What happens when you build a robot with two very large wheels? Well, you need a very large caster wheel to make it stable.
If you’ve ever tried to buy or make a caster wheel that will go over even modest steps, then you’ll realise that the diameter has to be considerably larger than the step you can roll over - at least 10-times bigger. So for a 10mm hump, you need a spherical caster of at least 100mm diameter, which is huge compared to the Pi Wars overall size limits.
The compromise solution is to use an Omniwheel. These are regular wheels that have smaller wheels at 90 degrees around the edge instead of a fixed tyre. They can go over bumps like normal wheels, but can also go sideways when needed to turn. As a result, they handle bumps easily on the forward direction, but only smaller bumps sideways - this isn’t normally a problem, except during turning on the spot.
For Dangly Too, we’re using a 38mm omniwheel in the nose pieces, but this nose generally doesn’t have much weight on it, so we think that is sufficient for bumps we’ll encounter
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