Page 177 - The Tribology Handbook

Gears B3

British Standard 545,1982 (Bevel gears)

Specifies tooth form, modules, accuracy requirements, methods of determining load capacity and material requirements for
machine-cut bevel gears, connecting intersecting shafts which are perpendicular to each other and having teeth with a
normal pressure angle of 20" at the pitch cone, whose lengthwise form may have straight or curved surfaces.
The load capacity of the gears is limited by consideration of both wear and strength, factors taken into account are:
Wear and strength factors: Include the speed, surface stress, zone, pitch, spiral angle overlap ratio and bending
stress factors.
Limiting working temperature: The temperature of the oil bath under the specified loading conditions.

Basic stress factors: Given for the various recommended materials.

British Standard 721 Part 2 1983 (Worm gears)
Specifies the requirements for worm gearing based on axial modules. Four classes of gear are specified, which are related to
function and accuracy. The standard applies to worm gearing comprising cylindrical involute helicoid worms and
wormwheels conjugate thereto. It does not apply to pairs of cylindrical gears connecting non-parallel axes known as crossed
helical gears.
The load capacity of the gears is limited by both wear and strength of the wormwheel, factors taken into account include:
Expected life: The strength is calculated to an expected total running life of 26 000 hours. Allows for
both steady and variable loads at different running speeds.

Momentary overload Momentary overload is considered as one whose duration is too short to be defined with
capacity: certainty but does not exceed 15 seconds.

Eficiency and lubrication: The efficiency, excluding bearing and oil-churning losses for both worm and wormwheel
driving.
Basic stress factors: Given for the various recommended materials.

American Gear Manufacturers Association Standards

The American Gear Manufacturers Association Standards are probably the most comprehensive coverage for gear design
and are compiled by a committee and technical members representing companies throughout America, both north and
south, Australia, Belgium, Finland, France, Great Britain, India, Italy, Japan, Mexico, Sweden, Switzerland and West
Germany and are being constantly up-dated.
The standards cover gear design, materials, quality and tolerances, measuring methods and practices, and backlash
recommendations.
Gear perforrnance is covered by a series of different standards as follows:
AGMA 170lI Design guide for vehicle spur and helical gears.

ACMA 210% Surface durability (pitting) of spur gear teeth
AGMA 21 1-05! Surface durability (pitting) of helical and herringbone gear teeth.

AGMA 212-02 Surface durability (pitting) formulas for straight bevel and zero1 bevel gear teeth
AGMA 215011 Information sheet for surface durability (pitting) of spur, helical, herringbone and bevel gear
teeth.

AGMA 21N1 Surface durability (pitting) formulas for spiral bevel gear teeth.
ACMA 21741 Information sheet - gear scoring design guide for aerospace spur and helical power gears.

AGMA 220-02 Rating the strength ofspur gear teeth
AGMA 22142 Rating the strength of helical and herringbone gear teeth
B3.7