(2) While being driven, the load distribution could become uneven across the gear face due to various parts' deflection causing the fatigue limit to become exceeded. (1) When an overload condition exists and the gear surface load exceeds the fatigue limit of the material. Progressive PittingĮven after gear surfaces are worn in and load is equalized, with time more pitting starts to occur and pits get enlarged. As gears are driven and surfaces become worn in, local convex portions disappear and the load is equalized and pitting stops. The initial cause comes from small convex portions of the gear surfaces contacting each other and the local load exceeding the fatigue limit. When the gear surface is repeatedly subjected to load and the force near the contact point exceeds the material's fatigue limit, fine cracks occur and eventually develop into separation of small pieces, thereby creating pits (craters). Transverse module m t = Troubleshooting Gears : Explanation of Terminology Pitting Normal module ( m n ) = 4 Helix angle ( β ) = 15° Tooth depth (h) is the distance between tooth tip and the tooth root. Please see Figure 2.4 below for explanations for Tooth depth (h) / Addendum (h a) / Dedendum (h f).
Basic gear design iso#
Introduced here are Tooth Profiles (Full depth) specified by ISO and JIS (Japan Industrial Standards) standards.
Tooth depth is determined from the size of the module (m). Dimensions of gears are calculated based on these elements. Module (m), Pressure Angle (α), and the Number of Teeth, introduced here, are the three basic elements in the composition of a gear. They are counted as shown in the Figure 2.3. Number of teeth denotes the number of gear teeth. (Important Gear Terminology and Gear Nomenclature in Fig 2.2) Recently, the pressure angle (α) is usually set to 20°, however, 14.5° gears were prevalent.įig.2.2 Normalized Tooth Profile of Reference Pressure angle is the leaning angle of a gear tooth, an element determining the tooth profile. DP 8 is transformed to module as follows m = 25.4 / 8 = 3.175 Pressure Angle ( α )
0 kommentar(er)
