional two-leg construction forming a V (as shown in yellow), the Merc’s lower wishbone was fashioned as a single compact piece with a forked end. It made for a much narrower triangulation; therefore giving it the equivalent strength of a conventional two-leg V was structurally challenging and brought a weight penalty. But the absence of the second leg made the creation of vortices aft of the tyre much easier and more effective.

Because of the 2014 limitation on front wing-span, the front wing endplates now reach only as far as half-way across the width of the front tyres rather than level with the outer sidewalls as previously. This has made generating enough downforce from the front of the 2014-generation car very difficult. One of the tricks used in the previous few years has been to use the endplates to guide the air around the tyre in such a way as to create a vortex (a spinning circular current of air) in the area between the tyre and the sidepod. This was much easier when the endplates went flush with the tyre.

Another vortex is formed from the contours of the central ‘neutral’ section of the wing beneath the nose. This too is formed in the area between the tyre and sidepod. The two vortices rotate in opposite directions acting as gear wheels, sucking airflow through the gap between them at a greater rate. The greater the force these vortices pull the air through the gap between them, the faster the air is pulled over the front wing, creating more downforce. The enhanced speed of that flow also carries to the downforce-producing devices as it travels down the car, over the ‘coke bottle’ body profile and rear brake ducts (which are shaped so as to create downforce).

The absence of a conventional second leg on the W05’s lower wishbone has enabled the aerodynamicists to get around one of the key aerodynamic limitations of the 2014 regulations – the narrower front wing.

Cleanly packaged sidepod internals

A key innovation of the Mercedes power unit is the siting of the compressor at the front of the engine rather than in the conventional position at the back in unit with the turbine. This feature is shared by all the customer teams, but the W05’s design team has taken spectacular packaging benefit from it.

With a compact water-air intercooler integrated into the chassis at the lower cockpit bulkhead, the sidepods are not required to accommodate this component and furthermore the inlet air has a much more direct path to the front-mounted intercooler and then to the inlet plenum and combustion chamber. With a conventional rear-mounted compressor, the air must travel from the intake at the front down to the back to be compressed, then towards the front again to be intercooled, then backwards once more to the inlet plenum. This creates a lot of space-consuming plumbing. In the W05 maximum advantage has been taken to keep the sidepod internals incredibly clean with some highly intricate engineering of ancillary pieces. This has minimised the width of the sidepods, so enhancing the benefit of the enhanced airflow created by the vortices which in turn have been enhanced by the layout of the front suspension.

The way that two key innovations of the car – the front lower wishbone design and the front-mounted compressor – come together at the sidepods to amplify the effect of each other is conceptually beautiful.

Short, high nose design

The W05 did the first three races with a compromise nose design as the originally conceived nose failed the crash test. But by the Chinese Grand Prix the original had been strengthened sufficiently to pass and was introduced onto the car there.

Within the regulations that lowered the front extremities of the nose for 2014, the W05 featured by far the biggest gap of any car between the underside of the nose and the regulation neutral central section of the front wing. This maximised the volume of air that could be fed through to the underbody and diffuser, potentially creating much more rear downforce.

The downside is that the gap is too big to create a diffuser effect in how it works in conjunction with the neutral section of the wing. Cars with a small gap there trick the airflow into delivering downforce from the neutral section by creating a low pressure area that sucks the air through harder. This creates some valuable front downforce, but at the expense of more limited flow to the rear. Mercedes got around the limitation of front downforce imposed by the nose design through its front suspension design instead.

The longer nose used in the first three races was easier to get through the crash tests but the further forward it came, the more it had to drop down, and this created a smaller gap between the underside and the wing, limiting its aerodynamic effectiveness.

Double skin gearbox casing

Like the 2004 Ferrari (like the W05, an Aldo Costa design), the W05 featured a twin skin gearbox. This feature was carried over from the 2013 Mercedes and was used for a different reason to that of the Ferrari, which had a carbon shield over a metal casing to increase strength. On the Mercedes it was to allow different suspension pick-up points without having to change the gearbox (which had to last five races under the 2014 regulations, increased from four in 2013). In this way the car’s set up could be tweaked from circuit to circuit more readily.

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