Steam & Excursion > Break-in runs vs. Shake-down runs.

When newly machined bearing surfaces ( NOT rolling-element bearings) are to be run for the first time, there is a “mutual polishing”
process before the two surfaces are able to maintain a micro-thin, uniform lubricating surface.  

( Plain bearings, when perfectly polished, have the moving piece and the fixed piece running on a micro-thin oil film...
the two parts must never physically make contact while operating ...the oil film must provide complete separation of the bearing elements ...—- the most common plain bearings everybody relies-on are the crankshaft bearings in automotive power plants ...
but, even in rail environments, plain bearings are relied upon for heavy-duty service—-especially in locations where pressing the inner race onto the shaft is not practical..  Rolling element bearings have a predictable life.... measured in thousands hours...
plain bearings have a virtually ‘infinite life’ ,   as long as the lubrication film is not broken or contaminated ... For an interesting comparison, water powered grist mills ( with a Pelton Wheel) often have the lower thrust bearing completely submerged under  water...)..

One of the mandatory fabrication principles is constructing plain bearings is to use two different hardness materials for the mating surfaces, like: Steel axle and bronze ( fixed) bearing surface.  ( At Silvis diesel shop, newly married axle sets ( and rebuilt T/Ms) with babbitt-lined suspension bearings, were run-in... with the angled motor, wheels-high, spinning merrily.   Tom Kelly had temporary 2 drip-oilers for the axle-hub lubrication...account there was no track-induced lateral slamming to lubricte the hubs... they ran the axle-to-the-suspension bearings together for several days, ‘round the clock... before releasing the married motor/wheel-set to be fully functional...)

Getting these two surfaces to become polished together, to a mirror finish, takes many miles of lightly-loaded running.
If over speeded, or over loaded too soon in the wearing-in process.....very hot and galled-ed bearings are a common outcome.
It is during this time, that there’s lots of slow running and inspection stops, common remote reading electronic thermometers make quantifying the bearings’ heat. ( the old upper-limit was ‘“hot enough to fry spit!”)...

Bearing breaks-ins are common for rod brasses, etc

A Navy practice with recentky completed (new or overhauled) operating systems, like ships, was the “the Shake-down “ run.
In the Shake-Down, the complete ship was put through its paces, at, or above its design limits...while observed by all the contributing entities and their representatives... 

Under these conditions, the ships were closely watched for delivered capacities and performance parameters...

So, if it was me, I’d try to get as much light running as I could, BEFORE a full-blown full-throttle workout..
However, “reality rears it’s ugly head”, and the diesels wil be responsible for the successful completion of these outings...

Glory Days ain’t coming back, any time, soon...

Wes 

( 12”-to the Foot, Lionel Big Boy, ( equipped with smaller flanges) with smoke, sound, steam hisses, cab “radio-chatter” and all ...)


to be proofed, yet...



Edited 2 time(s). Last edit at 04/07/19 15:00 by wcamp1472.

After the first rebuild for SP786 the retired SP Mike here in Austin many years ago, I was a volunteer on the rebuild spending many hours working ont he project.
When we did the intial break-in runs, we coupled to a bunch of empty gons from the Georgetown Railroad, a caboose on the rear and initially very slowly started our testing.
Checked bearing temps, brakes, etc.  Then over a matters of going back and forth in the several mile test area, probably about 5-9, we build up speed.
The contractor doing the work did this on a week day and the volunteers showed up on the weekends.
I assume a few bugs were found a addressed.
Then, we were permitted on get on the UP main line and come into downtown Ausin with the assistance of a diesel, which I hear died on the return trip back to the overhaul facility.
The UP rep was amazed as he rode in the cab.
Memories from a very long time ago.
I am sure that Con took lots of pictures also.
Pat
South Austin, TX

Con’s sister just donated 25 carousels of Con’s slides to our Tyler museum.
I have yet to tackle the task of scanning and identifying them.

Shane Murphy
Tyler, Tex.


sptno Wrote:
-------------------------------------------------------
> After the first rebuild for SP786 the retired SP
> Mike here in Austin many years ago, I was a
> volunteer on the rebuild spending many hours
> working ont he project.
> When we did the intial break-in runs, we coupled
> to a bunch of empty gons from the Georgetown
> Railroad, a caboose on the rear and initially very
> slowly started our testing.
> Checked bearing temps, brakes, etc.  Then over a
> matters of going back and forth in the several
> mile test area, probably about 5-9, we build up
> speed.
> The contractor doing the work did this on a week
> day and the volunteers showed up on the weekends.
> I assume a few bugs were found a addressed.
> Then, we were permitted on get on the UP main line
> and come into downtown Ausin with the assistance
> of a diesel, which I hear died on the return trip
> back to the overhaul facility.
> The UP rep was amazed as he rode in the cab.
> Memories from a very long time ago.
> I am sure that Con took lots of pictures also.
> Pat
> South Austin, TX

I really miss Con, he was a great guy with a wealth of information.
That is going to be a hudge task but there are lots of folks who would enjoy seeing them.
Thanks for doing that!
Pat
South Austin, TX

Thanks Wes. I just hope the proper people know this

Posted from iPhone

Another hint that makes life easier: when replacing consumable bearing components, fabricate the parts with much more liberal tolerances than what would’ve been ‘brand-new’ , tight-fit  bearing components.... give the replacement parts a couple of thousand miles more-liberal tolerances —-especially true with crown brasses...  ( remember that when breaking-in, new bearing  parts are going to run-hot for a couple of thousand miles....as tings heat-up, they expand... very quickly, tight tolerances disappear , and the swelling parts clamp-down on each other,  ruining ‘lubricating space’.... brasses wil rapidly overheat and become damaged...
  use very liberal tolerances on axle bearings..)

In fan trip service, there’s way-more tinkering than in the old days ...typical bronze rod bearings last 15,000 to 20,000 miles...
so there’s no need for ‘factory-tight’ tolerances...

Your’re  not recreating Lima, Alco, or Baldwin....so make your life way easier....give them plenty of ‘slop’..

Wes.

Very interesting information. Thanks, Wes. Turns out I'm just beginning to learn about bearings.Thought I knew a lot. Nope. d

Thanks for the information, Wes.

Question for those who know:  do diesel prime movers use plain bearings on the crankshaft mains and rod pins?

Scott Griggs
Louisville, KY

In my experience ... Yes, absolutely.

Remember, it’s the thin film of lube oil that is critical....there should NEVER be metal-to-metal contact in plain bearing uses.... that leads to failed bearings... very quickly.

Also, get to know the ‘happy range’ of temperature rises in plain bearing applications—- all plain bearings have a comfortable temperature rise, while in operation...

Use modern instant-read thermometers, they’re inexpensive and can be vital..

Operating Temps above 175 deg. F., are a red flag indicator ... find out what’s the cause..

W.

Posted from iPhone



Edited 1 time(s). Last edit at 04/08/19 07:24 by wcamp1472.

You wouldn't believe some of the sleeve bearing applications, there's a couple 1500 hp mine hoists in Nevada
where everything from the electric motor to the main drum are running on 7 to 10 inch sleeve bearings. We've
seen a couple applications where the housing was so old it and the bearings were long obsolete having been
in service for 20 plus years. Good care and proper lubcrication ie correct grease/oil and frequency of said
maintenance make a huge difference.

Out

This is a little off topic but some may find it interesting. For a time, I was restoring old water-pumping windmills and, on some of the early ones, like this 1880's IXL, the bearings were maple. The old timers swore that a wooden bearing would outlast babbit or roller bearings!

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