Design Basics of Industrial Gear Boxes

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Design Basics of Industrial Gear Boxes

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Gear reducers are used in all industries, they reduce speed and increase torque. You will find them between the prime mover (i.e.: electric motor, gas, diesel or steam engine, etc.) and the driven equipment: conveyors, mills, paper machines, elevators, screws, agitators, etc.).

An industrial gearbox is defined as a machine for the majority of drives requiring a reliable life and factor of safety, and with the pitch line velocity of the gears limited to below 25 m/s, as opposed to mass produced gearboxes designed for a specific duty and stressed to the limit, or used for very high speeds etc., e.g. automobile, aerospace, marine gearboxes.

To the competent engineer, the design of a gear unit, like any other machine, may seem a fairly easy task. However without experience in this field the designer cannot be expected to cover all aspects of gearbox design.

The purpose of this booklet is to set out the basic design for an industrial gearbox. It should help students not familiar with gearboxes, lay out a reliable working design. And it is intended for the reader to use his own experience in selecting formulae, stress values etc., for gearbox components.

TOC

Chapter 1: 6
BASIC KNOWLEDGE
1.1 Introduction 6
1.2 Basic size and selection 7
1.3 Torque selection 8
1.4 Materials and heat treatment 9
1.5 The size of the unit 12
1.6 Example 14

Chapter 2: 16
GEAR MESH
2.1 Ratios 16
2.2 Tooth-Pitch combinations 16
2.3 Pitch and module 16
2.4 Example 18
2.5 Face – widths 19
2.6 Detail of gears 20

Chapter 3: 24
SHAFT LOAD CALCULATION
3.1 Design description 25
3.2 Given data 26
3.3 Transmission torque 26
3.4 V-Belt pulley loads 26
3.5 Spur pinion loads 27
3.6 Free body diagram of the high speed shaft 27
3.7 Calculations and diagrams of bending moment (high speed shaft) 28
3.8 Torsion diagram 31
3.9 Critical section of the high speed shaft 32
3.10 Bearing loads of the high speed shaft 32
3.11 Minimal shaft diameter (for high speed one) 32
3.12 Simple method of shaft (minimal) diameter calculation 33
3.13 Minimal diameters of high speed shaft ends 33
3.14 Free body diagram of the low speed shaft 34
3.15 Calculations and diagrams of bending moment (low speed shaft) 34
3.16 Torque acting on the low speed shaft 35 3.17 Torsion diagram for the low speed shaft 35
3.18 Minimal shaft diameter (for low speed one) 36
3.19 Evaluation of minimal diameter for the low speed shaft with empirical method 36
3.20 Minimal diameters of slow speed shaft ends 37
3.21 Resume 37

Chapter 4 38
DEEP GROOVE BALL BEARINGS (Basis description and fundamentals calculation)
4.1 View 38
4.2 Application 38
4.3 Ball bearings description 39
4.4 Kinds of constructions 39
4.5 Theoretical basis 39
4.6 Life’s calculation basis 40
4.7 Example # 1 42
4.8 Example # 2 44

Chapter 5 47
NUMERICAL EXAMPLE OF BALL BEARING SELECTION

Chapter 6 53
RADIAL SHAFT SEALS
6.1 Seals design 54
6.2 Type and destinations of materials 54
6.3 Materials recommendation 55
6.4 Temperature limits according to material types 55
6.5 Design types of radial seals 56
6.6 Radial shaft seals diameters in accordance with ISO – 6194 57
6.7 Mounting of radial shaft seal in housing 58
6.8 Mounting of radial shaft seal on shaft 59
6.9 Radial shaft seals under the pressure 59
6.10 Frictional loss 59

Chapter 7 60 V-BELT DRIVES (Basis data and calculation in accordance with PN-M-85203: 1967)
7.1 V – belt power capacity 61
7.2 Small pulley equivalent diameter 61
7.3 Transmission ratio factor ki 61
7.4 V – belt length 62
7.5 Axis distance (recommended) 62
7.6 V – belt dimensions (in accordance with PN-ISO 4184: 2000) 62
7.7 V-belt length 63
7.8 Pulley Groove dimensions 64
7.9 Pulley diameters dp 65
7.10 Duty power per belt (power transmitted with one belt) P0 66
7.11 Belt length factor KL 67 7.12 Belt contact factor Kφ 67
7.13 Service factors KT (time and work conditions factor) 68
7.14 Example of V-belt drive calculation 70

Chapter 8 74 KEY JOINT (Keyway and key dimensions)
8.1. Key load sketch 74 8.2. Tension distribution 74
8.3. Durability calculation 75
8.4. Specification for metric rectangular keys and keyways 76

Chapter 9 79
GEAR – CASE DESIGN

Credits:

Andrzej Maciejczyk
Zbigniew Zdziennicki
Department of Vehicles and Fundaments of Machine Design