Main Reduction (Bull) Gear Segment

Main Reduction (Bull) Gear Segment. . , This segment of the main reduction gear was donated to the N/S Savannah Association in 2009 by the Southern Scrap Company of New Orleans, Louisiana. It weighs about 37,500 lbs, or nearly half of the weight of the complete gear. Notice that the hub section is solid, it contains the cut-off section of stub shaft that connected the gear to the propeller shafting. Notice also the key and slot that fixes the gear to the shaft, and prevents the gear from rotating against the shaft. , , In 1980, a full decade after Savannah last sailed under her own power, this gear was removed to replace a damaged gear in the naval tanker American Explorer. For many years mystery surrounded this evolution. The people who were witnesses could not be found, and available documents only stated that the gear was removed from Savannah; not how it was removed. Savannah's gear boxes inside the engine room are empty; clear evidence that the work was actually performed. Yet visitors to the engine room see no obvious path by which the gear was removed, and there are no marks on the outside of the hull to show where the gear was rigged out of the ship. So how did it happen? Read on to find out... , , After receiving a second lease on life from Savannah's gear set, American Explorer enjoyed another long decade of government service before finally being retired to the Maritime Administration's Beaumont (Texas) Reserve Fleet. The ship was sold for scrap in 2008, and during that process this gear segment was acquired by the Association. No mystery surrounded the removal in 2009; the entire engine room was cut away from around the gear before it was lifted out of the hulk of the ship! , , In a quirk of fate, American Explorer almost became America's second nuclear-powered merchant ship. Construction was suspended after the ship was launched while studies were made to install a compact merchant ship nuclear reactor (a General Electric Model 630-A). The plans were eventually cancelled, and the Explorer was completed to its original conventional design. , , As to the mystery... In late 2014, long-lost documents came to light when a former office was cleaned and remediated. These documents had descriptions of the work, and sketches and photos. The work was performed at Braswell Ship Repair near Charleston, SC, from April to May 1980, with the ship afloat. All the equipment in the forward, starboard corner of the engine room was removed by way of a large access cut made in the ship's side shell. The cut follows the weld seams of the shell plating; it is invisible on the outside beneath the paint, and not obvious inside unless inspected up close. After the engine room was cleared, the gear was rigged up, laid horizontal over the turbines, and slipped out through the hole in the side of the ship. Once it was out, all of the equipment was returned and the engine room was cosmetically restored in time for its museum debut in late 1981. , , ( photo caption ) , The images are construction photographs of the gear and the complete propulsion unit. They were taken at the plant of the De Laval Steam Turbine Company. The picture on top shows the bull gear with the stub shaft showing on the right. The gear was 176.6" in diameter, 48 inches across the gear face, and there were 583 gear teeth originally. A small segment of the gear face appears at the bottom of the propulsion unit.