Performance of rod sealing systems using chrome replacement coatings in landing gear shock absorbers, under conditions of short stroke reciprocating motion

摘要

The variation in friction and leakage of some commonly used seal designs consisting of a combination of PTFE and elastomer components is considered for conventional hard chrome plated and HVOF coated countersurfaces. The study will show through experimental testing that the use of elastomer materials in the rod sealing of landing gear shock absorbers is valid as long as the surface texture is adequately specified and the coated countersurface is free from defects associated with the HVOF process. Frictional instabilities associated with operation in a short stroke regime are also discussed and real time measurements of the friction profile as a function of stroke are presented. It is shown that there is a critical velocity present for a given tribo-combination (seal-countersurface) and when exceeded, friction behaviour becomes fully transient as the instabilities at the stroke extremities appear to propagate over the stroke.