Clock Facts  
Sigmund Rieflers´ Precision Regulators
Sigmund Riefler (1847-1912), photograph taken around 1900
The oldest existing clock movement by Sigmund Riefler with free spring-impulse escapement, made in 1890 (Inv. 2011-027)
Model of an escapement showing a free spring-impulse escapement, made by the Royal Württemberg School for Precision Mechanics in Schwenningen, early 20th c. (Inv. 2011-026)
Riefler pendulum clock No. 427 with seconds, made in 1920 (Inv. 2004-024)
Sigmund Rieflers´ Precision Regulators

The son of a clock-maker, Sigmund Riefler was born in the Allgäu region in 1847. After completing his training in mechanics, he began his studies at the Munich Institute of Technology.
In 1869 he came up with the idea for a new kind of escapement for precision clocks. His idea was to "transfer the force from the gear train to the balance wheel by means of the hairspring". Riefler completed a first model, but neither this one nor "any of all the other constructions that I had made over the years" were satisfactory.

Not until early 1889 did he succeed in finding a design “which is theoretically the ultimate in perfection, yet at the same time it stands out by its virtually astonishing simplicity. Moreover, the same design can be used for pendulum clocks with a fully free pendulum.”
Riefler applied for a patent for his invention and began developing a pendulum clock with seconds, which he perfected in the following year. His oldest existing movement dates back to 1890. It still shows many signs of the work he had done on it in the course of development.

“Free Spring-Impulse Escapement”

as Riefler called his invention, was just the beginning of an entire series of improvements for which Riefler had obtained patents:

1891: Mercury-compensated pendulum (DRP 60059)
1897: Nickel-steel compensated pendulum (DRP 100870)
1903: Electrical winding mechanism (DRP 151710)
1913: Gravity escapement (DRP 272119)

By the 20th century, the Riefler company was the leader in the manufacture of precision timekeepers. Scientific and state institutions throughout the world ordered their timekeepers from the Allgäu region.
Under ideal conditions, these clocks attained a rate variation of less than 1/100 second per day. Riefler won many prizes because of this and was even awarded an honorary doctorate by the University of Munich in 1897.

The steps that went into manufacturing the Riefler pendulum clocks were highly complex. For example, the Invar nickel-steel would be artificially aged in a process that lasted several weeks, thus rendering it an unstressed metal. After being mechanically treated, all pendulum parts would also be polished.

Such attention to detail had its price. A Riefler clock cost several times more than the average annual wage. Accordingly, only very few such clocks were made, and most of them were made for scientific and military establishments throughout the world.

The Riefler company continued to manufacture precision regulators even after Sigmund Riefler’s death in 1912. In all, somewhat more than 600 pendulum clocks and over 4000 pendulums were made between 1891 and 1965.