the mixture is ignited and gas expansion drives the adjacent pistons apart the mechanical energy of the pistons being moved apart by the gas expansion is coupled through a drive shaft to the load application_number US 63325175 A description as previously stated the description up to this point refers to the basic engine which is made up of fourteen parts the parts of the basic engine are as follows the numerals or capital letters after each part refers to reference designators in the drawings 2 housings a and b housing a fig2 housing b fig7 4 pistons 1a 1b 2a 2b fig9 mounted on plates pa and pb 1 crankshaft 4 fig5 left hand crank 4ca right hand crank 4cb 1 gear 5 fig5 mounted on one end of the crankshaft 4 the ports in housing a and b are not detailed as parts the ports are merely openings in the housings if an attempt were made to balance the single crankshaft basically required for this engine by means of a fixed mass as is usually the case with engines provided with crankshafts it would only be possible to do so approximately because a crankshaft being an eccentric mass its center of gravity varies continually as it rotates within the.