# How does a Steam Engine Operate>>??



## Bkubiak (Oct 20, 2013)

Curious minds want to know
If fire box is in front of the cab and that is where the fireman shovels the coal into how does the smoke get all the way to the front to come out the stack???

I know there are 4 chuffs per wheel rotation, why?

Are the steam pistons offset a tad from each other so they cannot get stuck??

What are all those domes on top of the Loco???

Where is the water stored??

Why does the smoke increase when the engine is going up a grade?


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## cv_acr (Oct 28, 2011)

Bkubiak said:


> Curious minds want to know
> If fire box is in front of the cab and that is where the fireman shovels the coal into how does the smoke get all the way to the front to come out the stack???


Tubes run through the boiler from the firebox to the smokebox. This is how the water in the boiler is heated, if only the water at the end with the fire was heated this wouldn't work too well, or boiler should be made far smaller, and would generate far less power. (See stationary vertical boilers.)



> I know there are 4 chuffs per wheel rotation, why?
> 
> Are the steam pistons offset a tad from each other so they cannot get stuck??


The main drive rods on each side are quartered (offset 90 degrees from each other).

And as one piston is on its power stroke, the other should be on its exhaust stroke, so that it's always under drive power.

Thus, each cylinder makes two power strokes per rotation, and the two cylinders are opposite each other. So that's 4 exhaust "chuffs" per rotation.



> What are all those domes on top of the Loco???


At least one of them will be a sand box; fine sand can be applied to the drive wheels using compressed air to aid in traction if the wheels are slipping.

Another will be a steam expansion/pressure release value.



> Where is the water stored??


The tender attached to the locomotive contains fuel *and* water tanks.



> Why does the smoke increase when the engine is going up a grade?


Whether starting a heavy train, or going uphill, the engine is working harder. Although I'm not totally clear on all the finer points of how the engine's speed/power is controlled.

Here's a good animation of how the engine works:

https://www.youtube.com/watch?v=g8LrAsL4oH0


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## traction fan (Oct 5, 2014)

*Steam Questions*

brubiack:

That's a lot of questions! I'll answer as many as I can remember. The fireman shovels coal into the firebox, which typically runs forward much of the length of the boiler. Only the doors where he scoops the coal in are at the front of the cab. A grate extends forward many feet and the fire covers this grate. Many tubes are mounted lengthwise in the boiler. these hold the water to be boiled into steam. The hot air is drawn forward, under the fire grate and goes up the stack at the front. Smoke follows this same path. Water is stored in the tender. A large hose carries water from the tender to the locomotive as controlled by the fireman.
The domes on top of the boiler contain steam and sand. The sand is used on the rail tops for extra traction when climbing a grade. Yes the loco works harder pulling all that weight uphill. 
This causes it to slow down, "bark" louder and emit more smoke. The crank pins and side rods are off set to allow the loco to move itself. Steam pushes one side's piston back while the opposite piston is moving forward. The offset crank pins continually position the pistons to alternate push strokes and keep things moving. If they were set directly opposite each other, the pressure on both sides at once would not turn the wheels.

This is one of those cases where one picture is worth a thousand words. I suggest you look at a library book, or google for more (and more accurate, and detailed info) 

Regards;

Traction Fan


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## Patrick1544 (Apr 27, 2013)

As the locomotive increases its load it uses up more steam as the throttle is opened slightly more for the upgrade. This necessitates the Fireman to shovel more coal onto the fire bed to increase the temperature and make more steam for the increased load on the engine. The inclusion of the coal being slung into the firebox sends small black particles of coal through the flues(due to the draft). The small coal particulate vaporizes almost immediately before it even hits the bed. This and the sudden combustion of the new coal entering and immediately igniting, exits the stack as a black/ gray mixture with the white steam exhaust.


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## Kwikster (Feb 22, 2012)

Also, the "chuffs" are the venting of exhausted steam thru ports in the stack (chimney if you like) which help create a positive draught on the smoke as it travels to the stack. One reason boilers are so long is to aid in extracting as much energy as possible from the fuel used, whether it be wood, coal, or oil. The reason they smoke more and chuff harder when pulling a heavy load or grade is the throttle and cut-off are both opened longer, thus more steam drawing more smoke and heat thru the tubes. As the load decreases the throttle is reduced and fuel usage improves, thus less smoke.






Think of it like an ordinary gasoline engine, more throttle, more fuel, more smoke. More power and louder exhaust. At cruising speeds, less throttle, smoke, fuel used and quiter operation.

