The Reduction Gear

After reading a few of my sea stories, Rear Admiral Lauren S. McCready, of the U.S. Maritime Service, persisted, “You should write about the eagle-boat reduction gear.”

He was especially interested in the subject because I, one of his former cadets at the U.S. Merchant Marine Academy, was involved and an eagle boat was his first ship. When he was six, he and his brother boarded the one that ran aground near their grandparent’s Long Island summer cottage.

Henry Ford built sixty of the two-hundred foot long subchasers during World War I just as he built Model-T automobiles, on production lines. As in the Model Ts the ships had planetary reduction gears. Each set included three, approximately twenty-two inch diameter planet gears that were simultaneously driven by, and that rotated around, a small diameter sun gear.

Each planet consisted of two separately machined gears that were keyed in place on a common bushing. The finished assembly was a self-aligning herringbone gear. The locations of the keyways were critical for self alignment.

On 1 December 1944, when I reported on board USS EAGLE 19 (PE 19), the oldest of the eight still active during World War II, the extensively damaged main propulsion turbine was being repaired. Civilian machinists at the Naval Operating Base in Key West were being supervised by a forty-five year old lieutenant. He was a mustang, that is, a former enlisted man. He was also cantankerous.

Since the engine room was gutted for removing the turbine, a decision had been made to replace the twenty-six year old worn reduction gear; two unused sets, left over from World War I, were available.


When the replacement set was assembled in EAGLE 19, one planet did not align with the others; it protruded axially by about one inch. The lieutenant ordered, “Button up the casing.”

I was stunned. I did not have his experience, but I had been trained at Brooklyn Technical High School and Kings Point to think analytically. I reasoned:

each of the planets was designed to transmit one third of the total power,

incomplete tooth contact will be made by the misaligned planet, therefore

what tooth contact there is will be overloaded.


I advised that the work was unacceptable and suggested that a stepped key be used to rotate one half of the planet with respect to the other half. That would cause it to align correctly. The lieutenant rasped his disagreement in no uncertain terms. My skipper, who was in a law office the year before, solicited advice from the squadron engineer, another mustang. The latter agreed with the lieutenant, so I recorded my opinion in the official engineering log that the skipper had to sign. I used my drawing skills to clearly illustrate the problem and my proposed solution that was not employed.

When outbound EAGLE 19 steamed just one mile past the buoy that marked the entrance to Key West’s main ship channel the reduction gear began to sound like a rock crusher. After being towed back to the Operating Base an inspection disclosed that one tooth broke off from the misaligned planet. Before the engine could be stopped the broken piece damaged all of the other gears.

A decision was made to replace the damaged set with the remaining unused set. In the same manner, one planet protruded axially by the same amount. One plausible explanation is sabotage by a machinist in 1918. Regardless, the lieutenant again rejected my proposed solution. He selected the least-damaged planet from the just-removed set and filed off the disrupted metal that projected beyond designed surfaces.

I again refused to accept the work and repeated virtually the same litany:

each of the planets was designed to transmit one third of the total power,

complete tooth contact will not be made because of the depressed surfaces, therefore

what tooth contact there is will be overloaded.

The exasperated lieutenant told the squadron engineer that I was trying to keep Eagle 19 in port because I had a girlfriend ashore. The incensed squadron engineer repeated the lie to the squadron commander, and the furious squadron commander ordered my skipper to put me in hack, that is, to confine me to my stateroom whenever I was not performing assigned duties. My skipper reluctantly complied. Demoralized because I had always wanted to be in the Navy, I left the stateroom after a full day in hack, when called for special sea detail.

When EAGLE 19 steamed just one mile past the buoy that marked the entrance to Key West’s main ship channel, the reduction gear again made that horrible noise. I was beside myself with joy as I secured the main engine and notified the officer of the deck. Within minutes, without any attempt to conceal a smile, I advised the skipper, “You should hear the reduction gear. It sounds like a rock crusher.”

During the next few days, the original, sorely worn, twenty-six year old planetary reduction gear was reinstalled in EAGLE 19.


Copyright © 2005 (text only) by Louis D. Chirillo