User-Centred Engineering Design of a Portable Lifting Device for Small Racing Vehicles: Multicriteria Concept Selection and Predictive Modelling

Small racing vehicles such as karts, Baja SAE and Formula SAE prototypes require frequent underbody inspections and adjustments under severe time constraints during competitions. However, most commercially available lifting systems are heavy, bulky, expensive, or dependent on fixed infrastructure, making them poorly suited for student racing teams and amateur karting. This paper presents the systematic engineering design of a portable lifting device specifically tailored to this context, developed within a structured product development framework. The work starts from a detailed analysis of ergonomic and operational needs, leading to a set of functional requirements and technical specifications for a compact, manually actuated system capable of safely lifting vehicles up to 250 kg with limited operator effort. Forty-one conceptual alternatives were generated and progressively screened using feasibility and economic filters. The five most promising concepts were then evaluated using the Analytic Hierarchy Process (AHP), considering four criteria: cost, versatility and portability, reliability of actuation and operation, and ease of use. Pairwise comparison matrices and normalized priority vectors were used to rank the alternatives, resulting in a near tie between two solutions and the final selection of a double four-bar (scissor-type) lifting mechanism actuated by a short-stroke hydraulic cylinder. Subsequently, topological and kinematic models of the mechanism were developed, including planar mobility analysis and a vector-loop formulation that relates platform height to actuator stroke. Closed-form expressions for position, velocity and acceleration were implemented in MATLAB to obtain predictive curves and support design decisions. A preliminary dynamic model was also derived to estimate the required actuation force and to conduct sensitivity studies regarding structural thickness, stiffness and safety factors. The resulting parametric CAD model provides a consistent basis for future structural optimization, prototype fabrication and business planning, while illustrating a replicable workflow for the design of portable lifting devices for small racing vehicles.