I was at CSRM the other day, which has a breathtaking collection of 19th century steam, typically American (4-4-0) type. I was looking at them with a docent, and we were wondering how steam gets from the boiler into the steam chest. There didn't appear to be any pipe connection from boiler to steam chest, save for very small (1" or smaller) pipe. Nor any exit from the steam chest to the exhaust stack. Is this a case of faulty restorations which omitted that piping? Or is there another path not readily apparent? And what is that bowl up top of the steam chest?

Robert, those engines, and many others prior to the advent of superheating, use slide or flat valves. These are a type of shaped plate that slides over the steam ports, and are usually noted by a square box above the cylinder, as in your photograph.

Steam piping is all internal, inside the cylinder block:

http://en.wikipedia.org/wiki/Slide_valve

http://oldenginehouse.users.btopenworld.com/slide.htm

http://oldenginehouse.users.btopenworld.com/vg.htm

http://www.animatedengines.com/locomotive.html

http://www.catskillarchive.com/rrextra/CHAPT17.Html

http://books.google.com/books?id=bLWzK4 ... es&f=false

As noted, slide valves were used on all types of engines, including stationary machines, tractors, and geared engines.

As to your other parts, the thin pipe you saw was likely a lubrication line, running from a displacement lubricator in the cab to the cylinder block, and routed under the boiler jacket.

http://en.wikipedia.org/wiki/Mechanical_lubricator

http://www.roundhouse-eng.com/pics/lube.jpg

The device on top of the valve box looks like a "snifter" or "anti-vacuum" valve to let air into the cylinders when the engine was drifting with the throttle closed. There was a possibility that the vacuum that would form without this device would suck in smoke and other things from the smokebox into the cylinders, and that wouldn't do pistons, rings, valves, etc., any good at all.

http://en.wikipedia.org/wiki/Snifting_valve

At least, that's what everything looks like; if I'm wrong, I hope someone sets me straight!

Robert,
There is indeed an pipe internal to the boiler;
First, the dome houses the throttle valve, the Brits call it a Regulator.
The main steam pipe travels downward and forward, then passes through the
Front Flue Sheet. Here, inside the SmokeBox, there is a Bull Headed Tee, which splits the steam flow two ways, then the flow is down and curving around through the two Wishbone Pipes, which lead to the cylinder Valve Chest. This piping is all hidden inside the SmokeBox. The Valve Chests have internal connections through the Cylinder Saddle. The Exhaust flows to the Exhaust Nozzle. This blasts upward through the Petticoat Pipe, which is also the base of the Smoke Stack. [img]boiler-machine.blogspot.com[/img]

The nicely polished bowl on the top of the Valve ( or Steam ) Chest is a lubrication pot.
In the early days, hot tallow was kept on top of the boiler in the locomotive cab. The fireman had to walk out the front doors of the cab when drifting downgrade, shut the steam valve at the bottom of the Tallow Pot, open the top ( at the risk of being splattered and scalded if there was residual steam pressure ) and pour hot tallow into the pot. Add: Rain, Snow, Ice, Jerking motion of the Locomotive in Motion.

Hence, the moniker " Tallow Pot " also refers to the Fireman in North American slang.
This method became obsolete, or at least secondary, with the development of the Displacement Lubricator, which was mounted in the cab, and delivered what evolved into Steam Cylinder Oil, 95 % heavy petroleum mixed with 5 % tallow and emulsifiers ( Phosphate ) which form an oily foam in the steam. http://www33.brinkster.com/iiiii/mccoy/

On a similar locomotive, inside the smokebox you can see the branch pipes that admit steam to the steam chests.
In the picture of the 4-4-0 Edison, you can even see the studs on top of the steam chest where similar steam cylinder oil lubricators were once located. Currently a Manzel mechanical lubricator supplies the oil.
Keeping the supply of steam internal keeps the steam from condensing.

