James Hunt, Manufacturing Officer from the Mercury Centre at the University of Sheffield, talks to AZoM about developing the 3D printed aerobars which Sir Bradley Wiggins used to break the world hour record on Sunday 7th June 2015.
Could you provide our readers with an overview of the history of the Mercury Centre at the University of Sheffield and briefly outline some of the research which is currently being carried out at the institution?
The Mercury Centre was established in 2010, part financed by ERDF funding (European Regional Development Fund), it brought together the existing expertise within the university of net shape manufacturing techniques and advanced characterisation, backed up with world leading fundamental materials knowledge.
Current research activities are focussed on developing new and novel materials that make the best advantage of advanced manufacturing methods such as additive manufacturing (AM : AKA 3D printing), metal injection moulding (MIM) and spark plasma sintering.
Video Credit: The Mercury Centre - Innovative Materials and Manufacturing/YouTube
We are also looking to optimise the processes to ensure they are robust and repeatable, with the consistency and quality that industry would expect. Another area of interest is complex lattice structures and metallic foams which can be used for high energy absorption and lightweight structures.
On Sunday evening (7th June 2015), Sir Bradley Wiggins broke the world hour record on a Pinarello bike fitted with 3D printed aerodynamic handlebars which had been developed at the Mercury Centre. How did the Mercury Centre get involved with this project?
Although the bars were not designed at the Mercury Centre, we did have some input into optimising the design for the manufacturing process. The chief designer on the project, Dimitris Katsanis working for Pinarello, approached the Mercury Centre as he knew we had the specific capability to manufacture large structural components via AM, having worked previously with F1 teams and aerospace companies.
How important is it to optimise the aerodynamics of a rider in a very controlled track cycling event such as an attempt at the hour record?
Aerodynamics is a big part of the equation for an attempt such as this, the air resistance seen by the rider and the bike increases exponentially with an increase in speed, so the faster you want to go, the more air resistance, or drag, will be seen.
If we can minimise the drag by putting the rider in the optimal position and making advanced aerodynamic shapes for the components, then the burden on the rider becomes less.
Image Credits: Graham Watson
Sir Dave Brailsford, the former performance director of British Cycling and current general manager at Team Sky, famously champions the concept of the ‘aggregation of marginal gains’. How much of a 'marginal gain' do you believe the 3D printed aerobars gave Sir Bradley on Sunday evening at the Lee Valley VeloPark?
That’s difficult for me to answer as I was not privy to all the backroom equations. Managing the airflow around the rider and the bike needs to be considered as a whole, since the way the air flows over one component can affect the drag on subsequent components in that now turbulent air.
Image Credits: Mercury Centre/University of Sheffield
Since the handlebars are the first component that pushes against the air it is very important that these are as good as they can be. More important is to place the rider in the ideal position, since the rider typically contributes 2/3rds of the total drag. 3D printing the bars allowed both of these factors to be fully optimised.
Why were the record breaking aerobars made from titanium rather than carbon fibre like the rest of the bike?
To make components in carbon fibre requires a mould or toolset to create the shape, these are typically machined from aluminium which can be a slow process. The carbon fibre then needs to be laid up in the mould, usually by hand, this is followed by resin infusion and finally curing in an autoclave. All of this takes time, several weeks from design sign off to having the components available.
Subsequently, any design changes that need to be made, even small ones, are costly and time consuming. 3D printing in titanium enabled a much more rapid turnaround of design iterations as we do not have to make a toolset to create the shape.
Currently titanium is the best material available to make such components via 3D printing, however, people are working on 3D printing with carbon fibre which may have given even better performance in terms of stiffness and weight.
What are the advantages of producing the handlebars using 3D printing technology rather than conventional casting methods?
Again the main benefit is speed of turnaround, with 3D printing we can start to produce the component as soon as we have the CAD file. With casting you would first have to make a mould which takes time and is not cost efficient for one off components such as this.
Furthermore 3D printing allows us to create more complex shapes with cavities placed in the right places to make them as light as possible.
How did Sir Bradley’s size and cycling style influence the design of the 3D printed aerobars?
These bars are not hugely different to conventionally made aluminium or carbon fibre bars. However, based on the results of testing at the track and stress analysis of the design, the team were able to place the material in exactly the right location to provide the strength and stiffness required. Sir Bradley tends to hold his hands in a certain way on the bar extensions, so these parts were modified to make them more comfortable.
Image Credits: Mercury Centre/University of Sheffield
Why specifically was an Arcam Electron Beam Additive Manufacturing machine chosen to create the aerobars?
The Arcam EBM system is ideally suited to making parts in titanium. It operates under a vacuum, so there is no chance of oxidising the powder during melting.
Secondly the process runs hot, in that we pre-heat each layer of powder before melting, this means that for the particular alloy we use (Ti6Al-4V) the microstructure evolved in the process is strong and ductile without the need for heat treatments such as stress relief or solution anneal that you might need from a laser system.
Do the Mercury Centre have any plans to be further involved in any other track or road racing projects in the future?
There are no plans as yet, but we are always keen to hear from other companies wanting to exploit the technology. We have in the past built components for other local bicycle manufacturing companies including; a novel seat rail design, chain rings and rear dropouts. So these parts could be appearing on bikes in the showrooms very soon.
About James Hunt
Sharing his time between developing Deep Repair technologies and Business Development, James is able to call upon his extensive experience of a wide range of industrial sectors and materials processing techniques to find the optimum solution.
Since graduating in Materials Science at Brunel University in 1997, James has spent much of his time in industry gaining firsthand experience of the commercial pressures and drivers towards developing new products and processes.
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