On July 23, 1996, at 2000 central daylight time (cdt), a experimental Steen Skybolt, N596E, was substantially damaged during landing on runway 16, at the Aero Estates Airport, Belleville, Illinois. The airplane was on its second flight since being completed by the builder/pilot. The pilot sustained minor injuries in the accident. The 14 CFR Part 91 flight was operating in visual meteorological conditions, and no flight plan had been filed. Research revealed that during landing the airplane's left wheel separated from the aircraft. After the location of left wheel separation ground scar marks consistent with a ground loop were visible. The airplane's lower left wing sustained a broken spar and crushing damage in the accident. Examination of the axle attachment area on the left landing gear revealed signs consistent with a lack of welding penetration during manufacture. No other abnormalities were noted on the airplane.