Imagine buying a product today that your family would cherish and still be using in 2160? I’m not talking about a piece of quality furniture or artwork, but an analog clock with some parts that are in continuous motion. This past weekend I once again got my grandfather clock, pictured to the right, functioning. This is a pendulum clock initially made for and installed at the NY Stock Exchange, then moved into a law office, and later a private residence. I inherited it some forty years ago, before becoming a teen, and it has operated a few times since it was placed in my care. This timepiece was manufactured in the 1880s, and it is a self-winding, battery-powered unit. Batteries were a very new technology in 1880. This clock shipped with two wet cells that the new owner then had to set up. The instructions called for pouring powered Sulfuric Acid from paper envelopes into each of two glass bottles, adding water, then stirring. The lids of the glass bottles contained the anode and cathode of the cell. The two cells were then wired in series and produced a three-volt battery.
When it was installed at the Exchange, around the time of Thomas Edison, it was modified with the addition of a red button on the side designed to synchronize the clock with the others on the Exchange. The button on this clock, and all others like it at the Exchange, would be pressed on the hour, prior to the opening of the market. It has since been rewired, so the button triggers an out of sync winding. During my childhood, this clock ran for a few years until it fell silent as a result of dead batteries. Over my adult life, it has run continuously several times, often only for a year or two at a stretch until the batteries were depleted. The issue, more often than not, was simply access to replacement batteries. In the 1950s, the batteries this clock required, a pair of dry-cell No. 6, were available in most hardware stores. Many devices were designed to use this No.6 cell, including some of the earliest automobiles, early in the 1900s it was a very popular power source.
We moved recently, and one of my wife’s conditions on hanging my grandfather clock in the living room was that it function. In 2005 after an earlier move from California to North Carolina, we hired a local clock repairman to restore this family timepiece. He cleaned out the old lubrication, replaced a few worn parts, hung the clock, and sold us his last pair of original No. 6 dry-cell batteries. For those not familiar with the No. 6, it was a 1.5-volt battery the size of a large can of beer, but the standout attribute of this battery was that it could provide high instantaneous current for a brief period of time. In the 1990s, No. 6 cells were banned in the US because they used Mercury. The replacements offered had the same size and fit, but couldn’t produce the required instantaneous current.
Last week after some research, and a little math, I realized that four, dual D-cell battery boxes connected via terminal strips to limit current loss, could produce about 30% more instantaneous current at three volts than the original pair of No. 6 cells. So, I glued the boxes together to form a maintainable brick, added two five terminal strips, one positive and one negative, then tested all the wiring and batteries. After rehanging the clock, leveling the case, installing the new battery box, and pressing the wind button, I raised the pendulum and let it go. The escapement rocked back and forth, enabling the secondhand gear to creep ahead one tooth at a time, but after ten minutes, the clock fell silent once again.
Several more attempts, each roughly ten minutes, and the internal switch eventually kicked in, and the batteries did their job. The clock wound automatically for the first time in well over a decade; I was elated. Alas though another few minutes later, the clock came to rest once more. After some additional research into how the clock was losing energy, I came across a few suggestions. The hands were placed correctly, secured, and didn’t touch anything. I shoved my iPhone camera into the side of the case to get a view of the pendulum hanging on the escapement and found that it was hanging a bit askew. I then sprayed a small amount of synthetic lubricant on the escapement, crossed my fingers, and gave the pendulum another nudge. Fifteen minutes later, it coasted to a halt. Tinkering a few more times with the pendulum, over the next few hours, and a bit more lubricant, the clock was eventually sustaining movement. That was Sunday, it’s now Tuesday night, and the clock is going strong and hasn’t stopped since. As of this morning, the clock was losing about three minutes every twenty-four hours.
Now the chase is one to improve the accuracy. This is done by changing the pendulum length through a nut below the pendulum’s bob. If you loosen the nut, it lowers the bob making the pendulum longer, and the clock runs slower. Tighten the nut, and the pendulum is shorter, and the clock runs faster. Perhaps a successive series of turns over the next few days will get this 140-year-old device down to a few seconds a day!
Update Friday, June 12, after some very gentle tightening of the pendulum, thereby shortening its length and speeding up its swing, we’re down from three minutes to 61 seconds a day. There may be a few threads left, so hopefully, we can get this loss down to less than 30 seconds a day.
Update Monday, July 6, the clock is running strong on the original eight D-cells from last month, I’m expecting about a year on each set, and it still sounds strong. Some additional tweaks and we’re now only losing 25 seconds a day or one every hour. So I just need to add a minute every two days, not bad.
Update Sunday, June 27, 2021, the clock has run non-stop for the past year and is still running strong on the initial set of eight Duracell D-cells. At this time the clock is still winding regularly every hour, and it is losing less than 15 seconds/day so I often adjust it every week or so setting it two minutes ahead. After inspecting all the cells for leakage, they look fine, and testing each one I’ve found they are all 1.44V plus or minus 0.001V, which is impressive. The four unused, lets call them control cells, have all maintained a voltage of 1.61V. From my reading it appears that until the voltage drops below 1.3V I should still get good performance out of them. So they will remain in service for another year. What an engineering marvel.