Lexicon

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A

Airpressure compensation:
Because its period of oscillation increases when the air pressure rises, the pendulum is additionally equipped with a barometric-error compensator. The compensation is achieved by aneroid capsules and a weight, which moves upwards or downwards according to the respective changes of air pressure, thus preventing a change of the oscillation period.

Amplitude:
The angle through which a pendulum moves from is central position to one extreme. On the pendulum scale you can read the amplitude in minutes of arc.

Aneroid barometer compensation:
Device to compensate for the influence of the changing air pressure on the accuracy of a clock.

Anodise:
Electro-chemical treatment of aluminium. Surface is treated in acid-bath. The result is a very durable oxidation layer.

Arbor:
Shaft in a movement.

B

Barrel:
Cylinder on the barrel arbor. When winding the weight the cable is wound around the circumference of the barrel. The barrel has grooves like a thread to prevent the cable from scratching.

Barrel wheel:
First wheel in the gear train. Mounted on the barrel arbor together with the barrel, the ratchet and the maintaining power device.

Ball bearing
A bearing in which balls roll in a groove between the inner and outer ring. The rolling friction is very low. This is why ball bearings have very low friction and almost no wear.

Beat adjuster:
Device to adjust the beat. With a screw your can adjust the relationship between the pallets and the pendulum by tilting the crutch.

Bezel:
Dial ring.

Blueing:
Heat treatment of carbon steel. If polished or ground steel is heated to ca. 300°C an oxide builds up on the surface which appears blue.

Brass:
Alloy of copper and zinc. The gears of the Sattler Clocks are made of brass. As protection against corrosion they are gold plated.

C

Calibre:
Type of movement.

Cannon pinion:
Part of the motion work. Attached to the minute wheel arbor. Drives the intermediate wheel.

Centre wheel:
Part of the gear train. Transmits power from the barrel wheel to the minute wheel.

Click catch:
Unit consists of ratchet wheel, ratchet and ratchet spring. Locks the barrel to the gear train. In the opposite direction it allows the clock to be wound.

CNC:
Computer Numeric Controlled. Manufacturing of parts with computer controlled turning and milling machines.

Compensation pendulum:
A specially designed pendulum that does not change its length when temperature changes.

Compensation tube:
Part of the pendulum. Sits on top of the regulation nuts and compensates for the linear expansion of the pendulum rod.

Concentric:
Two parts or circles have the same centre.

Concentricity error:
Result of production tolerances. Due to precise manufacturing in our workshop we are able to reduce the concentricity error to 0.02 millimetres.

Counter weight:
The minute hand is a unbalanced lever that absorbs power for half an hour, and supplies power for half an hour. To compensate this we installed a counter weight on the cannon pinion opposite to the hand.

Crutch:
Lever that connects the pallet arbor with the pendulum.

Cycloid:
Generating circle. A geometrical line, that appears when rolling a circle on a geometrical contour. Has served well for gears in clocks and is still used today.

D

Dome:
To dish. Method to enhance attraction of hands for example. For the Sattler Clocks hand-domed and blued hands are available as an accessory.

Drop:
Free motion of the escapement wheel, after the escapement wheel tooth slipped off the impulse face of the pallet fork. Drop is necessary to avoid pallets bumping into escapement wheel teeth.

E

Eccentric bush:
Bushing with an off-centre hole. Mounted into the pallet arbor bridge. By turning the bush, the engagement distance of pallets and escapement wheel changes and the drop can be equalized.

Engagement:
Engagement is the gearing of wheel and pinion. The transmission of force is better the more teeth are in the engagement.

Escapement:
Unit consisting of escapement wheel and pallet arbor. The escapement transmits the power to the pendulum that is necessary to maintain its amplitude. It also ensures that the gear train runs down gradually with the escapement wheel turning once a minute.

Escapement wheel:
Part of the escapement. Wheel that engages the pallets.
In the Precision pendulum clock it turns once every 60 seconds and is mounted with a bushing on the escapement wheel arbor to which the second hand is attached.

F

Fine regulation:
Exact adjustment of period of the pendulum by adding small weights on the fine regulation table. Adding weights speeds up the clock. Removing weights slows it down.

Fourth Wheel:
Part of the gear train between the minute wheel and the escapement wheel.

