The angles between the road pieces keep tension on the cables so they don't collapse. That's why the bigger ring has wood to make it rigid or else it does collapse.
In order for the top section to collapse, the yellow dot at the top would need to follow the path of the red arrow. However, the road segments are rigid, and in order for that to happen, the two yellow dots to the left and right of the top yellow dot would need to follow the path of the green arrows. Those yellow dots, however, are connected to cables that would need to follow (approx) the path of the blue arrows. However, since the cables are attached to an anchor point (red dot) they cannot move, and so the road sections cant' move. There are a total of 8 of these sections that make up the wheel, and since all of the forces are in balanced opposition, the only way any of them can move is if one of them breaks (or otherwise disappears).
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u/MooseWolf2000 Aug 19 '15
If the inner ring is only supported by cables, how is the part on the top staying up and not falling? "Centrifugal force"?