Catalogue_RR+FT_klein

12 1. Tires The type of tire is very important when selecting the proper wheel or roller because the load-carrying capacity and rolling resistance depend on it. Thus the wheels and rollers listed in this catalog are categorized according to the main criterion of tire type. 2. Operating conditions The condition of the traveling surface determines the tire quality and the wheel diameter. We recommend using large-diameter, elastic wheels for une- ven surfaces. The service life and the functionality of a wheel, roller or castor depends on, among other things, the extent to which the used materials or their surface finishes can withstand the effects of corrosion, temperature, and chemical substances. Steel, which is normally used in the production of wheels and castors, has hardly any resistance to humidity when it does not have a protective coating. The steel is then slowly destroyed by corrosion. This is why the surfaces of the wheel and castor components feature a protective layer. Apart from the degree of resistance offe- red by the different surface finishes, you must also consider that these protective layers can be damaged by mechanical influences. Parts which are protected by special coa- tings will provide reduced corrosion pro- tection when their protective coatings are damaged. Rust also starts to infiltrate the intact layer of coating located near the damaged area. When there is only minor damage, galvanized layers are advantageous because the zinc material provides corrosion protection. This is because the zinc portion of the zinc/steel combination corrodes first as a result of the electrochemical processes, and the bare area is not affected. The individual galvanized components are subjected to a supplementary che- mical treatment referred to as chroma- ting or passivation. There is a difference between blue and yellow chromate finishes: the yellow chromate finish provides a greater de- gree of protection against moisture than the blue chromate finish. Stainless steel provides good corrosion resistance. The predominant material (in 1.4301/AISI 304) is an 18-percent chro- mium-nickel steel alloy. Chemical resistance The chemical resistance of a castor or roller must be considered whenever aggressive media may come into direct contact with any components. The table on the following pages lists the different chemical resistances of materials used for tire treads and wheel bodies. The data in our tables should only be used as guidelines. The chemical resistance properties are not only dependent on the type of reacting chemical, but also on the chemical concentration, duration of contact, and environmental conditions such as temperature and humidity. Please contact us for advice if you are in any doubt about usage. Determining factors when selecting wheels and rollers Wheels Depending on their design, wheels can have very different rolling properties, resistances and load carrying capacities. They are made up of individual com- ponents: such as a press-on tire/tread or wheel, a rim or wheel body and a bearing. The characteristics of the wheel depend on the various treads and rim compo- nents. The type of bearing also influen- ces the load-carrying capacity, rolling characteristic, and rolling resistance of the wheel. T1 = hub length T2 = wheel width D = wheel diameter d = axle hole diameter Bearing Plain bearing: Simple, low-maintenance and impact-resistant bearing. No further bearing bushes are used in wheels made from polyamide or cast iron, since these materials have good gliding properties. Roller bearing: Sturdy, resistant, low-maintenance bearing. The most commonly used bearing for equipment that moves at low speeds. Featuring minimal rolling resistance. Ball bearing: Smooth running for con- tinuous use – even under heavier loads and at higher speeds. Ball bearings are mainly used in techni- cally demanding equipment rollers. www.torwegge.de/en