cyclos watch
Idea and History
Agents and Retailers

The idea for CYCLOS arose from the unsatisfying double meaning of the usual 12-hour scale. Every point on the scale designates both the day’s cycle and that of the night, without being able to differentiate between them. In the English speaking world one adds "ante meridian” or "post meridian” in order to make the distinction clear. The well known 24-hour clock, on which the hours are all ordered in one circle, has the disadvantage that one has to change ones perception of the angles of the hand in order to read the time.

In 1989 the architect and designer John C. Ermel, working on an order for a new watch design, had the idea of making the difference between the cycles of day and night obvious. This could be achieved by using a radially adjustable hour hand. He arranged the scale of hours on a so-called "Pascal’s spiral”, a conchoid of a circle, a special cycloid achieved by overlapping the usual clockwise rotation with translation in the radial direction – in this case a sine curve with a cycle of 24 hours.

See Animation

cyclos watch

The mechanism necessary for controlling such an hour hand took more than 10 years to develop and is a real marvel of Swiss watchmaking craftsmanship. In 1999 John C. Ermel applied for a Swiss patent on his idea, in 2000 for a worldwide patent. The clearest way of seeing how the system works is with the aid of the following illustrations:

The CYCLOS DualPhase module
The visible hour hand is mounted on a finger, which is attached to a radially adjustable arm beneath the dial. In the cutaway view the gilded brass gearwheels A, B, C and E are visible underneath the arm (light-gray). The dark-grey pin in the left foreground located in gearwheel E guiding the arm is the guide pin F.
The CYCLOS dual-phase module

The gearwheels A, B, D and E at 12h midnight and at 12h noon
The dark-grey point indicates the guide pin F and the broken curve shows the Pascal spiral.

Simultaneous representation of 5 positions of the gearwheels A, B, D and E, namely at 24h/0h, 3h, 6h, 9h and 12h, which is synonymous with "ante meridian". Gearwheel A in the centre remains fixed, gearwheel B is twice as large and turns around A once every 12 hours and rotates 540° around itself during the same time period. Gearwheels D and E are mounted on bearings on B so that they can rotate and, in conjunction with other hidden gearwheels, correct the parallel axis. The Pascal spiral, which can be described mathematically by the formula   ΔRf = ra + rb ± 2rf cos[(φ - 90)/2] , is formed in this way. In this formula ΔRf represents the variable distance of the guide pin F from the centre, ra = radius of gearwheel A, rb = radius of gearwheel B (whereby rb = 2ra), rf = distance of the guide pin F from the centre of gearwheel E.

The two initially available collections indicate two phases in the course of the 24-hour day in different ways:
  • on the sporty "a.m./p.m." models, the hourly scale is formed by an outwardly winding spiral in red which indicates the hours "ante meridian", and an inwardly winding spiral in blue which indicates the hours "post meridian". The two phases are separated at 12 noon / midnight.
  • on the elegant "day & night" models, one sees an outer loop in gold which indicates the daytime hours, and an inner loop in white or silver which indicates the nighttime hours. Here, the two phases are separated from each other at 6h/18h.

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