cam shafts
The crankshaft, sometimes abbreviated to crank, is the part of an engine that translates reciprocating linear piston motion into rotation. To convert the reciprocating motion into rotation, the crankshaft has "crank throws" or "crankpins", additional bearing surfaces whose axis is offset from that of the crank, to which the "big ends" of the connecting rods from each cylinder attach.
It typically connects to a flywheel to reduce the pulsation characteristic of the four-stroke cycle, and sometimes a torsional or vibrational damper at the opposite end, to reduce the torsional vibrations often caused along the length of the crankshaft by the cylinders farthest from the output end acting on the torsional elasticity of the metal.
Types of crank shaft:
1. Casting
2. Forging
3. Billet machined
Cast Cranks:
These are around for a long time and are found In a lot of engines and in both petrol and diesels.
As the name suggests these are cast and made from Malleable Iron. The shape being defined by a sand mould as with many other engine parts.
These are pretty cheap to make and hold up fairly well too so they are a common choice for manufacturers.
A sand mould is made comprising of a top and bottom half, a pattern is made in wood or other material and this forms the required shape the mould halves contain once they are brought together. The molten metal flows into this mould relying on gravity alone.
Both flat plane (single plane) and cross plane cranks can be made this way fairly easily.
A flat plane crank is one where the journals are 180 degrees apart common in all in-line four engines.
Therefore only two mould halves are needed to make them as the pattern can be withdrawn from the sand mould without locking. This leads to fairly quick production times.
Forging:
These are a more robust crank than a cast crank for a few reasons.
They are more commonly found in higher stressed engines and come standard in some 16v engines and almost all of the 1.8T engines. I do believe they feature in the new fsi engines too, although I have not yet got the pleasure of getting my hands on one>yet.
A forge crank is made in a totally different way to a cast one.
A set of dies are machined to the approximate shape of the crankshaft as below.
The dies are pressed together until the limit stops on the dies come into contact, once this happens the blank has been completely pressed and any excess is squeezed out the gap between the dies. It is this excess metal, or flash that makes a forged crank very easy to recognise. This flash is quite thick, sometimes as much as 10mm, as a result it has to be ground off before any finish machining can be done. This so called part line then ends up being quite wide and can be recognised instantly over a cast cranks faint part line
Billet Cranks:
Billet cranks are the best type of crank you can have in your engine if you want to get the most from it.
They start off again as a very high grade steel containing all the correct alloys needed to meet the demands. 4340 steel is normally used which contains nickel, chromium, aluminium, and molybdenum amongst other elements.
The Steel blank is then forged to align the grain and compact all the molecules closer together as in the case of the forged crank.
The dense blank is then ready for machining.
Here you can see a billet crank in various stages of production, it is from a Ferrari
videos:
http://www.youtube.com/watch?v=C7rXuaJMhOc
http://www.clubgti.com/forum/showthread.php?t=215166
It typically connects to a flywheel to reduce the pulsation characteristic of the four-stroke cycle, and sometimes a torsional or vibrational damper at the opposite end, to reduce the torsional vibrations often caused along the length of the crankshaft by the cylinders farthest from the output end acting on the torsional elasticity of the metal.
Types of crank shaft:
1. Casting
2. Forging
3. Billet machined
Cast Cranks:
These are around for a long time and are found In a lot of engines and in both petrol and diesels.
As the name suggests these are cast and made from Malleable Iron. The shape being defined by a sand mould as with many other engine parts.
These are pretty cheap to make and hold up fairly well too so they are a common choice for manufacturers.
A sand mould is made comprising of a top and bottom half, a pattern is made in wood or other material and this forms the required shape the mould halves contain once they are brought together. The molten metal flows into this mould relying on gravity alone.
Both flat plane (single plane) and cross plane cranks can be made this way fairly easily.
A flat plane crank is one where the journals are 180 degrees apart common in all in-line four engines.
Therefore only two mould halves are needed to make them as the pattern can be withdrawn from the sand mould without locking. This leads to fairly quick production times.
Forging:
These are a more robust crank than a cast crank for a few reasons.
They are more commonly found in higher stressed engines and come standard in some 16v engines and almost all of the 1.8T engines. I do believe they feature in the new fsi engines too, although I have not yet got the pleasure of getting my hands on one>yet.
A forge crank is made in a totally different way to a cast one.
A set of dies are machined to the approximate shape of the crankshaft as below.
Billet Cranks:
Billet cranks are the best type of crank you can have in your engine if you want to get the most from it.
They start off again as a very high grade steel containing all the correct alloys needed to meet the demands. 4340 steel is normally used which contains nickel, chromium, aluminium, and molybdenum amongst other elements.
The Steel blank is then forged to align the grain and compact all the molecules closer together as in the case of the forged crank.
The dense blank is then ready for machining.
http://www.youtube.com/watch?v=C7rXuaJMhOc
http://www.clubgti.com/forum/showthread.php?t=215166
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