Usually the wheel mounts onto a separate hub, that has weights that can be slid round a circular Tee slot and locked
Is that because it would usually be set up with one wheel?That's right, usually the wheel clamps in a hub which sits on a taper or keyed shaft. The Eagle has a 2-piece hub that's a more posh version of the plates on a bench grinder just clamped by the nut on the front.