Crutch and Pendulum Leader Problems: Beat Setting, Supplementary Arc, and Pallet Pin Wear in Ansonia Mantel Clocks

A clock that runs intermittently — starting and running for a few minutes, then stopping, then starting again when given a push — and whose crutch spends most of its time pressed against one side of the pendulum leader rather than alternating symmetrically between both sides, is showing you a specific diagnostic picture. The crutch is supposed to push the pendulum on the left side of each swing and pull it on the right side, with the leader's slot allowing the crutch pin to cross from one side of the slot to the other at the center of each swing. When the crutch rides against one side of the slot almost continuously, the clock is either significantly out of beat, has insufficient pendulum amplitude to bring the leader slot to the crutch pin on alternate strokes, or the crutch-to-leader clearance is so large that the leader barely contacts the crutch at all during the unfavored stroke. Understanding which of these conditions is producing the one-sided crutch contact determines whether the correction is beat setting, cleaning and oiling to restore amplitude, or a mechanical adjustment to the leader or crutch geometry.

This guide covers the complete diagnostic and repair sequence for crutch-leader interaction problems in Ansonia and similar American mantel clock movements — how to use supplementary arc as a direct measure of pendulum power margin, what the crutch being perpendicular to the plate means and why it matters for beat, how the Brocot open pin-pallet escapement used in Ansonia VE movements differs from the cut-leaf pallet common in other American movements and why it requires specific attention to pallet pin condition and depthing, how worn pallet pins produce symptoms that appear to be power problems rather than escapement problems, how to measure beat rate using a timing device and calculate whether a pendulum suspension rod needs to be replaced to bring the rate into adjustment range, how case mounting plate flatness affects beat stability, and why a movement that runs well on the bench may run poorly when reinstalled in the case. Taken together these factors explain why some clocks remain elusive through multiple service attempts until the root cause is identified through systematic observation.

Crutch Position and Its Relationship to Beat

What It Means When the Crutch Favors One Side

The crutch of a clock is the arm that connects the pallet arbor to the pendulum, transmitting escapement impulse to the pendulum while also receiving the pendulum's governing influence back through the crutch loop or slot in the leader. In correct operation, the crutch moves left and right alternately as each pallet releases the escape wheel — the crutch pushes the leader on one side of the swing and receives the leader returning on the other side, with the leader alternately pressing against the left and right inner surfaces of the crutch slot. When the pendulum amplitude is healthy and the beat is correct, the crutch appears to swing symmetrically with the leader clearly visible touching both sides alternately as the pendulum swings.

When the crutch rides against the left side of the leader slot for thirty or forty consecutive beats and only occasionally contacts the right side, one of several conditions is present. The most common is that the clock is significantly out of beat — the tick and tock intervals are unequal, meaning the escapement releases more readily in one direction than the other. The pendulum still swings but the asymmetric impulse drives it further in one direction than the other, and the crutch's natural rest position presses against the side of the leader corresponding to the favored swing direction. A second possibility is that the pendulum amplitude is so marginal that the swing barely reaches the far side on the unfavored stroke, and any slight asymmetry in the impulse or friction causes the pendulum to fall short before reaching the crutch on that side. A third possibility — relevant specifically to movements with Brocot-type open pin-pallet escapements — is that one pallet pin is significantly more worn than the other, producing unequal impulse depths on the two sides of the escape wheel that create inherently asymmetric pendulum drive.

Supplementary Arc as a Power Margin Indicator

Supplementary arc is the amount by which the pendulum swings beyond the minimum arc needed for the escapement to operate — the extra amplitude that represents the clock's power reserve above the threshold for reliable operation. A clock with large supplementary arc can absorb significant additional friction before it stops, while a clock with minimal supplementary arc will stop when any additional friction is introduced — a slight change in oil viscosity with temperature, a small adjustment to the mounting angle, or the minor friction of reinstalling the movement in the case. Measuring supplementary arc before and after any service provides a quantitative assessment of how much the service has improved the movement's power margin and whether that margin is adequate for reliable long-term operation.

To measure supplementary arc without a dedicated instrument, hold a piece of paper behind the pendulum without touching it. Move the pendulum manually from side to side until the escapement ticks — just barely releases on each side. Mark the paper at the pendulum's position at the extreme of each minimal-amplitude swing. These marks define the minimum arc boundary. Now start the clock and allow it to run for at least fifteen to twenty minutes before observing the pendulum's actual swing extent against the paper marks. The distance between the actual swing position and the minimum-arc marks is the supplementary arc. A clock with adequate power will show the pendulum swinging noticeably past the minimum arc marks — perhaps a centimeter or more past them on each side. A clock with marginal power will show the pendulum barely past the marks, and a clock that stops will show the pendulum settling back to exactly the minimum arc before the oscillation dies completely.

