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Why does a steam engine puff through the smoke stack??

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Why does a steam engine puff through the smoke stack??
Posted by ARTHILL on Friday, December 30, 2005 6:31 PM
What goes on inside that produces the puffing sound? I have loved the sound for decades, but I never asked why they do it.
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Posted by Texas Zepher on Friday, December 30, 2005 6:42 PM
The exhaust from the cylinders is pushed through the smoke stack to create a draft in the fire box. That way the fire burns better.
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Posted by Anonymous on Friday, December 30, 2005 6:50 PM
where could i see a diagram of how a steam engine works?
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Posted by Anonymous on Friday, December 30, 2005 6:53 PM
Try here:
http://travel.howstuffworks.com/steam.htm
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Posted by ARTHILL on Friday, December 30, 2005 7:07 PM
Wolvie. Thanks, that answers a 60 year question. Who says you can't still learn after retirement? That is if you remember to ask the question.
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Posted by Anonymous on Friday, December 30, 2005 7:16 PM
i'm in the process of looking at that link- one thing i observed while seeing steam locomotives on TV is they chuff 4 times for each turn of driving wheels
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Posted by Anonymous on Friday, December 30, 2005 7:32 PM
QUOTE: Originally posted by dingoix

i'm in the process of looking at that link- one thing i observed while seeing steam locomotives on TV is they chuff 4 times for each turn of driving wheels


Multiple cylinders…same reason a V-Twin Harley sounds different than an inline-4 sportbike.

I’m not totally sure…but I remember reading somewhere about “Double-Action” steam systems that re-use the exhaust venting once more as well…so that would also contribute to the differing “chuffs per revolution”. But take this with a grain of salt because as I said, I’m no expert in steam locomotives. Motorcycles, yes…but not locos…yet…
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Posted by edkowal on Friday, December 30, 2005 7:38 PM
You can also try here: http://home.new.rr.com/trumpetb/loco for an animated description of how Walshaert valve gear works, as well as other aspects of steam locomotive technology. This site has a number of useful links as well.

You might also like the following story on bringing a locomotive boiler up to pressure:
sdrm.org/faqs/hostling.html

One of the best ways to learn about steam locomotive technology is also one of the most fun. Many railroad museums and tourist railroads now have a guest engineer program. For a fee, you can spend a day operating a full size steam locomotive under the supervision of the museum staff, after a short safety course in the hows and whys of doing it. Each program is somewhat different, some are more thorough than others. A report of one person's experience is available at this web page: iceandcoal.org/mng/guest.html

-Ed

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Posted by Anonymous on Friday, December 30, 2005 7:45 PM
4 chuffs per revolution are actually 2 chuffs from the cylinder you are looking at. The exhaust "chuffs" when the piston reaches the ends of it's travels.

The other two chuffs come from the other side.
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Posted by Eriediamond on Friday, December 30, 2005 8:00 PM
QUOTE: Originally posted by Wolvie

QUOTE: Originally posted by dingoix

i'm in the process of looking at that link- one thing i observed while seeing steam locomotives on TV is they chuff 4 times for each turn of driving wheels


Multiple cylinders…same reason a V-Twin Harley sounds different than an inline-4 sportbike.

I’m not totally sure…but I remember reading somewhere about “Double-Action” steam systems that re-use the exhaust venting once more as well…so that would also contribute to the differing “chuffs per revolution”. But take this with a grain of salt because as I said, I’m no expert in steam locomotives. Motorcycles, yes…but not locos…yet…



A short, hopefully quick lesson why steam locos chuff 4 times per revolution of its drivers. There are two cylinders per engine, one on each side. these cylinders bothe push and pull. each cylinder pushes the connecting rod halve a revolution of the drivers then pulls the other half, thus each cylinder has two exhaust strokes per revolution of its drivers. This in itself does not create the four chuffs. what really causes the four chuffs is that the driver crank pins (what the connecting rods and side rods are attached to the wheels with) are what is called "quartered". The crank pins are positioned 90 degrees different on each side of the engine so that when the engine is stopped it can start again no matter the position of the the cylinder as at least one cylinder is not at the end of it's stroke. It's a little more technical, but thats the basic of it. Ken
Life's a short trip, so have fun on it. Play with trains. In the beginning, God created trains with steam engines and cabooses.And everything was good. Then man came along and screwed everything up and invented the diesel and did away with the caboose.
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Posted by howmus on Friday, December 30, 2005 8:58 PM
QUOTE: Originally posted by dingoix

where could i see a diagram of how a steam engine works?


