We all know the sound, CHUFF CHUFF, CHUF,CHUFF, of a steam locomotive. It is one of the best sounds, In my opinion, that man has ever created.
But something that I never have understood is what exactly is happaning when you hear that chuffing sound? I know it's something to do with airflow, but I don't know much else...
What is happaning during those shuffing sounds?
-Justin
The road to to success is always under construction. _____________________________________________________________________________ When the going gets tough, the tough use duct tape.
The cylinders exhaust through the blast pipe to aid the draft. Since the exhaust isn't continuous, the chuffing sound is the result. Compound locomotives will also have a different sound than simple locomotives.
The steam engine works by using steam that is created in a confined space (the boiler) and letting that steam into a cylinder that has a piston in it that can move due to the pressure of the steam. That moving piston is connected to the main rod to turn the wheels 1/2 turn.
When the piston has reached the end of its travel, there is still pressure in the steam and in order for the piston to return to the other end (and the wheel to continue to rotate) the pressure of that steam must be released.
The steam that is released is put to one more use after most of the pressure has been used in the cylinder to move the piston. That steam passes though some pipes to the bottom of the smoke box directly below the chimney. There a pipe, appropriately known as the "Blast Pipe" aims the steam directly up the chimney. The moving steam in the chimney creates a draft of air going up the chimney.
The air that is moved up the chimney has to come from somewhere and that is through the flue tubes in the boiler. That air has to come from someplace and that is from the firebox at the other end of the boiler. And of course, that air has to come from somplace and that is from the openings in the grate on bottom of the firebox where the fuel is being burned. The fresh air being drawn in that way helps the fire burn hotter which creates more steam to be used to make the pistons move and thus move the locomotive.
Anyway, it is that sudden release of steam up the chimney that makes the chuffing sound. On the most common configuration of a locomotive there are FOUR chuffs per revolution of the wheels. There are two pistons, one on each side of the locomotive, and each piston is alternately pushed to one end by steam and when the piston reverses direction and pushed from the other end by steam, the steam is released, creating a chuff. You hear a chuff from the front end of one cylinder, then a chuff from the front end of the other cylinder, then a chuff from the rear of the first cylinder and then a chuff from the rear of the other cylinder. At that point the first cylinder is already moving due to pressure in the front of it and the next chuff is from that end of that cylinder, which is the cycle starting all over again.
You will note that the pistons do not move in the same direction all of the time, nor do they move in opposite directions all of the time. When one piston is just starting to move one direction the other piston is in the middle of its travel in the same direction. When the 2nd one reaches the end of its travel and reverses direction the first one is in the middle of its travel. When the 1st one is reaching the end of its travel, the 2nd one is again in the middle of its travel but in the opposite direction. So half the time they are traveling in the same direction and half the time they are traveling in the opposite directions.
Anyway, it is the release of the "used" steam up the chimney that creates the CHUFF sound. When the throttle is open all the way to get the train moving is when the chuff is loudest. Once the train is moving, the throttle is closed a small amount (or more importantly the valve gear that times letting the steam into the cylinder and letting it out is changed to let less steam in) then the chuffing quiets down. Thus starting the train, acceleration or working up a hill makes louder chuffs than when just holding speed, and the chuffing can almost go away when slowing down.
There is a lot more to this, but it takes huge books to explain it all and the various differences that have been invented to make the locomotive more effecient or easier to maintain.
if you really, really want to understand all of this and like to read, I recommend the book "The Locomotive Up To Date" by Chas McShane. Get the 1909 edition! There are a couple of publishers that have reprinted it and it is not too expensive, but it contains some really good explanations. There are some more modern books, but the McShane book is a classic and can hardly be outdone.
Semper Vaporo
Pkgs.
CSSHEGEWISCH The cylinders exhaust through the blast pipe to aid the draft. Since the exhaust isn't continuous, the chuffing sound is the result. Compound locomotives will also have a different sound than simple locomotives.
Actually, when running compound, a Mallet sounds like a standard 2-cylinder simple loco - only louder.
What sounds different is a locomotive with two separate single-expansion engines (including Mallets in start-up all-simple mode.) The exhaust is not a simple uniform succesion of chuffs. Rather it's two sets, drifting in and out of synchronization but more often out than in. Then, too, locomotives with two sets of machinery could have one slip while the other gripped...
Three cylinder locos were different in that there were six chuffs per driver revolution rather than four.
