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 sever
This is of two types:Under floor systems.Overhead conveyors.
Both systems travel at slow speeds, over fixed pathways, which are obviously 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.
There are various types available – electric, petrol, diesel- and all allow much greater flexibility. Tractors to tow one or more trolleys have many advantages in flexibility. BUT they do mean that wheel and castors are often pulled at quite high speed over unsmooth surfaces, and can hit grates, rails, weather lips at doors etc… Therefore castors for powder towing must be especially strong. The rougher the use, the larger the wheel.
Tyre type: In theory a wheel transfers its load to a hard floor along a line of contact. In practice this is an elongated area which is: Narrow for Cast Iron Wheel, Wide for Polyurethane Wheels, Widest for Rubber Wheels. On smooth hard surface a hard cast iron wheel with the narrow contact area may roll more easily-BUT its unit load will be very high. The unit load (crushing pressure) is the total load divided by the area of contact. If this pressure is too high it will damage the floor. In practice the crushing pressure of cast iron wheel will often exceed the compressive strength of concrete, particularly when the load is further concentrated at expansion gaps, cracks etc., or when the loads are increased by speed and inertia. In practice cast iron recommend them for towed use. Polyurethane spreads the load sufficiently to avoid damage to floors, without a large increase in the ‘push’ necessary. Its great resilience and abrasion resistance makes it an ideal trying material. It also cushions the load, and avoids damage to the castor and trolley. The concrete floor of any warehouse or factory is probably the most expensive item of cost in it, and must be protected from damage by choosing the appropriate REXELLO CASTORS & WHEELS. Rubber is little used because it is too hard to push at high loadings, it can get adversely affected by oils, chemicals, etc., and its lasts only 1/5 (or less) the life of polyurethane.