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Offline SteamNut  
#1 Posted : 08 May 2015 19:14:08(UTC)
SteamNut

United States   
Joined: 11/05/2013(UTC)
Posts: 466
Why does the exhaust of steam exhaust seems to be mainly white while other times black? Fred
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Offline H0  
#2 Posted : 08 May 2015 19:26:48(UTC)
H0


Joined: 16/02/2004(UTC)
Posts: 13,498
Location: DE-NW
I read that black smoke indicates low efficiency (they wrote the fireman might as well through the coal out of the window).

Modern train drivers may sometimes do it to give impressive photos.
Regards
Tom
---
"In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS
UserPostedImage
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Offline witzlerh  
#3 Posted : 08 May 2015 19:31:50(UTC)
witzlerh

Canada   
Joined: 25/09/2010(UTC)
Posts: 416
Location: Sherwood Park, AB, Canada
White is the steam. The steam exhaust from the cylinders is shot through the stack to create vacuum to draw the exhaust gases from the fire box through the boiler (to heat water) and out the stack.
Now if you were coasting down hill, you do not need much heat so your fire is low and burning cleanly and creating white or light grey smoke. That is also why the "smoke" does not chuff high on down hills as there is little pressure applied to the cylinders.

Now if you were going up the hill, you need a lot of heat so you throw on a bunch of wood or coal or squirt much more oil. When this is done on a low fire, there will be a lot of smoke at first until it is all burning. There will still be a lot more of the dark smoke as compared to idle when the fire is at full "throttle" because you are continuously adding fuel.

If you ever make a fire out doors, the initially cold fire smokes a lot and the hot fire very little.
Harald
CS2 DB & Canadian Era 3-6
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Offline kimballthurlow  
#4 Posted : 08 May 2015 22:52:14(UTC)
kimballthurlow

Australia   
Joined: 18/03/2007(UTC)
Posts: 5,840
Location: Brisbane, Australia
Originally Posted by: witzlerh Go to Quoted Post
White is the steam. The steam exhaust from the cylinders is shot through the stack to create vacuum to draw the exhaust gases from the fire box through the boiler (to heat water) and out the stack.
.......


Hi,
Absolutely correct.

In my sub-tropical country, it is reasonably rare to see 'white' from the exhaust chimney of a steam locomotive.
That is because the steam turns to water immediately on evacuation.
So when the fire is new, all you see is black smoke, and when the fire is hot, the exhaust is completely colourless.
You don't see the water droplets.

However, when the temperature drops, or on early mornings, you see condensed steam mixed with the smoke, so it takes on a much more varied hue.
There are times when it is cold enough for the exhaust condensation to be pure white.

regards
Kimball
HO Scale - Märklin (ep III and VI, C Track, digital) - 2 rail (USA and Australia) - 3 rail (English Hornby Dublo) - a few old O gauge.
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Online Alsterstreek  
#5 Posted : 09 May 2015 12:17:14(UTC)
Alsterstreek

Portugal   
Joined: 16/11/2011(UTC)
Posts: 4,525
Location: Southwesternmost
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