-5,000 – wheel and axle

wheel

wheel

Prior to the wheel, heavy loads could be moved by dragging sleds and the sleds could be moved with more ease if rollers were placed beneath the sleds. At some point the rollers evolved into wheels that were attached to axles which were fixed to the wheels and turned with them. Eventually, the fixed wheel and axle evolved into an axle that was fixed to the chassis of the sled and the wheel revolved around the end of the axle.

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