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Technical Paper

Some Criteria about F.W.D. — Boot Applications up to 150°C

Presently, the majority of drive shaft boots are manufactured from CR elastomers. However, due to steadily rising ambient temperatures under the hood, e.g., due to engine encapsulation, the thermal capability limit of this material has been reached. Alternative elastomers such as ECO, VMQ, AEM, CPE, NEM and PUR - as well as the thermoplastic elastomer Hytrel*- were compared with CR in suitable laboratory tests as well as dynamic tests under simulated “Hot/Cold” operating conditions using injection molded boots. In some cases, good correlation was found between the results of the various tests. On the basis of the test specifications, CR could be used at temperatures up to 110 °C whereas PUR and VMQ can be applied at temperatures up to 130 °C. From the selected test materials, only ECO, NEM and AEM can be used at temperatures up to 150 °C, however only ECO has a low temperature flexibility that is close to that of CR.
Technical Paper

Sealing of Pressurised Media in Automotive Applications for Rotating Shafts

The rubber industry provides special oil seals from elastomeric materials to seal pressurised shaft applications. Normally these are small and simple looking devices, which can tolerate quite complex conditions. The design of the seal has a tremendous impact on good performance. Basic parameters for pressure oil seals made from elastomeric materials will presented. Application conditions must be balanced to the degree of seal stress. For example the right compromise has to be chosen for flexibility and stability of the lip section. The heat which is generated by friction must be dissipated through the shaft and the medium to be sealed. Medium and elastomeric material must not be overloaded thermally. The product of pressure and surface speed (p · v) is an important characteristic for the evaluation of how much a seal is stressed. A graph of achievable ‘p · v’-figures will be presented.
Technical Paper

Radial Shaft Seal with PTFE Sealing Lip

This paper discusses the engineering aspects for the application of PTFE or elastomeric radial shaft seals in the automotive industry. Primarily considered are frequently used materials compared to PTFE, the sealing lip contact of the seal on the shaft, the frictional torque as well as important functional operation differences between elastomeric and PTFE radial shaft seals. Finally, a description of various design versions are given to portray the actual PTFE radial shaft seal program.