2012/06/14 - C3H5N3O9 The indications of Experiment ZR012 are inspired by the Wankel engine


Experiment ZR012 by C3H5N3O9 features Wankel engine inspired hour and minute indications in an asymmetrical zirconium case with articulated and compound lugs.

At first glance the time appears to be indicated by centrally rotating triangular rotors; however, the triangles are actually Releaux polygons; they rotate eccentrically rather than centrally and track complex epitrochroid curves rather than circles. The system was inspired by the Wankel engine, which features orbital Releaux polygon rotors rather than the reciprocating pistons that power the majority of our cars and machines today.


In the image above, the time is 5:36

Experiment ZRO12 indicates hours and minutes with two Wankel engine eccentric rotating Releaux polygons (triangular-shaped rotors). Hours are indicated by the lower rotor along the front of the 'dial'. Minutes are indicated by the smaller upper rotor.


The case of Experiment ZR012 is in zirconium, which is derived from the mineral zircon. Visually zirconium is similar to titanium and is highly resistant to corrosion.

The lugs are in titanium. The articulated front lug and compound rear lug wrap ergonomically around the wrist and ensure a high level of comfort.

The case dimensions are 55mm x 44mm (excluding lugs).


Time is by the tips of the Releaux polygon rotors tracing epitrochoid curves.

To create the complex shape of the hour and minute epitrochroid curves with the high precision required, 180 separate points were plotted.

There is tolerance of just o.2omm between the triangular rotors - the special shape is actually called a Releaux polygon - and the hour and minute marked epitchroids surrounding them.


Turning Experiment ZR012 over reveals the power reserve indicator.

The movement has an autonomy of 39 hours and should be wound by the screw down crown when the indicator approaches the red zone.


The Releaux polygon (triangular-shaped) rotors are eccentric, i.e. not mounted directly to the central 'crankshaft' and they demand considerable time, skill and patience to set up correctly in assembly process.

At these minuscule dimensions, the thickness of one tooth on the gears is not fine enough to precisely align the hour and minute wankels - normally you adjust by a complete tooth. To ensure extremely high precision adjustment, the fixed wheels can be rotated slightly (then re-fixed) to allow fine adjustment and synchronised precision between the hour and minute indicators.

To understand how the eccentric releaux polygon indicators rotate, please view the animated illustration on the Wankel Engine detail page of this website


Experiment ZR012 indications were inspired by the Wankel engine.

In 1919, a 17-year-old German boy called Felix Wankel dreamt of a new type of engine. Despite no formal training, Wankel believed that he could design an engine in which the four stages of intake, compression, combustion and exhaust-took place in one rotation, rather than four separate reciprocations of a piston as in a normal engine.

It was an ambitious goal, which others had been unsuccessfully attempting since the 16th century. In 1924 Wankel created a small laboratory to develop his rotary engine and eventually tested the first prototype in 1957, over three decades later.

One of the main reasons development took so long is that Wankel’s orbital engine was based on a convex-triangle rotor rotating inside a epitrochoid combustion chamber. An epitrochoid is a very complex shape traced by a point on a small circle rotating around the perimeter of a larger circle and plotting that shape involves seriously complex mathematics.

x = cos(w1*t) + (R/L)*cos[(w1+w2)*t]
y = sin(w1*t) + (R/L)*sin[(w1+w2)*t]

From over 800 shapes considered, Wankel investigated nearly 150 configurations and variations – this was before computers – before settling on a fat figure-eight form. 

In standard internal-combustion engines, pistons reciprocate four times for every cycle of power; in the Wankel engine, power is smoothly generated each rotation with fewer moving parts enabling the motor to be lighter, more compact and more reliable than reciprocating engines.

The epicycloid curve has been of special interest to astronomers over the centuries as the shapes are often found in the coronas of stars. Wankel was the first to use an epicyloid in an internal combustion engine; Experiment ZR012 is the first to use an epicyloid indications in a wristwatch.

Technical Specifications

Experiment ZR012 is an edition of 12 pieces in zirconium
Hours and minutes are indicated by two Wankel engine inspired Releaux polygon rotors tracing epitrochoid curves 

  • Dimensions without lugs: 55mm x 44mm
  • Dimensions with lugs: 71mm x 47mm
  • Case and lugs: Zirconium case with titanium lugs
  • Number of case components: 60
  • Articulated front lug, compound rear lug
  • Sapphire crystal with anti-reflective treatment both side
  • Water resistance: 30m - 100’ - 3atm
  • Strap and buckle: Brown calf leather strap. Titanium and white gold folding buckle. 
  • Movement dimensions: 32.65mm x: 41.35mm: 11.55 mm 
  • Number of components: 328 
  • Number of jewels: 42 
  • Manual winding 
  • Power reserve: 39h 
  • Balance frequency: 28'800 
  • Finishing: satin finishing, sandblasted, circular graining on movement, black PVD treated components, black ruthenium treated components 
  • Number of plots to create epitrochoids for hours and minutes: 180 
  • Tolerance between hour and minute indication rotors and inside of epitrochoids: 0.20mm