Statics Analysis (1)

ME314 Fall 2017 Group Design Project

Conceptual Accessory Gearbox Design

Objective:

An accessory drive gearbox is to be designed for a commercial aircraft, and is designed to fit below the jet

engine compressor case. The gearbox is driven off the engine compressor shaft and drives the engine fuel

pump, the engine oil pump, the hydraulic pump and the electrical generator, and is attached to the engine by

three fittings that are bolted to the gearbox housing.

The gearbox is driven by an accessory drive shaft that receives power from engine compressor spool through

a compressor power transfer shaft. The compressor transfer shaft is connected to the accessory drive shaft

through a bevel gear at the aft transfer case. The compressor transfer shaft is driven by the engine compressor

at a speed of 6000 rev/min (ccw) and a torque of 790.4 ± 0.5 in·lbf , and the accessory drive shaft delivers a

torque of 1053.8 ± 0.5 in·lbf at a speed of 4500 rev/min (ccw). The gearbox housing has a structural weight

of 185 lbf without the gear train components or accessories installed. The accessory gear box shall meet the

specified package dimensions and shall weigh no more than 345 lbf with accessories and gear train

components installed.

ALL DIMENSIONS IN INCHES

UP

FWD

COMPRESSOR CASING

FWD

OUTBD

COMPRESSOR SHAFT

15.36

HYDRAULIC PUMP

OIL PUMP

FUEL PUMP

ELECTRICAL GENERATOR

ACCESSORY

DRIVE SHAFT AFT TRANSFER CASE

UP

ELECTRICAL GENERATOR

HYDRAULIC PUMP

FUEL PUMP

OIL PUMP

ACCESSORY

GEARBOX

NACELLE OUTLINE

GEARBOX OUTBD SUPPORT

GEARBOX INBD

SUPPORT

OUTBD

ACCESSORY

GEARBOX

GEARBOX AFT SUPPORT

GEARBOX AFT SUPPORT

ACCESSORY GEARBOX

COMPRESSOR TRANSFER SHAFT

The individual accessories are mounted to the aft face of the housing and are driven at the speeds specified in

Table 1, and their respective CG locations measured from the aft face of the accessory gearbox case are also

listed. Each component is mounted using the specified number of fasteners.

The gear train components are required to have a service life of at least 10 8 cycles.

Structural Considerations:

The gearbox assembly is supported from the

engine compressor casing by three links that are

connected to the three support fittings (INBD,

OUTBD, and AFT) that are bolted to the gearbox

housing. The support fittings are to be fabricated

from aluminum alloy with press-fit steel bushings

installed in the lugs, and secured to the MS14101

bearings in the links using steel bolts. The total

allowable gap between the lug fittings and the

bearing in the links is 0.038 ± 0.009 in.

A front view of the geometry of the gearbox housing is shown in the figure below:

9.42

8.78

23.65

20.24

16.64

12.81

9.06

5.17

3.04

11.40

7.22

8.07

2.69

8.64

5.59

0.78 5.17

4.32

25.77

1.00

12.25

0.78

4.32 6.37

2.97

7.43

SUPPORT FITTING

OUTBD

UP

ALL DIMENSIONS IN INCHES

10.19

1.13

10.97

MS14101-X BEARING

SUPPORT FITTING (TYP)

VIEW LOOKING AFT

A bottom view of the geometry of the gearbox housing is shown in the figure below:

A side view of the geometry of the gearbox housing is shown in the figure below:

3.82

2.34 3.26

3.89

2.48

HYDRAULIC

PUMP

OIL PUMP FUEL

PUMP

ELECTRICAL GENERATOR

SUPPORT FITTING

25.77

6.65

OUTBD

FWD

ALL DIMENSIONS IN INCHES

2.90

2.48

ALL DIMENSIONS IN INCHES

0.42

5.59

5.95

1.84

3.45

A

A

UP

FWD

VIEW A-A

VIEW B-B

1.77

6.03

3.15

4.67

6.30

1.77

B B 4.32

UP

FWD

GEARBOX INBD

SUPPORT

GEARBOX OUTBD SUPPORT

GEARBOX AFT SUPPORT

Tshaft

VIEW LOOKING UP

Loads Considerations:

The accessory drive housing supports the weight of the gearbox components. The details of the various

components are listed in Table 1.

Table 1: Component Specifications

Component Weight Drive Speed Mating Drive Max Torque Aft CG Bolt Pattern Bolt Circle

Oil Pump 21.00 lbf 9000 rev/min 8-Spine 263.5 in·lbf ccw 2.34 in 6  10-24-UNF-3A 2.97-in

Fuel Pump 23.00 lbf 15750 rev/min 8-Spine 150.4 in·lbf ccw 2.97 in 6  10-24-UNF-3A 3.68-in

Electrical Generator 28.00 lbf 5250 rev/min 12-Spine 451.2 in·lbf cw 3.89 in 12  8-32-UNF-3A 4.25-in

Hydraulic Pump 32.75 lbf 3375 rev/min 12-Spine 702.6 in·lbf cw 3.26 in 12  8-32-UNF-3A 4.25-in

The locations of the accessory drive pads are shown in the figure below:

Required:

Determine the reactions at the gearbox supports with the accessories installed and design/size the support

fittings.

Design/size the gearbox mounting fittings:

Reactions at the gearbox mounting points (INBD, OUTBD, AFT)

Reactions at connections between the support fittings and the gearbox housing

Loads of accessory mounting fasteners

Selection/sizing of mounting fasteners

Final material selection for the support fittings

Dimensioning/tolerancing of mounting lugs

Stress analysis of mounting lugs

Apply a fitting factor of nftg = 2.5 to reactions at the mounting lugs

Apply a minimum design factor of nd = 1.75 for the mounting lugs and a minimum design factor of

nd = 1.5 for the attachment bolts

Prepare a written report summarizing the design requirements and your proposed support fitting design

concept to meet these requirements. Describe how your proposed design will meet or exceed the problem

requirements. You are to work in teams of up to 10 students; only one report is required per team. Report is

to be typed and illustrations prepared using a graphics program.

1.77

6.03

1.42

3.47

10.05

5.66

9.49

5.73

HYDRAULIC

PUMP

FUEL PUMP

ELECTRICAL GENERATOR

DRIVE COUPLING

OUTBD

UP

ALL DIMENSIONS IN INCHES

DRIVE MOUNTING PAD

OIL PUMP

BOLT CIRCLE

Tfuel

Toil

Tgen Thyd Tdrive