Free Strasser escapement:
The escapement in the clock, consisting of the pallet assembly and escapewheel, is the connecting link between the gear train and the pendulum. The escapement must supply the pendulum with the energy lost due to internal friction in the suspension spring and in moving through the air. Before the free Strasser escapement was invented for pendulum clocks, it was the so-called Graham escapement which served as the connecting link between the pendulum and the gear train. In the case of this escapement the anchor and the pendulum form a rather rigid connection through the pallet fork, the disadvantage being that even the slightest variations in the driving force are transmitted from the gear train to the pendulum. These variations in force result in a change of the amplitude of oscillation of the pendulum and thus influence the time of oscillation to a small extent. By the invention of the »free Strasser escapement« it was now possible to improve the already excellent accuracy of the precision clocks once more. This is primarily achieved by de-coupling the clockwork from the pendulum to a large extent. The pendulum is linked to the pallet arbor just by the two thin strips of spring steel of the suspension spring. In order to supply the pendulum with the energy necessary for maintaining the oscillation, the two pendulum driving springs are twisted by an angle precisely defined angle by the geometry of the escapement. The pendulum is thus supplied with the same power every swing, every second. The escapements in our Secunda Accurata 1958 and 1968 can therefore be described as »constant force« escapements.

Friction:
When designing a movement, avoiding friction is a main goal. Therefore all gear train bearings are equipped with ball bearings. Sometimes friction is necessary, for example, at a friction spring acts as a slipping clutch in the motion work, to make setting hands possible.

Friction bearing:
Bearing where the pivot turns in a drilled hole. Since materials glide on each other, it is necessary to choose different materials and lubricate.

G

Gear train:
Gear train transmits force to the escapement. It is calculated in a way that some arbors make a fixed number of revolutions relating to time measurement. These arbors carry the hands.

Graham escapement:
Dead beat escapement. Invented 1720 by clockmaker George Graham of London. Thanks to the special shape of the pallets the escapement wheel is stationary while the pendulum makes the supplementary arc. The Graham escapement was an enormous step in precision clockmaking and has served well for centuries.

H

Height of fall:
Distance, the weight can run down.

High grade steel:
compound with other metals like nickel or chrome, gives steel special properties like anti corrosion.

Hour wheel:
Part of the motion work. Turns once in 12 hours and is driven by the intermediate wheel pinion. The pipe of the hour wheel carries the hour hand.

I

Intermediate wheel:
Part of the motion work. Sits on the intermediate wheel stud and is driven by the cannon pinion.

Invar:
Special Iron-Nickel alloy with 36.8% nickel. Tempered Invar has a thermal expansion ten times less than steel. The alloy was invented by Charles Edouard Guillaume at the end of the 19th century. Sigmund Riefler was the first to use it 1896 as material for pendulum rods in precision clocks.

Impulse:
Process where the driving force is transmitted to the pendulum.

Impulse face:
Inclined plane on the pallets. The tip of the escapement wheel tooth slides along the impulse face and transmits a driving impulse to the pendulum.

Isochronism:
The constancy of the period of the pendulum with changes in amplitude. Only achievable with small changes at low amplitude.

J

K

Kugellager:

Wälzlager, bei dem Kugeln in einer Rille zwischen dem Innen- und dem Außenring abrollen. Da die dabei auftretende Rollreibung sehr gering ist, zeichnen sich Kugellager durch geringste Reibungsverluste und nahezu keinen Verschleiß aus. Bei den geringen Belastungen der in Ihrer Mechanica M1 verwendeten Edelstahl-Kugellager benötigen diese kein Öl.

L

Locking face:
Curved plane on the pallet which arrests the movement of the escapement wheel.

Lock nut:
Knurled nut mounted under the regulation nut and prevents the regulation nut from turning.

M

Maintaining power mechanism:
Movement unit, consists of maintaining wheel, maintaining power spring, maintaining click. Transmits power while winding the clock.

Minute wheel:
Part of the gear train. Riveted to the centre wheel pinion but free to rotate on the minute arbor. Linked to the train by a friction spring. Drives the fourth wheel pinion.

Motion work:
Unit with two engagements. Transmits the motion of the minute hand with the ratio 1/12 on the shaft of the hour hand. Motion work has cannon pinion intermediate wheel, intermediate wheel pinion and hour wheel.

