On May 13, 2004, about 1645 Pacific daylight time, a tail wheel equipped Piper PA-22-20, N1829P, sustained substantial damage subsequent to a gear collapse during landing at Sanderson Field (SHN), Shelton, Washington. The airplane is registered to the pilot, and was being operated as a visual flight rules (VFR) local flight under the provisions of 14 CFR Part 91, when the accident occurred. The student pilot, the sole occupant of the airplane, was not injured. Visual meteorological conditions prevailed and no flight plan had been filed for the flight that originated at Shelton approximately 15 minutes prior to the accident. During a telephone conversation with the National Transportation Safety Board IIC, the pilot reported that he was practicing landings (wheel landings) in preparation for a check ride. He stated the touchdown was normal, however, shortly after landing (runway 05) the airplane swerved to the left. The pilot attempted to correct the situation using a combination of power and rudder inputs, but was unable to regain control of the airplane before it exited the runway (on to a paved surface adjacent to the runway). Shortly after exiting the runway, the airplane "snapped" to the right. The 1656 Shelton METAR observation reported weather conditions, in part, as: wind from 260 degrees at 10 knots; visibility 10 statute miles and clear skies. Post-accident examination of the right main landing gear and hydrasorb assembly installed on the airplane, revealed that one of the ears on the lower fitting assembly (used to support the shock cord) fractured and separated from the main strut assembly. Further examination of the gear assembly revealed that the lower support ear had been welded directly to the lower (distal) end of the strut assembly (refer to enclosed photos). The hydrasorb assembly (part number13148-00) for the PA-22 (and PA-22-20) consists of a lower strut fitting, an upper strut fitting and the hydrasorb unit (illustrated parts catalog attached). The lower strut fitting rests on the end of the hydrasorb and is held in place via the shock cord.