One of the rock drills of valveless type, developed at Atlas Copco Rocktec Division works at higher efficiency than the conventionally used rock drills. But the problem with this type of drill is that the piston swings between two large and highly pressurized oil volumes which causes strength problems in the housing of the rock drill. The aim of this work is to achieve the higher efficiency of the rock drill without having any strength problems. Therefore, some study and research is proposed to replace the large oil volume by one or two piston accumulator. The thesis work involves modelling, simulation, design and fatigue strength calculations of a piston accumulator and its implementation to the rock drill. Optimization of the piston accumulator has also been conducted while working with the rock drill so that highest possible efficiency could be achieved. The performance of the rock drill with piston accumulator has been analyzed and results are studied. In the end, a short fatigue life calculations are performed. This book is really helpful for students and professionals in understanding the working principal of Hydraulic Rock Drill through advanced simulation techniques.