Deflections of Shafts in Gear-Boxes

Topics: Gear, Torque, Gear ratio Pages: 25 (6724 words) Published: August 13, 2012
CHAPTER-1
INTRODUCTION
1.1GEARBOXES:
Usually, found near motors of some sort, gearboxes are used to reduce the load on the motor by using the motor's own momentum to keep it turning. Once a motor has reached a number of revolutions per minute, it is advisable for the operator to increase the gear, to drop the revolutions on the motor, yet still keep the same amount of power created. This reduces wear on the engine, allows more control, and allows greater speeds. Although, in practise, the main use of a Gearbox is to act as a reduction gear. These can be variable or non-variable, depending on the application. In other words, if when the motor is turning 2500 rpm the output shaft is turning 500, the gearbox is reducing the number of revolutions from input to output. This is usually achieved by use of cog wheels. If the input shaft is connected to a small cog, the output shaft is connected to a large, and two are meshed together in the gear box, then it will take several turns of the input shaft to make the output turn once. This not only decreases wear on the motor, but also allows greater acceleration. Larger the reduction ratio, larger is the acceleration. This lens will look at a few things associated with gearboxes, such as design, manufacture, how they work and similar pieces. 1.2 FUNCTIONS OF GEAR BOX:

A gear box is containing many gears of different number of teeth, arranged in different shafts which may be solid or spindle shaft. In solid shaft the gear are fitted in such a way that they can rotate only and cannot move in axial direction and also some gap is provided between two gears, where as in splined shaft two or three gear, which are already meshed together to act as a single unit are fitted in such way that they can rotate only and cannot move in the axial direction and also some gap is provided in between two gears, whereas in splined shafts two or three gears ,which are already meshed together to act as a single unit are fitted in such a way that they can rotate and also move in the axial direction

1.3 GEAR BOX DESIGN:
Gearbox design is a fairly difficult task, making sure that the designed and created gearbox is running at maximum efficiency for the task in hand. As such, we're unable to cover it here. Instead, here are some things we need to consider when designing a gearbox. Depending on whether the gearbox is used for a petrol engine or electric motor, it will vary the materials use and therefore the design. Each metal requires a certain cutting speed which may be different from the cutting speed of other metals because of their different hardness values. For example cast iron requires low cutting speed where as brass or copper requires high cutting speed. Practically it is not possible and advisable to provide a number of machine tools having single speed only for machining different kinds of metals. In order to obtain many cutting speed in a single machine tools, a special device, will be attached in between the prime mover such as motor or engine and the work holding device such as chuck or spindle etc. This device is known as gear box which content number of gears arranged in a specific format and by changing the position of some gear with respect to gear many speed can be received. Another important application of gear box is in automobile where low speed is required at starting and stopping and high speed at during running. 1.4 GEARBOX DESIGN FEATURES:

* The design of the gearbox includes the following features… * Input and output shaft relative position and orientation * Support of external forces on shafts
* Design and rigidity of casing
* Type, dimension and strength of gear
* Method of changing speed/direction if required
* Design and strength of gear shafts
* Gearbox bearings
* Gearbox seals
* Lubrication
* Noise and vibration
* Couplings to shaft
*...

References: Sl.No | TITLE | AUTHOR |
1 | DESIGN OF TRANSMISSION ELEMENTS | DR.T.J.PRABHU |
2 | HANDBOOK OF GEAR DESIGN | GITIN. M.MAITRA |
3 | DATA BOOK | PSG |
4 | DESIGN OF MACHINE ELEMENTS | V.B.BHANDARI |
5 | PERMISSIBLE STRESS | WIKIPEDIA |