Steam & Excursion > Watching work

On 9/11 I spent the afternoon in a lawn chair watching Ed Dickens get dirty.
4014 was off for a day for a UP Family Days viewing and Ed decided to check on the cylinder piston rod packing.  He said he occasionally pulls them and checks the wear pattern.  These are different from what we had on 1522 so it was interesting to watch.
There are bronze segments in the round piece closest to the cylinder that are spring loaded.  He pulled each segment out, cleaned it up, checked the wear pattern which looked good, took a file and very lightly broke the edges and put them back in with the spring keeper.  When all were done, painted the piston rod with steam oil and  pushed eveything back into the cylinder head and buttoned it up.
Our packing was 2 pieces of a softer metal and a taper that would take up when you tightened to packing gland.

You learn something new every day.

---

Interesting. I can't ever remember Doyle McCormack or Steve Lee EVER pulling the piston rod packing packing during a trip to "inspect and/or clean" it. Can't tell you how many miles/days AFT/SP4449 and UP 844 & 3985 traveled without such "attention".

I'll be interested to see Wes Camp's take on this.



Edited 1 time(s). Last edit at 09/20/24 17:55 by HotWater.

Frisco1522:

Todsy's lesson is on cylinders, piston rods and "sealing schemes"

The softer stuff you referred-to was manufactured by 
US Metallic Packing Co., Staten Island, NY.

The major portion of their business , after steam locos,
had been supplying and supporting the marine industry,
in NY Harbor. They're still in business, I think.

The two spiral cuts, in the circular rings, spaced 180-degrees apart,
allow the soft-metal 'sealing-ring’,
to adjust for central-wear by allowing
the pointed ends of the 2 halves to by-pass each other, as the packing wears;
thus, continuously, tightly contracts on-to the piston rods..  

However, if H.P.steam continues to blow-by the new 'packing', the continuously
blowing steam will erode grooves in the softer-metal, sealing ring --- then,
that set of sealing halves is ruined.  
I've never known of an instance where new piston rods were made, because of
'blowing-packing.  But, hey, I came around 10-years after 99% of steam
was scrapped!

The force that keeps the King Metallic packing clamped tightly ( the spring tension)
to the rod, the tapered, front face of the soft metal sealing elements, ( closest to
the cylinder) has about a 45-degree taper,... that mates to a 45-degree, concave
inner face, of the matching, steel  'cup'.   The two sloping  surfaces  ensure that
the forces acting on the center-bore of the packing, are concentrated onto  the rod.

The whole King packing assembly is kept compressed by a coil spring around
the piston rod. The boiler pressure in the cylinder & piston forces the sealing elements
to more tightly grip the piston rod.... ( Hint: that's an exam question)

Meddling with and taking apart the metalic-packing, and disrupting the finely-polished
sealing surfaces, further exposes the risks of premature rod-sealing failure.
King Metallic packing, if undisturbed --- can last to 60,000 to 80,000, miles -
-- if well protected and kept lubricated .  Most steam mechanics, working with
rod-packing 'systems' are loathe to dusrurb well-seated, piston rod-packing.

The steel spring, the 'cup' and large, square packing gland cover-plate are
slid onto the piston rod, before the large piston 'head' is mounted & secured by its
large-diameter hex-nut.  The only part of the packing assembly that touches
the piston rod, are the two, soft-metal sealing elements.  The two pieces 
are 'mated' at the factory, and should stay mated, for life --- no mix-or-match
berween paired halves.  And NO mix-or-match swapping, between packing sets 
fitted to other piston rods.  The other advantage of the two-piece packing elements,
is the easy renewal, when the original set finally wears, and starts leaking..
after tens, of thousands-of-miles.

It's vital that during lay-up periods, or years of display periods (exposed
to the weather elements) that the piston rods must be kept protected from
rusting due to humidity or rainfall.  

Wise care-takers remove the two soft metal sealing elements,
so that when the exposed piston rod develops a rust-layer, the soft-metal
sealing elements WONT get ruined when the rusted piston rods are moved.

