Project Description S14

MEGR 3221-001

Machine Design

Spring 2014

Project Description

Engineering Analysis of a Parallel Shaft Speed Reducer

Pictured below is a Dayton 4Z860 parallel shaft speed reducer with 17.5:1 speed reduction. It is

rated for input from a 3/4 HP motor running at 1725 rpm. This provides an output speed of 100

rpm with a maximum output torque of 454 in-lbs. In addition the shaft must support a

perpendicular “overhanging” load of up to 773 lbs. applied 3/4 inch from the oil seal of the

output shaft. The input shaft is assumed to be mounted co-axially with the driving motor, so no

external lateral loads will be present. The goal of this project is to do a complete engineering

analysis of this product to verify the load and life capability of the shafts, gears, and bearings.

The project will be completed in phases throughout the semester.

Item

Speed Reducer

Type

Indirect Drive

Shaft Orientation

Parallel

Duty

Standard

Input RPM

1725

Nominal Output RPM

100

Overhung Load (Lb.)

773

Nominal Ratio

17.5:1

Max. Input HP

3/4

Max. Torque (In.-Lbs.)

454

Output Torque @ 1/4 HP (In.-Lb.)

151


201


302


454

Number of Stages

1

Rotation

Forward/Reverse

Lubrication

Kluber Food Grade

Oil Seal

Double Lip

Bearings

Ball

Pinion

Hardened Steel

Gearing

Helical and Spur

Finish

Powdered Epoxy Paint

Output Shaft Dia. (In.)

1

Output Shaft Height (In.)

4.88

Project Breakdown (100 pts total)

1. Load analysis (25 points) Due Feb. 13, 2014

Create free body diagrams of all of the shafts (with gears in place) in both the horizontal and vertical

planes. Use the manufacturer’s maximum load/torque ratings as inputs and compute the reaction

loads on each shaft at the bearing locations, and at each gear mesh point. Use the dimensional

layout and shaft dimensions supplied to determine the intersection points of all of the gears, and

the resulting force directions. Note that the manufacturer allows an “overhanging” load normal to

the shaft axis of up to 773 lbs on the output shaft at a point 1 inch outboard from the oil seal, but

does not specify the direction of the load. Create your free body diagrams for this load in its worst

case orientation, and justify the selected orientation. Consider how the loads will change if the

direction of input torque is reversed, and choose the worst case for analysis.

Deliverables:

a. Report describing the loading cases selected for analysis, with justification

b. Free body diagrams for all shafts in horizontal and vertical planes

c. Summary table showing all bearing loads and gear tooth loads

2. Shaft calculations (35 points) Due Mar. 25, 2014

For each shaft, input shaft, countershaft, and output shaft, draw the shear and bending moment

diagrams in both the horizontal and vertical planes. Use the shaft dimensions supplied, and the

forces from the solutions provided for Part 1. Determine the critical section or sections to be

analyzed for each shaft, taking into consideration any stress concentrations. Determine the range of

stresses at each critical location as the device operates under full load. We do not know the

material alloy or heat treatment used for these shafts, and therefore do not know the strength

properties. Select a steel alloy for each shaft that will result in infinite fatigue life with a factor of

safety of at least 2. Make reasonable assumptions needed to complete the analysis.

Deliverables:

a. Report on stress analysis for each shaft, with shear and bending moment diagrams if the

horizontal and vertical planes and identifying the stresses acting on the critical sections.

b. Material selection report for each shaft with accompanying fatigue life calculations,

identifying any assumptions used in the analysis.

3. Bearing life (15 points) Due Apr. 10, 2014

Each of the shafts is supported by a two ball bearings. The bearing model numbers are provided in

the dimensional drawings below. Consult the tables in the text for the basic static and dynamic load

ratings for each bearing. Determine the expected life of the bearing based on the loads computed

in Section 1. Make any reasonable assumptions required to complete the analysis.

Deliverables:

a. Analysis of bearing life for all bearings.

