Part 3 (1/2)
In case of over compensation a spring of the same make, one coil smaller, will permit of s.h.i.+fting one or two pairs of screws toward the free ends of rims.
In a series of tests it was demonstrated that by duplicating or changing springs of the same make and size, on balances that had previously been compensated, there was very slight difference in the temperature variation of the watch. Also by changing pinning points or breaking out one-fourth to one-half of the coil around collet and adding weight to the balances to correct the mean time the difference in the variation was almost negligible.
On the other hand it was found that by replacing the springs with others of larger or smaller size, variations of from three to ten seconds were noted in all instances.
In selecting and fitting a spring that will be one coil larger or smaller, it should be noted that the inner coil of the original spring and that of the new spring are approximately the same distance from the collet. For if there was considerable s.p.a.ce between the collet and inner coil of the original spring, and the new spring was colleted quite close, there might be the addition of an extra coil in the inside only. This was found to produce only a very slight correction, compared to that obtained by the addition of a complete outer coil.
These tests indicate that the proportion of strength of the spring in the temperatures varies with any appreciable change in length while slight changes make practically no difference.
20. _Example Demonstrating that Temperature Variation is not Always Due to the Balance and Spring._
Fig. 7
+--------------------------------------------------+
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 a.s.sembled in the holes nearest the free ends of the rims.