tailshaft wear down

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silidiri
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tailshaft wear down

Post by silidiri »

During the construction of a ship the tailshaft weardown was measured by poker gauge as TOP: 57.3 and Bottom :56.5.

Three years later during a bottom in-water survey os same ship the the tailshaft weardown was measured again by poker gauge by a diver as TOP: 83.0 and Bottom :82.4.

I would appreciate if someone out ther could explain above mentioned situation. Thank you in advance for your attention.
Big Pete
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Re: tailshaft wear down

Post by Big Pete »

The total of the top and bottom readings should stay constant. (There is no wear of the shaft at the point readings are taken)
In water reading total 165.4 original total 113.8 difference 51.6 or 25.8 per reading.

The difference between top & bottom readings should change as the stern tube bearing wears down.
Original wear down readings show the shaft centreline 0.8 below the centreline of the stern tube.
The in water readings show the shaft 0.6 below the CL of the stern tube.
i.e the stern tube bearing is being built up, not worn down!!!

One or both sets of readings are obviously wrong, and the only way to resolve this is to take another set of readings.

Possible explanations: -

1) Different Poker gauge used from original.

2) Poker gauge damaged

3) Poker gauge not fully screwed home in pocket before measurements taken.
(check length of screw thread on body of gauge, if it is 25.8 the gauges weren't screwed into the socket at all!)

4) Seating surface for the body of the gauge, (under the sealing plug) damaged and higher than it was originally unlikely to account for such a large discrepancy.

5) The poker gauge was put in the wrong hole.

We will wait to hear what you find, good luck.

B.P.
It is always better to ask a stupid question than to do a stupid thing.
silidiri
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Re: tailshaft wear down

Post by silidiri »

during the bottom in water survey the readings were taken through the aft most chamber marked I of liner.

Diver said that access hole of rope guard was not allowing him to put the poker gauge vertically to the chamber I, so he had to cut it slightly.

thanks for your attention.
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JK
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Re: tailshaft wear down

Post by JK »

He cut what?
Big Pete
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Re: tailshaft wear down

Post by Big Pete »

I think JK has asked the crucial question here, if he cut an inch of the end of the poker gauge, all is clear.
BP
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The Dieselduck
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Re: tailshaft wear down

Post by The Dieselduck »

Oh, that one made me chuckle. That's a good one, cutting the poker gauge. Divers were never known to be rocket scientists that's fer sure. It would certainly explain the discrepancy.
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Re: tailshaft wear down

Post by Pacific Barbarian »

I was just gonna say! :lol:
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