A new BMW Motorrad patent for a carbon fibre swingarm brings the hi-tech, lightweight technology closer to mass production through a manufacturing process that makes it more affordable.
In 2018, BMW Motorrad won a JEC Innovation Award for the development and manufacture of a carbon fibre swingarm for its 2017 HP4 RACE (pictured above).
A new filing patent brings that technology closer to mass production.
Instead of a conventional swingarm pivot, the patent shows a flexible carbon fibre with the swingarm integrated into the chassis.
Carbon fibre and other lightweight materials are becoming more prevalent in motorcycle design with a wide range of benefits to handling, braking, acceleration, fuel economy and emissions.
The properties of carbon fibre that make it so attractive to motorcycle manufacturers is its light weight and high strength.
Carbon fibre and other lightweight materials are becoming more prevalent in motorcycle design with a wide range of benefits to handling, braking, acceleration, fuel economy and emissions.
The properties of carbon fibre that make it so attractive to motorcycle manufacturers is its light weight and high strength.
I switched to Blackstone TEK carbon fibre wheels on a 2006 Ducati GT1000 project bike and was stunned at the wide range of benefits it brought to the bike.
Ducati GT1000 with Blackstone TEK carbon wheelsCarbon history
Carbon fibre construction has come a long way since it was first used in a motorcycle in 1994 in Cagiva’s C194 500cc two-stroke.
It featured a chassis made of carbon-fibre and alloy, but was short-lived.
The other famous early use of carbon fibre was in chassis of the Britten V1000, designed and hand-built by Kiwi John Britten.
Britten V1000John, a brilliant, but dyslexic mechanical engineer, died of skin cancer in 1995 having hand-built only 10 V1000s.
Carbon fibre is today used extensively in motorsport and expensive automobiles and motorcycles such as the Ducati Desmosedici.
Carbon swingarm project
Carbon fibre is expensive because it is difficult to mass-produce.
However, manufacturing processes are improving, resulting in better quality finishes and cheaper products.
Joachim Starke, who is in charge of BMW’s lightweight composite fibres, says the HP4 RACE combined optimum technical qualities, uniform manufacturing quality and cost efficiency for the first time.
The HP4 RAE swingarm was made of carbon fibre reinforced plastic with CFP tape reinforcements using thermoplastic material.
BMW HP4 RACE swingarmBMW believes it will be possible to establish a cost-efficient manufacturing process suitable for the large-scale production of such injection-mould components.
He says they developed a technology that allows precise configuration of component properties by using a variety of composite and metal inserts.
“This scalability means that a single tool can be used to produce a wide range of different components at cycle times of less than a minute,” he says.
“The maximum strength can be adjusted by means of additional CFP panels which can be thermoplastically joined.”
BMW also used welding robots in the process to reduce costs.
The HP4 RACE carbon fibre project forms the basis for the use of carbon fibre in serial production of BMW motorcycles and automobiles.
BMW HP4 RACECarbon technology explained
BMW project manager Elmar Jäger explains the technology:
We opted for chassis components under continuous load since the requirements involved are especially demanding. While car chassis parts are concealed, the visible motorcycle rear swinging arm was ideal for our project since the forces at work are immediately evident. Our production technique uses CFP in the form of high-strength endless fibres where this is required by the stress pattern, while an injection mould part with short CFP recycling fibres is used where the stress levels are not as high. In this way, we developed a cost-efficient design that can be scaled according to requirements by inserting endless fibres with varying levels of strength in the same tool.