A couple photos of the OA cart I just finished (other than paint).
It's too heavy but rolls well.  About half the weight is the wheels.
They were cheap, but are cast iron and solid rubber.  There are a
couple of half inch steel pads welded under the front edge of the
bottom plate.  This keeps the cart resting on the tires and the pads,
which prevents rocking.  It seems pretty stable.

Pete Keillor