Steam locomotive smoke in tunnel question.

This is just a guess, going by videos I've seen of actual steam trains going through a tunnel.

It seems that most of the smoke concentrates at the top of the tunnel. And, I don't think there would be time for soot and ash to fall out enough to get someone's clothes dirty if they were on the train. There might be some smoke that gets into a boxcar, but probably not an excessive amount.

Also, I've been around furnaces that burns coal. The soot kind of falls out in little beads; it blows around unless it's touched or "smeared". If there was air being blown past, such as on a train, the soot would probably blow off.

Again, mostly a guess.

It depends. Tunnels vent differently depending upon length, slope, wind direction, vent tunnels, and some other factors.

But if you take the Moffat Tunnel in Colorado (6.2 miles long), Amtrak will shut the doors between each car, and you still smell diesel smoke.

What does your plot need? Shorter, well-vented tunnel they'll come out fairly clean. Longer, less well-vented tunnel and they'll barely survive. Some of the tunnels during the steam era required a certain length of time before a second train could go through because they would be so filled with smoke.

Best of luck,

Jim Clark-Dawe

Jim makes a good point about the length of the tunnel. I was assuming a fairly ordinary tunnel.

They could crawl under a tarp.

You're violating the first rule of engineering a railroad tunnel by combining a grade with a curve. Usually the idea behind a tunnel is to get rid of either a grade or a curve. But sometimes you've got to do what you've got to do in engineering.

Understand that both grades and curves cost speed for trains. It would be interesting to see what the tonnage limit is going to be here. (Tonnage limit is the amount of tons an engine can pull up a grade without stalling.)

Two hundred feet of elevation gain at a 2% grade (two feet of rise for every hundred feet of horizontal track) works out to about ten thousand feet of track. Normally the engineering would split this up by putting in fill from the tunnel and use a hundred feet of elevation gain before hitting the tunnel for the last hundred feet (good engineering practice calls for fill removed from a tunnel or a cut to be used as near as possible). Probably the last thirty feet of elevation gain would be done as a cut. With this approach, you'd reduce your tunnel down to about four thousand feet in length, with a cut of about one thousand feet.

But if you're going to put a spiral inside a cliff, what you'll do is run part of the spiral along side the cliff face, in effect creating windows that would serve as very effective ventilation shafts. (It would also make removal of material during the construction a lot easier and cheaper.)

Net result would be a rather slow tunnel (transit time about six minutes at 20 mph, which is on the high side for speed), with high steam usage (uphill more power is needed) with a tunnel with effective ventilation (the side windows as well as the vertical chimney effect). It could well be if the ventilation forces are strong enough, a train going uphill that is traveling in the 5 mph speed range could have all of the smoke rising in front of it.

Realize that if the smoke in the tunnel is too bad, railroads would electrify the tunnel. You've got to be able to get the train crew, and maybe passengers, through the tunnel.

Best of luck,

Jim Clark-Dawe

Remembering the few times I rode steam passenger trains, the smell of the smoke was noticeable in the cars. If my memory is correct, it was possible to open windows and some of the soot would come flying in.

So, for a boxcar, there would be smell and soot coming in any openings, more towards the back of the car than towards the front.

If you have an amusement park near you that has a steam train as one of the attractions, you might want to take a couple rides on it to get some first-hand ideas. Puma

jclarkdawe said:

You're violating the first rule of engineering a railroad tunnel by combining a grade with a curve.

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An interesting little side note that has nothing whatsoever to do with the question at hand; railroad curves are not the same as highway curves. Highway curves are based on a single radius (like a circle); railroad curves are more like part of a spiral--the curve gradually tightens as it goes along.

Yes, I work in engineering. ;-)

jclarkdawe said:

But if you're going to put a spiral inside a cliff, what you'll do is run part of the spiral along side the cliff face, in effect creating windows that would serve as very effective ventilation shafts. (It would also make removal of material during the construction a lot easier and cheaper.)

