On July 10, 2002, approximately 1215 Pacific daylight time, an experimental Bredl Fokker DR1 amateur-built triplane, N43SB, was substantially damaged in a nose over accident following the collapse of the left main wheel during the landing roll at Portland-Troutdale Airport, Troutdale, Oregon. The airline transport pilot, who was the airplane's sole occupant, was not injured, but the aircraft, which is owned and operated by the pilot, sustained substantial damage. Visual meteorological conditions, with winds from 310 degrees true at 5 knots, were reported at Portland-Troutdale at 1220. No flight plan had been filed for the 14 CFR Part 91 personal flight. The flight departed Evergreen Field in Vancouver, Washington, about 1200. According to the pilot, during his landing on runway 25, the aircraft bounced slightly and then touched down "normally," but during the landing roll, the left main wheel structure collapsed and the aircraft nosed over onto its top wing. This scenario was confirmed by a witness who was working near the runway and who had seen the aircraft land. An inspection of the wheel disclosed that all but three wire spokes had pulled out of the motorcycle style wheel rim. The pilot said that he had not noticed any loose spokes prior to takeoff, but that the grass strip he departed from was "pretty rough." The reason for the separation of the spokes from the wheel rim was not positively determined.