Antique & Vintage Clock Monthly Rate, Amplitude & Winding Log

ContextAt the beginning of each month (or logging cycle), set the clock precisely to your reference and record the reference time used. Before touching anything, also write down the clock's displayed time — this captures the rate from the previous period automatically, giving you two data points in one action. Use the clock's regulating mechanism to correct rate going forward; moving the hands to set the time does not change how fast the movement runs and should be noted separately to avoid confusing display corrections with regulation adjustments.

ContextAt the end of 7 days, compare the clock to your reference and note the total seconds gained (+) or lost (–) since the last reading. Divide by 7 to get the daily rate. A well-regulated English fusee bracket clock should hold within ±5 seconds per day; a quality Vienna regulator within ±2 seconds per day; a typical American shelf clock within ±15 seconds per day. Record the raw weekly total, not just the daily average — this reveals whether drift is accelerating mid-week or is uniform, which points toward different causes.

ContextEvery time you turn the regulating nut, slide the rating nut on a pendulum bob, or move the regulator index on a platform escapement, write it down: the date, the direction (faster or slower), and the amount if measurable. Without this record you will have no way to understand why the rate changed — was it the environment, or an adjustment you made three weeks ago and forgot? Use consistent notation, for example: '14 Mar — nut –¼ turn, clock was gaining 9 s/day.' Undocumented adjustments are the single most common cause of confusing log data.

ContextPendulum length changes with temperature: an uncompensated steel-rod pendulum loses approximately 0.5 seconds per day for every 1°C rise in temperature, because the rod expands and the pendulum swings more slowly. Recording temperature alongside rate allows you to separate genuine mechanical drift from thermal expansion effects. If the clock's rate swings with the seasons but is stable within a season, the pendulum material and suspension are almost certainly the cause rather than wear — an important distinction before you start adjusting the movement.

ContextStand directly in front of the clock and observe the pendulum's full swing. A healthy longcase grandfather clock pendulum typically swings 4–6 inches each side of center; a Vienna regulator usually swings 3–4 inches each side; a bracket clock pendulum with a short bob may swing only 2–3 inches. Shrinking amplitude — especially when gradual over several months — signals increasing friction in the pivot holes, oil degradation at the pallet arbor, or diminishing mainspring or weight energy. Record the arc in inches or centimeters; a ruler held near the bottom of the bob is sufficiently accurate.

ContextThe tick and tock should be equal in duration and volume. An uneven beat — where one side sounds heavier or one pause is noticeably longer — means the clock is out of beat and working harder on one side of the swing, which artificially suppresses amplitude. Always correct the beat before drawing conclusions about amplitude health, otherwise you'll chase a phantom mechanical problem. On most antique clocks, beat is set by gently bending the crutch or adjusting the beat adjustment screw if one is present. Note any beat correction in the log so you have context for the amplitude reading that follows.

ContextFor balance-wheel movements — most carriage clocks, mantel clocks, and bracket clocks without a visible pendulum — you cannot easily measure arc in inches. Instead, after a full wind, record the exact day and time the clock stops. A movement sold as a 7-day clock that consistently stops after 5 days has diminished power delivery, which directly corresponds to reduced balance amplitude. Comparing run-down time month to month is a reliable and repeatable proxy for amplitude health. If you have access to a smartphone timegrapher app (see the tools section), use it for a more precise beat-error and amplitude reading.

ContextIf your first three months of logging established a baseline arc of 5 inches each side and you are now seeing 3.5 inches, that is a 30% drop and warrants investigation. The most common causes in antique clocks are dried or congealed oil in the pivot holes (particularly the pallet arbor and escape-wheel pivot), a mainspring approaching end-of-life, or a worn click spring failing to lock maintaining power. Do not attempt to compensate with oil — adding lubricant to a dry pivot without cleaning spreads debris and accelerates wear. Document the percentage drop in the log and trigger a professional service review if it persists for two consecutive months.

ContextFor key-wound spring clocks, count the clicks of the ratchet or the number of quarter-turns until resistance is clearly felt. For weight-driven clocks, record whether you wound to full height and the approximate cord or chain height before winding began. A consistent winding character — always 14 clicks to full, every time — tells you the mainspring is storing its full energy reliably. If full winding suddenly requires noticeably fewer turns, the spring may be broken at the outer coil and is no longer storing its designed energy. If it requires noticeably more turns, the click or click spring may be slipping.

