nedjelja, 7. srpnja 2013.

Materials for cylinders

In the wide field of new technologies and knowledge, the regular adaptation to new approaches to production and processing of materials for motors in motor vehicles many elements of functional and economical operation adapt to new technologies and strives so. Downsizing is one of the key factors in achieving this goal, the cylinders and high tech materials that are used when creating such. Cylinder as the element in a motor mechanism plays an important role, serving as a supporting element or piston rod that performs the function of the linear motion of the TDC to BDC. Large thermal expansion occurring within that element and the material from which the cylinders are made must also be good heat implementers. Temperatures are in the high ranges, and it is very important to maintain an optimum temperature range in order to avoid overheating and in order to make usable engine for longer period . New approaches in mixture injection are making more difficult situation to cylinder constructing and therefore gives more indication to adaptation and the development of a certain normal and optimal lifetime motor functionality period (most optimal does not exist, and never will be!)

When developing the designer has more choices for element cylinder/piston, but everything has its advantages and disadvantages.Some of the features are:
Steel liner, Cast Iron piston
Cast Iron liner, Cast Iron piston
Steel liner, piston Steel
Steel liner, piston Aluminium, Cast Iron ring (s)
As alone two elements are interrelated function play a very important role and it is therefore very important to maintain an optimal working relationship between these two elements, because such operating parameters are very important.
There are other possibilities, but these above are actually the nearest optimal and most cost.
Machining processes that help in this are honing and turning.
Honing is an abrasive machining process that produces a precision surface on a metal workpiece by scrubbing an abrasive stone against it along a controlled path. Honing is primarily used to improve the geometric form of a surface, but may also improve the surface texture.
Turning is a machining process in which a cutting tool, typically a non-rotary tool bit, describes a helical toolpath by moving more or less linearly while the workpiece rotates. The tool's axes of movement may be literally a straight line, or they may be along some set of curves or angles, but they are essentially linear (in the nonmathematical sense). Usually the term "turning" is reserved for the generation of external surfaces by this cutting action, whereas this same essential cutting action when applied to internal surfaces (that is, holes, of one kind or another) is called "boring". Thus the phrase "turning and boring" categorizes the larger family of (essentially similar) processes. The cutting of faces on the workpiece (that is, surfaces perpendicular to its rotating axis), whether with a turning or boring tool, is called "facing", and may be lumped into either category as a subset.Turning can be done manually, in a traditional form of lathe, which frequently requires continuous supervision by the operator, or by using an automated lathe which does not. Today the most common type of such automation is computer numerical control, better known as CNC. (CNC is also commonly used with many other types of machining besides turning.)

Steel liner, Cast iron piston
This combination gives the highest possibility of producing a runable and durable engine that will have expected working life under predicted quality. Enginners prefer this combination for small and medium size engines. Very important part when using this combination is that the bore should be pointed, wider below the exhaust ports.

Cast Iron liner, Cast Iron piston
This is a little bit difficultier operation then the last one because of the brittle nature of thin walled cast iron turnings. The liner requires care and a bit of prior experince in workholding.
In this process, the cylinder is roughed out, then the bore is finished, but not honed. It is next packed with case hardening compound using a bolt and two large washers to cover the ends. It is not "case hardened" as such, and is significantly softer, but the results are worthwhile. This combination doesn’t give any specific advantage in regard to previous combination.

Steel liner, Steel piston
Both components must be hardened, with piston tempered to 10 Rockwell c points lower than liner to minimize gailing. Higher oil usage is preffered for this combination. Tolerances are very small.

Steel liner, Aluminium piston with Cast Iron ring(s)
This combination has a highest priority. Requires experencied workers for making this combination possible for combination in engine. Errors are not allowed. Ringed piston doesn’t need honing.
best suited for larger engines. If its created with precision and care, the combination will produce an excellent, long lasting engine