Gear box

Machine Design II

Prof. K.Gopinath & Prof. M.M.Mayuram

Module 2 - GEARS
Lecture 17 – DESIGN OF GEARBOX
Contents
17.1 Commercial gearboxes
17.2 Gearbox design.
17.1 COMMERCIAL GEARBOXES
Various commercial gearbox designs are depicted in Fig. 17.1 to 17.10. These include single to multistage ranging from spur, helical, bevel to worm gears.

Fig.17.1 Commercial Gearbox Design

Fig. 17.2 Two stage helical gearbox

Indian Institute of Technology Madras

Machine Design II

Prof. K.Gopinath & Prof. M.M.Mayuram

Fig.17.3 A single stage bevel gearbox

Fig.17.4 Worm gearbox

Indian Institute of Technology Madras

Machine Design II

Prof. K.Gopinath & Prof. M.M.Mayuram

Fig.17.5 Worm gearbox, sectional front and side views

Fig.17.6 Worm gearbox, without cooling fins, sectional front and side views

Indian Institute of Technology Madras

Machine Design II

Prof. K.Gopinath & Prof. M.M.Mayuram

Fig.17.7 Helical gear lubrication with idler gear

Fig.17.8 Spur gear lubrication with stream by nozzles

Fig.17.9 A double reduction spur gear box

Indian Institute of Technology Madras

Machine Design II

Prof. K.Gopinath & Prof. M.M.Mayuram

Fig.17.10 Bevel gear – Spur gear transmission
17.2 HELICAL GEARBOX DESIGN - PROBLEM 1
In a turbine drive 300 kW power is transmitted using a pair of double helical gear. The pinion speed is 2950 rpm and that of the gear is about 816.5 rpm. There are no space constraints on the gear drive. Selecting suitable materials, design the pinion and the gear to last for 108 cycles. Design the gearbox completely.
Data: W = 300kW; n1 = 2950rpm; n2 ≈ 816.5 rpm; Desired Life 108 cycles.
Solution:
1. Angular speed of the input shaft

ω1 

2πn1 2π x 2950

 308.77 rad / s
60
60

1000W 1000x300

 971.6Nm ω 308.77

2. Torque:T1 

3. The details of the gear design carried out are given in Table 1 and 2.

Indian Institute of Technology Madras

Machine Design II

Prof.