How do you take crankcase deflection?
How do you take crankcase deflection?
The amount of deflection of a crankshaft may be determined by the use of a straight gauge which is simple to apply. The straight gauge is merely a dial reading inside micrometer used to measure the variation in the distance between adjacent crank webs when the engine shaft is rotated by barring the engine over.
How does a deflection gauge work?
Deflections are measured by detecting the misalignment of main bearings. Both horizontal and vertical misalignment is checked. In the past, a dial gauge was used for this process. Using a crankshaft deflection indicator such as the modern type Prisma DI-5 deflection indicator requires only a few minutes of your time.
When should I take crankshaft deflection?
Conditions under which crankshaft deflection to be taken:
- Ship should be afloat (i.e. not in dry dock)
- Calm weather.
- Comparison should be made under same temperature and loaded condition.
Why is crankshaft deflection not taken at BDC?
Crankshaft Deflection Measurement Procedure The crank webs are punch marked to ensure that the readings are taken in the same place each time. The latter two measurements are required as it is not possible to measure at BDC due to the Con rod. > The measurements are always taken starting at the same starting point.
How do you tell if a crank needs to be turned?
Generally speaking, if the crank shows less than 0.001-inch runout, it’s probably fine. If the crank shows more than 0.001-inch runout, it needs to be either straightened or replaced. Crank straightening is a precision task that should only be handled by a skilled specialist.
What causes crankshaft damage?
INSTALLATION FAULTS AND WEAR ARE THE MOST COMMON CAUSES OF DAMAGE TO THE CRANKSHAFT AND CRANKSHAFT BEARINGS. Softening of the bearing journals due to previous bearing damage or improper modification work, e.g. excessive regrinding. Incorrect tightening torques and/or old bearing cap screws were used.
What is crankshaft deflection?
Crankshaft deflection occurs over time, during the repeated and continuous use of the crankshaft. It is a process that occurs in the background as the engine operates and, though it can’t be seen without a detection instrument, it causes significant damage to the mechanism.
How do you measure the deflection of a crankshaft?
As should be obvious from the image a dial gauge is placed between the crank-webs to discover the distance between them. If the deflection is measured after a specific time interval, it is must that it should be taken at the exact same point otherwise the reading won’t give a genuine reflection about the level of deflection.
Why does my crankshaft position gauge go up and down?
Therefore as the engine runs, due to some friction between the bearings and crank pin, the bearings wear out and maintain imbalance across the length of the crankshaft. When this occurs, you experience high readings which will indicate the actual position ( either closed or open).
How does a crankshaft work?
As you may know, the engine crankshaft comprises of the Journal, crank pin, and crank webs; these are all supported by the main bearings via the Journals. Therefore as the engine runs, due to some friction between the bearings and crank pin, the bearings wear out and maintain imbalance across the length of the crankshaft.
Why is deflection measured at the exact same point?
If the deflection is measured after a specific time interval, it is must that it should be taken at the exact same point otherwise the reading won’t give a genuine reflection about the level of deflection. Typically a center punch is utilized to make markings with the goal that each time the deflection is taken at a similar point.
