Aircraft experienced unsafe right main gear indication several days prior to the incident. Mechanics found a damaged micro switch mounting plate which they repaired enough to hold until a new plate could be ordered and installed. On day of incident pilot received unsafe right main gear indication and upon landing placed a side load on the gear to check it for security. At this time a loud bang was heard from the area of the right main gear and the gear began to collapse. A balked landing was performed and on the second attempt to land the right gear again began to collapse. The pilot flew the aircraft back to his departure point and on landing the right gear collapsed. Post crash inspection of the aircraft revealed the right gear over center brace had failed along with its mounting bolt. Metallurgical examination of the failed components revealed they failed due to overstress with no indications of previous cracks or presence of corrosion.