[20.]Example Demonstrating that Temperature Variation is not Always Due to the Balance and Spring.
| No. .................... Make................... | |||||||
|---|---|---|---|---|---|---|---|
| HEAT | -10 | -10 | + 4 | + 4 | + 1 | + 1 | |
| NORMAL | - 6 | + 4 | + 5 | + 1 | + 4 | + 3 | |
| COLD | +12 | +18 | + 1 | - 4 | + 7 | + 3 | |
| 28 | 8 | 2 | |||||
The following example is submitted to show that temperature variation is not always due to the balance and spring, and that the general condition of the watch may be responsible. The second column of Fig. 7, indicates an error of twenty-eight seconds slow in heat with all screws assembled in the holes nearest the free ends of the rims.
Examination proved that the motion of the balance in cold was reduced to about one-fourth of a turn. In heat the arc of motion was at least one full turn. This difference in motion was sufficient to prove that there was some binding in the train.
A very close fitting of the escape pivots was found and this undoubtedly caused binding of the pivots in heat due to slight expansion. Expansion of the stone would also tend to close the hole, and while the degree of temperature would hardly have any bearing on this point it is sufficient to show in what direction the tendency would be. The fourth wheel end shake was very close and probably caused binding of the wheel in cold, due to greater contraction of the bridge than of the fourth pinion. Furthermore the mainspring was only 0.02 of a millimeter narrower than the space in the barrel box. This no doubt also caused binding through greater contraction of the barrel than occurred in the mainspring.
The above defects were remedied and the rate was found to be eight seconds plus in heat as per third and fourth columns Fig. 7.
This made it necessary to shift several of the screws away from the cut, in almost the same position in which they were before the alteration which caused the close assembling of the screws was made. The final rate was two seconds slow in heat as shown in fifth and sixth columns.
The variation of thirty-six seconds between the second and fourth columns was entirely erroneous, and was due to condition of the watch irrespective of the balance and hairspring. Should the variation with the screws assembled have been by chance within the limits of allowance the watch would undoubtedly have been a very unreliable timepiece. The errors in the watch would no doubt have been corrected during the position adjustment later, but the large error in temperature which would have been introduced by wrongly moving the screws, would have prevented reliable timing until possibly at some future period a test in temperature would have been made and the screws replaced in the proper positions.