Chuck
I got to witness the N&W Y6's in action in 1956 and when running in the compound mode and they were hushed compared to when they were in simple mode. We were amazed at the quiet sound of the Y6b class compared to the A class, which were really loud. The recording available in the coal fields for the Y6a class were in simple mode when they were working slowly if that was your reference. The reason that the compound mode is hushed compared to the simple mode is the large cylinders are using exhausted steam from the smaller rear cylinders and the total presure in the larger compound cylinders is reduced to a lower level. That is the reason the front compound cylinders are larger to have the same amount of force with less PSI.
In simple mode, those Y6's were very loud because the full steam presure was coming out of those 39" size compound cylinders.
CZ
Question: Am I to understand the Mallet's such as the Y6's with the two different size cylinders....are capable of running in "compound mode", and also run in "simple mode"....?
And what is the difference between the Y6a and b class....?
If both "modes" are available in the Y6's....how is the different size pistons dealt with when running in "simple mode"....? Does that cause slipping problems....?
If it is possible to run both or at least one of the above class engines in both "modes", that would seem to be an advantage for starting power, and then switch to compound mode for running...and perhaps use less steam....
Any comments on this...?
Quentin
The N&W perfected the Compound locomotive and made many changes over the first version that was designed by the USRA. The Y6a and Y6B had a valve or control that the engineer could start a train in Simple mode for extra tractive effort. The N&W designed this control valve which was not used on any other compound locomotive that I am aware of. The Y6a and Y6b had a traffic effort listing of 152,206 in simple and 126,838 in compound. Traffic effort was always calculated on steam presure along with piston force and in the case of the larger 39" cylinders with the boiler presure, the traffic effort was much greater. You also have to realize that on poor or wet rail, this extra force might not be so useful at times. I know the engineers tended to use them in simple mode for switching out coal at mines since the engine would respond better than waiting for the steam to exit the high presure cylinders and start towards the low presure cylinder for extra force. With the locomotive in simple mode, you got response when the thottle was yanked. And you are correct about switching to compound for normal running and saving steam for a coal savings also.
I would have to make a guess about running in simple at higher speeds, but this would probably had caused a lot of rail pounding since the large cylinders would be exerting way too much force and would overcome the normal counter balancing. These engines were designed to run in compound once the train was underway on the road.
I know the Y6b had the SA feedwater system and the Y6a had some other type, but most of the rest of the details were common to the Y6a. Both were equal in the traffic effort tables and both were very capable locomotives. The one at St. Louis museum is a Y6a if I remember correctly.
.....Thankyou { CZ}, for that interesting, and comprehensive answer....What you say of the designs and operating sure makes sense to me.
.....Oh what history...! Never heard anyone comment of such an engine before. Wonder if "Google can produce a photo"....?
A couple of comments on what I've read about mallets: To start, you almost had to be in simple mode since only one engine would be working. The low pressure cylinders ran off the exhaust from the high pressure engine, so if you were just starting, there was nothing to feed the low pressure engine in compound mode.
In simple mode, the steam being fed to the low pressure cylinders was run through a pressure-reducing valve or regulator first. If you ran full pressure to the those big cylinders, they would exert much more force than the high pressure cylinders so that you would not get much effort from the smaller cylinders before the big ones would slip.
_____________
"A stranger's just a friend you ain't met yet." --- Dave Gardner
Thanks for sharing the two links, Kootenay Central. I had never have seen anything(maybe never noticed anything) quite like these two classes of Locomotives.
http://members.shaw.ca/cprsteam/m2.htm
FTL: "...the Richmond or cross-compound system, was particularly adaptable to freight locomotives such as No. 778. In the Richmond system, the high-pressure cylinder was placed on the right-hand side of the locomotive, with the low-pressure cylinder in corresponding place on the opposite side. The illustration above shows this arrangement clearly, the much larger low-pressure cylinder, with an inside diameter of 35", appearing prominently in the foreground. The diameter of the high-pressure cylinder was only 22"; both, of course, had the same stroke: 26"..."
http://www.flickr.com/photos/imlsdcc/5020620389/sizes/z/in/photostream/
This flickr photo is fasinating, I've never seen a cylinder set up like this one on this; A TANDEM Compound configuration on this CPR Locomotive.
.....And again, {Paul}, that certainly makes sense. I wonder if it was possible to switch back to "compound" then....after the load was under way in moving. On the other hand....doesn't seem that would have been any help in "power"....Just economy, so to speak.
Now, I'm starting to wonder where the advantage might have been to have available the two different modes of control....It almost sounds to me the only advantage to reverting back to compound...would be the less use of steam / fuel...water......
Understand powering the large cylinders at start up, and doing so thru some kind of steam supply orfice....so I really don't see any "power" advantage to this compound / simple control......
Makes one think though....
