Carbon fiber rims

 


On technical tracks characteristic of Formula Student competitions, the weight and its distribution are decisive in terms of vehicle dynamics.

From the FS.06, we chose the concept of suspension with 10 „tires and discs of its own design. Not only have we managed to reduce the weight of the wheel group by 2.8kg, ie over 11kg in total (about 5% of the weight of the whole car), but also saved this mass in the most critical place – unsprung rotary masses, which are far away from the center of gravity of the car. We managed to reduce the moment of inertia of the wheel (even with a smaller diameter) and moments of inertia of the whole car.

The aim was to design and manufacture 10 „7.5“ discs weight up to 1.5kg with sufficient stiffness and especially manufactured in our conditions. The design of the carbon disc is designed to suit installation and stiffness requirements, and last but not least, the technological requirements.

The real challenge, however, was the core of the disk, which, in the composite materials of the sandwich structure, transfers the shear stresses between the layers. Typically, very expensive foams are used for this purpose, able to withstand high temperatures when curing prepreg and yet have a very low density. However, in cooperation with MCAE, we have succeeded in replacing the foam with a plastic core having a full central part, where it is important to transfer the wheel load to the wheel hub and the honeycomb structure around it, which serves predominantly as a support for preforming and curing the prepreg.

We succeeded in meeting the goals, as the resultant disc weighs 1320g. Disc Testing helped us in TUV-SUD, where the first prototype underwent a bending test on rotation machine, the same as all commercial drives have to go through.

In the future, however, we are planning a lighter and more rigid variant thanks to the experience gained during this season.