The Brocot Open Pin-Pallet Escapement

How the Brocot Escapement Differs from Cut-Leaf Pallets

The Brocot escapement used in Ansonia, Seth Thomas, and other American mantel clock movements of the Victorian and Edwardian periods is an open pin-pallet design where two cylindrical steel pins mounted on the pallet arbor serve as the pallet surfaces, engaging the escape wheel teeth through a gap in the movement's front plate that is visible from the front of the clock when the dial is removed. Unlike the enclosed recoil or deadbeat pallet designs common in other American movements, the Brocot escapement operates entirely in view and is accessible for inspection and adjustment without disassembling the movement beyond removing the front bezel and dial. The cylindrical pallet pins receive the escape wheel tooth on their curved forward surface, and the impulse is delivered as the tooth slides across this curved surface before releasing.

The specific geometry of the Brocot escapement — the cylindrical pin surface receiving the impulse tangentially at the apex of the curve — makes the depthing relationship between pallet pins and escape wheel critical for reliable, efficient operation. The escape wheel teeth must fall just past the apex of the pin's curve when they lock on the pallet surface, and the impulse must be delivered across a controlled arc of the pin's cylindrical surface. If the depthing is too deep, the teeth lock too far up the pin's surface and the impulse arc becomes inefficient, reducing the power delivered to the pendulum. If depthing is too shallow, the teeth may slip off the pin surface before completing the impulse, producing a double-tick or irregular escapement action. The pallet pin adjustment capability built into most Brocot escapement designs allows the pins to be moved toward or away from the escape wheel to set the correct depthing — an adjustment that must be revisited after any service that changes the plate spacing or bushing positions.

Pallet Pin Wear and Its Symptoms

Brocot pallet pins are made of hardened steel and are designed to resist the wear produced by escape wheel tooth contact, but after many years of operation and particularly in movements that have run with inadequate lubrication or incorrect depthing, the pins develop wear grooves — ruts worn into the cylindrical surface at the points where the escape wheel teeth contact during normal operation. These ruts change the effective contact geometry from the original smooth curve to an irregular surface where the tooth initially contacts the groove edge rather than the smooth curve, producing an inconsistent impulse that varies with each escape wheel rotation. The symptoms of rut-worn pallet pins include inconsistent pendulum amplitude, a tick that sounds strong on some beats and weak on others, difficulty maintaining steady beat even when the clock appears to be correctly in beat, and intermittent stopping that does not correlate obviously with any mechanical binding elsewhere in the train.

Inspecting the pallet pins requires removing the pins from the pallet arbor or at least examining them carefully under magnification while still in place. Wear ruts on cylindrical pallet pins appear as narrow grooves or channels worn across the forward surface of the pin — visible as a dull band across what should be a uniformly shiny curved surface. Deep ruts may be visible to the naked eye, while shallower ruts require magnification to distinguish from the surrounding undamaged surface. The depth of the ruts relative to the pin radius determines whether the pins can continue in service without replacement — shallow ruts that have not penetrated significantly into the flat backing may allow the clock to run acceptably after other service work is completed, while deep ruts that have penetrated into the flat portion of the pin have compromised the functional geometry beyond what can be corrected by depthing adjustment alone.

Swapping Pallet Pin Positions

Before replacing worn Brocot pallet pins, consider whether the pins can be swapped — moved from their current position to the opposite hole in the pallet arbor — to present fresh, unworn surfaces to the escape wheel teeth. The contact zone on each pallet pin is limited to a portion of the pin's surface, and if the pin is held in its arbor hole with a friction fit or lacquer, removing it and reinstalling it rotated 180 degrees presents the undamaged side of the pin to the escape wheel. This approach provides the equivalent of new pin surfaces without requiring new pins, and is particularly worth attempting when replacement pins of the correct diameter are not readily available. After swapping, verify that the flat portions of the pins — which provide the lock face that holds the escape wheel at rest between impulses — are correctly oriented and that the depthing is adjusted to the correct position for the new pin presentation.

