From: Mil-Veh Co. (milveh@sbcglobal.net)
Date: Mon Apr 25 2005 - 14:13:13 PDT
Amazing the talent you find on this chat net.
I'm pretty sure we could crew that gun boat or almost
anything, from tanks to bombers with the talent we
find right here.
--- Fred Martin <mung@in-touch.net> wrote:
> As a former tender sailor....machinery repairman
> (machinist) I've had
> some experience machining the thrust bearing
> surfaces...on a tincan
> about 3' diameter....pretty good sized lathe
> required and a horizontal
> boring mill to bore and cheek and oil groove the
> spring bearings that
> support the shaft as it goes back thru the shaft
> alley. The thrust
> bearings were segmented and there were several of
> them fitted around the
> thrust surface of the shaft. Also the bearings had
> to be hand scraped to
> fit the shaft with Prussian bluing and hand
> scrapers. Would also need
> molders and pattern makers to make up the molds for
> the bearings and
> pouring them and plenty of high speed babbit. If
> you can picture a
> destroyer with it's wake behind it pushing the ship
> forward...it puts a
> lot of push against the propellor shaft and it
> requires a lot of bearing
> surface to handle it....and you can't forget to cut
> in the lube oil to
> it as in one case I'm referring to. They court
> martialed the black gang
> that forgot. Had to cut hatches and doorways just to
> get it out and over
> on the tender. Took pictures of it after every
> move....even me as I
> machined it and afterward when it was done. Fred
> Martin USS Arcadia
> and USS Shenandoah....tenders.
>
> Mil-Veh Co. wrote:
>
> >I believe the shafts are considered rebuilt when
> they
> >are cleaned, checked for true and for metal
> fatigue,
> >then balanced and the bearing surfaces are turned.
> >Sometimes they are sprayed with molten metal on the
> >bearing surface and then turned. No small feat on
> a
> >1000-2000+ lb. shaft, but its been 30 years since I
> >had a class in that, so they might do a lot more
> >now...I dunno.
> >
> >Ship shafts (say that 10 times real fast) have one
> >problem area where the shaft passes thru the hull.
> >This is typically where you might find a thrust
> block.
> > The thrust area is usually controlled by some
> modern
> >version of an old "Kingsbury" type bearing with
> >collars holders that are rigid mounted to the hull
> and
> >this is what gets rebuilt in port..expensive.
> >
> >On older vessels this can also be a thrust bearing
> in
> >conjunction with an "iron wood" bushing type
> bearing
> >which doubles as a seal, cheaper.
> >
> >In the more modern version there is several
> composite
> >seals and a soft metal bushing which is designed to
> >wear out at the same rate as the thrust bearings,
> >which is ok because its saving the shaft bearing
> >surface which is harder and expensive to fix.
> >
> >If the drive shaft is pretty long, say 1' wide
> shaft
> >that is more than 10' long, then that would require
> an
> >additional support bearing to handle the vibration,
> >torque and keep the shaft from warping at rest,
> >another additional cost too.
> >
> >Those support bearing points almost never wear out
> and
> >long as they are greased...thrust bearings wear out
> oh
> >around 6000-10,000 hours on avearge depending on
> the
> >type of vessel and power. On the real large ships
> the
> >shafts must be rotated even while in port to keep
> them
> >from warping.
> >
> >I'll bet you can get the props and shafts cleaned,
> >balanced, trued and surfaced for well under
> 25k...IF
> >you are at the right ship yard.
> >
> >So who wants to sign up for the black gang (engine
> >room for you landlubbers)?
> >
> >....Bridge to Mr. Scott, we need MORE power, now
> >Scotty! Aye Capt., I'm given er all she's got and
> if
> >I give er any more she'll blow!
> >
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> >
> >
> >
>
>
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>
This archive was generated by hypermail 2.1.4 : Sat May 07 2005 - 20:42:56 PDT