Read the following and learn something:
http://www.catskillarchive.com/rrextra/mallet.Html
.
.....That's a lot of homework....But we'll get to it and work on it. Thanks.
Quentin,
My understanding is that the Y-6b's were always in compound - i.e. the exhaust from the high pressure cylinders went to the low pressure cylinders. To get extra tractive effort, some high pressure steam was admitted to the piping between the high pressure and low pressure cylinders to increase the pressure being admitted to the low pressure cylinders which then increased he tractive effort.
- Erik
erikem Quentin, My understanding is that the Y-6b's were always in compound - i.e. the exhaust from the high pressure cylinders went to the low pressure cylinders. To get extra tractive effort, some high pressure steam was admitted to the piping between the high pressure and low pressure cylinders to increase the pressure being admitted to the low pressure cylinders which then increased he tractive effort. - Erik
.....Thanks fellows. Seems I opened up a subject that requires quite a bit of studying, and understanding just what the capability of these brutes were.
I never realized they could be fed steam in two different ways before these conversations.
Can't right now, but we'll study what is here to see, and I'm sure we'll understand a bit better what really was possible with these engines.
Today, we think that "high tech" is computers, but "back in the day" these machines were every bit as High Tech as today's computers. They were anything BUT "simple". There were all kinds of intricate technology developed and built into the machines to make them work as effeciently as possible.
The only difference between now and then is that today you need a massive scanning electron microscope to see the parts, and back then it took massive cranes and jacks to pick up the parts to see them.
....The mechanical engineering age, vs the electronic engineering age.
All one has to do {that has an interest, and a bit of knowledge of what is happening}, just observe one of these steam brutes pass by with all the rotating parts, and cams, 200 tons of mechanical parts that have to work together....and reliably so, to really "see" the marvel in these machines.....and of course, someone with knowledge how to make it work {best}, for him....{or her}.
There seems to be a bit of confusion about when and how Mallets shifted from simple to compound operation. To (hopefully) clarify:
Starting from a dead stop, the locomotive was in simple mode. The high pressure cylinders got steam from the boiler at full pressure and exhausted to the atmosphere through the blast pipe. The low pressure cylinders had steam fed through a reducing valve to keep them from slipping the drivers, and exhausted to the atmosphere.
At some relatively low speed, the high pressure cylinder exhaust would be diverted to the receiver, and thence to the low pressure cylinders, by the intercepting valve. This happened automatically. (The major difference between the Y6b and earlier Mallets was that the interceptor valve wouldn't go to compound mode until the locomotive reached 10MPH, and would revert to simple if the speed dropped below 10MPH. Earlier Ys changed over at 4MPH.)
When running in compound mode the engineer could give the low pressure cylinders a shot of reduced-pressure boiler steam by using a valve which was controlled manually. This came standard on the Y6b, and was retrofitted to earlier locos as they went through the shops.
That long treatise from 1914 referenced earlier ended with the two design features that soured the Santa Fe on articulateds - the jointed boilers. They were maintenance nightmares, prone to problems. All of Santa Fe's jointed-boiler articulateds were rebuilt into normal 2-cylinder rigid-frame locos by 1916. The next articulateds to carry Santa Fe numbers were the Y3s purchased from the N&W during WWII.
Chuck (Modeling Central Japan in September, 1964 - with one articulated that never ran there)
Thanks to all for the stellare explanation of the "Chuff"! Glad to know much much more about how these great machines worked!
Semper Vaporo Today, we think that "high tech" is computers, but "back in the day" these machines were every bit as High Tech as today's computers. They were anything BUT "simple". There were all kinds of intricate technology developed and built into the machines to make them work as effeciently as possible. The only difference between now and then is that today you need a massive scanning electron microscope to see the parts, and back then it took massive cranes and jacks to pick up the parts to see them.
So true!
So the Y6's had massive low pressure cylinders on the front end of the boiler, up by the pilot truck, and had smaller high pressure cylinders back closest to the cab?
So the way I take it, steam from the steam dome was sent to the, small, high pressure cylenders first, and once it went through it's two stroke cycle adn became cooler and more expanded, then it was piped up to the massive low pressure cylinders to be used again beofre being sent up through the blast pipe and out the stack? I would imagine that the draft comming through the flue tube was massive with all that steam being exhausted! That make a lot of sense actually.
And in simple mode, steam was directly fed from the steam dome to both the high pressure and the low pressure cylinders at the same time. This, in turn, made the locomotive seem louder that it would have been in compund mode.... Lightbulb Moment!!!
Very interesting indeed!
Makes me appreciate these mamoth machines even more.
