MECHANICAL DAE: Mechanical Energy

MECHANICAL DAE: Mechanical Energy: Mechanical Energy The Mechanical Energy Mechanical energy is the energy which is applied to an object due to its motion or due to ...

CLASSIFICATION OF GEARS

The gears are classified as follows:

1: The gears which connect parallel shafts such as spur, Helical and double helical gears.

2: The gears which connect inclined and intersecting shafts such as straight bevels and spiral bevel gears.

3: The gears which connects non-parallel and non-intersection shafts such as spiral gears and worm and worm wheel

TYPES

There are many types of gears some of following are important

1: SPUR GEARS:

2: HELICAL GEAR:

3: DOUBLE HELICAL OR HERRINGBONE GEARS:

4: INTERNAL GEARS: 

5: BEVEL GEARS:

6: RACK AND PINION:

7: WORM AND WORM GEAR:

SYSTEM OF GEAR TEETH

The following four systems of gear teeth are used to manufacture gears.

1: 14 1/2 degree composite system.


2: 14 1/2 degree full depth involute system.

3: 20 degree full depth involute system.


4: 20 degree stub involute system.

The # 1: system is used for general purpose gears.
It is stronger and has no interchange ability. 
The tooth profile of this system has cycloid curve at the top and bottom and involute curve at the middle portion. The teeth are produced by form cutters on milling and by hobs on hobbing machine. 

The tooth profile of the 14 1/2 degree full depth involute system was developed for use with gear hobs for spur and helical gears. The tooth profile of 20 degree full depth involute system may be cut by using hobs on hobbing machine. 

The increase of pressure angle from 14 1.2 degree to 20 degree cause to make the gear teeth strong. 
The gear tooth in service acts as a beam and is wider at the base. 

The 20 degree stub involute system has a strong tooth to transmit heavy loads.

GEAR METERIAL

The selection of material used to manufacture the gears depends upon the conditions like strength, noise and resistance to wear. The gears are manufactured from metallic as well as from non-metallic material. The metallic materials means steel, cast iron, bronze and brass etc. While non-metallic materials include hard wood, raw-hide, compress paper, synthetic resins and nylon etc.
Metallic gears are used to transmit heavy torque while non-metallic gears are used for low and medium power transmission and specially to reduce noise as in case of plain paper photo copier.

The cast iron is most widely used to manufacture gears due to its easy machining, better resistance to wear and ease of producing complex shapes by casting method. The cast iron cut gears are used where smooth action is not important. The phosphor bronze is widely used foe worm gears to reduce wear of the worm.


 

SPUR GEAR

INTRODUCTION

When it is required to transmit power from one shaft to another parallel to each other at long distance, we use wire rope or flat belts. 
For moderate distances,
V-belts is used for the said purpose. The shafts situated at minimum distances are  provided with gears. 
The only requirement for transmit power is the exact central distance between shafts. 
They previous methods cannot be used to get exact velocity ratio due to slipping between belts and pulleys, therefore toothed wheel or gears are used.

TERMS OF SPRING

PITCH OF SPRING

The pitch of the spring is the axial distance between adjacent turns in uncompressed state.

SPRING INDEX

It is the ratio of mean diameter of the coil to the diameter of the wire. Mathematically;
Spring index = D/d where D = Mean diameter of coil 
d = Diameter of the wire



SPRING RATE


Load required oer unit deflection is called spring rate or stiffness.

FREE LENGTH

It is the length of spring measured parallel to the axis when load is completely removed from it.

SPRING MATER

The material for the spring largely depends upon the sirvice for which they are used. 
The springs are mostly made from oil tempered carbon steel wires containing.
Music wire is used for small springs.
Non ferous material like phosphor bronze, monal metal, and brass may be used. 
The wire of less than 10mm diameter are usually wound cold to make springs while the largr sizes are wound hot.