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We solve different types of problems on mechanisms and assemblies (aerospace and non-aerospace). We also bring our skills and expertise in the optimal engineering of new solutions.


Under certain conditions, the cage of a ball bearing (also called retainer or separator) may exhibit an erratic movement or cage whirl. This is particularly the case for poorly lubricated or heavily stressed bearings. In the event of such dynamic instability (or bearing squeal), the energy exchanges involved can then lead to cage rupture. This is a common problem with turbopumps or with the reaction wheels of space probes or satellites, which can result in an unwanted change or termination of the mission. This is also a problem encountered in the spindles of machine tools for example.

Although this phenomenon has been studied for more than 50 years, it had not been fully modelled or solved…

Until recently. We dit it with the Butterfly Cage. Patent is pending (ref. PCT/EP2023/072689).


cage instability

The unconditionally stable butterfly cage

Videos Courtesy of ESA/ESTL (ESR Technology, UK)

This new intrinsically stable cage, opens new perspectives in many applications, notably in the space industry.


But beyond the cage itself, it is the related R&D journey that is certainly uncommon.


Indeed, the Butterfly cage is the result of more than 10 years of intense research, where the approach has been to understand in depth the physics of the bearing, and in particular the kinematics of the balls. It is only at the cost of this long, continuous effort that this innovation have been able to see the light of day. 


See here the Butterfly cage R&D pathway.


We offer a specialized engineering service focused on analyzing the dynamic behavior of ball bearing cages with the unique and original concept of STABILITY MAPS.


More info here.

stability map cage bearing

Other problems we solve:

A lot of industrial applications imply that relative rotation of the rings of a ball bearing is accompanied by a combination of axial and radial loads.


Those miscellaneously loaded bearings induce misalignment of the rings that lead to the Ball Speed Variation phenomenon (ball advance at non-constant speed). This phenomenon can lead to cage failure, noise, vibration and excessive heat


















Current available bearings only provide a partial answer to this problem. Deep groove and angular ball bearings can indeed only tolerate a small amount of misalignment, rollers bearings must also respect a perfect alignement of the rings, and self-aligning bearings, if they can tolerate more significant misalignment, cannot support axial loads due to the outer ring geometry. 

After decades during which the designers of mechanisms had to accept difficult compromises, APO-GEE offers them a solution which opens up new perspectives: the Cobweb Bearing (patent drafting ongoing). The design of this new Cobweb bearing significantly decreases the bad effect of the misalignement. It is capable to support a combination of axial and radial loads, exactly as deep groove and angular bearing but with a considerably extended acceptable misalignment.

Yes, we have engineered the bearing that has the most precise functioning in the world.


Friction at the contact between the balls and the races induces significant heating and energy dissipation.

In some situations, the heat produced cannot be properly evacuated and leads to thermal instability of the ball bearing, resulting in loss of the ball bearing.


At very high rotation speed, the bearing may lose some of its stiffness. Since the bearing is the link between the shaft it supports and the rest of the mechanical assembly, the exact calculation of stiffness is fundamental to ensure the proper functioning of the assembly.


While finite element design methods are commonly used to design rotating machines and describe vibrations, they are ineffective in modelling bearing stiffness.


Poor design of the bearing may lead to premature rupture of the bearing.

Depending on the functionality of the mechanical component in which the bearing fits, a trade-off must be found between mechanical strength and dissipated power.





our solutions


Based on our deep understanding of the kinematics of the bearing and dedicated tools, we have the unique ability to model and accurately predict the cause of all ball bearing instabilities (thermal, dynamic…) . We anticipate, calculate and predict the behavior of bearings of any types, according the operating conditions, regardless speed, load, temperature, or other imposed stresses.


Specifically regarding to the dynamic instability of the cage, we highlight the link between the properties of the bearing and the entry of the cage in unstable phase, to remove it from the design stages.


our value


We provide the means to ensure the performance and the reliability of the mechanisms with optimized bearing designs. We reduce or eliminate the undesirable effects of poor dimensioning or design such as overheating, unsatisfactory lifespan... and prevent any bearing breakage.


We spare you time, costly intensive research, possible disasters and reduce the risk associated with any poor design.


The technologies and methods we have developed for space also allow us to meet technical challenges in other types of industry (medtech, machine-tools, ...).

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