Comments on “Determination and Analysis of the Theoretical Production of a Bucket Wheel Excavator” / Uwagi I Komentarze Do Pracy: ”Określanie I Analiza Teoretycznej Wydajności Pracy Koparki Wielonaczyniowej Kołowej”

Abstract

This paper comments on the recently published work dealing with the problem in the determination of the theoretical output of the bucket wheel excavator. It also includes remarks on the inadequacy in the problem approach and highlights the mistakes in the mathematical model. This work emphasizes the demand for a much wider and deeper approach to the problem of determining the output of the bucket wheel excavator.

Archives of Mining Sciences

“…Bucket wheel excavators (BWEs), machines operating in harsh working conditions, under the influence of loads of pronounced dynamic and stochastic nature, have a key role in surface mining systems. Tendencies towards increasing their capacities (Bošnjak, 2015;Che & Chen, 2014) and enabling excavation of soil of higher workability classes (Machniak & Kozioł, 2017) have not been adequately supported by the calculation methods. Inevitable reconstructions, conducted as a consequence of various types of technological (Bošnjak & Zrnić, 2012) and structural (Bošnjak & Zrnić, 2012;Rusiński et al, 2010) failures, as well as failures of vital mechanisms (Dudek et al, 2011;Savković et al, 2011) represent a solid proof of this statement.…”

“…Solving it requires a solution to three subproblems, related to (Bošnjak et al, 2006): (1) dimensions of the chip cross section; (2) specific resistance to excavation; (3) disposition of components of the resistance to excavation. The problems of determining the dimensions of the chip cross section and the disposition of components of the resistance to excavation, for the most general configuration of the working device, are successfully solved by applying the model presented in (Bošnjak, 2015). Having in mind the fact that the specific resistance to excavation represents a fundamental source of stochasticity in the BWE system, its temporary values are simulated with a random number generator (Bošnjak et al, 2006).…”

“…This is the consequence of vibrations of the bearing structure and the superstructure slewing mechanism. The model presented in (Bošnjak, 2015) enables coupling of the excitation and the system response, which leads to a principle change in the character of the BWE mathematical model. Namely, some of the stiffness coefficients become stochastic time dependant variables, i.e.…”