Here is a picture of the current progress:

The motor mounts are built into the chassis, and held in place with a retainer disks:

I now have to somehow fit all this inside...

At least the fan fits nicely!

Method

It was printed by i.materialise using the Rubber-like material.

Results

Unfortunately while the material is more flexible than the typical additive manufacturing it does not provide much grip. This could be improves slightly with a different tread pattern, with something like a straight knurl; but I still don’t think this material is suitable for producing tyres.