Combination of slidercrank mechanisms and gearrack drives allows four wheels turn synchronically. Bar dimensions are selected in such a way that the wheel turning centers are nearly concurrent.
Advantage: The quadrilateral created by contact points of four wheel with the ground (base area) almost is unchanged when turning.

STEP files of this video:
https://www.mediafire.com/file/od3wxp...
Inventor files of this video:
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