STEERING WHEEL OF A FORMULA STUDENT CAR – ABOUT COMPOSITES AND MORE

The use of various composite materials is a standard practice in motorsports. One of the most commonly used materials is carbon fiber laminate, which is employed wherever a high strength-to-weight ratio is required.

In this article, you will learn how the PUT Motorsport team utilizes carbon fiber laminates and creates one of the main structural components of their new race cars. 

When creating components for each new car, we draw inspiration from previous designs. We analyze all the pros and cons of each subassembly and strive to improve them to the fullest extent possible. Following the famous quote “mass is the enemy of acceleration,” we aim to ensure that every component, while fully functional and sufficiently durable, has the lowest possible weight. In this regard, laminates come to our aid. Laminates are composite materials formed by combining two or more materials with different mechanical, physical, and technological properties.

At PUT Motorsport, we mainly utilize carbon fiber laminates, which combine carbon fiber with resin. Such material exhibits excellent mechanical properties (up to 5 times stronger than certain types of steel) even with very thin laminate layers.

“One of the best remedies against aging is frequent driving of a racing car.”

Juan Manuel Fangio, Argentine Formula 1 driver, five-time world champion

  The steering wheel is an essential element of any vehicle. Without it, the driver would not be able to change direction. Based on our steering wheel design, we want to showcase how our team utilizes modern materials, from conception to execution.

Starting from the beginning, we need to determine the actual purpose of our steering wheel. It is evident that it will assist the driver in steering, but is it just a wheel attached to the steering column, as seen in current Formula 1 cars? No! It contains numerous buttons that control various aspects of the car during driving.

When designing the steering wheel for our Formula Student cars, we opted for a user-friendly interface. Compared to Formula 1 cars, our Formula Student cars have far fewer complex systems, reducing the need for continuous adjustments while driving. Therefore, we decided to place four buttons in such a way that the driver can operate them using their thumbs—two buttons on the right side and two on the left side. Additionally, we included two rotary switches, one on each side, to modify the traction control level and engine torque.

After defining the functionality of the steering wheel, the next crucial factor for the driver is ergonomics. Racing on winding and narrow tracks during FS competitions requires a secure grip on the steering wheel. With the driver’s confidence in mind, we designed several prototype grips (the elements held directly while driving) and tested them to determine the optimal grip for each driver.

Before starting the actual design process, we need to predefine the manufacturing method and materials for our steering wheel. Considering the low weight and high stiffness requirements, we naturally chose carbon fiber. The steering wheel had to be designed in a way that allowed the creation of molds for laminate preparation.

During the design phase, we determined that the steering wheel would consist of two parts: front and rear. Consequently, we needed to design two negative molds. Molds can be made from various materials such as epoxy boards, MDF boards, plastics, or metals. Considering the repeatability and durability of the molds, we chose the latter material—specifically, aluminum. Thanks to our collaboration with AW ForgedAW Forged, the molds were manufactured according to our design using CNC machining.

We distinguish two types of carbon fiber – dry and wet (prepreg).

Dry fiber refers to unimpregnated carbon fabric. Only after applying resin (preferably epoxy), the carbon fabric forms a strong composite.

Prepreg, on the other hand, is fabric already impregnated with resin mixed with a slow-curing hardener during production. Prepregs are stored at a sufficiently low temperature to prevent them from curing during storage. The advantages of prepregs include a precisely defined, exceptionally favorable ratio of fabric (reinforcement) to resin. However, the downside is the higher cost of the material and the high cost of implementing production based on prepregs. Prepreg carbon fiber is used, among others, in Formula 1 cars and super sports cars such as Pagani or Koenigsegg.
We will use prepreg fiber to make the steering wheel.

Alright, we have the molds and the chosen method of production. Now, let’s get to work!
First, it was necessary to prepare the molds. Although they came out smooth from the machine, it’s not the surface finish necessary for the steering wheel to have a glossy appearance and for the laminate to be easily separated from the mold. Therefore, manual sanding and polishing were necessary.

After preparing the mold, we can proceed with lamination. Initially, we apply several layers of mold release agent, followed by a chemical release agent to facilitate the easy separation of the final laminate from the mold. Then, we start laying down the previously prepared carbon layers. The number of layers and their arrangement differ for each case and component, depending on the required strength.

Once all the layers are laid, we need to ensure that they are firmly bonded and tightly adhere to the mold. For this purpose, we enclose everything in a vacuum bag and remove all the air using a vacuum pump.

To achieve the desired properties of the final laminate, we need to cure the prepreg fiber at the appropriate temperature. This is commonly done in large chambers called autoclaves. In our case, considering the size of the mold, a small oven heated to 120°C is sufficient. The curing time also varies depending on the desired properties. In the case of the steering wheel, it took about 2-3 hours.

It is crucial to extract the laminate using proper tools to avoid accidental damage.

The final laminate is manually processed using tools to remove excess material. To ensure greater strength, our designers filled the steering wheel with high-stiffness but low-density foam.

Finally, we add buttons and assemble all the necessary mounting components. We install the steering wheel in the car, and it’s ready to go!

If you’ve made it this far, thank you very much for reading the entire article. We hope that knowledge about how we make carbon fiber parts will be useful to you in developing your hobby and contribute to creating extraordinary things with carbon fiber! If you want to see how the entire process looked like, we encourage you to watch a short video showing the individual stages!

See you on the TRACK!!!! 🏎️