We talked energy efficiency with some
major players in the lubricants industry—
but with a focus on their products’
impact regarding energy efficiency of
gears and gearboxes in wind turbines.
Gears with an asymmetric involute gear tooth form were analyzed to determine their bending and contact stresses
relative to symmetric involute gear tooth designs, which are representative of helicopter main-drive gears.
In the majority of spiral bevel gears, spherical crowning is used. The contact pattern is set to the center of the active tooth flank and the extent of the crowning is determined by experience. Feedback from service, as well as from full-torque bench tests of complete gear drives, has shown that this conventional design practice leads to loaded contact patterns, which are rarely optimal in location and extent. Oversized reliefs lead to small contact area, increased stresses and noise, whereas undersized reliefs result in an overly sensitive tooth contact.
Hypoid gears are the paragon of gearing. To establish line contact between the pitches in hypoid gears, the kinematically correct pitch surfaces have to be determined based on
the axoids. In cylindrical and bevel gears, the axoids are identical to the pitch surfaces and their diameter or cone angle can be calculated simply by using the knowledge about number of teeth and module or ratio and shaft angle. In hypoid gears, a rather complex approach is required to find the location of the teeth—even before any information about flank form can
be considered. This article is part seven of an eight-part series on the tribology aspects of angular gear drives.
Design innovation, superior engineering properties, high
end-market visibility and sustainability distinguish the winners
of the 2011 Design Excellence awards, the annual powder metallurgy (PM) design competition sponsored by the Metal Powder Industries Federation.