The pilot reported that the alternator failed while the aircraft was between Birdsville and Broken Hill. The pilot reduced the aircraft's electrical load to preserve battery power. On arrival at Broken Hill the battery was flat, and the pilot was unable to lower the landing gear either by normal or emergency methods. After emergency services were in position the aircraft was landed with the landing gear retracted. When the aircraft was raised by engineers the landing gear was able to be extended normally. The investigation disclosed that the alternator body securing bolts had loosened thereby allowing the rotor to contact the windings, shorting out the electrical supply. The battery had depleted prior to arrival at Broken Hill; therefore the electrically powered hydraulic pump that normally retracts and extends the landing gear was rendered inoperative. No fault was found with the landing gear system. Upon reflection the pilot advised that he most probably did not hold the emergency gear extend lever down long enough to bleed off the hydraulic pressure and allow the landing gear to extend. The pilots operating handbook advises that under normal conditions the lever should be held down for approximately 10 seconds. However, industry experience is that it can take up to 20 seconds. The pilot advised that during his endorsement training on this aircraft he was taken through the emergency extend procedures but did not activate the system. He therefore did not have an appreciation of either the effort or the length of time the handle was required to be held down.