Beat Setting on the Ansonia VE Movement

Crutch Perpendicularity and Its Effect on Beat

The crutch on the Ansonia VE movement and similar American mantel clock movements must be perpendicular to the movement plate — extending straight back at a right angle to the plate surface — for the beat to be symmetric. A crutch that leans to one side will contact the pendulum leader at an off-center position, shifting the crutch's effective neutral position away from the pendulum's true center of gravity. The result is that the pendulum's natural rest position does not coincide with the crutch's natural rest position, and the clock will be out of beat in proportion to how far the crutch leans from perpendicular. Checking crutch perpendicularity is a quick visual inspection that should be performed before any beat adjustment — correcting a crutch that is not perpendicular by bending the beat-setting lever rather than straightening the crutch only masks the underlying geometry problem.

On the Ansonia VE movement, the crutch is bent to set the beat — there is no dedicated beat-setting lever. The crutch arm is carefully bent at its base where it attaches to the pallet arbor, moving the loop at the end of the crutch to one side or the other to change the beat setting. This bending must be done carefully because the crutch is a thin spring-steel component that can develop a fatigue crack if bent repeatedly. Use smooth-jaw pliers to make very small bends, test after each adjustment, and avoid bending the crutch back and forth more than necessary. The goal is the minimum bend that produces equal tick and tock intervals when verified with a timing device — not a theoretically perfect crutch geometry.

Using a Timing Device for Accurate Beat Setting

Beat setting by ear — listening for equal tick and tock intervals — is adequate for many clock types but is challenging for movements with Brocot escapements where the tick and tock sounds are similar in character and difficult to time accurately without a reference. A smartphone clock timing application provides a more objective assessment of beat error, measuring each tick-tock interval numerically and reporting the deviation from equality as a beat error percentage or in milliseconds. Using a timing device, the beat can be adjusted to a very small residual error — typically less than one percent — that is genuinely beyond the ability of the ear to detect but still within the range where it may affect long-term reliability in a clock with marginal power margin. Set the beat with the timing device while the movement is on the bench in its running position, verify the beat in the same orientation the clock will be used, and confirm that the beat remains stable through several minutes of operation before considering the adjustment complete.

Pendulum Suspension Rod and Leader Length

Beat Rate and Pendulum Length Matching

The beat rate of a clock movement — the number of complete oscillations per hour — is fixed by the gear train ratio from the great wheel to the escape wheel, and the correct pendulum length for that beat rate is calculable from standard pendulum physics. A movement whose measured beat rate is 7920 beats per hour requires a pendulum of a specific effective length — from the suspension spring pivot point to the center of the bob — to produce this rate with the bob adjuster at approximately mid-position in its travel range. If the pendulum is too short for the movement's beat rate, the clock will run fast even with the bob at its lowest position, and if too long, the clock will run slow even with the bob at its highest position. When the rate nut or adjuster is maxed out at one extreme and the clock still does not keep correct time, the pendulum suspension rod is the incorrect length and should be replaced with one of the correct length for the specific movement caliber.

The Ansonia VE movement used a suspension system with a feather-top leader — a flat spring suspension with a distinctive shape at the top that provides the correct stiffness for the pendulum weight. If this leader has been replaced with one of a different length, the effective pendulum length changes and the rate may fall outside the adjuster's correction range. The correction is to replace the leader with one of correct length for the movement — available from clock parts suppliers in standard Ansonia-compatible sizes — rather than attempting to compensate for a wrong-length leader by adding or removing pendulum rod length elsewhere. Matching the leader to the movement caliber and adjusting the bob position for fine rate correction is the correct sequence for rate adjustment, not compensating for incorrect leader length through extreme bob positioning.

Measuring Beat Rate to Identify Rate Adjustment Needs

Measuring the actual beat rate of a running movement using a timing device — counting beats over a known time period and dividing by that period in hours — gives the definitive current rate of the specific movement regardless of what any reference table states. The beat count divided by hours of timing equals beats per hour. A count run for four hours provides good accuracy; a shorter run introduces more error from startup conditions and timing measurement uncertainty. With the measured BPH established, compare it to the theoretical BPH calculated from the gear train tooth counts, and compare both to the adjustment range available with the current pendulum and leader combination. This three-way comparison identifies whether the movement's gear train is correct, whether the pendulum is the correct length, and whether fine adjustment through the bob will reach the correct rate.

For the specific case of the Ansonia Madrid movement with an eight-marked leg, historical clock reference sources document the movement's beat rate specifications that allow comparison against measured data. If the measured rate matches the historical specification and the clock is running fast or slow beyond the adjuster range, the pendulum length is the variable that must be corrected. If the measured rate does not match the historical specification, a non-original replacement movement or pendulum may have been installed at some point, and identifying the correct pendulum for the installed movement rather than for the original clock design is necessary for accurate rate setting.

