Method of improving the pivoting of a wheel set

A method to improve pivoting of a wheel set or of an equipped wheel set for a scientific instrument or timekeeper, said wheel set or said equipped wheel set being manufactured to include a first principal longitudinal axis of inertia close to a wheel set axis or coincident therewith, and including at least one arbor arranged to pivot or oscillate about an axis of oscillation aligned on an wheel set axis formed by an axis of said arbor, the method comprising:

• prior to static balancing of said wheel set or said equipped wheel set, machining a flange, which is comprised in said wheel set or said equipped wheel set, with a portion causing an unbalance by a predetermined value, there being a median plane of said wheel set or said equipped wheel set within a thickness of said flange, said median plane being defined by two other principal axes of inertia, creating an unbalance and/or a resulting unbalance moment in a particular angular direction, and off-center in relation to said median plane;
• performing the static balancing of said wheel set to bring a center of gravity onto said wheel set axis;
• determining a desired value for the resulting unbalance moment of said wheel set about said wheel set axis, corresponding to a predetermined desired divergence between the first principal longitudinal axis of inertia of said wheel set, and said wheel set axis;
• setting said wheel set in rotation at a predetermined speed about said wheel set axis, the unbalance and/or the resulting unbalance moment being measured with regard to said wheel set axis;
• and
• performing dynamic balancing by adjusting a value of the unbalance and/or the resulting unbalance moment of said wheel set about said wheel set axis within a given determined tolerance with regard to said desired value,
• wherein at least a part of said adjusting is accomplished by deformation of said wheel set or said equipped wheel set.