CYCLOS – The 24-hour DualPhase® watch

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 meridiem’ or ‘post meridiem’ in order to make the distinction clear. The well known 24-hour clock, on which all the hours are 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.

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 first prototype of the CYCLOS watch was presented at the BASEL 2001 World Watch and Jewellery Show.

The clearest way of seeing how the system works is with the aid of the following illustrations:-

The CYCLOS dual-phase 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 gearwheels A (blue), B (red), D (green) and E (magenta) at 12h midnight and at 12h noon: The black 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 Rf = ra  rb  2rf cos( – 90)/2, is formed in this way. In this formula Rf 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.

Two designs depict, in different manner, the dual-track scale of these unique watches:-

– 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 meridiem”, and an inwardly winding spiral in blue which indicates the hours “post meridiem”. 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, silver or luminous which indicates the night time hours. Here, the two phases are separated from each other at 6h/18h.


The new 24-hour dual-phase watch combines the advantages of a classical analogue display with a clear differentiation between a.m./p.m. or the day and night cycles. This is achieved by dividing the double meaning of the usual 12-hour scale into two loops. A radially adjustable hour hand follows this eccentric curve and indicates thus all 24 hours clearly although rotating with normal angular velocity.

The first watches of production run have been delivered since summer 2003. They are available in two variations on principle: the sporty “a.m./p.m.” models in stainless steel cases or the elegant “day&night” models in gold cases, with dark or light dial each.

As a further elegant enhancement to the brand the exquisite “day&night PARITY” was introduced at the BaselWorld Fair 2004. The combination of a light and dark dial makes the unique CYCLOS time display even more seductively visible: “daytime outside – night time inside”.

Technical details

Mechanical with automatic winding, ETA caliber 2892-A2, luxury finish (perlage, blued screws), certified COSC chronometer, modified with a patented DualPhase® module for controlling the length of the hour hand, logo engraved into the rotor (Geneva stripes)

Hours, by means of continual radial displacement of the hour hand on a dual-phase scale (Pascal’s spiral), minutes, centre seconds hand, date at 6 o’clock

Either black or silvered finish in all versions, colour differentiation of the dual-phase hour scale (a.m./p.m. or day/night), with a raised outer ring for minute and second graduations, Superluminova luminescent numerals and hands (except model “Transparent”)

Diameter 39,0 mm, height 12,8 mm, stainless steel (sporty models), 18K yellow or red gold (elegant models), 18K white gold (model “Parity”), water resistant to 50m, sapphire crystal front and back. All models are available with a diamond setting to client order.

Calfskin or Alligator, black, brown or white/anthracite

CYCLOS has been developed by a motivated team of young, qualified experts. Chiefly responsible are:-

Idea, Design and Project Leadership
John C. Ermel, Dipl.-Ing. Architect and Designer, Managing Director of Cyclos Watch, Dornach, Switzerland

Construction of the Mechanism and Prototypes
Robert Greubel, Watchmaker/Techn. Project Manager and Stephen Forsey, Watchmaker/Chief Constructor at CompliTime, Haute Horlogerie, La Neuveville and La Chaux-de-Fonds

Product Design, Virtual Prototyping
Stephan Messmer, Product Designer and Alex Seiler, Marketing Manager at Messmer & Seiler, Industrial Design, Basel

Sales and Distribution, CYCLOS North America
John-Michael Ermel, Managing Director of CYCLOS International LLC, Chicago, USA

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