An engine comprising: at least a first disc (3; 40; 57; 84) having an axial hole and at least a first offset hole (9; 59; 100); at least a first piston (17; 41; 51; 81) connected to a circumference of said first disc by a peg and sleeve structure (11, 16) that pivots with respect to the first piston for converting a linear oscillating motion of the first piston into an angular oscillating motion in said first disc; a main shaft (4; 66; 91) passing through said axial hole; at least a first crank shaft (5; 65; 92; 95) passing through said first offset hole and comprising a gear for connecting to a corresponding gear on said main shaft said main shaft for converting a rotation of said first crank shaft into a rotation of said main shaft; a second disc (3'; 40; 60; 85) having an axial hole and a first offset hole (9; 59; 100), wherein said main shaft passes through said axial hole of the second disc and wherein said first crank shaft also passes through said first offset hole of said second disc; a second piston (17; 41; 51; 81) connected to a circumference of said second disc by a second peg and sleeve structure (11, 16) that pivots with respect to the second piston for converting a linear oscillating motion of the second piston into an angular oscillating motion in said second disc; a first connecting mechanism (30; 93) including a cam provided on said crank shaft for engaging said first offset hole of said first disc for generating a rotation of said first crank shaft from said oscillating motion of the first disc; and a second connecting mechanism (31; 93) including a cam provided on said crank shaft for engaging said first offset hole of said second disc for generating a further rotation of said first crank shaft from said oscillating motion of the second disc; wherein said first piston is arranged to oppose said second piston. at least a first disc (3; 40; 57; 84) having an axial hole and at least a first offset hole (9; 59; 100); at least a first piston (17; 41; 51; 81) connected to a circumference of said first disc by a peg and sleeve structure (11, 16) that pivots with respect to the first piston for converting a linear oscillating motion of the first piston into an angular oscillating motion in said first disc; a main shaft (4; 66; 91) passing through said axial hole; at least a first crank shaft (5; 65; 92; 95) passing through said first offset hole and comprising a gear for connecting to a corresponding gear on said main shaft said main shaft for converting a rotation of said first crank shaft into a rotation of said main shaft; a second disc (3'; 40; 60; 85) having an axial hole and a first offset hole (9; 59; 100), wherein said main shaft passes through said axial hole of the second disc and wherein said first crank shaft also passes through said first offset hole of said second disc; a second piston (17; 41; 51; 81) connected to a circumference of said second disc by a second peg and sleeve structure (11, 16) that pivots with respect to the second piston for converting a linear oscillating motion of the second piston into an angular oscillating motion in said second disc; a first connecting mechanism (30; 93) including a cam provided on said crank shaft for engaging said first offset hole of said first disc for generating a rotation of said first crank shaft from said oscillating motion of the first disc; and a second connecting mechanism (31; 93) including a cam provided on said crank shaft for engaging said first offset hole of said second disc for generating a further rotation of said first crank shaft from said oscillating motion of the second disc; wherein said first piston is arranged to oppose said second piston.