World Journal of Mechanics, 2018, 8, 200-209 http://www.scirp.org/journal/wjm ISSN Online: 2160-0503 ISSN Print: 2160-049X DOI: 10.4236/wjm.2018.85015 May 22, 2018 200 World Journal of Mechanics Investigation of the Effects of Profile Shift in Helical Gear Mechanisms with Analytical and Numerical Methods Gultekin Karadere 1 , Ilhan Yilmaz 1,2 Abstract Keywords 1. Introduction