Large scale Cylinders; weldment or cast iron?

[Loco112]

Men I am considering the production of my cylinders for my 3” scale K-36’s. I have the cast gray iron option or the built up welded component method for construction options to consider.

I was thinking about using stainless steel weldments for the cylinder blocks, because of its resistance to corrosion and its insulating qualities. Has anyone seen a stainless steel built up cylinder block before?

By using really tight tolerances on the welded components by using precision methods of cutting them I.E; plasma, laser or water-jet, to precisely cut the plates that wrap around the cylinder and vale tubes, and by lathe cutting registers into these tubes to register into the saddle plate, the components should all create a very tight-fitting assembly and hopefully this will keep warpage to a minimum. I am hoping that this plan would be enough to keep the weldment square and avoid the need for post weld machining, if it can be avoided, maybe it can not. The weldment would have not have a central parting line like traditional cast cylinder blocks use, so these would be welded into one integral assembly that has both right and left side cylinders in one piece, like Frank Allen used on his 5/12-scale Baldwin 4-4-0 he named the “Sonoma”.

I want to build four sets of cylinders for four locomotives, one set is to be a spare for those locomotives (as a “just incase” later on). With 5 sets, and using the traditional cast gray iron method of construction, that would be 10 identical side castings, and that would probably be right at the “break even” cost for creating patterns and tooling to have them all cast and machined vs. the cost of creating the weldment components and having them welded.

Because of my scale and the large size of the K-36 cylinders, these will be fairly large cylinders. The piston dia is 4.5” the stroke is 5.5”, the vales are 2.75” di. The cylinder width as mounted on the loco is 30”. The boiler saddle is for an 18” dia. boiler. I expect that one side of the cylinder block casting would weigh about 80-100# ea.

Because of the limited foundry selection that I have to work with I doubt I could get these cast in Ductile, so I expect that plain old gray iron is my only option for cast material.

I hope we can all have a discussion about the advantages/disadvantages of using the built-up cylinders vs. the traditional cast iron cylinders.

So, can I get some pro’s and “con’s from you guys on the two aforementioned methods, and any other methods you can think of can also be discussed.

The “podium” is free, the “mic” is open!

Thanks, David

[Rob Gardner]

David,

Option 1 - Cast Cylinders

The biggest upside to cast cylinders is the minimal amount of machine work to finish them off once you get them cast. Getting them cast, however, requires a lot of precise pattern making work. You will then need to find a foundry willing to cast them. Further, the machine work involved is some of the most precise machine work involved in building a reciprocating drive steam locomotive. This type of work will be viewed as specialty low production/quantity work and unless you can find a foundry that takes an interest in your project, this may be harder than getting the patterns made and may come with a cost prohibitive price tag. The prototype K36's used two identical Left and Right cylinder halves that would bolt together in the center. As a recomendation, I'm currently studying all of Dave Sclavi's postings on pattern making as I'm interested in doing some wheel patterns for various projects. This might help you in making your decision.

Option 2 - Fabricated Cylinders

For one-off type locomotives, this is a very attractive route to take. I'm not a metalurgist, but I don't know of too many well known live steam locomotive builders who have fabricated their cylinders out of stainless steel. The addtional cost involved with stainless probably doesn't yield that much in return to make it cost effective. Personally, I'm planning on fabricating the cylinders for my 1.6" scale C&O Greenbrier (4-8-4) because I want to get them to match the prototype as closely as possible. I plan to use basic mild steel with pressed in cast iron liners.

When it comes to cylinder liners, take some time and research what sizes of cast iron automotive cylinder liners are availabe on the market before resorting to hogging them out of solid material. I know of more than one builder that found cylinder liner stock material that comes made to preengineered ID's and OD's. Just make sure your cylinder and piston chambers are premachined to the corresponding tolerances. You may only need to layout and machine your ports into the liners and they're pretty much ready press in. You're dead on about controlling the distortion in the welding process and then properly stress relieving the weldment.

In the end, for any amount of money anything can be built. Each builder, though, must consider the finances available and compare the real costs associated with each option. Personally, I'd love to say I was capable of making the necessary patterns and cores to produce a museum quality one-piece piston valve cylinder assembly, but I think that's a little less attainable for me than fabricating the equivalent.

Hope this helps.

Rob Gardner

[ALCOSTEAM]

Rob makes excellent points.

