Meccanica (2009) 44: 613–621 DOI 10.1007/s11012-009-9220-4 Width modiﬁcation for gears with low contact ratio Hüseyin ˙ Imrek Received: 17 October 2007 / Accepted: 30 April 2009 / Published online: 13 May 2009 © Springer Science+Business Media B.V. 2009 Abstract In this study, teeth width modiﬁcation on spur gears with low contact ratios is introduced. The modiﬁcation essentially relies on maintaining constant Hertz surface pressure along single and double teeth proﬁles. With this aim, adjustments were made in tooth width along the single mesh area. It is intended that, with this modiﬁcation, negative effects caused by high Hertz pressures along the single mesh area will either be minimized or completely removed. Keywords Gear · Tooth modiﬁcations · Width modiﬁcation · Hertz surface pressure 1 Introduction In order to make involute gears operate more quietly, to increase their load carrying capacity and to im- prove upon other similar properties, innovations have emerged which modify the proﬁles and widths of these gears. Gear meshing is often associated with impacts, strains, and other irregularities. In order to prevent these disorders, modiﬁcations are made on the gear teeth. Teeth width modiﬁcation also plays an impor- tant role in providing better contact conditions against H. ˙ Imrek ( ) Faculty of Mechanical Engineering, Selcuk University, Konya, 42250, Turkey e-mail: imrekh@gmail.com Hertz surface pressure, as well as creates a suitable lu- brication environment. So far, many studies have been conducted on gear modiﬁcation. Some of these studies [1–3] involved the effects of addendum modiﬁcation on temperature rise, scoring limit load, and gear life in gear systems. Addi- tionally, studies on the effects of tip relief, facewidth crowning, and lead correction modiﬁcations to gears have also been conducted. Here, the investigation aims to show how these modiﬁcations reduce gear surface failures caused by shaft misalignment and assembly deformation [4, 5]. Other studies [6–9] have investigated the effects of convex proﬁle modiﬁcation on vibration reduction caused by static transmission and time-varying mesh stiffness errors in gears. Li [10] investigated the effects of tooth modiﬁcation (lead crowning) on transmission errors, whereas Seol et al. [11] studied the effects of the amount of crowning on the service life of gear sys- tems The list of gear modiﬁcations does not end with these studies, as some researchers have conducted studies aimed at decreasing deformation and balanc- ing heat distribution in plastic gears by drilling holes on gear teeth to study the service life of gears [12, 13]. Senthilvelan et al. [14] focused on the effects of tooth ﬁllet variations on gear failure. This paper deals with gear teeth width modiﬁca- tion. The modiﬁcation is introduced particularly to prevent negative effects of high Hertz surface pressure