oldtacomamarine
Registered: March 26, 2008
Posts: 10
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| June 11, 2008 at 01:49 PM |
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Reply with quote | #1 |
We posted a blog entry describing how the NOAA boat John N Cobb prematurely ended its research season with a broken crankshaft here.
We don't know yet what caused the break, but we want to hear your informed speculation. Comment to this thread with possible reasons that the crankshaft broke.
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oceansailor
Registered: Feb 23, 2008
Posts: 5
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| June 14, 2008 at 06:13 PM |
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Reply with quote | #2 |
RE: Crankshaft failure Fairbanks Morse 31A 81/2 X 12 8Cylinder.
I have never seen or heard of a fairbanks Morse Crankshaft Failure, EMD-yes,
Cummings -yes , dETROIT dIESEL yes. until now, its sad that this happened to a Heavy Duty Slo-Speed Engine.
My suggestions not speculation:
1.-Do not attempt repairs until the actual cause is found, its possible that a multiple cause could be responsible, a through investigation is reguired to separate the cause from the result.It will of course be necessary to repair both the cause and the result.Start the teardown, take notes, this is serious and expensive.
2.-Start looking for a crankshaft, Call FMC-parts, they recently told me that
there were 31A's at a texas Power Generating Co. that were taken out of service because new equipment has taken their place, the company will sell parts and may have new parts plus used parts available.
Locate the large former Canadian Icebreaker, that is now a museum ship, this
ship will be dry berthed and no longer needs its' spare parts, it had 31A's for generators and most likely has a F/M for a main propulsion, they will most likely trade parts for "a donation".
3.-What were the crank web deflection readings, were they in spec.
4.-What were the main bearings and rod bearings mike. readings , were they in spec.?
5.-What were the crank journal and con rod journal mike .readings , were they in spec.?
6.Examine #1 cyl for a possible hydraulic lock, cracked head/liner, broken
piston, bent rod , evidence of overheating, loose nuts on the cross head or
rod flange, and rod and main bearings.
7.-Check the oil for evidence of contamination: water, metal, fuel dilution ect.Send a sample for analysis, and compare to the last sample. Is the oil being used correct for the engine? IE: 20/40 high detergent ?
8.- Check the vibration dampers, there may be more than one on an 8-cyl.
crank, check the measurements of the moveable counterweights pins and
bushings they must be within spec to function properly.
9.Check the injection timing and rack settings for compliance . check firing
pressures and exhaust temp., last recorded.
10. Check scavenging pump drive, and bearings for excressive lost motion.
11.-Check spring drive on the front of crank for alinement with water pumps
and lube oil pumps, check for any binding and bad bearings.
12.-Compare all measurements with those of the last overhaul for variances,
compare the running temp. and pressure recordings, rack settings with the last full power trial (after the last overhaul or the most recent for variances.
13.-the block will probably have to be elevated or tilted to port or stbd., or
possibly the oil pan dropped to remove the crank, check the main bearing alinement readings and check the spec. for compliance at this time.
14.-Im sure Ive forgotten something, If anything comes up after my brain reboots, I'll post it.EX:how were the last piston to head clearances ?
Good Luck, BLH meant Baldwin-Lima Hamilton, but it really meant "Bring Lots of Help".
john jdkopke@cablespeed or 443-854-4311.
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oceansailor
Registered: Feb 23, 2008
Posts: 5
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| June 14, 2008 at 06:48 PM |
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Reply with quote | #3 |
More comments account of previous brain clutch slipping.
!.-Because the 31A has a cast iron block, I dont think there could be a crankshaft alinement problem, unless there was major overheating.
So I think there is a very high probablity of an effective repair , with the engine continuing its career for at least another two generations.
2.-The engine build date on my engine from Beloit Wisc. was found on the control side of the baseplate almost directly below the engine controls.
My 31A has a date of 1957 , not even close to WW-2.
3.-This is not exactly an example of one of the worst "Caterostrophic Failure" 4.-Check #1 cyl. head for missing parts on the underside, what were the head to piston clearances, were the within spec ?
Ive seen much worse when a rod breakes and then proceeds to destroy the engine block, particularly a fabricated block by punching holes and distorting structural portions which cannot be economically straightned and realined, of course when this happens to a cast iron block it may also destroy the block, but most non structural holes can be repaired by welding.
But then again Ive seen engines thet were removed with a shovel (not Pretty).
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