Case Mounting and Beat Stability

Case Mounting Plate Flatness and Movement Twist

A movement that runs well on the bench but runs erratically or stops when installed in the case has encountered a mechanical condition introduced by the case installation. The most common cause is that the case's mounting plate — the back plate or seatboard — is not perfectly flat, causing the movement to be slightly twisted when all four mounting screws are tightened. This twisting changes the spatial relationship between the crutch and the pendulum from the relationship that existed during bench testing, potentially taking the clock out of beat or changing the depthing of the pallet pins relative to the escape wheel. A movement that has been beaten and adjusted perfectly on the bench will change its behavior when twisted by a few thousandths of an inch during case mounting.

The practical solution for a mounting plate that is not flat — causing the movement to twist when all four mounting screws are tightened — is to mount the movement on only three screws rather than four. Three mounting points always define a plane regardless of their relative heights, while four points may define two planes and produce twisting when constrained by all four screws simultaneously. Removing the screw that corresponds to the highest corner of the casting eliminates the twisting force and allows the movement to sit in a consistent, untwisted position on the remaining three mounting points. The trade-off is that the movement has less mechanical constraint from three mounting points than four, but for a mantel clock sitting on a stable surface this is rarely a practical problem. Verify after removing the fourth screw that the beat is stable and that the movement cannot rock or shift in operation before considering the installation complete.

Beat Setting After Case Installation

The beat must always be verified and adjusted with the movement installed in its case in its final operating orientation, not in the orientation used during bench testing. The pendulum hangs under gravity from the suspension spring, and gravity's direction relative to the movement determines the crutch's natural rest position. If the case is tilted even slightly from the bench position, the crutch's rest position shifts proportionally, and the beat setting that was correct on the bench will be incorrect in the case. Level the case using a spirit level, hang the pendulum, start the clock, and verify the beat with a timing device in the final operating position. Make any final beat adjustments with the movement in the case in its installed orientation, and confirm that the clock maintains stable beat — without the crutch consistently favoring one side of the leader — through at least fifteen minutes of operation before closing the case and returning it to display.

Complete Service Sequence for the Ansonia VE Movement

Previous Bushing Work and Its Implications

A movement that shows extensive bushing work — many pivot holes that have been bushed by a previous technician — deserves careful evaluation before assuming the bushing work was done correctly. Bushing work that was done well leaves pivot holes that are centered correctly, sized correctly for the pivots they accommodate, and perpendicular to the plate. Bushing work done poorly leaves holes that are off-center from the original positions, sized too large or too small, or tilted from perpendicular — all of which affect the gear mesh depth and the freedom of rotation at each affected position. Before accepting a bushed movement as mechanically sound, check each bushed pivot hole for correct pivot fit, check the gear mesh between each bushed wheel and its neighboring pinion, and confirm that the wheel spins freely through the full range without position-dependent binding. A previous bushing job that changed the center positions of multiple pivot holes may have inadvertently altered gear mesh depths in ways that add friction to the train even though the holes themselves appear clean and correctly sized.

The Ansonia VE movement's Brocot escapement is particularly sensitive to any bushing work in the escape wheel pivot holes or the pallet arbor holes, because these positions directly determine the depthing relationship between the escape wheel and the pallet pins. A bushing that shifts the escape wheel pivot hole position by even a few hundredths of a millimeter changes the depthing from the original setting and may require the pallet pin position to be readjusted to compensate. Always verify the escapement depthing after any service that involves bushing the escape wheel or pallet arbor pivot holes, and adjust the pallet pin position if necessary to restore the correct tooth engagement geometry.

Cleaning and Lubrication After Long Storage

A movement that has been stored for many years without running — or that has been run without service since its last cleaning — will have old lubricant that has thickened and oxidized at every pivot hole. This old lubricant increases friction and reduces the power available to the escapement, producing exactly the marginal amplitude and one-sided crutch behavior described at the beginning of this guide. In many cases, cleaning and fresh lubrication is the entire solution to an intermittently running clock — the movement is mechanically sound but has been operating at the very limit of its power budget with degraded lubrication, and any slight variation in position or temperature tips it from barely running to stopped.

Clean the movement by removing it from the case, disassembling to the individual wheel and plate level, cleaning all components in appropriate clock cleaning solution, pegging out all pivot holes with pointed peg wood, and reassembling with fresh clock oil applied at each pivot hole. The improvement in supplementary arc after cleaning is often dramatic — a movement that barely ran with dirty oil will swing the pendulum through a significantly wider arc with clean pivots and fresh lubrication, and the crutch will contact both sides of the leader symmetrically rather than riding against one side. This improvement confirms that the power margin improvement was genuine and that the clock should continue to run reliably through the normal service interval before requiring cleaning again.

