Or if this helps...here is a photo of the plates and casters that are on the missile carts we make from time to time in our shop.. the casters look small compared to the plates and the cart over all...
Here is the overall look.
Side view:
Top view:
End view:
Also the caster has a plate on it, Then we bolt it to the footplate on the frame. This footplate on the frame is a 5"x7" and the leg on the frame is 3"x3" with a 1-5/8" stiffener post & the caster is 4" dia, so you can get a size comparison on the components.