Adding to that I would make the suggestion of looking into having lost foam patterns made for the cylinders. It makes the foundry process so much easier and you get a superb near net shape casting with little or no draft normally associated with standard type patterns. I really think you could even make your own foam molding pattern as easy or easier than conventional patterns.
My thought is two foam molds, front and back half of a cylinder side, to be glued together after they are molded and then coated in refractory in preparation to casting. The best thing about the lost foam process is you have no cores, the foam piece is exactly what you end up with.

tim

[Rob Gardner]

Tim,

Any resources out there on the web to educate us on the process. I am intrigued by this technology. What is the best way to cut and form the foam material? Can it be machined or cut and fabricated piece by piece to get the desired finished product?

From what you are saying, then it stands to reason that a one-piece cylinder set could be cast with one complete front and back foam pattern, right?

Explain again in a little more detail how the passageways would be cast without the use of cores?

BTW, how's the 12" Greenbrier coming along?

Thanks in advance,

Rob Gardner

[pat1027]

Dig up the July/August 2003 issue of Live Steam. It has an article on a beautiful New York Central Niagara built by Fred Bouffard. In the article there are a few photos of one method of fabricating cylinders. I've run my dad's Pacific and the late John Pugh's Hudson (two great locomotive to run) which both used fabricated cylinders with thinner end plates and tube passages rather than porting through the end plates.

[Dick_Morris]

Here is a good page on casting with the basics on lost foam - http://www.ray-vin.com/frtech.htm and another on lost foam http://www.buildyouridea.com/foundry/lo ... howto.html.

My understanding of commercial operations is that they blow styrene beads into a metal mold and inject steam to make the beads expand. I used to have a good URL for a place that offered decoy molds and styrene beads, but I can't find it.

I have an unfinished set of fabricated cylinders for my S-160 Consolidation which has been a bit forlorn for several years. Construction was fairly straight-forward after I got my mind around how to make them. I probably would have bought cylinder castings, but nothing available had an anything close to the right appearance.

Mine are one piece with the line of bolt holes in the simulated bolting flanges drilled to size before they were welded into place.

I can email copies of a couple of articles that gave me inspiration.

On liners - I found that there were two main suppliers, mine says it came from Ohio Piston and Pin Co. The other has a name something like L.A. Liner or L.A. Sleeve. On mine, the O.D. is finish machined, but you have to machine the I.D. after it's pressed in. My source was a shop that rebuilt motorcycle engines.

Several people here are fans of using large bronze bushings for liners and I've considered going that way to avoid having to machinine the liner and to prevent corrosion.

[Dick_Morris]

I found a photo of my cylinder block. To the left is the angle plate on which it's mounted. I posted the same photo several years ago, but it doesn't look any different today.

[Rob Gardner]

Dick,

Thanks for the photo of your cylinder block as well as the info on the lost foam process.

Regarding your passageways, were they built up from individual pieces to make each between the cylinder and piston? Do your ports in the valve chamber line up vertically with the ports for the steam inlet/exhaust to the piston chamber or are they offset some amount?

Rob Gardner

[SteveM]

take a look at Jan-Eric Nystrom's cyliders at:

http://www.sci.fi/~animato/steam/460/460o.html

Here's one of the pics showing the parts before assembly:



Steve

[Fender]

The best thing about the lost foam process is you have no cores, the foam piece is exactly what you end up with.

tim

In general I agree with this statement, although I believe it will be necessary to use conventional sand cores for the steam passages. I am in the process of designing a foam mold for my cylinders, and plan to use sand cores for the exhaust steam passages, as well as the passages between the valves and cylinders. Basically the mold will be built up from pieces of foam cut on the bandsaw to the proper shape, and glued together with rubber cement. The refractory coating is important, otherwise the mold may collapse, letting loose sand into the casting. Also the casting is very rough if you don't use the coating. I know because I've experienced these problems.

[Greg_Lewis]

A couple of other thoughts:

1. For built-up cylinders, consider furnace brazing. No weld distortion that way.

2. For cast, be sure to contact the foundry you plan to use BEFORE making the patterns. They may have ideas that would save you time or money, and may also have specific requirements about the nature of the patterns.

A foundry you might talk to is Sunset Foundry in Valley Springs, CA. They have done other live steam stuff and will work with you.

[Bill Shields]

Dan:

I have a friend in Germany that works for a company that uses lost foam for all sorts of complex castings...including internal passages...

Things like intake manifolds and transmission housings for automobiles...all the foam patterns are made automagically, cores and all...and they get away with it....of course they are working in aluminum, not iron, if that makes any difference.

If you need some pointers, Karl's English is quite good and he would be happy to assist.