Many cameras have a built-in self-timer, so that the photographer may snap the shutter and then quickly scuttle off to join whatever or whoever is in the picture to be taken. When I bought a used Pentax single-lens reflex 25 years ago, it did not have this feature. However, the camera store had a fine little accessory timer with the brand name “Autoknips.” I purchased it and used it for many years.

I’ve had several cameras since, and I recently got rid of the old Pentax on eBay. However, my newly acquired interest in clocks made me curious about my little Autoknips, so I thought I’d take it apart to see what sort of clockwork caused it to buzz so forcefully as it counted down the exposure time.

Figure 1 shows the exterior of the unit. On the side of the timer is a winding lever with a red dot. This lever is given a twist, which withdraws the plunger that protrudes to the left from the threaded portion of the unit. The small lever on top of the unit is then moved sideways to lock everything in place.

With the unit locked, it is screwed into the cable-release socket of the camera. The photographer makes whatever final camera alignment he deems necessary, moves the small lever to unlock the unit and begin timing, and scurries into his place. He watches the red dot to see the progress of the timing.

How does it work? Figure 2 shows the Autoknips with the back cover removed. It is seen that a small pinion drives a rack to the right, which forces the plunger out. With the unit screwed into the camera, this trips the shutter.

The small pinion is mounted on the opposite end of the spring arbor from the winding lever. Figures 3 and 4 show the works removed from the case.

The self-timer mechanism is similar to the “strike” side of a clock, although smaller than most. The spring arbor, wound from one end and delivering its power through the other end, is speed-controlled through a tiny gear train that terminates in a minuscule fly. It’s the whirring of these gears that makes the buzzing sound.

About the Author

Peter Riegel is a retired mechanical engineer. In the course of running many marathon races, he became interested in their measurement, and he now travels the world measuring the routes of many of the major big-city marathon races. He measured the 1984 Los Angeles course, and was in charge of the measurement of the 1996 Atlanta Olympic marathon measurement. He is a relative newcomer to clocks, having joined NAWCC only two years ago. He may be reached at riegelpete@aol.com.