An engine piston is a cylindrical part that reciprocates inside a cylinder. This part is an integral part of the engine of any motor vehicle. It is designed to convert the pressure difference of a gas, steam or liquid into mechanical energy.
Piston Production Material
Material for the production of pistons. Material for the production of pistons for the first internal combustion engines was cast iron. However, the details made from it were quite heavy. With the development of technology, they began to use a lighter metal, aluminum, for the production of transport parts. Thus, the aluminum piston had many advantages over the cast iron. This is due, primarily, to the fact that the aluminum piston increased power and speed, while reducing the load on the parts and improving heat transfer.
Since the start of production of aluminum pistons, engine power has increased significantly, and the temperature and pressure in the cylinders of modern vehicles have become such that aluminum has reached its ultimate strength. In this regard, in the past few years, steel has been used for the manufacture of pistons, since steel parts can withstand heavy loads. Steel pistons differ from aluminum in the first place in their lighter weight. This is due to the design of the new pistons – they have lighter walls and a significantly lower compression height (the compression height refers to the distance from the bottom to the axis of the aluminum finger).
Piston Quality Requirements
All of the above applies to the pistons of any vehicle, including a motorcycle. As mentioned above, the power of the engines of modern vehicles is very high. Since the piston is assigned one of the main roles in the operation of the engine, special demands are made on its quality.
The fact is that motorcycles are equipped with single-stroke and two-stroke engines. The operation of any engine is divided into cycles. In the cylinder there is a so-called over-space in which the fuel burns.
In each cycle of the engine during its combustion, heat is generated in large quantities, which pushes the piston down with enormous force, thereby starting the engine. The temperature in the cylinder reaches 20000С, however, to start the engine, not all heat will be needed, but only some of it, the rest of the heat along with the exhaust gases will be removed through the exhaust pipe.
Thus, the piston of a motorcycle must meet the following requirements:
By its movement in the cylinder, it should allow the expansion of compressed gases, the fuel combustion product, thereby performing mechanical work. This means that it must be stable to work in conditions of high temperature conditions, as well as gas pressure, and reliably seal the cylinder channel.
To minimize mechanical losses and, consequently, wear, the piston must meet the requirements of a friction pair as best as possible. This is due to the fact that the piston cylinder and piston rings together represent a linear plain bearing.
It must be highly resistant to mechanical stress during the test loads from the side of the chamber to combustion and reaction from the connecting rod.
Moto piston during reciprocating movements with high speed, should provide a minimum load on the crank mechanism by inertial forces.
Thus, taking into account all the above, the piston needs cooling during its operation. If this is not, then it will simply melt, which can harm the engine as a whole.
Motorcycle piston cooling system
There are four piston cooling paths, the first of which are piston rings.
The main role is assigned to the first ring, which is located closer to the bottom. This path is the shortest to the coolant. The rings are pressed simultaneously to the piston grooves and to the cylinder wall. They provide more than half the heat flux.
The second way is the oil in the engine. It is it that has access to the warmest parts of the engine. In this regard, a significant part of the heat is carried away by oil mist into the oil pan.
The third piston cooling path runs through the massive bosses into the finger, after which the heat enters the connecting rod, after which it enters the oil. This way is less interesting, since during its overcoming there are still thermal resistances, such as gaps and steel parts, which have a significant length and low coefficient of thermal conductivity.
The fourth way is that the fresh air-fuel mixture that has just entered the cylinder takes heat.
Despite such a seemingly sufficient number of cooling paths for the motorcycle piston, the most important is the transfer of heat through the piston rings. If this path is blocked, then the engine will not have a chance to withstand heavy loads.