On May 27, 2016, about 1050 Pacific daylight time, an amateur built - experimental Bob Howell, Howell Special airplane, N4393H, sustained substantial damage during the landing roll at the Minden-Tahoe Airport (MEV), Minden, Nevada, following a landing gear collapse. The private pilot and sole passenger on the airplane were not injured. The airplane was registered and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight which originated from Bryant Field Airport, Bridgeport, California, about 1015. The pilot reported a normal landing, however, during the landing roll he noticed the airplane started to veer to the left. He counteracted the veering with right rudder, and brake. Shortly thereafter, about 400 ft down the runway, the right wing suddenly dropped and impacted the runway. He was unable to maintain direction control of the airplane as it veered off the runway. There were no witnesses to the accident. Examination of the airplane by a Federal Aviation Administration inspector revealed that the right wing was substantially damaged. The wreckage was transported to a secure location for further examination. Postaccident examination of the right landing gear assembly revealed that the right main wheel and tire assembly had separated from the airplane. Further, the remaining main gear, a-frame structure, had a strut that had separated about at the midpoint. The bolts and their respective attachment structures that attached the gear assembly to the airframe were intact. All fracture surfaces of the main gear assembly were sent to the NTSB Materials Laboratory for further examination. The laboratory determined that the fracture features in the tubular steel structure portions showed matte gray features on slant angles consistent with a ductile overstress fracture. Some areas were observed that were consistent with sliding contact between the fracture surfaces under bending or shear loads. The end fitting was fractured in the threads and also had matte gray fracture features and the adjacent deformation of the threads was consistent with a ductile overstress fracture. No evidence of preexisting cracks or significant corrosion was observed. The owner/builder stated that several years earlier he made a repair to the landing gear where he heated the welds to realign the gear. However, a ductile overstress fracture would be consistent with a hard landing and/or side loading on the main gear.