Interestingly, the function of the coil-spring around the piston rod, is to 
keep the assembly slightly compressed at times when engines are 
sitting around, cold. The sealing elements stay in close-contact 
while sitting around, maintaining their fit to the piston rods.

The design of the two, mating, 45-degree faces --- uses steam pressure 
in the cylinders to more-tightly grip the piston-rod, when steam is used 
to power the train.

With new rod-seals ( railroaders call the soft-metal sealing elements:
"rod-packing"j,  no matter how finely-machined the piston rod and 
the sealing elements, the first several miles of operation with "new packing"
will see steam blowing-by the packing and piston-rod.  It takes several mies
of the piston rod and the 2 soft-metal, sealing pieces to 'polish' their respective
running surfaces, and to polish to each-other.  
Once 'seated', they are matched, for life.

The KEY concept is that high steam pressure in the cylinders,
applies strong "clamping" pressure at the 45-degree, new, mating-faces 
of the 'cup' and the two-halves of the packing elements, which are being 
forced to more tightly grip the piston rod, with each stroke. The curved,
by-passing points of the set, are crucial to tighter clamping, and crucial to many 
thousands of miles of tight rod packing!  As the rod-packing wears, it continues 
to seal the piston rod.

Thought question, for the students of steam:
What determines the greatest pressure that can be built-up
in the piston/cylinder assembly ?  What role does high cylinder pressure
play with respect to new rod-packing?

​W.

( That square backing plate, with 4-bolt holes --see 4014, above-- is it's own
    bit of sealing magic.  People have spent a lot of time "barking up the wrong tree",
   in thinking  the only steam-leak could be around the piston-rod. 
   If the ground-joint is the source of the leak,  it's very hard to tell where the 
    leaking steam is coming from!   It could be from around the piston rod,
    or NOT !  New piston rods won't solve leaks at defective, 'ground-joints'.

   You want to be sure that the 'ground-joint' between the square-retainer plate
    and the cylinder casting is not compromised..... uncorrected leaking, there
    could be more extensive, if the steam-cutting is deep enough... 
    
   On some, specialized,  flat surfaces, no gasketing is used, the two mating
   surfaces are precision-finished, and manually lapped-together with
   progressively-fine grades of "lapping compound" until they are both virtually
   flat and mated perfectly, together..  it's crucial when cylinder sleeves and the 
   cast-frame must be identically lapped-laaoed at the face matching the flat rim
    surface of the cylinder head.

     That,  precision, 'ground-joint" [ using "grinding-compounds"] is the seal 
     between the cylinder-heads and the front-face of cylinder casting & also the 
     face-edge of the cylinder "sleeve-insert'" that contains the piston.  
     And, yes, the piston rides inside a renewable cylinder sleeve.  
     There are NO head-gaskets, where 'ground-joints' are used.
     
    The sleeve can be re-bored a couple of times...
    The bottom-half of the sleeve wears more than the top-half, and, if um orrectec,
    will also blow-steam around the front and back faces of the piston...
     "Re-bores" were done in the Roundhouse, about 250,000 miles, and possibly
      two re-bores, before a new sleeve would be pressed-in, and a light-cut taken
        --- for a nearly perfect cylinder sleeve.
     
     A new sleeve, and a tight " press-fit", will distort the new cylinder sleeve's-wall,
     So, a light-cut of the new cylinder wall, once pressed into place, will be bored,
     true, to the specified diameter.  And, 'universal' sectional piston-packing wil
      be applied to the piston's packing-grooves.  

     The 'sectional' piston packing consisted of 2 mating sets of "packing-secrions",
     about 5 or 6 sections of rings --- paired  to off-set their end-gaps--- in one piston
      groove --- so that. steam does not leak through the sectioal-joints.  
       The mating rings in each groove, are pinned together, so that no two ring-gaps
        line-up to form a steam-gap. There are typically three ring-gloves, & 3-pairs
        of packing rings, per piston.  

