The following factors should be considered when deciding upon a castor:
Swivel or Rigid Fitting:
How it will be fitted to the trolley. If appropriate - choose the attachment required. Springs take impact strain off trolley, protect loads, and provide greater comfort. Swivel & wheel Locks make trolley rigid & stable.
Directional Lock:
Allows for good tracking when locked, and maximum maneuverability in confined spaces, when unlocked.
If fixed and swivel Castors are to be used together, have the fixed castors at the front, the trolleys turns more easily. Never try to get the unevenness out of a warped trolley by half inserting fittings. You can get up to 8 mm of adjustment with washers, but do not let it float.
How to Tow:
Tractive power can come from either fixed track chain towing, or free movement tractors. Tractors used indoors, in warehouses, factories etc., are restricted by necessity to about 10 kmph. But even at this slow speed, both the wheel and the castor can suffer severe impacts from uneven surfaces. The castors and wheel chosen must be strong enough to cope with this. Outdoor use can be even more severe.
Fixed Track Towing:
These are of two types: Under floor systems and overhead conveyors.
Both systems travel at slow speeds, over fixed pathways, which are smooth. Therefore, high impact is not a problem with these systems. However, regular maintenance is critical, to eliminate wheel failure, which could mean unattended trolleys being dragged along, causing damage.