Another good page on how a steam locomotive works is theis one from Streamtown USA: http://www.nps.gov/stea/locowork.htm If you are able, take a trip to Scranton, PA and visit Steamtown National Historic Site. Well worth the effort and you can take a steam train ride behind a beauty like this:

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Posted by edkowal on Friday, December 30, 2005 9:15 PM
QUOTE: Originally posted by Wolvie

Multiple cylinders…same reason a V-Twin Harley sounds different than an inline-4 sportbike.

I’m not totally sure…but I remember reading somewhere about “Double-Action” steam systems that re-use the exhaust venting once more as well…so that would also contribute to the differing “chuffs per revolution”. But take this with a grain of salt because as I said, I’m no expert in steam locomotives. Motorcycles, yes…but not locos…yet…




A "double action" steam system means that you are admitting steam alternately to the front and then rear of the piston in the cylinder. This differentiates it from the original invention, which was a single action sytem. All steam locomotives are "double action" engines.

If you reuse the steam exhaust you've got a more complicated beast. What you're describing is called a compound steam engine. Mallet articulated locomotives were of this type. There were in essence two steam engines under a single boiler. High pressure steam was admitted to a small diameter cylinder first. The lower pressure exhaust was then used by a larger diameter cylinder in front. The twice used steam was then exhausted up the stack. Because the steam was exhausted only by the large diameter, low pressure engine, you'd only hear four chuffs per revolution.

But there was another type of articulated engine, called a simple articulated. This was also two steam engines under one boiler, but they were not interconnected. Each engine used high pressure steam from the boiler. You can identify a simple articulated by the fact that both front and rear cylinders are the same diameter. Because the two sets of cylinders were essentially independent of each other, you would wind up with eight chuffs per revolution, four from the front engine, and four from the rear engine.

-Ed

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Posted by Anonymous on Friday, December 30, 2005 9:19 PM
there are 2 on MOST steam engines but as you probbally know there are variatons of 3, 4,& 6(triplexes) cylinders. Now what Eiredimond was explaining is a walscherat valve gear, although there are otheer conbinations of rods including the british inside cylinder formation, the ephraim shay geared &coupled rod systems, & the climax mecanics heres a diagram on the walschart system http://home.new.rr.com/trumpetb/loco/
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Posted by Jacktal on Friday, December 30, 2005 9:30 PM
The "Double Action" steam management referred to is the Mallet concept.Clever but more complex,this design redirected steam pressure coming out of high pressure cylinders to lower pressure cylinders,maximizing the use of energy.

All the locos that I know of using this concept were called Mallet's and were very powerful for their size but significantly slower,making them excellent at mining chores specially in moutaineous terrains.They could pull huge convoys in the harshest conditions but were no match for Challengers,Big Boys and Allegheny's as multi-purpose locomotives.
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Posted by Anonymous on Friday, December 30, 2005 9:40 PM
I'll elaborate on a point mentioned above.

When steam is exhausted from the cylinders, it is directed toward the base of the exhaust stack within the smokebox. That base is at perhaps the midpoint of the diameter of the smokebox, and is flared out (this portion of the stack is sometimes referred to as the "petticoat").

The drum-shaped smokebox is airtight, except for the exhaust stack, the exhaust jets from the cylinders, and the flues which run horizontally from the smokebox back to the firebox. As steam is exhausted from the cylinders and up through the stack, a vacuum is created in the smokebox. This vacuum draws combustion gasses, through the flues, from the firebox. Not only does this draft fan the flames in the firebox, but it increases the efficiency of the boiler: the heat induced to the flues by the combustion gasses further heats the surrounding water in the barrel of the boiler.
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Posted by Anonymous on Friday, December 30, 2005 9:46 PM
...unless you're talking about a Shay. Then it's eight chuffs per revolution.

QUOTE: Originally posted by jcmark611

4 chuffs per revolution are actually 2 chuffs from the cylinder you are looking at. The exhaust "chuffs" when the piston reaches the ends of it's travels.

The other two chuffs come from the other side.
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Posted by selector on Friday, December 30, 2005 11:55 PM
Driving piston slides past an exhaust port, lettting used steam escape out the port and into an inverted Y-pipe that has the vertical steam aimed out the smoke stack. The explosive 'chuff' is only that, liberated steam. As stated above, it acts as a venturi mechanicsm and draws hot flue gases more efficiently through their tubes and shoves them out the smoke stack. However, by this time, the piston is reversing inside the cylinder and sliding back down to the other end under the influence of steam admitted via an uncovered inlet. As it accelerates down the cylinder, it eventually uncovers the same exhaust port, and we hear another chuff. That is two chuffs per stroke, or per dirver revolution, or per valve-gear cycle.

