AGMA 911-A94 pdf free.Design Guidelines for Aerospace Gearing.
4 Design approach
4.1 Deslgn requlrements and goals
The design procedure begins with a definitionof the application, requirements, and goals for the project.It is sometimes dfficult to clearly define all aspects of the project at the start, but a complete tabulation of the following parameters should be made to provide a working definition of the project.
4.1.1 Power/speed and torque/position
The complete range of power and speed or torque and position (actuators) must be tabulated including a definition of growth capability. A duty cycle definition is required for calculation of life. Within these parameters a design point must be selected
for sizing purposes.
4.1.2 Gear ratio and dlrectlon of rotation
Gear ratio must be specified with an indication of allowable deviation. Input and output directions of rotation are required and are important in selection of the hand of helix or hand of spiral for thrust direction and lubrication considerations.
4.1.3 Life
A clear definition of required gear and bearing system life must be provided. Life is defined at a specified survival level.
4.1.4 Weight
System weight is critical in aerospace applications.A value for gear system weight should be specified as dry gearbox weight or gearbox plus lubrication system weight.
4.1.5 Size limitations
In most applications, gearbox location and maximum envelope will be defined. These details must be made available to the designer.
4.1.6 Rellabllity
Reliability requirements are typically speified in terms of mean time between failure (MTBF). A historical data base of typical component reliability will permit calculation of system reliability. New products are more difficult to characterize. Techniques toquantity rlibilit levels must be specified for a new gearbox system.
4.1.7 Maintainability
Guidelines for field service work, space requirements, andtool litations mustbe specified early in the project.
4.1.8 Cost :
Aerospace gearing is generally more costly than commercial gearing because of the necessary performance, quality and traceability requirements.Life cycle cost is often established at the start of the project asa goalor as a requirement. Life cycle cost is defined as the total cost of ownership of a system over its operating life.
4.1.9 Efficiency
In most aerospace applications, gearbox efficiency is an important design consideration because it influences system weight and power requirements.Efficiency requirements and goals will provide the designer a clear indication of the project objectives and may afect key decisions inthe design process.
4.1.10 Altitude/attitude requirements
Altitude and ttitude specifications are required for lubrication system design, since oil pump and oil passage design are dependent on these parameters. In lieu of any specific application data MIL-E- -8593C provides general requirements for aerospace applications.
4.1.11 Externally generated gearbox loads
Extemal loads can be generated by rotor loads,fight maneuvers, gravity and gyroscopic effects,hard or crash landing requirements, or vibration, as applicable. All must be considered in the design of the gearbox housing, mounts and their effects on misalignment of bearings and gears within the gearbox. Typical loads are given in MIL-E- 8593C.
4.1.12 Mount locations
Mount locations must be specified to allow design and analysis of the housing and internal structure under external loading conditions. Mount location requirements may also affect maintainability considerations.AGMA 911 pdf download.