## Aapproximate straight line mechanisms:

This approximate straight line mechanisms are the modification of four bar chain mechanisms.
They are explained as follows:
1.Watt's mechanism
2.Grasshopper mechanism
3.Tchebicheff's mechanism

### 1. Watt's mechanism:

It is used for early steam engines to set the piston rod in a cylinder to get a straight line motion approximate, this is a crossed four bar mechanism which is a Watts mechanism.

### 2. Grasshopper mechanism:

It is the modified mechanism of scott-russel's  mechanism. And it is a four bar mechanism and all the pairs are turning pairs.in this mechanism the center D and A are fixed.
The grasshopper mechanism is used in early days as an engine mechanism, with the help of this mechanism we can get a long stroke by short crank.

### 3. Tchebicheff's mechanism:

It is also a four bar mechanism. In this cross links of AB and AB1 are equal in length.in this point O is middle point of AC traces out an approximate straight line parallel to AA1.

#### Tchebicheffs Mechanism

INVERSION OF FOUR BAR CHAIN : READ HERE