4. Gear calculations (25 points) Due Apr. 24, 2014

Analyze the pinion gears in each gearset using the tooth forces obtained from Part 1. The

manufacturer states that the steel gears have been induction hardened, but does not provide a

specific hardness. Assume that the steel pinions have been hardened to 500 Bhn, and find the

required face width for each pinion to provide infinite life with a Factor of Safety of at least 1.4,

based on both a Tooth Bending Analysis and a Surface Fatigue Analysis. Make any reasonable

assumptions required to complete the analysis.

Deliverables:

a. Report on pinion gear tooth analysis, identifying any assumptions used in the analysis.

Fig. 1. Speed reducer interior

Fig. 2. Speed reducer interior showing cover with countershaft and output shaft

Input Shaft

Support for countershaft bearing

Countershaft

Output shaft

Support for output shaft bearing

Output gear

Input gear – on countershaft

Output pinion – on countershaft

Housing

Cover

Fig. 3. Speed reducer interior from bottom showing input shaft pinion

Fig. 4. Speed reducer interior from bottom with output shaft removed

Input helical pinion – integral with input shaft

Input helical gear

Output pinion – integral with countershaft

Output gear

Countershaft

Output shaft front bearing support

Output shaft

Input shaft helical gear

Fig. 5. Speed reducer interior with countershaft and output shaft removed

Fig. 6. Speed reducer cover with shafts

Input shaft helical gear

Countershaft front bearing support

Countershaft

Output shaft

Output shaft

Countershaft

Input shaft helical pinion

Fig. 7. Input shaft assembly showing cover and retainer

Fig. 8. Countershaft

Cover

Input shaft retainer

Input shaft

Countershaft front bearing

Input gear – meshes with input shaft pinion

Output pinion – meshes with output shaft gear

Countershaft rear bearing

Fig. 10. Output shaft

Fig. 11. Input shaft

Output shaft front bearing

Output shaft gear

Output shaft rear bearing

Input shaft front bearing

Input shaft rear bearing

Input shaft helical pinion

Input Shaft dimensions (not to scale, all dimensions in inches):

5.95

2.05

2.18

2.87

1.20

2.95

1.40

3.44

1.55

4.00

1.65

4.07

Centerline of 204 BRG

0.677 DIA

0.980 DIA

0.985 DIA 0.788 DIA

0.655 DIA

1.160 DIA

0.750 DIA


Keyway - .125W X .063 D

All fillets 0.01 Radius

Countershaft Dimensions (Not to scale – all dimensions in inches)

4.40

0.45

4.16 3.49

1.88

3.18

3.28

0.36

0.23

0.67 DIA 0.67 DIA

0.65 DIA

0.81 DIA

Output pinion integral to shaft Centerline of 203 BRG Centerline of Input Gear


Keyway: 0.19W X 0.09D X 0.75L All fillets 0.01 Radius

Output Shaft Dimensions (Not to scale – all dimensions in inches)

6.60

6.38 6.15

5.40 4.75

4.25

2.88

2.63

2.25

1.30

2.40

0.67 DIA

0.82 DIA

0.98 DIA 1.37 DIA

1.18 DIA

1.00 DIA


Centerline of L06 BRG

Location of 773 lb. overhanging load

Centerline of output gear Keyway: 0.25W X 0.19D X 0.75L

Keyway: 0.25W X 0.19D

All fillets 0.01 Radius

Shaft Layout - looking from input end towards output (Not to scale, all dimensions in inches)

O: Centerline of output shaft

I: Centerline of input shaft

C: Centerline of countershaft

�� = 1.383"

�� = 2.219"

�� = 1.857"

OCI = 38.4°

OIC = 85.1°

COI = 56.5°

X

C I

O

Y

Output Gear

Input Gear

Output Pinion

Input Pinion

Countershaft

Output Shaft

Input Shaft

Gear specifications:

Input Pair

Input pinion: 16 teeth

Pitch diameter = 0.571 inches

Diametral pitch = 28

Pressure angle = 20°

Helix angle = 11°

Input gear: 88 teeth

Pitch diameter = 3.143”



Helix angle = 11°

Face width = 0.63”

Output pair

Output pinion: 17 teeth

Pitch diameter = 1.063



Output gear: 54 teeth

Pitch diameter = 3.375”



Face width = 1.00”

Project Description S14

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