On the other side of a typical 2-cylinder steamer, the other mechanism is doing the same thing, but timed so that the cylinder action on the right precedes the one on the left by approximately 90 deg.

Chuff-chuff............chuff-chufff.......
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Posted by edkowal on Saturday, December 31, 2005 12:41 AM
As I alluded to in a previous post, when originally proposed, the steam engine did not resemble what we are now familiar with. It was invented by Thomas Newcomen in 1712 following earlier work by Thomas Savery. In this engine, more properly called an atmospheric steam engine, the steam is not directly involved in the power stroke. Before the power stroke, the steam, which is at roughly atmospheric pressure, has been drawn into the vertical cylinder by the rising of the piston. After the cylinder is full of steam, a jet of water is sprayed into the now closed chamber, which cools the steam and condenses it, causing a partial vacuum in the chamber. Atmospheric pressure presses down on the top of the piston in the power stroke, lowering the piston and causing a water pump attached to the piston to operate a single stroke. The chamber is reopened to the steam source, and the weight of the beam raises the piston, drawing new steam into the chamber. For an illustration, see technology.niagarac.on.ca/people/mcsele/newcomen.htm

Note in this explanation, there is only one power stroke, in one direction. The piston moves in the other direction by action of the weight of the beam, which has been raised in the power stroke. Because power is exerted on only one side of the piston, such a steam engine is "single action." Another example of a "single action" piston would be any of the pistons in an internal combustion engine in an automobile. The power stroke in the cylinder of an automobile engine always acts on one, and only one side of the piston.

James Watt was able to make many improvements on Newcomen's invention. For instance, rather than spray water into the cylinder, which lowered the temperature of the cylinder with each stroke, Watt condensed the steam using a separate condenser chamber. But his engine initially was also a "single action", atmospheric engine. In the course of further improvements, he realized that rather than using the condensation of steam to cause the atmosphere to power the engine, he could use the expansion of pressurized steam to power the piston directly. He also realized that he could derive a power stroke from both directions of piston movement if the cylinder was designed to do so.

In proposing these improvements, James Watt invented the "double action" steam engine, the modern steam engine. It is "double action" because there are two power strokes, one in each direction.

QUOTE: From A HISTORY OF THE GROWTH OF THE STEAM-ENGINE.
Chapter 3
by ROBERT H. THURSTON, A. M., C. E.,
history.rochester.edu/steam/thurston/1878/Chapter3.html


The double-acting engine was a modification of the single-acting engine, and was very soon determined upon after the successful working of the latter had become assured.

Watt had covered in the top of his single-acting engine, to prevent cooling the interior of the cylinder by contact with the comparatively cold atmosphere. When this had been done, there was but a single step required to convert the machine into the double-acting engine. This alteration, by which the steam was permitted to act upon the upper and the lower sides of the piston alternately, had been proposed by Watt as early as 1767, and a drawing of the engine was laid before a committee of the House of Commons in 177S'75. By this simple change Watt doubled the power of his engine. Although invented much earlier, the plan was not patented until he was, as he states, driven to take out the patent by the " plagiarists and pirates " who were always ready to profit by his ingenuity. This form of engine is now almost universally used. The single-acting pumping-engine remains in use in Cornwall, and in a few other localities, and now and then an engine is built for other purposes, in which steam acts only on one side of the piston; but these are rare exceptions to the general rule.


Watt also invented the compound steam engine, the principal of which was used by Anatole Mallet to develop the type of articulated locomotive named after him.

Compound steam engines are common in marine engines for example. An excellent illustration of a compound marine engine can be found in the Wikipedia article at http://en.wikipedia.org/wiki/Steam_engine It is an example of a triple expansion compound steam engine with double-acting pistons.

-Ed

Five out of four people have trouble with fractions. -Anonymous
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Posted by tatans on Saturday, December 31, 2005 8:15 PM
Don't get fooled when you look at a steam engine and see a steam cylinder on each side and assume it's a 2 cylinder loco. when I was in Britain about a 1000 years ago, I noticed the locos made a different and quicker chuff-chuff sound and an old geezer said it had 3 cylinders, the 3rd cylinder is in the middle underneath and between the other 2 cylinders. I can't remember what north American locos had 3 cylinders,do you??
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Posted by Eriediamond on Saturday, December 31, 2005 8:56 PM
tatans, yes 3 cylinder engines were built back in the 20's for the UP in a 4-12-2 wheel arrangement. 88 were built as simple ( not compound) engines. To carry this a little further, there were also 4 cylinder ingines built also as compound engines. these included 4-2-2 and 4-4-2 Atlantics. On the Atlantics the inside cylinders were attached to the front drivers while the ouside cylinders were attached to the rear drivers. These compound engines, even though they had 4 cylinders, still only produced 4 chuffs per revolution. Ken
Life's a short trip, so have fun on it. Play with trains. In the beginning, God created trains with steam engines and cabooses.And everything was good. Then man came along and screwed everything up and invented the diesel and did away with the caboose.
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Posted by SP4449 on Sunday, January 01, 2006 10:16 PM
[?] Can anyone explain the difference between US steam locos with a steam/smoke stack on the front of the engine and the British steam locos with a smoke stack on the front and another stack near the cab that seems to be an exhaust for the spent steam? [?]
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Posted by gmcrail on Sunday, January 01, 2006 11:03 PM
QUOTE: Originally posted by On30Shay