Semper Vaporo The steam engine works by using steam that is created in a confined space (the boiler) and letting that steam into a cylinder that has a piston in it that can move due to the pressure of the steam. That moving piston is connected to the main rod to turn the wheels 1/2 turn. When the piston has reached the end of its travel, there is still pressure in the steam and in order for the piston to return to the other end (and the wheel to continue to rotate) the pressure of that steam must be released. The steam that is released is put to one more use after most of the pressure has been used in the cylinder to move the piston. That steam passes though some pipes to the bottom of the smoke box directly below the chimney. There a pipe, appropriately known as the "Blast Pipe" aims the steam directly up the chimney. The moving steam in the chimney creates a draft of air going up the chimney. The air that is moved up the chimney has to come from somewhere and that is through the flue tubes in the boiler. That air has to come from someplace and that is from the firebox at the other end of the boiler. And of course, that air has to come from somplace and that is from the openings in the grate on bottom of the firebox where the fuel is being burned. The fresh air being drawn in that way helps the fire burn hotter which creates more steam to be used to make the pistons move and thus move the locomotive. Anyway, it is that sudden release of steam up the chimney that makes the chuffing sound. On the most common configuration of a locomotive there are FOUR chuffs per revolution of the wheels. There are two pistons, one on each side of the locomotive, and each piston is alternately pushed to one end by steam and when the piston reverses direction and pushed from the other end by steam, the steam is released, creating a chuff. You hear a chuff from the front end of one cylinder, then a chuff from the front end of the other cylinder, then a chuff from the rear of the first cylinder and then a chuff from the rear of the other cylinder. At that point the first cylinder is already moving due to pressure in the front of it and the next chuff is from that end of that cylinder, which is the cycle starting all over again. You will note that the pistons do not move in the same direction all of the time, nor do they move in opposite directions all of the time. When one piston is just starting to move one direction the other piston is in the middle of its travel in the same direction. When the 2nd one reaches the end of its travel and reverses direction the first one is in the middle of its travel. When the 1st one is reaching the end of its travel, the 2nd one is again in the middle of its travel but in the opposite direction. So half the time they are traveling in the same direction and half the time they are traveling in the opposite directions. Anyway, it is the release of the "used" steam up the chimney that creates the CHUFF sound. When the throttle is open all the way to get the train moving is when the chuff is loudest. Once the train is moving, the throttle is closed a small amount (or more importantly the valve gear that times letting the steam into the cylinder and letting it out is changed to let less steam in) then the chuffing quiets down. Thus starting the train, acceleration or working up a hill makes louder chuffs than when just holding speed, and the chuffing can almost go away when slowing down. There is a lot more to this, but it takes huge books to explain it all and the various differences that have been invented to make the locomotive more effecient or easier to maintain. if you really, really want to understand all of this and like to read, I recommend the book "The Locomotive Up To Date" by Chas McShane. Get the 1909 edition! There are a couple of publishers that have reprinted it and it is not too expensive, but it contains some really good explanations. There are some more modern books, but the McShane book is a classic and can hardly be outdone.
This is one of the best posts that I have read in Train's forums. I am not an engineer, but I am able to understand what you have said. Also, many of the responses are equally informative.
All this information is absolute. To realise this more one would have to have been there standing by the ROW when one went by ~~ to feel the power as the ground shook . This is hard to imagine, I know I was there many times . Has any one stood by one and listened to it simmer and sputter andthe air compressor chuff ?? ~~~ Y6b s evergreen in my mind
Cannonball
Y6bs evergreen in my mind
......And don't forget the "rain" of small cinders falling down as it passes, especially if it's working hard....and your on the side of the track to which the wind is blowing.
Modelcar ......And don't forget the "rain" of small cinders falling down as it passes, especially if it's working hard....and your on the side of the track to which the wind is blowing.
As a child, I remember attending a B&O Pittsburgh Division company picnic that was held at a picnic ground adjacent to the B&O's P&W Subdivision at Mars, PA which was about midway up the Bakerstown Hill that extended from Etna, PA to Bakerstown, PA. Recall watching a coal train, working hard, headed upgrade with a Mallet on the head end and two Mallet's on the rear end - as I recall, it rained cinders for about 15 minutes after the passage of the train.
Never too old to have a happy childhood!
As to the rain of cinders, one evening as I waited by the engine for the Pelican to leave Bristol, I was warned about the coming shower by an N&W employee. It was always a beautiful sight to see the J handle the train that the Southern had brought in from New Orleans behind two E's, especially since two sleepers were added in Bristol (one for New York and one for Richmond). Incidentally, no one ever questioned my presence by the engine back then (1954-1957).
Johnny
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