Carl


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## shaygetz (Sep 23, 2007)

You can 'splain it in academic prose all you want, but until the scent of hot oil and hot water waft across your nose, you'll n'er unnerstand...


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## CTValleyRR (Jul 26, 2014)

I agree with Shaygetz -- there's nothing like the smell of an operating steam locomotive! Why else do you think I volunteer at a steam tourist road?

A couple of clarifications to the above. 

The steam dome (usually only one) on top of the boiler is where the steam accumulates, from which it is sent to the throttle. For a variety of technical reasons, you don't want a lot of steam accumulating in the boiler. You want the boiler to contain very hot water. Too much steam (or air) in the boiler creates voids between the boiler tubes where no water is heated, decreasing the efficiency of the boiler and reducing power and increasing fuel consumption. Similarly, too much water loss (into steam) means too much cool water enters the boiler to replace it, likewise reducing power (it is possible to introduce so much cool water into the boiler that it stops making steam, bringing the train to a halt until it heats up again). Feedwater heaters mitigate this risk and improve efficiency.

The steam relief valve may be integrated with the steam dome or not. It is calibrated to keep the pressure in the boiler from exceeding its maximum rated pressure.

Someone said that the firebox extends much of the length of the boiler. That isn't true. Heat is transferred from the exhaust gasses of the fire as they travel through boiler tubes. Although some heat does transfer directly from the firebox, that's not the primary means of heating the water. The fireman tries to spread the coal as evenly as possible, to keep ash from reducing efficiency, and because he's shoveling it in from the rear, he can't get it very far under the boiler.


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## Bkubiak (Oct 20, 2013)

CTValleyRR said:


> I agree with Shaygetz -- there's nothing like the smell of an operating steam locomotive! Why else do you think I volunteer at a steam tourist road?
> 
> A couple of clarifications to the above.
> 
> ...


What happens to the ashes as the train moves along.

Where does a steam engine get the air to operate the air brakes?

I now understand why the smoke puffs from the stack. it is because the exhaust steam in the drive piston blast up thru the stack.

I also see that piston is powered in both directions of travel and the exhaust steam goes up the stack

How did the head lights get power to operate??


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## Kwikster (Feb 22, 2012)

They used a steam turbine to power accessories such as a dynamo and compressor. The dynamo provided electricity and the compressor the needed air. Without such systems, they would had to rely on wheel speed, and would have been ineffective at idle, thus the turbine. 

http://www.steamlocomotive.com/appliances/dynamo.php

Some of the particulate matter traveled out thru the exhaust during combustion. The remaining ash dropped into an ash pan below the firebox. During suel/water stops the pan would be cleaned as needed.

That link also holds a great wealth of information, great if you want prototypical spec and photos.


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## Big Ed (Jun 16, 2009)

Early steam locomotive lights were powered with kerosene and acetylene lamps.
Then locomotives began using electric carbon arc headlights toward the end of the nineteenth century.

Though the electric carbon arc lights were not trouble free.

Interesting read here for those who want to look.
Pictures for those who don't like to read.:smokin:


http://www.historyinsidepictures.com/Pages/SteamLocomotiveCarbonArcHeadlights.aspx


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## Bkubiak (Oct 20, 2013)

Kwikster said:


> They used a steam turbine to power accessories such as a dynamo and compressor. The dynamo provided electricity and the compressor the needed air. Without such systems, they would had to rely on wheel speed, and would have been ineffective at idle, thus the turbine.
> 
> http://www.steamlocomotive.com/appliances/dynamo.php
> 
> ...


So getting up a head of steam means the steam dome is full of steam with sufficient pressure to move the loco??

In looking at the detailing on my K4 I see that every wheel on that loco and tender has brakes


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## CTValleyRR (Jul 26, 2014)

Exactly. Getting up enough steam to operate can take 24 hours or more on a big boiler, especially if the loco is coming out of a cold lay-up.

Brakes -- it was common practice to apply braking power to as many wheels as possible. Unlike a car where you have epoxy or asbestos pads, train brakes are steel on steel (hence the squeal when they are applied -- that same sound your car makes when it's long overdue for a trip to Pep Boys is normal on a train). This means the braking force of each individual brake unit is not that strong, so the more the better.


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## shaygetz (Sep 23, 2007)

It takes 15-20 minutes to build up enough steam for my little ones, and that is with pre-heated water. Real steam engines were kept pre-heated if they were to run withing a week. They used piped steam from a boilerhouse over service tracks similar to this John Allen roundhouse scene...


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## Kwikster (Feb 22, 2012)

Here's a link to firing up a steam loco, pay attention at around 7:34 for the dynamo being operated.


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