PROPELLERS

The propeller shafts were made in segments of forged steel, each about 30 feet long. For the reciprocating engines the shafts were approximately 26 inches in diameter with a 12-inch hole bored through the center. The tail of each shaft (the part that projected beyond the hull) was encased in brass, which gave it a slightly wider diameter, though it tapered to 6 inches at the tip. The tail was designed to be detachable for purposes of inspection, cleaning and replacement. The wings that carried these shafts to the propeller attachment points were just over 12 feet above the keel and 191/2 feet out from the centerline of the ship. The shafts were serviced with an automatic lubrication system.

The turbine’s shaft was slightly smaller, being 201/2 inches in diameter with a 10-inch central hole, and the tail-shaft was 221/2 inches in diameter, tapering to 5 inches. This shaft left the hull 121/4 feet above the keel.

Each shaft left the hull through a stern tube, which was both a bearing and a waterproof gland. The tube was lined with an expensive, oily hardwood, lignum vitae. The propellers themselves were of two types. The wing propellers each carried three manganese-bronze blades that were rustproof and resistant to extremes of heat and cold. These were attached to a cast-steel boss by heavy-duty studs and nuts, and were of impressive proportions: 231/2 feet in diameter with a pitch (or

Workers fit the starboard tail shaft to the stern of Titanic. The propellers will be fitted later. Once again, the men's size gives a sense of the scale of the liner.

Angle of attack) of 341/2 feet and a total surface area of 160 square feet. As yet, no precise record of Titanic’s center propeller has come to light, but it was probably similar, if not identical, to Olympic’s, which was also of manganese bronze, though carrying four blades. It was 17 feet in diameter, had a pitch of 141/2 feet, and a surface area of 125 square feet.

Once the propellers were in place, they were capped with a coneshaped “fairwater” to streamline the end, and all water-vulnerable joins were carefully sealed.