What I did:

I first did a simple manual draw of my project, both 2D and 3D.
Then I tried GIMP and Inkscape (2D softwares), and quickly I decided to use Inkscape.
I did not encounter major issues using Inkscape, I just had to take care of the dimensions settings, at starting.

Results

2D manual drawing

3D manual drawing

2D design in Inkscape

2D design in Inkscape (zoom)

What I did:

I used Rhino3D as 3D software
As a template for my 3D, I imported the 2D file (using .dxf format as pivot between Inkscape and Rhino).
In Rhino, I did not encounter major issues, but I spent a lot of time to understand the way of using the different commands (there is so much).

Results

3D design in Rhino - starting view

3D design in Rhino - building the wheel system (gearedmotor+axe, rim, tire, motorbox)

3D design in Rhino - final view

What I did:

I did a video of my 3D design using Quicktime
I convert the video from .mov to .mp4, using the command tool ffmpeg (command: ffmpeg -i 3D-design-video.mov 3D-design-video.mp4)
I uploaded it on Toutube, then I shared it and integrated it in my website.

Results

Please find here all the files I created:

A zip file with inside my 2D files (.svg, .dxf) from Inkscape and my 3D file (.3dm) from Rhino3
My video (.mp4 format)