RTG (Rubber Tyred Gantry) cranes are essential in the port and container handling industry. These mobile cranes, mounted on tires, allow for efficient and flexible handling of containers in storage yards, maximizing space and optimizing loads and unloads. A fundamental aspect in the design and operation of these cranes is the determination of their centroid. The centroid is the point where the entire mass of an object is concentrated. In the context of an RTG crane, the centroid is crucial to ensuring stability and safety during its operation. The correct location of the centroid ensures that the crane can move and lift loads without the risk of tipping or imbalance. Once the cranes have reached the end of their useful life, they are dismantled for scrapping. The dimensions, weight, and morphology complicate this process. One of the most innovative methods is the so-called collapse pseudomechanism, consisting of lowering RTGs by longitudinal folding. It involves locating the points where, with controlled cutting operations, RTGs are transformed into pseudomechanisms and, by defining the point of application of the force and its value, the cranes can be lowered safely. To allow folding, and prior to cutting operations, the four corners of the trolley and the upper crossbars must be fixed by welding. For the point of application of the force, it is essential that the load is applied in a point where it is evenly distributed between the four supports. In this regard, for example, for a 900 T and 30 m high RTG, it is proposed that the pulling force be distributed at two points 22.5 kN each at the ends of the posts, so that the effort is transmitted to the rear posts through the upper crossbars. Additionally, it is important that the pulling angle is as horizontal as possible to avoid transmitting vertical loads to the crane, so it is proposed to pull at a distance of 55 m from the base. The weight of the trolley and its position is essential to determine the position of the RTG's centroid, which will determine the pulling force and angle. The objective of this study is to determine, through graphical methods, the optimal position where the trolley should be fixed to minimize the pulling distance while still allowing controlled lowering.