This is my own design for a sim racing steering wheel. It has 8 push buttons which can be used in games as DRS, navigation buttons or any other setting you like. It also has paddle shifters just as a race car.
Here is the list of components you need to build your own one:

• 3D printed parts: - 1x main body
  • 1x central cap
  • 1x central spacer
  • 1x left handle front
  • 1x left handle back
  • 1x right handle front
  • 1x right handle back
  • 2x paddle body
  • 2x paddle arm
  • 1x left handle front
• electronic components: - 8x push button (the bigger ones 12x12mm)
  • 8x push button cap (for the buttons)
  • 2x end limit switch (for paddles)
  • wire
• other components: - 4x spring (2 for each paddle shifter, 9.5x19mm springs)
  • 12x M4x25mm countersunk screw
  • 4x M4x30mm countersunk screw
  • 18x M4 nut
  • 2mm thick strong wire

How to assemble:

Step 1
Get all the required parts

Step 2
Soldier all the buttons to different wires in a way that is possible to connect them like in the picture with the Arduino board. You need 2 wires for each button. Follow the provided image ignoring the potentiometer.

Step 3
Assemble the paddle shifters. For that you will need to insert the end switch in the body of the paddle, then put 2 springs in the body, align the arm of the paddle with the holes in the body and insert the wire through both components, forming this way a hinge like mechanism that is pushed open by the springs. Finally mount the handle on the paddle and repeat this steps for the other paddle.

Step 4
Mount the paddles to the back of the main body with 8 M4x25 screws and nuts

Step 5
Glue the buttons to the existing squares on the body and back handles.

Step 6
Assemble the handles. Join the front and the back of each handle and fix them with the M4x25 screws and nuts.

Step 7
Put the handles in the main body. You should end up with something that looks like a F1 steering wheel without front cover (see the image).

Step 8
Pun on the central spacer and central cap aligning holes with the buttons and the screw holes. Then finally fix them together using the 4 M4x30 screws and nuts.

All you need to do is to wire it to an Arduino board or whatever controller you like and mount it on a steering wheel base. I also made my own steering wheel base that I may cover in a different thing.

I hope you like my design and feel free to modify it as you wish. Good luck building it and have fun.