What goes on inside that produces the puffing sound? I have loved the sound for decades, but I never asked why they do it.
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.
where could i see a diagram of how a steam engine works?
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.
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…
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:
www.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: www.iceandcoal.org/mng/guest.html
-Ed
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.
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
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:
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
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/
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.
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.
…unless you’re talking about a Shay. Then it’s eight chuffs per revolution.
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…
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 www.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 ca
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??
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