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Minimum load Supplementary designations DS Split needle roller and cage assembly In order to guarantee satisfactory operation, needle roller and cage assemblies, like all ball and roller bearings, must always be sub- jected to a given minimum load, particularly if they are to operate at high speeds or are subjected to high accelerations or rapid changes in the direction of load. Under such conditions the inertia forces of the needle rollers and cage of the assembly, and the friction in the lubricant, can have a detri- mental influence on the rolling conditions in the bearing arrangement and may cause damaging sliding movements to occur between the rollers and raceways.The requisite minimum radial load to beapplied to needle roller and cage assembliescan be estimated usingF The designation suffixes used to identify certain features of SKF needle roller and cage assemblies are explained in the following. DSTN DS + TN SORT Gauge of the needle rollers of anassembly. The figures following indicate the gauge limits in µm,e.g. SORT–1–3 TN Injection moulded cage of glassfibre reinforced polyamide 6,6 VG052 Split cage of polyether ether ketone (PEEK) ZW Double row cage ZWDSTN ZW + DS + TN 39
rm = 0,02 CwhereF
rm = minimum radial load, NC = basic dynamic load rating, NWhen starting up at low temperatures orwhen the lubricant is highly viscous, evengreater loads may be required. The weightsof the components supported by the bear-ing, together with the external forces, gener-ally exceed the requisite minimum load. If this is not the case, the needle roller andcage assembly must be subjected to an additional radial load.

Needle roller bearings (4703 /IE) - 5564 3

Equivalent dynamic bearing load Needle roller and cage assemblies can onlytake radial loads, thereforeP =
Fr Equivalent static bearing load Needle roller and cage assemblies can onlytake radial loads, thereforeP
=
Fr