This paper is a follow-up to last year research presented at ECER02 Lisbon: "University-industry partnership project assessment in engineers training: a legitimacy approach" which concerned the final assessment of the Centrale Lille two years engineering training project. This project works in a partnership involving the engineering-university, engineering-professors, firms partners, and engineering-students. The theoretical references were researches on partnership between firms (Kaddouri, 1997; Zarifian, 1997) and in other professional fields, like teachers training (Zay, 1997, 1994). The results of this first study showed that the legitimacy of the project final evaluation depends less on the positioning of partners in the jury than on the dynamic of the partnership during the project. The jury acted as a revelator of hidden pressures: notably the gap between explicit and tacit targets of each partner and a tendency to hide conflicts behind an apparent consensus. This new paper focuses on the same engineering training project in partnership with a new perspective: it focuses on these pressures and difficulties during the partnership. This problem is increased in an evolving context: the engineering university has set up an additional partnership with a management university which implies a common work. Thus the partnership becomes multipolar (management university / engineering university / firm). We observe the evolution from a dual partnership to a multipartnership. We analyze how partners converge or diverge and the emerging coalitions. - The first theoretical basis for this analysis is Ferrand (97) and Landry and Mazalon (97) to examine the positions and institutional relational structures of the partners and Caplow (68) to examine the system of strategic alliances, oppositions or negotiations. - A second theoretical frame examines this evolution with the process of interactions between the different levels (institution, teaching staff, students teams) of partners: Can we find "interactors" (Kaddouri 97), or mediators that act as "cultural bridges" (Crane, 98) who help the different levels (university, teachers, students) converging on a common explicit target. These actors can also have a role on the evolution of actors' own representations of themselves, others (Rouchy, 97) and of the partnership (Landry, 97). This study is conducted thanks of semi-structured interviews and an analysis of the students' reports on the partnership progress. The eight experimental projects which experience this multipolar partnership are examined. The first results lead us to thinking that the institutional partnership has a clear influence on the different actors' partnership representations. But the key insight is that the involvement of a new management partner obliges all actors to begin to manage the partnership. This means sharing representations of each others and building the common target and planning. This effort can be greatly influenced by interactors, who have a reason to get involved in the partnership.