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usual problem with a crankshaft

Crankshafts are under stress and vibration by their very nature of design. Some crankshafts crack more frequently than others.
The most common cracks appear in the crankshafts out of the oil holes and in the radius areas. Some minor cracks can be removed
when grinding to an under-size.
A crankshaft is a shaft driven by a crank mechanism, consisting of a series of cranks and crankpins to which the connecting rods of
an engine are attached. It is a mechanical part able to perform a conversion between reciprocating motion and rotational motion.
In a reciprocating engine, it translates reciprocating motion of the piston into rotational motion, whereas in a reciprocating
compressor, it converts the rotational motion into reciprocating motion. In order to do the conversion between two motions,
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.
A broken crankshaft is not a common occurrence. Cranks can break due to a casting or forging flaw but this is very rare.
Today’s quality control systems for forging and machining crankshafts are state of the art. Very seldom do you here of
a new crankshaft breaking “out of the box”.
Cracked
Picked Up
Seized
Flogged
Bent
Broken
Worn Out
Crankshafts are under stress and vibration by their very nature of design. Some crankshafts crack more frequently than others.
The most common cracks appear in the crankshafts out of the oil holes and in the radius areas. Some minor cracks can be removed
when grinding to an under-size. Shafts that are prone to cracking should be crack tested before and after grinding. Some causes of
cracks can be a faulty harmonic balancer, revving the engine above manufacturer specifications or out of balance shaft and associated
components. As a common rule all diesel shafts should be crack-tested at time of engine overhaul.
Crankshafts will crack in the radius area as a result of incorrect grinding. If the correct radius is reduced or the grinder produces
a step edge this crank will be more likely to crack and become unserviceable than one ground correctly. Great care has to be taken to
ensure no scratches or marks are evident in the radius area.
Oil holes have to be re-chamfered after grinding and all burrs removed. Caution has to be taken to retain the correct size and chamfer.
This area is very thin due to the angle of the oil drilling and will crack if not reshaped correctly after grinding.
The reduction of vibration by balancing engine components will reduce the likelihood of crankshaft cracks. Shot peening and rolling of
the radius area will also strengthen these areas against increased stress produced in high performance diesel's and racing engines.
The Best Way To Test Crankshaft Cracks In Different Ways, Simple To Understand
Regardless of which crank you choose to use during an engine reconditioning or crankshaft crack testing, it is obvious to take the time
to check and inspect it in detail. If you are checking a previously used crankshaft, it is also necessary to check its crack testing.
If you inspect it before installing, it will clarify its condition and allows to avoid problems.
Analyzing Crankshaft Cracks
Though many cracks may be clearly seen once parts have been disassembled and cleaned, other cracks are nearly invisible or may only
be seen under special circumstances such as porosity leaks in heads and blocks.) Some cracks are also there which are totally invisible,
and normally these kinds of cracks are inside casting.
It is suggested that never assume crankshaft is okay just because you can’t see any visible cracks. Always assume there may be cracks,
then you will be able to figure out the crankshaft cracks.
How To Do Crankshaft Crack Testing?
Every work or process have some steps involved through its completion. Same is the case with crankshaft crack testing. In the first and
the foremost step, especially when you are dealing with an old or used crankshaft, clean the crank thoroughly.
It is preferred to wash it in a hot tank or with a jet wash. Once it is done, check it for cracks. The crack testing is preferably
perfectly done on a magnetic particle inspection station which is known as magnaflux machine. By doing this, the crack is mounted
horizontally on the inspection bench and passes through a large diameter circular magnet and is inspected with an ultraviolet black
light which is visible as whitish lines.

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Every care has been taken in writing this information and procedures, but no responsibility can be excepted for errors, omissions or
misuse of this information and procedures. The information available on this site is for your instruction only and cannot be copied for sale, hope you like our products, crankshaft and connecting rod ...


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