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Google "Tunnel Mountain" images to see a good example of this. It's fascinating to see the same train running on different levels. (Our freights here run to 2KM long.)

jclarkdawe said:

You're violating the first rule of engineering a railroad tunnel by combining a grade with a curve. Usually the idea behind a tunnel is to get rid of either a grade or a curve. But sometimes you've got to do what you've got to do in engineering.

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Two years ago I visited British Columbia on a drive/camping excursion. While there, I stopped at a famous spiral tunnel (of which I forget the name), made necessary by the topography. From an overlook, I watched a train double back on itself, with the engine emerging on the track above the trailing portion of the train, which was, of course going in the opposite direction. So it can be, and is, done in some places.

caw

blacbird said:

Two years ago I visited British Columbia on a drive/camping excursion. While there, I stopped at a famous spiral tunnel (of which I forget the name), made necessary by the topography. From an overlook, I watched a train double back on itself, with the engine emerging on the track above the trailing portion of the train, which was, of course going in the opposite direction. So it can be, and is, done in some places.

caw

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The Big Hill Spiral Tunnel, at the Kicking Horse Pass? Never seen it, but heard about it, apparently quite a sight.

frimble3 said:

The Big Hill Spiral Tunnel, at the Kicking Horse Pass? Never seen it, but heard about it, apparently quite a sight.

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Yes. That's the one. You'd think a half-assed intelligent person could remember a name that vivid, but I must have been using the other half.

It is quite a spectacular place, and view. The overlook is above the gorge they needed to climb, and quite close to the tracks.

You live on in B.C. and you've never driven over there? For shame. Interior B.C. is a wonderful place to drive aboot in the summertime.

caw

Rufus Coppertop said:

... would the freight wagon end up filling with smoke and steam?

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Boxcars of the steam era were 40 feet long, and almost always had door on both sides. If the kids left a door partially open, yes smoke and soot would enter the space, just as it would enter the passenger cars of the era if a window was left open. Just as it still does on many 'scenic' or historical railroads today.

Rufus Coppertop said:

Would they end up with dirty, sooty clothes?

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Yes. But, this depends a lot on how slow the train is, how far back the boxcar is from the engine (if the engine is it out of the tunnel before the boxcar goes in... possibly less) - how wide open the door is, and lastly, the which direction the train is traveling ie: is it under full power climbing the grade or is it under very low power as it rolls down grade. It really makes a difference in how much smoke is being produced.

There are several operating 'historic' and 'scenic' steam train rides currently operating, and many do warn of the possibility of sooted clothing during the trip. This is esp true in the tunnels if you do not close a window or have decided to be brave and ride an 'open air' car. Some people insist on doing just that so to fully appreciate the experience.

blacbird said:

Yes. That's the one. You'd think a half-assed intelligent person could remember a name that vivid, but I must have been using the other half.

It is quite a spectacular place, and view. The overlook is above the gorge they needed to climb, and quite close to the tracks.

You live on in B.C. and you've never driven over there? For shame. Interior B.C. is a wonderful place to drive aboot in the summertime.

caw

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I live in spectacular B.C. but I don't drive. My experiences of the Interior are from way-back when I was a kid and my dad (who loved to drive) took us everywhere my mother's patience would endure.
Next time my sister visits, we're thinking of a driving vacation. We get along best when we're staring out a windshield together.

As for the name thing: 'Big Hill' is so obvious that the mind skips right over it. You can imagine the surveyors coming across it.
"Wow, that's some big hill, Jimmy!"
"Yeah, but what're we going to call it?"

As one...

who regularly made train journeys in the good old days of steam trains, I can say one certainly did get smut and grit flying in an open window, especially if the train was going through a tunnel.

Steam trains are lovely things but they are dirty. If it was summer white gloves were always kept inside your bag but my white socks always got dirty smuts on them. The worst was a fragment of cinder flying into your eye. That really hurt!

Carriage windows were usually kept closed and I can imagine that an open box car behind a steam train would collect a lot of smuts and grit!