Marussia Coanda Duct – 3D Printed Titanium

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Since 2010 this blog has covered a lot about exhaust blown Diffuser (EBD) technology, especially in the latter years when it was allowed in F1, with the use of the Coanda effect.  Now three years on, some of the manufacturing processes that allowed such rapid development of EBD’s can be revealed, especially with the use of 3D printed titanium parts.  Here we have a printed titanium coanda duct from the Marussia Team.

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Let us briefly review what was going on with exhaust technology back in 2012-2013, rules were written to raise the exhaust clear of the car’s floor in attempt to prevent is directly blowing the diffuser or tyre deck gap for aerodynamic benefit.  Now the exhaust tail pipe had to be pointing upwards in a position quite far forward and high up on the car.  Teams realised the exhaust plume could be persuaded to be redirected down towards the floor, via two aerodynamic effects, jet-in-crossflow and coanda. Both curved the upwards exhaust flow down towards the floor just head of the rear tyre.  While jet-in-crossflow was a much less discussed effect, the easier to understand and more visually obvious ‘Coanda’ effect captured the media attention and the solution gained the term ‘coanda sidepods’.

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The exhaust tailpipe exited tangentially to a downward curved surface, the exhaust followed the curved surface via the coanda effect and this directed the plume to the floor.  The curved sidepod surface was typically buried within a deep channel in the sidepods, to better direct the plume to the floor towards the diffuser-tyre gap.  Depending on the team’s budget, timescales and resources the coanda duct could be made either from high temperature composites such as Pyrosic, which was hugely expensive and the material in short supply at the time.

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Or teams could turn towards a metallic component.  Typically, such complex curved ducts would have been made from CNC milled blocks of material or fabricated from thinner sheet material, both were time consuming.  So with the demand for relative cheap, accessible, accurate and critically rapid turnaround, the use of 3D printing became very attractive, with the advent of laser melted\sintered components being able to be produced from Titanium, Inconel and even cobalt steel.

Thus, the printed coanda duct was the first overt use of this technology, with teams finding huge performance gains from changing the geometry of the duct, the ability to rapidly produce different iterations of their duct and get them on the car, this process became a competitive advantage.

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The duct I have in my collection of F1 parts is from Marussia, thus was blown by the outgoing Cosworth V8 normally aspirated engine.  The part is made in Titanium and bolted both to the exhaust tail pipe and into the surrounding carbon sidepod panel. Clearly from the blueing of the metal, its apart that has been run on the car.  Also it’s interesting to note the part has an unfinished surface, the slightly rough finish clearly not an issue for the team, where as other teams with printed ducts, such as Lotus, clearly polished the surface to a high finish.  Also its evident the heat has cracked the metal towards end of the duct, with black marker pen showing the two cracks.  I understand exhaust tailpipe temperatures were around 800c, with the plume cooling rapidly and heat at the floor being under 200c.

A part such as this would take around 12 hours to print, with several sets required for each car and their spare bodywork, there was quite some manufacturing time devoted to these parts.  As a result, much of this production would have gone to third party companies, to produce the parts, where the team either had no metal printing capability or not enough capacity for the production run required.