Prior to landing the gear was selected down and a normal gear down indication obtained. The touch down was normal but when the airspeed was reduced to about 65 knots a vibration similar to a wheel shimmy developed. Attempts were made to keep the aircraft straight with brake and rudder but when it was realised that the right maingear was not supporting the aircraft the right engine was shut down. Investigation revealed that the uplock bracket spring had become detached from the uplock bracket. This along with some corrosion and stiffness in the bracket pivot bolt caused the bracket and uplock not to be withdrawn during the extension sequence. As a result the extension rod was bent during the extension cycle and the right gear did not extend. There is no provision made for lubrication of the bracket pivot bolt and no requirement for regular removal and servicing of this item. The pilot was unaware of the gear malfunction due to the design feature of the system which does not indicate gear-leg position but only the extent of gear-box travel.