The last time the tower clock at the Old South Meeting House struck the hour, Ulysses S. Grant was president, Alexander Graham Bell had just received a patent for the telephone (landline only), and the United States was celebrating its centennial.
For 136 years, the tower was silenced. But that ended on Thursday when the clock, created in 1766, struck a bell cast by Paul Revere in 1801.
Getting that bell to ring wasn’t easy. It took months of trial and error for horologist — clock expert — David Hochstrasser to reverse-engineer the missing pieces that strike the bell and regulate the timing and number of the strikes.
“We have to do this a lot in clock restoration, but usually we have something to go by,” said Hochstrasser, who restored the rest of the clock three years ago. “This is the only tower clock known by this maker. It was his first [tower] clock and apparently he didn’t make any others.”
That clockmaker was Gawen Brown, an 18th-century Bostonian known for his watches and grandfather clocks. Perhaps because he was a novice in the construction of tower clocks, Brown made future repairs more difficult by making the unusual decision to construct the clock such that it has to be almost entirely disassembled to remove any gear or mechanism.
Other clocks made using a so-called birdcage frame — where horizontal bars attach to pillars and support vertical bars — have the horizontal bars put on first, then the vertical bars, then nuts that hold everything in place. This makes it simple to remove a single vertical bar and release a gear train or individual gear without taking apart anything else, Hochstrasser explained.
But Brown made his clock backward, with the horizontal bars outside the vertical bars.
“I daresay he made a huge mistake, the way he put this together,” Hochstrasser said.
But when the congregation of the meeting house relocated to Old South Church in Copley Square in 1876, they took the bell along with them, and it wasn’t replaced until last year, when the Revere bell was purchased from a closed church in Westborough, Mass., and raised to the meeting house steeple.
Somewhere in those 136 years, the pieces that struck the bell and regulated the timing of the strikes disappeared.
To replace them, Hochstrasser had to reconstruct about 10 missing pieces through trial and error, making up a regulator assembly based on those found in similar clocks and then replicating the parts in different sizes until he found the right fit for the Brown clock. It took three or four tries, designing new parts on a computer and having them fabricated, he said, to strike the right balance.
“The few publications that are out there that I was able to use for reference to making things like this pretty much say, ‘Start with this and experiment from there,” he said. In the end, Hochstrasser said, his version is “probably a more modern interpretation of what could have been there.”