Introduction

When ISO 10300:2001 (all parts, withdrawn) became due for (its first) revision, the opportunity was taken to include hypoid gears, since previously the series only allowed for calculating the load capacity of bevel gears without offset axes. The former structure is retained, i.e. three parts of the ISO 10300 series, together with ISO 6336‑5, and it is intended to establish general principles and procedures for rating of bevel gears. Moreover, ISO 10300 (all parts) is designed to facilitate the application of future knowledge and developments, as well as the exchange of information gained from experience.

Several calculation methods, i.e. A, B and C, are specified, which stand for decreasing accuracy and reliability from A to C because of simplifications implemented in formulae and factors. The approximate methods in ISO 10300 (all parts) are used for preliminary estimates of gear capacity where the final details of the gear design are not yet known. More detailed methods are intended for the recalculation of the load capacity limits when all important gear data are given.

ISO 10300 (all parts) does not provide an upgraded calculation procedure as a method A, although it would be available, such as finite element or boundary element methods combined with sophisticated tooth contact analyses. The majority of Working Group 13 decided that neither is it sufficient for an International Standard to simply refer to such a complex computer program, nor does it make sense to explain it step by step in an International Standard.

On the other hand, by means of such a computer program, a new calculation procedure for bevel and hypoid gears on the level of method B was developed and checked. It is part of the ISO 10300 series as submethod B1. Besides, if the hypoid offset, a, is zero, method B1 becomes identical to the set of proven formulae of the former version of ISO 10300 (all parts):2001.

In view of the decision for ISO 10300 (all parts) to cover hypoid gears also, an annex, called: “Calculation of virtual cylindrical gears — Method B2”, is included in this part of ISO 10300. Additionally, ISO 10300‑2 is supplemented by a separate clause: “Gear flank rating formulae — Method B2”; regarding ISO 10300‑3, it was agreed that the former method B2, which uses the Lewis parabola to determine the critical section in the root and not the 30° tangent at the tooth fillet as method B1 does, now be extended by the AGMA methods for rating the strength of bevel gears and hypoid gears. It was necessary to present a new, clearer structure of the three parts, which is illustrated in Figure 1 (of this part of ISO 10300). Note, ISO 10300 (all parts) gives no preferences in terms of when to use method B1 and when method B2.

The procedures covered by ISO 10300 (all parts) are based on both testing and theoretical studies, but it is possible that the results obtained from its rating calculations might not be in good agreement with certain, previously accepted, gear calculation methods.

ISO 10300 (all parts) provides calculation procedures by which different gear designs can be compared. It is neither meant to ensure the performance of assembled gear drive systems nor intended for use by the average engineer. Rather, it is aimed at the experienced gear designer capable of selecting reasonable values for the factors in these formulae, based on knowledge of similar designs and on awareness of the effects of the items discussed.

NOTE Contrary to cylindrical gears, where the contact is usually linear, bevel gears are generally manufactured with profile and lengthwise crowning: i.e. the tooth flanks are curved on all sides and the contact develops an elliptical pressure surface. This is taken into consideration when determining the load factors by the fact that the rectangular zone of action (in the case of spur and helical gears) is replaced by an inscribed parallelogram for method B1 and an inscribed ellipse for method B2 (see Annex A for method B1 and Annex B for method B2). The conditions for bevel gears, different from cylindrical gears in their contact, are thus taken into consideration by the longitudinal and transverse load distribution factors.

Figure 1 — Structure of calculation methods in ISO 10300 (all parts)

^a	One set of formulae for both, bevel and hypoid gears.
^b	Separate sets of formulae for bevel and for hypoid gears.

BS ISO 10300-1:2014

Calculation of load capacity of bevel gears - Introduction and general influence factors

Published:

31 Mar 2014

Withdrawn:

31 Aug 2023