What am I missing?

I am looking at that massive "wheel" which appears to be cast in one piece. The hub is bored and spilt. They appear to be cutting the keyway. There appears to be 4 bolts to clamp the hub to the shaft by squeezing the 2 halves of the hub together. Each half of the hub is attached to the outer rim rim of the wheel by 3 stout spokes.

Something has to move when they squeeze that hub down onto the shaft. Does it flex that massive wheel?

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