Piston-chain arrangement in IC engine is a method to replace the crank shaft by chain/belt and two connected sprocket/wheels. This method can convert the rotational motion of the crank shaft to a combination of rotational and linear motion. The main advantage of this method is its high efficiency. In the present IC engines, the diameter of crank shaft is equal to the stroke length and the crank angle at the beginning of power stroke will be much less. So, major portion of piston force will be wasted in the crank shaft and a small portion of piston force will be used for rotating flywheel. At 10 degree crank angle, about 88% of power is lost but only 66% of power is lost at 20 degree. The solution is to connect a small wheel and chain arrangement to piston without reducing the stroke length. If we reduce the wheel diameter of piston crank mechanism to 33%, the increase in power will be 22%.
In Piston-chain arrangement, the piston is directly connected to a chain or a belt which is free to run over tow sprocket/wheels connected to two different shafts. Either or both of these wheels can be connected to the flywheel. It also has a system to avoid slipping of chain/belt from the wheels. During power stroke, the piston will push the chain/belt and will move from one wheel to the other ie, from point A to B as in Fig 2. This will be a linear motion. At point B, the piston end will change its direction and follow a circular path till point C. From point C to D is again linear motion and it is the exhaust stroke. From point D to A is circular motion and from point A to B is linear motion of suction stroke. Then again point B to C is circular motion and point C to D is the compression stroke. So the four strokes can be accomplished by two semi circular and two linear motion.
There are many advantages of this design compared to the present one.
1. Crank angle at the starting of power stroke can be increased resulting in increase in efficiency
2. Friction of piston with the cylinder wall is reduced which increase the efficiency.
3. Frictional heat can be reduced, resulting low wear and tear and also a simple cooling system can cool the
4. High stroke to bore ratio can be achieved.
5. A small cylinder with small diameter will provide a small combustion chamber and so the heat dissipation
loss can be reduced.
In conclusion, the overall efficiency of the IC engine can be increased and its size and maintenance cost can be reduced by piston-chain arrangement or by converting rotational motion of crank shaft to combination of rotational and linear motion as in piston-chain arrangement.