01-04-2010, 09:19 PM
Design and Fabrication of GearBox
AIM: To design and fabricate a automobile gearbox
Objectives
To design a Helical gear box
Study of various gear manufacturing processes
Fabrication of gear box
Representation of Gearbox
Market Survey
Market research was done at following places regarding type and cost calculation of the Gearbox.
Sokhi heli-wom gears pvt.ltd in Ghaziabad
Hi-tech gears in Manesar
Junk market in Mayapuri
Gearbox
A transmission or gearbox provides speed and torque conversions from a rotating power source to another device using gear ratios, including for a motor vehicle partly because of the limitations of internal combustion engines. Torque converters, hydraulics, electrical power and hybrid configurations may also be used for the same purpose.
Uses of Gearbox
Gearbox has different uses at different places.
In Automobiles, engine speed is about 5000 rpm ,but wheels rotate at 1000 rpm.Machine tool spindle rotates at 50 rpm while the motor is at 1440 rpm.
Automobile gearbox can have variable output and input speeds ,and few reduction ratios in between.
Gearbox types
It can be classified as
Manual
Automatic
Manual Gearbox can be further divided as
Synchromesh and Non Synchromesh
Non synchromesh includes
liding mesh type Synchromesh GearBox
Constant Mesh Gearbox where diagonal cut helical gear sets are constantly "meshed" together, and a dog clutch is used for changing gears. On synchromesh boxes, friction cones or "synchro-rings" are used in addition to the dog clutch. This type of gearbox is used in modern cars and trucks these days.
Material Selection
Keeping in mind cost effectiveness. It was intended to design a general purpose Gearbox, where cheaper materials would be used.
So, Plain Carbon Steel will be used for moving components and Cast iron for Frames and bodies ,because of intricate shape they can be easily casted.
Materials contd.
Plain Carbon Steel with 0.4% carbon or EN8 material is selcted for shaft.
Further,Hot rolled being cheaper than cold rolled and heat treated materials , hot rolled will be selcted.
For gears : 30 Ni 4 Cr 1 is selected with Sut=1500Mpa
For gears, additonal cheap alloying element,such as manganese (0.87%),to make it Strong , giving ultimate strength of 600 Mpa.(P.S.G Design data book 1.13)
Automatic Gearbox
This type of transmission are easy to use.  Automatic transmission will select an appropriate gear ratio without any operator intervention .
Sun and planet gear are mainly used
Design of Automobile Gearbox
Gearbox are incorporated to match performance of variable speed internal combustion engine.
Lowest reduction ratio is needed at highest speed of operation, and vice versa, values of these reduction ratio lies b/w 3.5 to 4.5 for cars and 5 to 7 for commercial vehicles.Gearbox provides reduction ratio between 1:1 to 1:4 for cars to 1:1 to 1:7 for commercial vehicles.
Special features of Automobile Gear box
Universally accepted number of gear ratios is 4.These four are in geometric progression, However ,overdrive gear is provided to enhance performance at higher speeds
Additional reduction ratio is provided to enhance performance during higher gradient operation.
Results Obtained
Gear Ratios
Layout
Results
Gantt Chart
Conclusion
Designing of gears and shafts has been done and near
future we will be starting with fabrication of gearbox.
Bibliography
P.S.G Design Data book
Handbook for engineers
Material Science By Rk Rajput
Mechanical System Design By S.P . Patil
Theory of machine By Khurmi & Gupta
Machine Design By Khurmi & Gupta
