In order to fabricate a simple dolly for the Yi camera I purchased a Lego Technic kit which appeared to contain appropriate parts. I first assembled the two versions of the model according to the instructions to understand how the pieces joined. Here they are in motion (stop motion animation shot with iPhone 6, edited on Adobe Photoshop CS6).
The Xiaomi Yi camera has its lens fixed to one focal length, which according to reviewers, was set up for hand-held selfie distances. For my use, this set focus was slightly too far, but for most reviewers it was too close as distance action shots were not in focus.
Consequently, there was a plethora of sites explaining how to unfix the focus length by popping off the front facia and removing the three glue spots that held the lens in its pre-set focus. I wanted to be able to manually change the focus for different shots, so I also needed to remove the bezel around the lens so that I could continue to adjust the focus once the front facia was back in place.
After struggling to fit my iPhone 6 and Panasonic video camera into my models I decided that I needed to investigate smaller cameras. I also found it difficult to preview the shot when the camera was inside the model, along with their integral previewing screens, so needed a camera that also allowed remote preview. Action cameras fit this bill and after some investigation I decided to buy the Xiaomi Yi action camera.