Mantel Clock

Overview

A mantel clock is a self-contained spring-driven clock sized for a shelf or mantelpiece, and the classic form carries three independent gear trains in one movement: one to keep time, one to chime the quarter hours, and one to count out the hour. Each train has its own mainspring barrel, so the Going Train, Chime Train, and Strike Train can be wound and run without robbing power from each other. A full wind through the three arbors of the Winding System stores about eight days of running, which is why these are traditionally wound on the same day each week.

The movement is built between two brass Movement Plates joined by pillars, with every wheel pivoting in holes drilled through the plates. The whole unit sits inside the Wooden Case, a hardwood box that does double duty as furniture and as the sounding board for the gong rods screwed to its base.

How it works

Timekeeping starts at the Going Barrel, whose coiled steel mainspring drives the Center Wheel at one revolution per hour. The Third Wheel steps the motion up to the Escape Wheel, where the Escapement & Pendulum meters power out one tooth at a time. The Anchor rocks with the pendulum, alternately locking the escape wheel and receiving a small push from it; that push is what keeps the pendulum swinging against air drag and pivot friction. The pendulum itself hangs from a thin Suspension Spring rather than a bearing, and the clock is regulated by turning the rating nut under the Pendulum Bob: raising the bob shortens the effective pendulum and gains time, roughly a minute per week per turn on a typical movement.

The hands are geared off the center arbor through the Motion Work, a small cluster of wheels giving the 12:1 reduction between the Minute Hand and Hour Hand. A friction clutch in the cannon pinion lets the hands be set without forcing the train.

Chiming and striking

The chime side is mechanically a music box. Pins on the minute arbor unlock the chime train at each quarter, and the Chime Barrel spins the Pin Drum, whose studded surface lifts the five hammers of the Hammer Bank in the Westminster note order. Each hammer falls onto its rod in the Gong Rod Set, a graded set of hardened steel rods that ring like tuning forks; the case amplifies them. One phrase plays at quarter past, two at half past, three at quarter to, and four on the hour. Tempo is governed not by the escapement but by the Chime Fly, an air-brake fan whose drag rises with speed, so the tune plays at a steady pace whether the spring is freshly wound or nearly down.

After the fourth-quarter phrase the chime train releases the strike train. The blow count comes from the Rack & Snail: a stepped cam (the snail) turns with the hour wheel, and a toothed rack falls against it; the deeper the step, the more teeth must be gathered back up, and each gathered tooth is one blow of the Strike Hammer on the Hour Gong. Because the count is read from the snail position rather than accumulated, the strike stays synchronized with the hands even after the clock is stopped and reset. The Strike Fly paces the blows at about one per second, powered by the dedicated Strike Barrel.

Most movements include a self-correcting quarter rack so that if the chime is let down or the hands are moved, the trains resynchronize within an hour, plus a night-silencing lever that locks the chime lift between roughly 10 pm and 7 am.

Winding and service

Each barrel is wound through a squared Winding Arbor using the Winding Key; a Click & Ratchet on each barrel holds the charge between strokes. The chime barrel takes the most turns because it works four times an hour. Service amounts to cleaning and re-oiling the pivots every three to five years and replacing mainsprings when they set; access is through the Back Door. The Dial Plate and hands come off as a unit for movement removal, and the case rides on Brass Feet that keep the resonating base clear of the shelf.

The format dates to late-19th-century French and German factory movements and was made in enormous numbers through the 1950s; Hermle and Kieninger still produce triple-train mantel movements to essentially this design today.