Raymond J. Drago, RE.
Senior Engineer, Advanced Power Train Technology
Boeing Vertol Company
35.1 INTRODUCTION / 35.1
35.2 TYPES / 35.2
35.3 ADVANTAGES / 35.2
35.4 GEOMETRY / 35.5
35.5 LOAD RATING / 35.8
REFERENCES / 35.57
The following is quoted from the Foreword of Ref. [35.1]:
This AGMA Standard and related publications are based on typical or average data,
conditions, or applications. The standards are subject to continual improvement, revi-
sion, or withdrawal as dictated by increased experience. Any person who refers to
AGMA technical publications should be sure that he has the latest information avail-
able from the Association on the subject matter.
Tables or other self-supporting sections may be quoted or extracted in their entirety.
Credit line should read: "Extracted from ANSI/AGMA #2001-688 Fundamental Rat-
ing Factors and Calculation Methods for Involute Spur and Helical Gear Teeth, with the
permission of the publisher, American Gear Manufacturers Association, 1500 King
Street, Alexandria, Virginia 22314."
This reference is cited because numerous American Gear Manufacturer's Associa-
tion (AGMA) tables and figures are used in this chapter. In each case, the appropri-
ate publication is noted in a footnote or figure caption.
Helical gearing, in which the teeth are cut at an angle with respect to the axis of rota-
tion, is a later development than spur gearing and has the advantage that the action
is smoother and tends to be quieter. In addition, the load transmitted may be some-
what larger, or the life of the gears may be greater for the same loading, than with an
equivalent pair of spur gears. Helical gears produce an end thrust along the axis of
the shafts in addition to the separating and tangential (driving) loads of spur gears.
Where suitable means can be provided to take this thrust, such as thrust collars or
ball or tapered-roller bearings, it is no great disadvantage.
Conceptually, helical gears may be thought of as steppe