     The sectional packing was sold as a "one-size, fits-all"  bores.
     However, they were sold in like 3 or 4 'gross'  sizes ... like: 25-inch 
      packing would seal bores 24" to 26", etc.  Often times, bores might 
     vary -- in diameter---by a 1/2" or so, due to wear and rebores --
    and engines could have slightly different, bores, side-to-side.  

    Nowadays, sectional packing is no-longer available -- so, most shops,
    today would use one [brass] ring per groove...  
    You machine a new new ring to fit each piston groove .... a little oversized
     in diameter for the actual bore.  

    Smack the new ring 's edge on the floor, to find its weak pont...
    where it breaks...  [ hopefully in only one place!]   Then, fit the
     ring into the bare cylinder, with the two ends over-lapping..

    You mark one end and cut-off the over-lapping piece.  
     The ring spreads-open, becoming "spring-loaded" against the
     cylinder wall, when the piston is re-installed.... ( remember you made
     the 'ring' a little 'over-sized' for the actual bore of the cylinder --)
    so the new ring fits snugly, into the bore, and can last many thousands of 
    miles; they should last 100,000 miles..

    On large, 'modern' cast-steel frames, the rear cylinder-heads are cast integral,
    with the frame, and only the piston rod needs its own rod-packing.. 
    A simpler proces because it  eliminates a 'ground-joint' for the rear cylinder head).






 



Edited 11 time(s). Last edit at 09/21/24 05:11 by wcamp1472.

Thanks, Wes, learned at lot!

Thanks Wes and Frisco for another fascinating (As Spock used to say) lesson in steam mechanics!

Wes I read 1/2 way through your lesson bur have to bookmark it, and take off to work this morning, I promise to finish reading it this weekend though.

What is the deadline before the exam is handed out to us to take?
😁

Jim Baker
Riverside, CA

1522's was US Metallic like Wes described.  4014 is Paxton-Mitchell which the crew made the segments in the Cheyenne shops from bronze.  Wear pattern looked good.  Checked out, cleaned and piston rod doped with valve oil.  Good to go.

wcamp1472 Wrote:
-------------------------------------------------------
> Frisco1522:
>
> Todsy's lesson is on cylinders, piston rods and
> "sealing schemes"
>
> The softer stuff you referred-to was manufactured
> by 
> US Metallic Packing Co., Staten Island, NY.
>
> The major portion of their business , after steam
> locos,
> had been supplying and supporting the marine
> industry,
> in NY Harbor. They're still in business, I think.
>
> The two spiral cuts, in the circular rings, spaced
> 180-degrees apart,
> allow the soft-metal 'sealing-ring’,
> to adjust for central-wear by allowing
> the pointed ends of the 2 halves to by-pass each
> other, as the packing wears;
> thus, continuously, tightly contracts on-to the
> piston rods..  
>
> However, if H.P.steam continues to blow-by the new
> 'packing', the continuously
> blowing steam will erode grooves in the
> softer-metal, sealing ring --- then,
> that set of sealing halves is ruined.  
> I've never known of an instance where new piston
> rods were made, because of
> 'blowing-packing.  But, hey, I came around
> 10-years after 99% of steam
> was scrapped!
>
> The force that keeps the King Metallic packing
> clamped tightly ( the spring tension)
> to the rod, the tapered, front face of the soft
> metal sealing elements, ( closest to
> the cylinder) has about a 45-degree taper,...
> that mates to a 45-degree, concave
> inner face, of the matching, steel  'cup'.   The
> two sloping  surfaces  ensure that
> the forces acting on the center-bore of the
> packing, are concentrated onto  the rod.
>
> The whole King packing assembly is kept compressed
> by a coil spring around
> the piston rod. The boiler pressure in the
> cylinder & piston forces the sealing elements
> to more tightly grip the piston rod.... ( Hint:
> that's an exam question)
>
> Meddling with and taking apart the
> metalic-packing, and disrupting the
> finely-polished
> sealing surfaces, further exposes the risks of
> premature rod-sealing failure.
> King Metallic packing, if undisturbed --- can last
> to 60,000 to 80,000, miles -
> -- if well protected and kept lubricated .  Most
> steam mechanics, working with
> rod-packing 'systems' are loathe to dusrurb
> well-seated, piston rod-packing.


