According to multiple websites, BMW has filed a somewhat unusual patent application. They say that the application shows a carbon fiber frame integrated with the swingarm. Yes, you read that right, both the frame and the swingarm are a one-piece assembly.
It’s not unusual for moto companies to use carbon fiber liberally. Many of the large manufacturers produce race bikes (and street bikes) that utilize carbon fiber, frames, swingarms, and wheels. But combining the frame and swingarm is quite novel.
Carbon fiber plusses
At first blush, carbon fiber would seem to be ideal for these components. But there are significant issues that will have to be sorted before such a design could make it to a motorcycle application.
Carbon fiber is strong and lightweight. It can be manufactured to be very rigid in a certain axis and at the same time provide some measure of flex when appropriate in another axis. This is very important for a motorcycle swingarm which would require both vertical flexibility and lateral rigidity.
Carbon fiber minuses
But, the material has its drawbacks as well. It can also be brittle, especially as the material ages. And, while the amount of flex can be tuned in to a certain level, it’s not clear from the patent drawing how such a setup would provide the dampening that would be required on a motorcycle.
It’s unclear because the patent application drawing does not show damper (or spring for that matter). It’s likely that ultimately some kind of damper will be used. Perhaps the final application to the machine will be able to have a smaller or lighter version of those currently found on motorcycles.
It will be interesting to see what BMW ultimately comes up with if anything at all. But the patent application does say one thing. BMW is thinking outside the box.