Supersport TT 1
The new 9cento Concept and HP4 RACE are the latest BMWs to feature carbon fibre
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Last April we highlighted BMW’s carbon-fibre reinforced plastic swingarm. Primarily constructed out of injectionmoulded plastic with carbon at the high-stress parts it is a possible production item on cheaper bikes. But BMW have already pioneered cost-effective carbon production.
BMW have made huge steps in mass-producing structural components from carbon, so it’s been getting extensive use in their cars. Now this tech is filtering its way down to two wheels, most noticeably on the recent Concept 9cento which has structural carbon components and the HP4 Race which has carbon-fibre wheels and bodywork. Here’s how they do it.
The process
“We produce carbon through an injection moulding process called Resin Transfer Moulding (or RTM),” explains Karl Viktor Schaller, Head of BMW Motorrad Development. “The key to our process is that you don’t just look at the moulds but also the tools used to create the shapes.” During a normal RTM process, carbon sheets are laid into a mould and resin injected. The whole mould is pressurised and heated, giving a shape when the resin cures. BMW, however, have taken this a stage further. “For structural components you need hollow spaces within the mould, which we achieve through either several balloon-type bladders or a hard expandable foam,” says Schaller. “This structure provides pressure on both sides of the carbon sheet, creating a hollow area once the resin is injected. On the HP4 Race’s wheels, there is lightweight foam within the spokes, which remains inside once the wheels are created. A ‘sock’ of carbon is knitted using a machine and slipped over a foam shape. This is then put into a mould and more carbon added before the resin to create the final wheel. Should metal inserts be required, such as in the frame’s steering head, these are also added to the mould before the resin is injected.”
Repeatability is key
The fact this process is easily repeatable and the components produced identical in their structure means it is suitable for mass production as BMW are confident that each item is the same and therefore passes safety inspections. “Understanding the structure is the trick to using carbon,” explains Schaller.
‘Understanding the structure is key to using carbon’
BMW’S KARL SCHALLER