reusing soundbox balance springs

[welshfield]

In a recent thread about rebuilding a Victor No 2 soundbox, one contributor commented, "I've found that most (balance) springs, whether broken or not need replacing since they lose their temper, which will cause issues trying to balance them."

However, elsewhere in this thread he says he uses only new-old-stock balance springs. Won't these also have lost their temper?

John

[HisMastersVoice]

No, they only lose their temper when they are continually moved back and forth during use. If the springs have not been used, they should be fine.

[welshfield]

Except that motion is quite minor --nowhere near fatigue limit or anything else. How would such minor deflections effect temper? The "metallurgy" isn't there.

I would agree that severe surface rust on used springs may effect temper; but even for that, light sanding of light rust ought to make those original springs as good as new.

[JerryVan]

I believe that the thinking is that the balance springs will loose their temper by being under constant tension for approx. 100 years, much like a mainspring sitting wound tightly for many years and then loosing its temper. I use the term, "loosing temper" loosely. I really believe that, in both cases, the springs have simply taken a "set", or in other words, have been plastically deformed by the application of a constant force over a long term.

[welshfield]

sI agree with JerryVan that a spring will deform plastically after holding a position for a very long period of time. Nevertheless, unless there is sufficient heat generated by flexing the spring, which would not be the case for a balance spring of the soundbox, then the temper will be just as it came from the factory. Would not simply flipping over the original balance springs be satisfactory in soundbox rebuilding?

[JerryVan]

sI agree with JerryVan that a spring will deform plastically after holding a position for a very long period of time. Nevertheless, unless there is sufficient heat generated by flexing the spring, which would not be the case for a balance spring of the soundbox, then the temper will be just as it came from the factory. Would not simply flipping over the original balance springs be satisfactory in soundbox rebuilding?

Flipping over a Victrola #2 balance spring is not an option. Although some other reproducers may have simple, flat springs that would allow this.