Towing Castor Arrangements

	Power Towing Trolleys to be power towed need special arrangements. Four swivel castors will not trail properly behind the towing unit - they will cut corners rather than follow the unit. They will also tend to 'whip' - to overcorrect any sideways displacement and sway sideways as they travel. These problems become more acute if two or more trolleys are linked in a train. If two fixed castors are used at the rear of a trolley it eliminates the whip, but the trolley does not trail properly. If two fixed castors are mounted in the centre of the trolley it now trails properly, but the whip problem returns. A good compromise is to mount the fixed castors 1/3 of the length of trolley from the rear. This gives little whip, and good trailing. Note though, that such trolleys should not be loaded with a heavy load concentrated at the rear end or they will tip backwards. If this is possible, safety stop (legs) should be installed at the rear corners to within 30mm of the floor.
	When positioning the two hitches, experiment to ensure the trolleys do not hit each other (or the tractor) going around tight corners. The wider the trolley, the further out the tow hitches will need to be. Paint the tow hitches a bright yellow for safety. If you make them to fold up out of the way, then fit them with safety catches so they do not drop down on someone's head. ALWAYS, ALWAYS, ALWAYS make the mounting pads rigid enough not to bend under severe use. Castors must be mounted with the mounting plate truly horizontal if the castor is to swivel freely. If the mounting bends the castor will crab to the side.
	Fixed Track Towing This is of two types. 1. Overhead conveyors. These can be used to pull trolleys by chains or rods. This system can be installed at any time, but gives less trolley control, and cannot handle trolleys as heavy as the under floor system. 2. Under floor systems (Towveyer). This gives a clean and open layout, but must be planned and installed carefully, usually before the concrete floor is poured, and cannot be altered easily. Both systems travel at low speeds, over fixed pathways, which are obviously made 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.
	See also The Why, Where and How of Towing Towing Castor Series Towing Castor Choice