ME 314
Engineering Design: Mechanical Components
Gear Train Design
Department of Mechanical Engineering
Summer 2021
2
Abstract
The purpose of this report is to present a design for the gear train within the acc
...
ME 314
Engineering Design: Mechanical Components
Gear Train Design
Department of Mechanical Engineering
Summer 2021
2
Abstract
The purpose of this report is to present a design for the gear train within the accessory component gearbox. This gear train will be supplied a torque from the accessory drive shaft, that will hold two gears to power both sides of the gear train. The required torques and speeds of the accessory gears are in Table 2, with their respective locations displayed in Figure 1. All gears and respective components had to follow the design requirements stipulated in Table 1 and had to satisfy the package constraints of the accessory gearbox itself. Using the design requirements, it was decided that the gear train would utilize 29 spur gears made of Carburized and Hardened Grade 1 Steel, which resulted in safety factors of safety of 1.08 and 1.84 for bending and contact at the highest loaded points respectively. To mount the gears, 17 shafts are used with keyways and retaining rings. This project only required the design of the main accessory drive shaft, which required a minimum safety factor 1.5. For this main drive shaft, it was decided that it would be made of AISI 1050 CD Steel, which resulted in the shaft having a factor of safety of 1.82, which satisfies the minimum design requirement.
3
Table of Contents
Abstract. 2
Design Requirements. 6
Gear Train Design and Layout.. 7
Gear Design and Selection.. 8
Gear Analysis – Gear Loading.. 9
Gear Stress Analysis and Factors of Safety . 10
Gear Analysis – Bending Stresses 11
Gear Analysis – Contact Stresses . 12
Shaft Analysis and Sizing . 13
Shaft Loading.. 14
Shaft Geometry .. 14
Conclusion 16
Appendices:.. 17
4
List of Tables
Table 1: Design Constraints 6
Table 2: Component Specifications 6
Table 3: Geometry of All Gears 9
Table 4: Gear Loading 10
Table 5: Bending Stress Analysis . 11
Table 6: Contact Stress Analysis .. 12
Table 7: Shaft Support Reactions . 14
5
List of Figures
Figure 1: Accessory Component Locations 6
Figure 2: Labeled Gear Train Layout 7
Figure 3: Parametric Drawing of Representative Gear. 8
Figure 4: Fatigue Life Curve for AISI 1050 CD Steel Shaft .. 13
Figure 5: Reaction Locations of Shaft 14
Figure 6: Drawing of Main Accessory Drive Shaft with Dimensions 15
Figure 7: Model of Accessory Drive Shaft with Gears attached .. 15
6
Design Requirements
The main objective of this project is to design a gear train, and the main accessory drive shaft for a gearbox that is designed to fit below the jet engine compressor case for a commercial aircraft. All components of the gear train will follow the American Gear Manufacturer’s Association (AGMA) standard and the design requirements listed in Table 1.
Table 1: Design Constraints
Spur or Helical Gear Precision, Enclosed Units
Pressure angle of 20° Gearing to be adjusted at the assembly of the accessory gearbox
Uncrowned Teeth Loading is moderate shock, power is uniform
No. 6 quality standard for all gears Operating temperature is below 250℉
98% Reliability Service life equivalent to 108 cycles for all component
The specifications for the accessory components, including the torque and drive speed are listed in Table 2. The torque directions are when facing
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