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This is a view of the front of the modern reconstruction of a Roman Cart that is on display at Sepphoris.
This is the front of the cart and an animal (horse?) would be placed between the extended "arms" to pull the cart. Note that the front axle pivots on a single pin that in turn supports the cart. If this is correct, that pin must have been very strong! Note too, that there was clearance space for the wheels under the cart as it turned.
Note also, that the reconstruction of the wheels seems to imply that there was some type of material that was embedded into them for the cart to "ride on." The half-cylinder body seems a bit odd to me, but I am not an expert on Roman Carts!