Today I've built a basic frame and a mechanism to make the wheels turn. I was admiring the work of Keith Newstead who often makes all the movements originate from the wheels which are on rollers (check this video out). This seemed like a good idea and a fun challenge. My main problem was creating a smooth action where the wheels meet the rollers, if this isn't ok then the whole thing fails. I tried various wooden wheels but it quickly became clear that my cutting skills were not accurate enough; cutting a perfect circle is really hard, ask Giotto and he only had to draw one!
So I opted for using plastic bits I had in my junk box. I think they actually look better than the wooden ones anyway, you can see both versions in the photo. The rollers are covered in a piece of soft textured foam for traction.
Once this was worked out I cut a basic frame and base onto which everything else can go. The next problem is how to make the wheel movement operate the engine. I had planned to use an elastic drive from the wheel shaft to the next mechanism, but this just doesn't seem to have enough traction. So it will need a cog or crank on the wheel shaft. That is a problem for another day.