Locomotives with this type of steam chest were also sometimes upgraded with a Franklin Economy Steam Chest. It allowed the use of superheat without the expense of new cylinder saddles.
http://photos.nerail.org/showpic/?photo ... y%20Museum
Leverett Fernald

I thank 0-6-0 for setting me straight that I was looking at the old tallow-pot lubricators instead of snifter valves, but now I have a question--where are the snifters on the portrayed 4-4-0 in Mr. MacDowell's original post? They are quite prominent in the photo of the Edison (they are the cylindrical objects with the holes around the top edge on the fronts of the valve chests), but there is nothing similar on the unidentified 4-4-0.

And which engine in the collection is it? There isn't quite enough of it visible to identify it, at least not easily, although it looks like it might be from the V&T.

Going "modern," we see flat valves, internal steam pipes, and the snifters in this shot of a pretty 2-8-2:

http://www.railpictures.net/viewphoto.p ... 796&nseq=0

0-6-0 also reminded me that the familiar shelf above the firedoor in a steam locomotive was originally put there for the cans of tallow for lubrication. The heat at that location kept the tallow fluid; otherwise, like your kitchen tallow, or lard, it would solidify.

Lubrication certainly has come a long way from then, along with a lot of other things.

It's worth noting that slide valves were ideal for the time period. Machining being not so precise, the slide valve surfaces would wear into each other forming a more perfect seal over time. But as locomotive design evolved and steam pressures got higher and most especially with the introduction of superheating, they became less suitable and the switch to balanced piston valves took place.

As has been pointed out, many older locomotives were converted either with adaptations fitted to the old steam chests or replacing the entire cylinder / valve / boiler saddle.

Slide valves are often hidden within what outwardly look like piston valves on live steam model engines. Simpler to build and adequate for the steam pressure and temperatures involved.

Steve

Simple answer to the snifter question, snifters are an accessory, not a necessity, many locomotives were built without them. GM&N 425 only got hers after being restored to service on the Blue Mountain and Reading, they are simply swing checks mounted to a street elbow and replaced the "house" valves installed by Baldwin. Drifting was done with a slightly cracked throttle, K4 1361 has a drifting port on the outside of the throttle casting and was designed so that the first 3 or 4 throttle notches would open the pilot valve and allow sufficient steam to carry the lubricant to the cylinders. When using saturated steam lubrication was not as critical as with superheated steam, as the condensate worked as a poorman's lubricant. The flat surface of the slide valve was hard to lubricate at the edges of the passages way which would cause higher levels of wear and lead to superheated steam cutting of the seating surfaces, which led to the widely accepted piston valve.

Mike Tillger

your talking about 4-4-0 engines and similar? Internal, yeppers.
I have been all over NKP 765 and you may think it would pick steam and the steam dome... nopers, a large pipe runs up closer to the firebox with an input facing upwards, it gets the hottest steam there. Then it runs down to the throttling mechanics then thru the superheaters which then go to the pistons, rather elaborate.

Words fail me.........mechanics choking each other and the superheaters breaking loose and making for the cylinders..............what's next?

Yes, slide valve lokies, including very late-built industrial tank engines - like New Hope Valley RR 17 - have internal steam passages cast integrally with the saddle. It wasn't for condensation remediation, since plenty of condensation happens in the valve chest and cylinder with what's left useful of the steam doing all the work, but because it was the best way to get steam from here to there. Remember, slide valves have admission steam surrounding the valve and filling the chest, so leading it through a subterranean passage was easy. The external steam piping common on larger piston valve locomotives lead right to the area of the valve bore between the actual valves - inside rather than outside admission - so, running the steam by way of that piping is more direct. Thick insulation - and later, the addition of superheaters to make the steam hotter and drier - helps forestall early condensation, again, until the steam hits the valve and cylinder walls.

Slide valves wearing into a perfect fit may be a brief reality, or a mechanical legend. I've yet to see a slide valve in service for any length of real operating time in the kind of sealing condition piston valves seem to retain for longer service intervals. Even the balanced ones make grooves and tracks in the sealing surfaces, and any chunk of grit the gets in gives birth to a steam cut that will grow up and make itself a pest.