FAQs

Why does the crutch keep pressing against one side of the pendulum leader?

A crutch consistently pressing against one side of the pendulum leader indicates either that the clock is significantly out of beat — the tick and tock intervals are unequal, producing asymmetric impulse that drives the pendulum further in one direction — or that the pendulum amplitude is marginal enough that the pendulum barely reaches the crutch on the unfavored stroke. Begin by verifying that the crutch is perpendicular to the plate, then set the beat using a timing device, and assess supplementary arc by marking the minimum escapement amplitude and comparing it to the actual running amplitude. A clock significantly out of beat will show the crutch riding against one side; a clock with marginal amplitude will show the crutch intermittently missing the pendulum on the unfavored side.

What is supplementary arc and why does it matter?

Supplementary arc is the amount by which the pendulum swings past the minimum arc required for the escapement to operate — the power reserve above the threshold for reliable function. A large supplementary arc means the clock can absorb significant additional friction without stopping; a small supplementary arc means the clock is operating near its margin and will stop when any small additional friction is introduced. Measure supplementary arc by marking the minimum escapement amplitude positions with the pendulum barely ticking, then comparing to the actual running amplitude. A movement that has just been cleaned should show notably more supplementary arc than the same movement with old degraded oil, confirming that the service improved the power margin.

What are Brocot pallet pins and why do they wear?

Brocot pallet pins are cylindrical hardened steel pins mounted on the pallet arbor that engage the escape wheel teeth in a Brocot open pin-pallet escapement — a design used in many Ansonia, Seth Thomas, and other American mantel clock movements. The pins receive the escape wheel tooth on their curved forward surface, and wear ruts develop where the tooth repeatedly contacts the same position on this surface over years of operation. Deep wear ruts change the effective contact geometry and produce inconsistent impulse, contributing to erratic amplitude and beat. Worn pins can sometimes be swapped — rotated 180 degrees to present fresh, undamaged surface — before replacement is necessary.

How do I know if my pendulum is the wrong length for the movement?

Measure the clock's actual beat rate by counting beats over a known time period and calculating beats per hour. Compare this to the theoretical beat rate for the movement calculated from gear train tooth counts. If they match closely and the clock still runs fast or slow beyond what the bob adjuster can correct, the pendulum effective length is wrong for the movement — either the suspension rod is the wrong length or the bob is not at the correct position. A rate nut that is maxed out at one extreme with the clock still out of rate indicates that the suspension rod is too short or too long and should be replaced with one of the correct length for the movement caliber rather than compensating through extreme bob positioning.

Why does my clock run correctly on the bench but stop when installed in the case?

A clock that runs well on the bench but stops when installed in the case has encountered a mechanical condition introduced by the case installation. The most common cause is that the case mounting plate is not flat, causing the movement to be twisted when all four mounting screws are tightened. This twisting changes the crutch-to-pendulum relationship and may take the clock out of beat or alter pallet pin depthing. Try mounting on only three screws — removing the one at the highest corner of the casting — to eliminate the twisting force and allow the movement to sit in an untwisted, consistent position. Verify the beat after case installation and adjust as needed, because the beat setting in the case may differ from the bench setting due to the change in orientation and any residual twist.

Is it worth replacing worn Brocot pallet pins?

Before ordering replacement pallet pins, try running the movement after cleaning and fresh lubrication to see whether the worn pins produce unacceptable behavior in service. Shallow wear ruts that have not penetrated significantly into the flat portion of the pin may still provide adequate impulse geometry for reliable operation, particularly in a movement that has been cleaned and is running with good supplementary arc. Also try swapping the pins — rotating them 180 degrees to present fresh surface — before ordering replacements. If the worn pins produce inconsistent amplitude or irregular beat that cannot be corrected by depthing adjustment, replacement with correctly sized hardened steel pins is the appropriate next step. Measure the pin diameter carefully before ordering, and verify the new pins' fit in the arbor holes before committing to installation.

How do I set the beat on an Ansonia crutch without a beat-setting lever?

The Ansonia VE movement's crutch is bent at its base where it connects to the pallet arbor to change the beat setting, rather than using a dedicated adjustable beat-setting mechanism. Use smooth-jaw pliers to make very small bends in the direction that will center the beat, verify with a timing device after each bend, and work incrementally to avoid creating fatigue at the bend point from repeated reversals. Make the minimum correction needed to produce a beat error of less than one percent as measured by a timing device. Verify the beat in the final operating orientation with the clock installed in the case — beat settings made on the bench may shift slightly when the case orientation changes.