A Waltham Vanguard RR Watch: How The Power Reserve Indicator Works by Robert Porter

This is the story of an interesting watch repair to restore a fine old 16 size, 23 jewel, Waltham Vanguard railroad watch with power reserve indicator, which peaked my interest to understand how the power reserve indicating mechanism works.

I could not find any useful information about the power reserve mechanism in any of my many watch repair books, nor could my watchmaker friends, some of whom had taught watch and clock making, help me. The solution presented here is my own method of figuring out the input to output path resulting in the angular movement of the power reserve indicating hand.

The calculating method presented here has also been used to unlock the secrets of chronograph minute and hour indicating mechanisms as well, an example is included beginning on page 11.

The designers of this top-of-the-line Vanguard railroad grade watch really knew what they were doing, considering that watch design calculations were done by hand with paper and pencil. The transistorized hand-held calculator was not available when this watch was designed. I had the advantage of using a Hewlett-Packard scientific calculator which made calculations much easier.

As watch enthusiast, we are also avid collectors of nuggets of knowledge about the miniature time machines we repair and collect.