Rotary wheel set system of a horological movement

A rotary wheel set system of a horological movement, the system comprising:

• a rotary wheel set;
• and
• a first and a second bearing, for a first and a second pivot of an arbor of the rotary wheel set,
• wherein the wheel set including a mass centre G in a position of its arbor,
• wherein the first bearing includes an endstone comprising a main body equipped with a pyramidal cavity configured to receive the first pivot of the arbor of the rotary wheel set,
• wherein the cavity includes at least three faces,
• wherein the first pivot is configured to cooperate with the cavity of the endstone in order to be able to rotate in the cavity, at least one contact zone between the first pivot and a face being generated, the normal at the contact zone or zones forming a contact angle αh relating to a plane perpendicular to the arbor of the pivot, and
• wherein the contact angle αh is less than 45° , and
• wherein the second bearing cooperates with the second pivot to enable the rotary wheel set to rotate about its arbor, the second bearing comprising a second pyramidal cavity including at least three faces, the second pivot being capable of cooperating with the second cavity of a second endstone in order to be able to rotate in the second cavity, at least one second contact zone between the second pivot and a face of the second cavity being generated, the normal of the second contact zone forming a second contact angle αb in relation to the plane perpendicular to the arbor of the second pivot, wherein the contact angles αh, αb of the two pivots and of the two bearings are defined by the following equation,
• cot
• ⁢
• α
• h
• +
• cot
• ⁢
• α
• b
• =
• 4
• ⁢
• cos
• ⁢
• π
• N
• ≥
• 2
• ,
• where N is the number of faces of each pyramid.