.

If you get a copy of American Machinist Handbook the 6th edition there is a railroad section which pages gives drawings.. and clearances for most wearing running gear steam locomotive parts gives back shop standards , roundhouse standards and worn out. I believe these were PRR standards . Very easy to use. the very common 7th edition does not have those standards .

Just as a note with my recent conversations with a engineer at Dura-Bar one of the big suppliers of cast iron bars He did not recommend using Ductile Iron for piston Rings . BLW standard was class 30 grey iron, He states that the ductile iron which has spherical graphite instead of the grey iron flake graphite is not suitable for most piston ring material[ductile only used for Hydraulic piston rings running in oil] I do know ductile has been used in locomotives but seem BLW practice of using grey iron is the better .

" I do know ductile has been used in locomotives but seem BLW practice of using grey iron is the better ."

Well, ductile cast iron only became widely available in the 1960's about the time that BLW went OOS / Belly Up / Kaput...

So if steam locomotives had survived as a viable product into the 2020's BLW might well have upgraded to ductile cast iron versus "gray iron" as their "standard" for piston rings.

I suspect the "surface properties" of the piston ring / cylinder bore interface is much more important that the "bendability" of the piston ring metal.

Just my opinion, Kevin.

I think it is more the wear properties than the flexibility that make a difference for our purposes. Plain grey cast is the better way to go. We tried the AD rings as well and found they had too much tension built in and really hard to install.

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Prior to the use of ductile iron, and going back to the early 20th century, something called malleable iron was used. In agricultural, construction, industrial, and rail equipment, malleable was used in certain applications where a durable metal was required in higher stress areas, and where grainier gray iron would not stand up.
There are many recipes for cast metals, depending on the job for which it is intended. Like great-gramma's recipe book, ingredients, and heating temperatures and heating times are critical for the desired result.
For piston rings, it is probably best to research the metal recipes used by builders and railways back in the day. Although there are certainly some new-age metal recipes that might be suitable, one has to acknowledge that locomotives successfully ran many tens of thousands of miles with the piston rings of the day.
As Mr. Anderson notes above, one does not want piston rings made from a material that will aggressively wear the cylinder liners.

Do not use ductile Iron for Shoes and Wedges it galls and wears at a high rate . Does not seem to have good sliding properties . I as know of it being used on some locomotives. Bronze or grey iron should be used

Is there a way to flag a topic as "Best of RYPN"?

Because this one deserves it.

There is a good reference regarding piston rings to be found in the .........

Engineers Hand Book, American Hammered Piston Rings,
Third Edition, 1935

Take care,

Dave

The carbon in grey iron takes the shape of graphite flakes, which as we all know is an excellent lubricant. The reaction that creates ductile iron converts the graphite flakes to nodules of carbon which does not have such lubricating properties. The graphite flakes are in fact what makes grey iron so brittle, each flake being a tiny fracture plane. converting the flakes into nodules is what gives ductile iron its strength.

Many of the replies regarding materials used seem to only mention locomotives, and the time frames in which they became obsolete. Obviously there are some operations that still run them (some in heavy operation, ie ex D&RGW roads) and may be a good contact. The other thing is that a number of Great Lakes ships were still running reciprocating steam engines into the mid 1990s, and even early 2000s in a few cases. One ship made it until 2013 running a Skinner and the Badger still runs with her original Skinners. What were these engines using in later years? Who was making them?

For any of you interested in taking a deep dive into the subject, the Advanced Steam Traction Trust in the UK published a series of technical papers by Argentinian engineer LD Porta. Volume 1 is a compilation of papers on tribology and lubrication, which includes a section on piston rings. It’s available for purchase here:

https://www.advanced-steam.org/books-fo ... -volume-1/

Porta spent a lot of time studying internal combustion engine piston ring design which was much more advanced than steam practice. He strove to minimize wear and minimize steam leakage, and claims to have achieved records for both these with the Mitsubishi built 2-10-2’s he modified on the Rio Turbio railway in Argentina in the early 1960’s.

Ideally the bore out of round/taper should be less than .001" per inch of diameter. A minimum clearance of .001" per inch of diameter from the minimum diameter of bore that can be found may work if the rod run-out is less than .005" vertical and horizontal. Ring stresses at piston speeds above 500 ft/min increase greatly from .002" per inch of diameter total clearance and are avoided in stationary practice, however, may be necessary to accomplish free movement of the piston when the locomotive is in curves, going through track irregularities, or reversing. Consult appropriate manufacturer or railroad practices. Chamfered outer ring edges will minimize scraping oil off. Ring grooves should be trued - side clearance according to width. Manually brazing is ideal - Oxweld 25M interchanges to EWSAB All-State Low Fuming Bronze FC. Thermal sprayed aluminum bronze or Naval brass works well but typically has less mechanical bond strength. Both are subject to porosity from off-gassing trapped oil. VLC can provide rings from Durabar G2/ ASTM A48 Class 40.

Matt Janssen
Vapor Locomotive Company
mjanssen@vaporlocomotive.com

P.S. Where were the I-R compressors?

While thinner rings contour to cylinder irregularities better than thicker ones, my experience is that steam rings can get too thin to resist mechanical shock from priming, loss of lubrication, and stresses from deflection outward while passing over valve ports. Also, if a ring is too thin you can't chamfer it to reduce port clipping and oil scrapping. Porta was trying to design to accommodate running down to a very irregular cylinder and still have good sealing. I think it is better to maintain reasonable tolerances. More rings can be an improvement if you have the rider band area to support the piston as it reduces the pressure differential across each ring increasing its sealing effectiveness and service life.

While hammered piston rings which have constant tension throughout their circumference are no longer made, rings for diesel ship engines are CNC cut to shape. There are also a number of end cut innovations from stationary compressors which greatly reduce pressure losses accross worn rings.

Cook Compression was still making sectional duplex rings for the HP pistons on the S.S. Badger a few years ago. My company is supporting a number of stationary engines in industrial service and these plain gray iron rings are sourced from OEM and aftermarket manufacturers who supply the process compressor market. A number of locomotive groups are making sectional duplex rings on their own as this is outside the scope of contemporary industrial applications. It is my understanding they are CNC'ed. Up until a few years ago my company maintained the Skinner stock of rings for the other Great Lakes vessels in service which dated back decades.