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Overview |
Pivot Bent or Broken |
|
 Fig. 1 |
Balance Bearing Fig. 1 shows a common balance bearing. The balance should rotate with low friction, and therefore some provisions are made: 1) The balance staff 1 is thick and rugged to allow assembling the whole balance risklessly. 2) For low friction, both ends are rather thin (ca. 0.1mm diameter). These ends are called pivots. 3) The pivots run in hole jewels 2. For low friction their holes are not cylindical but waisted. 4) Further there are cap jewels 3, carrying the balance if the watch is deposited dial up or down. 5) The gaps between jewels and pivots are so narrow that an oil film (blue) is carrying the balance. |
 Fig. 2 |
Oops - dropped down Dings in old pocket watches demonstrate that this can happen within several decades. No problem if the watch were a jam toast, which always falls with the (soft) jam side down. Unfortunately a watch meets the floor in any random position, and mostly the frame is hitten. Until short above the floor no trouble, but then the motion is suddenly stopped. The balance tries to continue falling, but it can't. A strong force P shown in Fig. 2 appears, and damages the weakest parts: One or both pivots. With bad luck the pivit will break off. There are artists who tinker this anyhow like shown here. But actual help is only a new balance staff or drilling in a new pivot. Both is expensive enough to make one or the other watch a total write-off. With more luck the pivot is only bent. Not serious at the first glance: As Fig. 2 shows, the oil film is still intact due to the shape of the jewel hole. But with bent pivots the balance becomes an out-of-balance, featuring different speeds in various upright positions of the watch - e.g. crown up, right, down, or left. If you imagine that already a tiny, just 1/100mm thick washer under one of the balance screws compensates such a position error of some 20s per day, it is easy to understand what happens when the whole heavy balance is just 1/100mm out of center: The rate varies several minutes per day in different positions, and this makes the watch useless as timekeeper, although it is still happily ticking. |
| Figures (cf. Service Prices) | ||
| EUR 10.00 removing and
reinserting movement EUR 40.00 correction position error, under 60s/day EUR 50.00 minimum total (in 2011) |
Often
the pivots are just faintly bent, and it is senseless trying to align
them.
It will do to correct the position error. 60s/day was common for medium
grade watches from factory when timing machines were not yet available;
if higher accuracy is demanded, it will become more expensive. If
pivots need aligning, or if even the balance staff must be replaced it
will become much more expensive. So better check the rate of a purchased old watch carefully. Sellers tend to trivialise or even don't mention such flaws, and most have either not the equipment or not the time to check watches sufficiently.
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Oops - Dropped Down The watch was given as present in 1935, and since then once very badly dropped down - not strange after such a long period. The more sharp Fig. 4 shows at A (better if magnified), where and how the watch touched the ground. The chip on the crystal surface indicates a stone floor, a very hard shock though. Fig 5 shows the according spot A on the movement: The balance bearing B is located near A on the line between A and the gravity center C of the movement - hardly to become worse. When landing, the pivot is pushed with full power onto the cap jewel. |
 Fig. 6 |
The Tiny Damage Fig. 6 of the balance staff shows (better if magnified) that the pivot is distorted like the head of a chisel after being too hardly tortured with a hammer. I.e. the pivot became a bit shorter and in return a bit thicker at the end. |
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Dial Down Fig 7 shows the dial-side balance bearing consisting of staff 1, hole jewel 2, and cap jewel 3, short before touching the ground. Fig. 8 shows the same in the moment of landing. The case is stopped, the staff wants to fall further, but can't. So the mass of the balance pushes the pivot with the force P onto the cap jewel. Often this will be chrashed - but not here. Instead the pivot end was headed. If the watch is left in this position, it will continue to run properly, since the (blue) oil film is still intact - nothing jams nowhere. |
Fig. 9 |
Dial Up Now the weight of the balance pulls the thick "head" of the pivot into the narrow section of the jewel hole (Fig. 9). The oil film (blue) doesn't work any longer, the pivot sits tight like a cork in a bottle neck, and nothing oscillates any longer. This damage appears not as often as a bent or even broken pivot (cf. above), but still more frequently than expected. The watch runs, often even pretty accurate, as long as the dial is positioned down. But as soon as die dial is turned from vertical position a bit upside, the watch instantly stops. If the watch drops down with the metal back first to the floor, mostly nothing happens. The back is elastical and absorbs the shock. To hunter case watches and watches with plastic crystal this damage scarcely happens, because they are elastical on both sides. |
| Figures (cf. Service Prices) | ||
| EUR 10.00 removing and
reinserting movement EUR 20.00 disassembling the balance, pivot repair EUR 40.00 correction position error, under 60s/day EUR 70.00 repair total EUR 90.72 price example watch incl. shipping EUR 160.72 total for example watch (in 2011) |
No really attractive price, as the auction
result demonstrates, but the entry
of the movement into the archive is also a kind of return. With
some luck the pivot is only nailed not bent, and the costs
for position adustment fall away. 60s/day was common for medium
grade watches from factory when timing machines were not yet available;
if higher accuracy is demanded, it will become more expensive. If the
distortion is too serious, the staff must be replaced, and this will
raise the costs further. So better check the rate of a purchased old watch carefully. Sellers tend to trivalise or even don't mention such flaws, and most have neither the equipment nor the time to check watches sufficiently.
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Stone Pit |
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Watch Description It should be mentioned: Perfect sellers do exist This watch was bought via ebay to fill this gap in the movement archieve. As Fig. 10 and 11 show, as well the exterior as the interior looked crispy. The watch also ran in all positions, but only with dial up properly. In all other positions the performance was rather poor. This was a reliable sign that the balance bearing on the dial side was damaged, and this turned out to be true after disassembling the watch to get movement photos. Anyway, the seller provided a perfect repair, and the watch could be reselled later nearly with chronometer accuracy. Here the according archieve entry. |
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Oops - Dropped Down The watch was made in 1935, and since then at least once very badly dropped down - not strange after such a long period. Fig 12 shows (better if magnified) that the balance had punched a bigger hole into the jewel, and it is not surprisingr that this allowed any but reasonable performance; remember that manufacturers have good reasons to apply jewels with round holes. Also the cap jewel was damaged (Fig. 13). As the center was still intact, a replacement wasn't actualle necessary, but nevertheless the seller replaced it also. |
| Figures (cf. Service Prices) | |||
| EUR 10.00 removing and
reinserting movement EUR 5.00 removing and reinserting balance EUR 30.00 replaceing two jewels EUR 40.00 correction position error, under 60s/day EUR 85.00 repair total (in 2009) |
Actually I paid nothing, because
the seller cared for the repair. As by a miracle the balance staff
wasn't affected, there was also no need to correct any position error.
Thus the figures aren't real; they just demonstrate what to expect
after dropping a watch to the floor, or what to expect from many
watches offered without careful investigations.
|
 ...the alternative - free of charge! |
Dr. Roland Ranfft Im Eichfeld 8 41844 Wegberg-Wildenrath Germany |
phone +49 (0)2432 491604 fax +49 (0)2432 491605 email: info@ranfft.de |
Last update: 09-07-11 |