My point exactly, i.e. if it ain't broke, don't F%&* with it!

Re Jim Baker's question ... about exam date.
September 31...

Some students fell asleep, half-way through.
In old style churches, ushers wandered around with long sticks:
One end had a feather ... for people dozing..
Other end had wooden knob --- for those that were snoring...

I'm glad it made sense.

The correct answer has to do with packing being assisted in the "seating-process",
 with highest possible cylinder pressures, and long duration.
Sustained Cylinder-pressures are dependent on dragging a heavy load
of cars.  A stong throttle only "races" the engine --- like revving a car engine,
with the tranny in Neutral....Or, motorcycle guys revving their 'bikes, 
while stopped for red-lights...

 Light train weights are pointless, and risk prolonged steam blow-by,
which can erode the sealing element, if blow-by is persistent.
Eroded seals must be discarded...

As the saying goes "Opinions are like rectal orifices".  If I made all new segments in my shop and had some down time, I would want to do a quick check to see how they are seating.  I spent a lot of time doublechecking work we had done on 1522 just to "Be Sure".

The oft repeated mantra of pulling big trains just ain't gonna happen with 4014 no matter how hard we wish.  She has her hard working moments on hilly divisons.  BP is constant no matter what, hot fire and while not doing what she was built to do, she does pretty damned good.

I for one am glad it is running.  Its a hell of a PR tool and the crowds are enormous.

I worry more about the smaller engines running on branches with no real knowledge supporting them.  Some day, some chickenshit, ill maintained toy is going to have a disaster and be the last steam engine running. That's who needs all the advice and lectures.

Wcamp's synopsis about Rod Packing in this thread reminded me of WMSR 1309 problem for some reason, something about the rods and packing....maybe...?

Jim Baker
Riverside, CA



Edited 2 time(s). Last edit at 09/21/24 19:41 by RailRat.

No, Jim Baker while it may be the problem with one of them but not the 4014.  I know nothing about the 1309 other than a few opinions, some of which may bear some truth.
The rumor mill in this hobby or "business" runs 24/7/365.
Seems like no one is ever happy any more.

Frisco1522 Wrote:
-------------------------------------------------------
> No, Jim Baker while it may be the problem with one
> of them but not the 4014.  I know nothing about
> the 1309 other than a few opinions, some of which
> may bear some truth.
> The rumor mill in this hobby or "business" runs
> 24/7/365.
> Seems like no one is ever happy any more.

There we go Frisco! I added to my original comment to more accurately describe my thoughts,
Nothing to do with your Exellent original post about Ed checking 4014 rod packing.

Jim Baker
Riverside, CA

Seems to me it was a good time to check things out and  put a list together if you're going to need something while they're down for what, a couple weeks on the boiler wash in Texas, eh? 

Cheers, Dave

Hmmmmm….let me get this right: it’s better to have armchair experts deciding what maintenance is needed on an operational Big Boy—with which they have no actual 4-8-8-4 experience—vs. the man in the saddle who (with his crack steam team) is successfully getting this iron horse over the road all over the country, and who felt it was an appropriate maintenance action….hmmmm, I wonder who to believe? Uh-huh…got it.

Pictures that might be helpful to some folks understanding Wes's description of the King Metallic piston rod seal:

1. The assembly
2. The "soft metal" sealing element.  Note the spiral cuts that separate the ring into 2 pieces.  In the first picture, this part is labeled #6, the King Packing Ring.

I looked these up in the 1938 Locomotive Cyclopedia.

---

---

Worked well for our 1926 1522.  Our piston rods had a good finish and were round and diameter constant throughout the length.

I thought the standard rod packing on the UP was Paxton-Mitchel. That is the system that 844 and 3985 had.

4014 IS Paxton-Mitchell equipped.  Not sure why King keeps coming up.