The function of the reciprocating engine is to convert the reciprocating motion into rotary motion. It is a simplest from of single slider crank chain mechanism. In reciprocating engine there is one sliding pair and three turning pairs. In figure there are three turning pairs and the sliding pair is formed between the cross head and the guides. Link 1 is fixed (frame). Link 2 will act as a crank, which rotates. Link 3 is a connecting rod and link 4 is a crosshead.