On the sixth floor General Rodman installed the clock that has become the symbol of the building. Its four 12-foot faces are twice the size called for on the plans. Original Ordnance plans called for a more modest clock with six-foot faces chiseled into the stone surfaces of the tower.
General Rodman selected the nationally known A. S. Hotchkiss Company of Williamsburg, New York, to build the clock. Mr. Hotchkiss not only designed and built the clockworks at his Williamsburg shop, he brought them to Rock Island on December 30, 1867, to personally assemble and install them.
The clockworks sit today where they were installed in 1868, along the east wall of the sixth floor of the tower, in a solid frame of cast iron 7 feet, 9 inches long, supported by four iron columns.
The Hotchkiss clock is impressive to see close up. The time main wheel, 3 feet in diameter, revolves once in twelve hours. It has the hours painted on its face, with a pointer denoting the hour of the day. The second wheel, 27 inches in diameter, revolves every hour. Minutes are painted on its face with a pointer denoting the minute of the hour. The second wheel also has a lifting pin attached to unlock the striking mechanism.
The escape wheel, 8½ inches in diameter, revolves in three minutes and has the seconds pointed off. The arrangement of wheels and numbers precludes the necessity of any dial work on the movement.
The escape wheel has 30 pins of a special shape designed by Mr. Hotchkiss to prevent oil being attracted to the wheel. This leaves the pins dry and solves one of the main problems of pin escapements. The pallets are of agate, with both pins and pallets having a high polish.
The main strike wheel has 32 steel rollers for raising the hammer. All of the wheels in the works are of bronze (gun metal); the journals or bearings are bossed with the same metal. The pinions are made of steel, while the wheels used for winding the clock are of engine-cut and polished iron.
A system of rods and gears running from the clockworks to the center of the room, and from there to the four dials, runs all four sets of clock hands simultaneously.
Each of the 12-foot wooden clock faces forms a "porthole" in one wall of the tower. Around the center of the dial in a six-foot circle are twelve round glass windows at the hour points. Near the edge of the dials an arrangement of "stars and bars" marks off the hours, with stars representing the hours of 3, 6, 9, and 12, and bars representing the remaining hours. At the very edge of the dial, small raised bars mark off the minutes. Dials, markings, and carved hands are all of wood, with hands and markings painted white to set them off from the black dial.
An observer looking out the windows in the dial can watch the hands visibly move with each tick of the clock.
The pendulum hangs down through two stories of the tower, its wood shaft and 350-pound ball vibrating every three seconds. Its length to the center of oscillation is 29 feet, 6 inches, giving a whole length of nearly 32 feet.
Power to operate the clock comes from weights suspended by wire ropes from an 18-inch spiral-grooved drum in the clockworks.
A 1,200-pound weight, at the end of a wire rope 250 feet long, creates 250 pounds of tension to operate the striking mechanism.
A 1,000-pound weight, at the end of 150 feet of wire rope, creates 150 pounds of tension to drive the time mechanism.
By January 20, 1868, Mr. Hotchkiss had the clock in perfect order. The works were enclosed in a wood and glass case by the head carpenter at the Arsenal.
Mr. Hotchkiss adjusted the clock to keep local time, the actual sun time on the Island. Nearly all of the businesses in the surrounding towns kept "Chicago time," also called "railroad time," because Midwestern railroads ran by it. Uniform time zones were not established until 1883; in 1868 there were more than 100 time zones in the United States. The result was that the Clock Tower clock ran between 12 and 15 minutes behind most other clocks in the area.
General Rodman's dealings with the clockmaker were very satisfactory. The contract for the clock came to $5,000. Mr. Hotchkiss supplied the works, all weights, wire rope, all hands, pulleys, hammers, and gearing for the dials. He paid all the freight bills to the Arsenal and personally installed the clock at no additional expense. He also warranted his work and all the parts.
The bell for the clock was bought from Fairbanks & Co., New York, and manufactured by E. A. & G. R. Meneely of West Troy, New York. It weighed 3,538 pounds and cost 47 cents per pound, or $1,662.36.
Residents complained that the bell was too loud, and it was eventually disconnected. In 1945, when the clockworks were extensively overhauled, the bell was reconnected at the lowest possible level -so faint that it can seldom be heard inside the building.
Originally the Clock Tower clock was wound by hand, a job that took two men twenty minutes once each week. On the walls of the clock room, among a number of unofficial names and dates of times when repairs were made, is an entry dated July 7, 1907, which reads: "Carrie Passig and daughter Ruth and Hattie Pratt came with Papa (W. J.) Pratt to see him wind clock. Papa started to wind clock in 1867 and missed winding three times in 1867 to 1907."
In 1950, on an experimental basis, the clock was switched over to electric winding. In 1955, an electric motor and gears were installed permanently. Otherwise, the clock still has all its original parts.
The Hotchkiss clock has lived up to its reputation. It is the only known clock of its type still running. From the first, it has only lost or gained an average of 15 seconds per week in good weather. Snow and ice occasionally slow or jam the hands in winter, but seldom for long. It has faithfully noted the minutes and hours of more than a hundred years of American history.