ContextHealthy winding feels smooth with gradually increasing resistance that firms up clearly at full wind. A hard spot — a sudden increase in torque at a specific point in the wind — suggests a bent or damaged coil in the mainspring, or debris caught between coils. A slipping sensation, where the key turns without the ratchet engaging, means the click or click spring is worn or broken. Forcing through either symptom risks catastrophic mainspring breakage, which can damage pivot holes, bend wheel teeth, and scatter debris throughout the movement — a repair that can cost several hundred to over a thousand pounds or dollars. Stop, record the symptom precisely, and inspect before winding again.

ContextA clock sold as an 8-day movement should run 7–9 days between windings under typical household conditions. If it consistently stops after 5–6 days, the power reserve is diminished. This can stem from a shortened mainspring (a previous repair involving re-tempering or section replacement), a worn or slipping maintaining power, or excessive friction consuming energy before it reaches the escapement. Record actual run time for each wind cycle — three consecutive short cycles without an environmental explanation (unusual cold, clock moved, case door left open) is a trigger for professional inspection.

ContextRecord the key size for every clock in the log — for example, 'No. 8 double-ended key, 4.5 mm square' or 'No. 12 single-end gut-line key.' The winding squares on antique clock arbors are soft brass and round off quickly if the key fits loosely or is even slightly oversized. Once the square is damaged, the repair requires movement removal and arbor replacement. If you ever need a replacement key or if someone else winds the clock in your absence, this entry prevents an expensive mistake. Store the correct key with the log or note where it is kept.

ContextPendulum clocks must be level side-to-side; even 2mm of lateral tilt on a longcase clock significantly affects the beat symmetry and puts uneven load on the escape-wheel teeth and pallets. Use a small bubble level placed on the clock case sill or dial frame. Floors settle, furniture shifts, and buildings move — check level every month, not just on installation. If the clock was moved for cleaning or redecoration, always re-level and re-check the beat before starting the next log period. Record any re-leveling with the date and direction of correction.

ContextCentral heating in winter routinely drops indoor humidity below 30%, which causes wooden clock cases to shrink, can shift the pendulum suspension point, and stiffens suspension springs. High summer humidity causes expansion. These forces can alter rate, shift beat, and — in severe cases — crack case joints or lift veneer. If you have a combined digital hygrometer and thermometer near the clock, record the monthly minimum and maximum alongside the average. Knowing the environmental context that preceded a rate change is often the key to diagnosing it without disassembling the movement.

ContextA clock that was bumped, transported, repositioned, or sat near a repeatedly slammed door will show unexplained rate irregularities that look like mechanical problems in the log. These events rarely cause immediate visible damage but accumulate wear on pivot holes over years of repetition. Log them with a brief description. If a repairer later finds unusual wear on specific pivots, your log may explain the source. For mantel clocks on stone or granite surfaces, note whether the surface transmits vibration from nearby speakers, appliances, or HVAC equipment — sustained resonance is a slow but cumulative killer of pivot-hole brass.

ContextAt month-end, total all weekly rate readings and divide by the number of observed weeks. Plot or simply compare this figure to the previous three monthly averages. A clock that needs progressively faster regulation month over month — without a seasonal explanation — has increasing friction at the escapement; each adjustment is compensating for new wear rather than correcting a one-time shift. A clock needing progressively slower corrections may have a pivot gradually seizing. Three consecutive months of directional drift without an assignable environmental cause is a clear trigger for professional service.

ContextCompare this month's amplitude observation to the baseline you established in the first three months of logging. Write a plain-language judgment in the summary box: 'Stable,' 'Down 10% — monitor next month,' or 'Down 25% — service required.' A single anomalous month can be environmental or a beat issue; a shift sustained across two or more months is a mechanical trend. These summary judgments are the most time-efficient part of the log for future owners or horologists to scan — a single page of monthly summaries tells the story of the clock's last decade at a glance.

ContextRead back through every winding entry for the month. If nothing unusual occurred, write 'Winding normal — no flags.' If a hard spot, slippage, or shortened run time was noted, carry it forward explicitly into an action column: 'Hard spot at turn 9 — inspect click spring before next winding.' An observation without a named follow-up action is just data; an observation that generates a specific, dated action item is maintenance intelligence. Never let an anomaly sit in the log body without surfacing it in the summary — that is how small problems become expensive ones.

ContextYour initials and the date on the summary line transform the log from a private note into a provenance document. For clocks of significant collector or heirloom value, a consistent signed log dated across many years substantially increases buyer confidence and can be cited explicitly in auction or sale descriptions. Each signed monthly entry is one brick in the clock's documented history. Clock auction specialists have noted that well-maintained written service and performance logs add measurable premium to important horological pieces — the log itself becomes part of the object's value.