 Joined: 11/05/2013(UTC) Posts: 488
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Why does the exhaust of steam exhaust seems to be mainly white while other times black? Fred
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 1 user liked this useful post by SteamNut
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Joined: 16/02/2004(UTC)
Posts: 15,443
Location: DE-NW
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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  |
1 user liked this useful post by H0
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 Joined: 25/09/2010(UTC) Posts: 417 Location: Sherwood Park, AB, Canada
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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 |
3 users liked this useful post by witzlerh
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 Joined: 18/03/2007(UTC) Posts: 6,763 Location: Brisbane, Australia
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Originally Posted by: witzlerh  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 II-III and VI, C Track, digital) - 2 rail HO (Queensland Australia, UK, USA) - 3 rail OO (English Hornby Dublo) - old clockwork O gauge - Live Steam 90mm (3.1/2 inch) gauge. |
4 users liked this useful post by kimballthurlow
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 Joined: 16/11/2011(UTC) Posts: 5,843 Location: Hybrid Home
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1 user liked this useful post by Alsterstreek
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