Conceptual Design of an UnloadingSystem for Continuous Tracks : How to increase the load capacity of tracks with the use ofhydraulic cylinders

Abstract: This report presents the result of a Master thesis course done at the Machine Design department at KTH. The thesis was written at the company Svea Teknik in collaboration with the tunnel boring machine manufacturer Atlas Copco. The high longitudinal force needed when the Remote Vein Miner is boring is achieved by the friction when clamping the machine between the tunnels ceiling and ground using hydraulic cylinders mounted on the top and bottom of the machine. A new generation of machines doesn’t allow for the bottom cylinders to be fitted on the machine. The pair of continuous tracks used to propel the machine must bear these loads but the tracks aren’t strong enough to alone support the weight of the boring machine. This creates the need for an unloading system which unloads the inner wheels of the track so they don’t fail. Concepts were generated using a morphological matrix with the load sharing unit broken down to sub functions with several solutions paired to each. The iterative process led to nine concepts, where two proved more promising than the others when they were subjected to a Pugh’s evaluation matrix. The two concepts were developed further where a feasibility analysis indicated that only one concept was feasible with the dimensions given in a CAD model together with the load provided by Atlas Copco. The remaining concept is based on hydraulic cylinders lifting the inner wheels of the track to unload them while the machine is boring. The machine is then resting on a skid mounted inside the track. A CAD model was made of the new concept and the new components strength was analyzed using FEM-models.