Design of a main transmission gearbox for a very light helicopter with integration of a freewheel and a clutch

Details

Supervisors

Herman, Benoît ; Fisette, Paul

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil mécanicien, à finalité spécialisée

Abstract

enThis thesis presents the pre-study and first-iteration design of a new main transmission gearbox for a very light helicopter, integrating a freewheel and an engagement mechanism. The work is carried out in collaboration with Dynali Helicopter Company, a Belgian ultralight helicopter and drone manufacturer, in the context of their new Dynali V4 engine, which requires a complete redesign of the existing transmission chain. There is a significant technology gap between ultralight and commercial helicopter transmissions, driven by differences in needs, certification requirements, development budgets, and engineering expertise. Ultralight machines have historically relied on simple belt and-pulley architectures with modest efficiency. This project aims to bridge part of that gap by bringing a more compact and efficient planetary gearbox architecture to the ultralight class. The design follows a classical mechanical engineering methodology: evaluation of the current transmission, specification definition, state-of-the-art review, morphological analysis, concept evaluation, component dimensioning, and 3D CAD modelling. Fifteen transmission concepts were generated and evaluated against eleven weighted criteria. Two finalists were selected and developed to a complete first layout. All main components have been dimensioned using ISO standards, engineering textbooks and manufacturer catalogues, and both solutions have been modelled in SolidWorks. Solution 1 is the recommended path forward; Solution 2 exceeds the mass specification in its current form.