Slide valves are heavy and bulky and have a lot of pressure on them - even balanced ones - more so than the wearing pressures between piston valve rings and bores. It isn't chance that combined the advent of outside valve gear, superheat and piston valves at about the same time, but the inability of slide valves, wet steam and Stephenson to fit into smaller spaces between the frames that wouldn't permit locomotives to expand as freight loads grew heavier. To make larger locomotives, we needed to evolve.

dave

FWIW, inside steam delivery passages (through the cylinder saddle) saw limited use up to the very end of steam. Two existing examples are UP 844 and N&W 611.

OH NO ! ! Now we have to talk about inside or outside admission regardless of whether your branch pipes (steam pipes) connect to the cylinder saddle inside or outside the smokebox!
And Dave called it well ( mechanics throttling each other and such!), although 0-6-0 has it a little askew. On the NKP 765, the NKP removed the traditional dry pipe 90 degree elbow up into the steam dome and replaced it with a fabricated pipe. This was flange bolted to the original dry pipe where the elbow had been connected - but this pipe detoured around the steam dome and continued back towards the combustion chamber at the top center line of the boiler. In the last three feet, the top of the pipe was opened up into a rectangular box. This was where the steam was admitted from the boiler to the dry pipe. This was done to save labor during required boiler interior inspections. No elbow to remove and easy access for a man right down the dome into the boiler. The NKP could use this arrangement on the relatively table top flat mainline divisions of the NKP from Buffalo to Chicago since drastic changes of water level were not encountered. When we first restored the 765 in 1979 and began operations over many roads other than the NKP mainline, we encountered a tendency for the engine to work water when higher levels needed to be carried on some grades. So we removed the fabricated pipe to the rear of the steam dome and built a 90 degree elbow as per it's original construction that rises into the steam dome to within about 1-1/2" of the dome lid.
Tillger is also correct that not all engines were built with snifter valves which really is only an automatic "house" valve. Larger more complex "drifting" vlaves were patented to relieve steam chest vacuum when you shut off the throttle and turn the engines' running gear into air compressors. But ! ! Lubrication was always a problem. Steam loco "valve" or "cylinder" oils can lubricate up to about 750 degrees in a non-oxygen environment - but only are good for about 500 degrees in an oxygen environment - so when you close the throttle and open up the snifters or drifters or suck air down through the exhaust nozzle(which includes smoke and cinders) - your oil flashes to carbon and lubrication is lost. Some steam flow is needed to carry the itomized steam cylinder oil through the valves and into the cylinders. Some railroads just chose to train their engineers to "NEVER DRIFT THE ENGINE WITH THE THROTTLE CLOSED!". This was called setting a "drifting throttle" and refers to the slight opening of the throttle needed to allow enough steam to carry enough lubrication but not produce any power. The NKP perfected this type of operation calling it "open throttle braking" which worked the engine right down to the moment the wheels stoppped turning - also keeping the train's slack stretched out and reducing damages. The NKP 765 has no snifter or drifting valves on the steam chest. And to be correct - the steam flows throught the dry pipe into the superheater header where it then travels through the superheater units and back up into the header AND THEN through the American Multiple Front End Throttle (past the throttling mechanics????) and then down the right or left branch pipes which pass outside the smokebox onto the top of the steam chest where it awaits admission past the valve rings into the cylinders.
This method allows steam at almost boiler pressure to be right at the valves and be admitted to the cylinders.
ETC, ETC, ETC. !!

Sorry 0-6-0, I meant to say dinwitty.

Greetings:
Gary is correct about drifting with the throttle open slightly on American locomotives not equipped with drifting valves. At the Valley, our engineers are instructed to drift with the reverser in full gear in the direction of travel, and the throttle open sufficiently to see steam at the steam chest relief (sniffter) valves.
I would note however, that all Chinese built steam locomotives, including the six imported to the United States, are equipped with Troffimoff valves. The Troffimoff is a fairly simple form of drifting valve and when drifting, the valve gear is centered and the throttle closed. Extra lubrication points are provided to insure sufficient lubrication while drifting.
J.David

When were piston valves first introduced, and who introduced them? I assume it might be fairly accurate to say that all superheated locomotives had piston valves. But were all locomotives with piston valves superheated?