fig3 c the rotor 3a is just coming up to the end of its complete combustion cycle where rotor portions 5a and 5a 39 are approaching rotor portions 5b 39 and 5b respectively on the still stationary rotor 3b however at this point the compression portion of the cycle is at a maximum whereas the power portion of the cycle is at a minimum such that the rotor 3a in fact begins to provide a driving force on rotor 3b to push rotor 3b from behind and to move rotor 3b such that rotor portions 5b and 5b 39 assume the fig3 d position at the same time rotor 3a continues itself to rotate to the fig3 d position at which time plug 25 again fires causing a power portion of a new combustion cycle to be produced between rotor portions 5a 39 and 5b such that the latter rotor portion is driven in the direction of arrow 8b while at the same time producing a driving force against rotor portion 5a 39 in the opposite direction however rotor 3a and its rotor portions 5a 39 and 5a are prevented from reversing by means of spring clutch 15a so that rotor 3a now becomes stationary while rotor 3b moves through its combustion cycle as the two rotor shafts rotate in sequence with one another there is alternating drive applied to torque receiving shaft 13 common to both of the rotors however it must be remembered that both of the gears 19a and 19b are always in geared contact with torque receiving gears 21a and 21b respectively therefore.