Hamilton Spinfinity Maxi-Duty Dual Swivel Caster 13.5"

Start with total system weight (payload + structure + fixtures), divide by casters that actually share the load, and keep continuous working load per caster at or below roughly 75% of catalog capacity (~25% margin). Heavy-duty kingpinless frames are often used on uneven floors, docks, and towed trains where dynamic load transfer is common — do not assume perfect four-caster share. If impact, drop-offs, or shock loading is expected, treat the margin as a floor, not a stretch goal, and confirm capacity at the wheel diameter and tread you select on this PDP. Dynamic and side loads are separate from static catalog ratings; call out towing or AGV duty when you quote so we can sanity-check the configuration.

Stay with polyurethane when floors are relatively smooth, temperatures stay inside the PU service window, and you want floor protection plus rollability. Move to phenolic, glass-filled nylon, or other high-temp / high-hardness options when heat, certain chemicals, or very high point loads push past what standard PU can sustain. Kingpinless construction solves swivel durability under thrust; it does not raise the wheel’s temperature or chemical limit. Use the wheel material and temperature fields on this product (and sibling SKUs) to match the environment — heat duty and side-thrust duty are independent selection axes.

Kingpin swivels concentrate clamping and much of the axial stack through one pin. Towing hitches, AGV corrections, and side scrub introduce lateral and moment loads that work that pin and the race faces harder than hand-pushed carts. Typical early wear modes include kingpin stretch or hole elongation, race brinelling, and increasing swivel play. Kingpinless designs replace that single-pin stack with a machined or forged raceway that carries thrust through the race path, which is why they are the usual spec for powered towing and higher side-load industrial carts. Pair kingpinless swivels with a wheel and bearing package rated for the same duty — the swivel upgrade alone does not fix an undersized tread or bearing.