Steering Wheel

Steering Wheel – Completion

Unfortunately the assembly of the steering wheel had to be rushed. This was in order for it to be finished in time for the formula student event last year. Even though it was not quite complete, we still took and displayed the model. Alongside the other prototypes it attracted a lot of attention and provided topics for discussion with the judges.

During some free time after the event, the steering wheel was cleaned up and vinyl tint was applied to the display covers. It will now act as a display model for future events. The model is popular as it can be picked up, handled and inspected closely quite unlike a CAD model.

The team this year will hopefully progress with the experience that was obtained by building this for the first time. There was many mistakes in both design and manufacture that can now be easily overcome with foresight and planning.

Launch Event Display

Steering wheel on display alongside other components at the launch event

Keyshot was used to render views of how the steering wheel could of looked if it was complete and functional. The software allowed for easy selection of material properties and lighting conditions. The outcome is a professional and realistic render.

Steering Wheel Front Render

Keyshot render of the front, red anodised base plate with all displays lit

Steering Wheel Rear Render

Keyshot render of the rear, electronic covers and quick release boss

Finally, even though the event was last July, I have now finished blogging about the design and manufacture of the steering wheel project. I will still be involved with Formula Student for another year so expect more posts in the future.

Now for the next project…

Steering Wheel – Electronic Design and Assembly

The task of designing the PCB, to be mounted to the steering wheel assembly, proved to be tough. With only some experience from GCSE electronics, this part of the project was accompanied with a steep learning curve.

Through recommendation on a number of Arduino forums, the software of choice was Eagle v6 from CadSoft. This is a powerful tool with an extensive library of electronic components. The user interface wasn’t the most user friendly, instead relying on keyboard shortcuts. Although it was easy to learn by following a selection of YouTube tutorials by Jeremy Blum.

The size of the board (51mm x 110mm) was dictated by the space available between the top of the steering wheel and the steering boss, leaving adequate clearance for covers. Placement of the display components upon the board were already decided. This left only the other electrical components and tracks to be placed and routed.

The board was fabricated by Spirit Circuits and their free 48-hour prototyping service “Go Naked”. They provided us with a two sided aluminium coated board with just the essentials, tracks and holes. Their customer service was exceptional in helping to meet our needs. We promptly received a professional high quality board that only required cutting to size prior to use.

Initially the assembly and soldering of the electronic dash went to plan, with the majority of the components fitting without a problem. A couple of overlooks included; attachment of the switch and warning LED, placement of the ribbon cable and selection of connectors.

When linked to the Arduino and powered for the first time, all of the display lit up and ran through the start-up test routine a few times. But before too long, it was noticeable that the display was not functioning entirely correctly. The central RPM range LED failed to blink and the LCD display would occasionally flicker with random characters. This suggested that either a faulty component had been used or the board was shorting. After inspecting the soldering and replacing components, it was found that a grounding fault was the cause. Although it’s exact location was unknown.

While it was disappointing that the display did not work correctly. It proved to be a great prototype and provided us with a number of improvements for the next revision. The main points being; bigger tracks, pads and clearances along with smaller components.

Next… Steering Wheel – Final Assembly

Steering Wheel – FEA

Whilst designing the wheel shape in Solidworks, there was uncertaintly around material choice and plate thickness. Within the university we had a selection of sheet metal, including steel and aluminium. Fortunately during research we stumbled upon a document concerning driver contol requirements by FSAE judge, Steve Fox.

Minimum driver applied forces, you should be designing/building/testing for:

  • Steering System Lateral Force – The steering wheel and steering column should be able to withstand at least 660 N (150 lb) lateral (radial) force before failure.
  • Steering System Torque – The steering system should be able to withstand a minimum of 100 Nm (75 ft lb) force, applied at the steering wheel, before failure.

Using these forces and FEA (Finite Element Analysis), the main plate was subject to numerous load tests with a variety of materials and thicknesses. The results for von mises stress and displacement observed in these load tests were studied to decide which material and thickness was most ideal.

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Unfortunately this process was rushed and carried out with little thought of overall mass. Our selected material, Aluminium 5083 with a thickness of 6mm, resulted in a total assembly mass of around 800 grams. This was considerably heavier than alternative off-the-shelf steering wheels with electronic displays which tended to be around 400-500 grams in total. As mass is an incredibly important factor for Formula Student cars, the design would have to be revised and lightened before another wheel is made.