The pilot of the of the vintage tailwheel airplane reported that the touchdown was normal; however, after rolling out about 1,500 feet, his left heel was not fully centered in the rudder shoe and accidentally depressed the left brake. The airplane then departed the left side of the runway and rotated 180 degrees on concrete, before coming to rest. The rotation on concrete resulted in separation of the right main landing gear. The pilot added that there were no preimpact mechanical malfunctions with the airplane. Examination of the airplane by a Federal Aviation Administration revealed damage to the lower right fuselage, where the right main landing gear attached.