...unless you're talking about a Shay. Then it's eight chuffs per revolution.

QUOTE: Originally posted by jcmark611

4 chuffs per revolution are actually 2 chuffs from the cylinder you are looking at. The exhaust "chuffs" when the piston reaches the ends of it's travels.

The other two chuffs come from the other side.



On a 3-cylinder Shay, there'd be 6 exhausts per revolution of the drive shaft, with many more than that per revolution of the wheels.... [:)]

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Posted by marknewton on Monday, January 02, 2006 5:03 AM
On a 3 cylinder Shay, it works out to 13 exhaust beats or chuffs per revolution of the wheel.
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Posted by Eriediamond on Monday, January 02, 2006 5:22 AM
QUOTE: Originally posted by SP4449

[?] Can anyone explain the difference between US steam locos with a steam/smoke stack on the front of the engine and the British steam locos with a smoke stack on the front and another stack near the cab that seems to be an exhaust for the spent steam? [?]


To be honest, I'm not that familiar with British steam, except to say they made some eligant, colorful engines. I do suspect that what you see in that second stack is the exhausting steam from the safety pop-off valve and maybe the exhaust from the steam driven generater and -or air pumps. To take this a little further and back to US locos, you will sometimes see steam exhausting out of a tender. Some railroads operating in the cold country piped steam through the tender to keep coal and water from freezing. Ken
Life's a short trip, so have fun on it. Play with trains. In the beginning, God created trains with steam engines and cabooses.And everything was good. Then man came along and screwed everything up and invented the diesel and did away with the caboose.
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Posted by marknewton on Monday, January 02, 2006 5:39 AM
There weren't many locomotives in the UK with air pumps or turbo-generators. I wonder if the OP is referring to Kitson-Meyer articulated locos, some of which did have a second funnel/stack.

All the best,

Mark.
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Posted by Eriediamond on Monday, January 02, 2006 6:03 AM
Could be Mark, I thought of that after I posted my answer, only I didn't know the name of the articulateds, Ken By the way Mark, I have a video tape of, for lack of better words, steam restorations in Australia. It's about an hour long and covers locos and trains from "puffing billies to the big stuff. It's in my "big rig" right now or I could tell you the name of it. Some great and beautiful work "down under".
Life's a short trip, so have fun on it. Play with trains. In the beginning, God created trains with steam engines and cabooses.And everything was good. Then man came along and screwed everything up and invented the diesel and did away with the caboose.
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Posted by dinwitty on Monday, January 02, 2006 6:26 AM
the N&W 2-8-8-2's could switch between simple and compound.

also if the 2 wheelsets are out of sync in simple, and often, you'll get a gallup sound.

IHB 0-8-0's were 3 cylinders
look at the Rivarrosi
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Posted by BRAKIE on Monday, January 02, 2006 6:42 AM
How many of you know about the "no smoke" rule many railroads had? That means the fireman had to watch his fire to insure it burn clean and not put out excessive smoke.Of course bad coal that contain slate would not burn clean and would put out excessive smoke.At one time firemen feared anybody track side with a camera as it could be a company man taking pictures of the"no smoke" rule violations.[:0]

Larry

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Posted by selector on Monday, January 02, 2006 11:42 AM
QUOTE: Originally posted by Eriediamond

. Some railroads operating in the cold country piped steam through the tender to keep coal and water from freezing. Ken


And to warm the fuel oil if it was oil-fired.
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Posted by Anonymous on Monday, January 02, 2006 12:32 PM
Them Mallets might not have been a match for the Big Boy but the Big Boy will have a hard time doing a coal turn in the east.

To take this one step further, does the "Stack Talk" give the crew any useful information?

Regarding the British Steam, it is my thinking that they are designed to much greater capability. The "Little Engine" that can if you will. I suppose the maintaince is rather high and the speeds are really fast compared to American Steam which I think leans towards reliability, ease of access and brute strength in the harsh land.

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