N

 

O

Oil sink:
Hemispherical hole at the outer opening of a bearing. The oil sink hold a small amount of oil as reserve.

P

Pallet:
Part of the pallet arm on the pallet arbor, made of hardened steel or jewel. The pallets are ring segments inserted in the pallet arm. The centre of the ring segments is identical with the rotation centre of the pallet arbor. The polished inclined planes are called impulse faces.

Pallet arbor bridge:
Bearing of the pallet arbor on the back plate.

Pendulum:
Still today’s best mechanical oscillation device. The period is determined by the length of the pendulum and the force of gravity.

Pendulum bob:
Heavy cylindrical weight at the lower end of the pendulum rod

Pillar:
Also movement pillar. Keeps distance between the plates.

Pinion:
Gear with less than 20 teeth. Manufactured in most cases of hardened steel. In the Sattler Clocks are mostly 5 hardened pinions. Intermediate wheel pinion, centre wheel pinion, fourth wheel pinion, escapement wheel pinion, minute wheel pinion.

Pitch:
The distance between two tips of teeth, i.e. the circumference of the pitch circle divided by the number of teeth.

Pivot:
Thin end of a shaft. Part of the shaft which turns in the bearing holes of the plates. The pivots are made of hardened steel.

Plates:
Hold the bearings and are the base for all other movement parts.

Precision pendulum clock:
Sophisticated timekeeper with extremely high accuracy. Clocks with compensated pendulums were used until the late 60´s as reference time for science and official standard time.

Q

R

Rate:
Daily rate is the time difference between the clock being tested and the standard time (radio controlled clock).

Reading:
The time that the clock displays.

Regulation:
Refer to fine or rough regulation.

Regulator dial:
Classic precision clocks have this special way of displaying time with separate dials for hours minutes and seconds. This avoids the need for motion work but requires the gear train to be modified so that one arbor (for the hour hand) turns twice a day. The hour hand never obscures the seconds dial.

Regulation nut:
Knurled nut at the lower end of the pendulum. With the regulation nut the pendulum bob can be raised or lowered. Shifting the bob upwards makes the clock faster.

Regulation pin:
Stainless steel pin which has to be inserted into the lateral hole at the tip of the pendulum. With this pin you can hold the pendulum when turning the regulation nut and avoid damage of the suspension spring.

Regulation weights:
Small metal pieces that make the clock run faster when put on the regulation table. With the regulation weights you can adjust your clock to an accuracy of a few seconds a month.

Rough regulation:
Adjusting the accuracy of the Clocks with the regulation nuts at the tip of the pendulum. You can adjust Sattler Clocks up to ca. 1 sec. a day.

S

Spring:
The beat adjuster has a coil spring.

Supplementary arc:
Oscillation phase of the pendulum. Outbound supplementary arc: pendulum travels from the end of the drop to the turning point. Inbound supplementary arc: pendulum travels from turning point to locking.

Suspension spring:
Spring steel strip between brass jaws. The suspension spring holds the pendulum.

 

T

Temper: Carefully controlled heat treatment of the Invar rods to relieve stresses in the material. Only tempered Invar rods have predictable thermal expansion.

Torque: Turning force.

Transmission ratio: Determined by the number of teeth in a pair of engaging gears. Expressed as the number of turns the driven gear makes when the driving gear turns once.

Tungsten: Very heavy metal, density 19,3 g/cm3.

Temperature compensation:
The accuracy of a pendulum clock does not exclusively depend upon the mechanical properties of the mechanism, but also on external physical influences. The oscillation period of the pendulum is primarily determined by the pendulum length. Variations in temperature however result in a corresponding change of the pendulum length due to the linear expansion of the materials used. The pendulum rod of the Secunda Accurata 1958 consists of an iron nickel alloy, called super invar. This is characterised by an especially small linear expansion when temperature changes. In order to compensate for this residual expansion as well, the pendulum is equipped with a temperature compensation device. A small residual temperature error may however occur. It is therefore advisable to expose the clock only to small variations of temperature. If this is considered when the location of the clock is chosen, deviations of less than 1 sec. / month can be attained.

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U

 

V

 

W

Winding period:
Time a fully wound clock will run without rewinding. The winding period depends from the height of fall, the measurements of the barrel and the gear ratio.

X

Y

Z