Baby micrometer

The Micrometer

The engineering of time

Issue 19 May 2022

News

Rotary broach

After a three-year break, this issue of The Micrometer offers two papers exploring a deeper understanding of the engineering design of mechanical clocks over the centuries. Firmly rooted in engineering, it is intended that the articles will be a balance between scientific research and practical implementation, an example of the latter (photo, left) for a perhaps future issue being the author's design, construction and use of a rotary broach for cutting square holes.

The format of the web-site is now far simpler than that used for previous issues of The Micrometer, the .html and .css source files now being directly coded by the author whose expertise in using essentially W3C standards is at best elementary. Coded for viewing on a desktop or laptop (the web-site is not very responsive to small screen sizes), the main technical content is provided in downloadable pdf format. It is a limitation that I hope readers will not find too inconvenient.

Clock lines

An exploration of driving lines for weight-driven and fusee clocks

Clock lines

Clock lines have received little engineering assessment in the horological press, with much opinion being based on received wisdom and what has been found to work. This three-part paper (in pdf format at the links below) explores representative clock lines from an engineering perspective: Part 1: Stranded steel and brass/bronze lines, Part 2: Natural gut and synthetic lines, and Part 3: Comments on the significance of creep together with a few concluding remarks.

Part 1 investigates the different types of construction of stranded steel and brass/bronze lines. Part 2, which is perhaps the most significant, reports on the author's creep trials on natural gut and nylon-6 synthetic lines conducted over a 6-month period and their extrapolation to a 20-year in-service life. Part 3 discusses the possible implications of creep on non-metallic weight-driven and fusee lines before drawing together a few overall remarks.

Clock lines Part 1 (689KB) Clock lines Part 2 (1.6MB) Clock lines Part 3 (212KB)

Readers are invited to comment on the three papers and make any recommendations leading to a greater validation of the author's concluding remarks.

Clock mainspring sizing

A design approach based on a statistical analysis

Going barrel mainspring

The maximum strain energy available from a mainspring is delivered if one could arrange for the bending strain to change from yield strain to zero between the fully wound and fully unwound condition at all points along its length. With careful choice of the arbor diameter, the spring thickness and the material's yield strength, this can be approximated for the innermost coils but cannot be achieved in the outer coils. Even if the mainspring yield strength were known with any accuracy, mathematical calculation would be difficult, and still would not give any indication of the energy needed to keep a clock of a given size running for its going period.

The paper (in pdf format at the link below) suggests a possible alternative approach using a statistical analysis of seventy successful spring-driven clocks serviced by the author. It tentatively concludes with two simple formulae (one for a platform escapement and one for a pendulum clock) that link the primary barrel dimensions with the chapter ring diameter, the latter being a measure of the size of the clock.

Mainspring sizing (684KB)

Readers are invited to comment on the approach, the author's aim being to validate a simple design methodology suitable for craftsmen and craftswomen who wish to design a new construction clock.

The Micrometer has been developed for use on a desk-top computer, coding being written in Adobe Dreamweaver and validated in the Safari browser running on an Apple iMac desktop. Comments on articles appearing in The Micrometer are invited. In the first instance, the author asks that readers wishing to make comments introduce themselves via the E-mail address below (this is a composite image file used for the avoidance of spam, so cannot be double-clicked and will need to be typed into the reader's E-mail application).

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