My previous windup vehicles were open chassis designs (e.g. no body) so I could enjoy watching the gears in motion (strange hobby I guess) but also to reduce weight.
Dual Mode Windup Car is my first attempt at a "rolling body" design, but I did leave the windows down so I can still watch the gears. For a description of "dual mode", see here:  https://www.myminifactory.com/object/dual-mode-spring-motor-rolling-chassis-26862.
This design is a significant weight increase over the previous designs, and to compensate I did increase the final drive gear ratio from 1/25 to 1/16 to increase the torque. As such, I also strengthen the axles and gears to handle the increased torque. After testing, this vehicle easily traveled around 40 feet over smooth surfaces.
The wheels and body top as shown in the photographs are designed for a dual extrusion printer, however I have included single extrusion versions of all the necessary parts.
The first image is of the prototype, the second is an orthographic view of the bottom…