Application of resistance strain gauges to determine stresses on the tooth flanks of toothed segments of the KOMTRACK advance system of a longwall shearer

Issues related to the general design and purpose of shearer advance systems, taking into account key historical solutions and global experience gained from the operation of longwall systems in underground mines, are presented. Currently used shearer advance systems are based on chainless systems with a toothed drive wheel cooperating with toothed bars mounted in the chain conveyor troughs. This design, in different variants, is used in many countries as the primary system responsible for moving the shearer along the mining face. Despite its many advantages, the Eicotrack advance system also has a disadvantage resulting from the rigid design of the toothed bars. These disadvantages are accentuated by premature wear of the gear teeth and toothed bars, especially on non-linear sections of the longwall conveyor route. As part of the KOMTRACK research project, co-financed by the European Regional Development Fund, an attempt was made to develop an innovative advanced system with the flexibility and adaptability of toothed segments mounted in guides to the current position of the gang wheel. In addition to design work, a number of studies were conducted using various testing techniques. One of the research directions was to determine approximate stress values at the contact surface between the toothed segment and the gang wheel tooth using resistance strain gauges. The testing methodology and the results, along with their analysis, are presented. It has been concluded that the developed testing methodology, based on resistance strain gauges, can be successfully used to identify stresses at the contact surface of the friction pair formed by the gear wheel tooth and the tooth of the toothed segment. Stresses determined from the measured strains for a single gear wheel provide repeatable results after approximately twenty contacts between the gear wheel and the gear segment. A higher number of loads results in the strain gauge system becoming decalibrated, leading to significant discrepancies in the results or a loss of the strain gauges' measurement capabilities.