Tunnel Running Smoke Hoods and The Like

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Tunnel Running Smoke Hoods and The Like
Posted by mj3200 on Wednesday, November 22, 2006 6:03 PM
Viewing old footage I have noticed that exiting tunnels some steam locomotives seem to be releasing smoke that they have built up during the run through, but how is that possible if they are working, surely the draught from the blastpipe would pull the gasses through from the firebox whether desired or not. Also what was the thinking behind the smoke hoods on the Bigboy?
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Posted by tomikawaTT on Friday, November 24, 2006 9:03 PM

It's not the locomotive releasing the smoke, it's the tunnel!

When transiting a tunnel, exhaust gasses tend to stay with the train unless there is a really powerful artificial ventilation system at work.  The blast from the stack might be able to lift smoke well clear in the open, but there's no place for it to go under a couple of megatons of rock.  When the train exits, it drags the exhaust gasses with it.

Toward the end of steam operation in Japan, locomotives used on lines with tunnels (which describes most of the Japanese rail system) were fitted with blast deflectors that directed the exhaust back in a fan-shaped cloud that tended to stick to the tunnel roof.  IMHO this was probably done more to protect the tunnel linings from direct blast effect than for any other reason.  The deflectors made the normal stacks resemble giant mushrooms.  The retractible deflectors on Big Boy were supposed to serve the same purpose - shoot the exhaust along the tunnel roof, hopefully past the cab.


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Posted by Anonymous on Sunday, November 26, 2006 6:00 AM

Here's an article I typed for the "Our Place" thread, way back on page 266. Hope this helps!

Smoke Deflectors by Herbert G. Monroe from Railroad Magazine Feb. 1941

In 1902, This Rogers Consolidation was the Great Northern’s answer to smoke nuisance in the Cascade Tunnel. Big motors, working singly or in tandem, Now glide through the 3 ½ mile bore.

Ever since 1833, when construction engineers drove America’s first railway tunnel through a hillside four miles east of Johnstown, Pa., motive power men have cudgeled their brains for a solution to the difficult problem of smoke deflection. True, their first efforts were scattered and half-hearted, since early bores allowed worlds of atmospheric clearance for iron colts whose stacks reached high above slim boilers and gothic-windowed cabs. But there came a day when locomotives were to burst their brass belting and grow in girth until their stacks resembled nothing so much as warts on a Sequoia log.

Those of us who spent the period of transition in smoke-filled engine cabs will never forget the experience. When a big freight hog, with something less than a thousand loads at her tail, thundered into a tunnel and the dynamiting exhaust struck the ceiling like the muzzle-blast of a rapid-fire cannon, belching smoke was instantly deflected downward to enshroud us in a shriveling black fog. Somehow, we usually managed to weather through, but more than one good rail came out cooked like a Thanksgiving turkey.

Not only did the tunnels endanger the lives and health of engineer, foremen and head-shack, but very often the exhaust blasted key-bricks from the arched ceiling, thereby threatening to drop the mountains above straight through the open holes. It has been told how an engineer named Clancy – or maybe it was Moriarty – saved enough bricks on the “Rat Hole” run in a year to build a fine house. Most of them he took from the running board, but now and then one bounced through the window and clicked him on the cranium.

Back in 1907, when I was braking on the Southern, those falling bricks annoyed Master Mechanic W.H. Dooley, of the CNO&TP. Besides, he was tired of listening to the crews cuss. So it was that he went about building what might be termed the first “modern” smoke deflector. Unfortunately, Mr. Dooley soon found himself in the position of the man who built a cabin cruiser in his basement. He had the boiler makers in the Ferguson Shops at Somerset, Ky., cut out and fit an extension over the stack of one of the engines; an elbow pipe like the kind you’ll find behind a kitchen stove.

This member was about two feet high, and hinged in such a manner that it could be raised and lowered by a contrivance that included a set of gears and an air cylinder. Everybody gathered around to see the epic-making locomotive start off, and Mr. Dooley was as proud as a new father. The hogger cracked under the throttle, but he forgot to lower the smoke deflector and it knocked down part of the building. This was better than jarring the portal off a tunnel, for it was discovered that the device was too high to clear the main lines bores anyway.

Not disheartened, Mr. Dooley made another one. This was a right angle bonnet, or flop-over deflector. It was operated by a mechanism similar to the first, but, though the air was left on in the tunnel, the exhaust had a tendency to blast the bonnet off the stack. Dooley then cut off a third of the elbow, which allowed free passage of some of the exhaust until the deflected portion struck it, whereupon the entire exhaust was turned from the tunnel ceiling. The pressure at the top edge of the bonnet held it firmly against the stack. These bonnets are still used on some of the Southern’s engines, and a careful survey discloses that the original right-angle deflector, with minor changes, is a favorite on the Canadian Pacific, Great Northern, Santa Fe, the Milwaukee and several other top-ranking railroads.

As I have already stated, I was braking on the Southern about that time, on a run in the Atlanta-Chattanooga district. Athwart that route, just south of Braswell, Georgia, old Braswell Mountain stood glowering, plainly resentful of the snorting trains that rummaged around in her bowels. It was in this bore that I heard Gabriel trumpeting his call to man the Heavenly Express, on my first trip over the line.

The hogger and fireman had coaxed that hand-fired, saturated freight hauler up the grade with 1200 tons on her tail. When we hit the portal the steam pressure was down to 160 pounds. The tallowpot had been working his heart out, trying to wind her up against the pin, but the coal was tough, the fire was dirty and the old gal wasn’t what she used to be. Each long-drawn grunt threatened to prove her last. The added tonnage of a jay bird lighting on a box car would have stalled us. Every shovel of coal added to the density of the smoke belching from the stack. Just before we blasted underground, the hoghead eased the throttle off a few notches and dropped the Johnson bar down in the corner. Then he reached for the sander valves. Seeping water and exhaust evaporation would make the rails in the tunnel as slippery as a county fair greased pig.

Meanwhile, the foreman had gone to the gangway to gulp down a last breath of clean air. Already, we’d closed the windows and soaked big gobs of waste with water. The last trickle of daylight faded. The labored thunder of the exhaust slugged at our eardrums, the heat and the smoke grew ever more intense. It was like slow-baking in a Dutch oven. We buried our faces in our caps and the wet waste – coughing and choking. I had visions of stalling, and tried to steal a glimpse of the gage. I thought of the tank and wished I was in it to my neck – and then some. About that time the drivers started to dance, But the hogger caught her, like a wayward wench being dragged to her feet by a true Southern gentleman.

We were suffocating, and yet we burrowed deep in coats and jumpers, trying to shut out that stifling heat and smoke fumes. My ears rang – or, perhaps, it was chimes. I vowed that if I ever got out of Braswell Tunnel, I’d lead a sweeter, purer life. And then, suddenly, we were through, and Braswell Mountain was behind us.

Along in 1917, a pusher was located on Braswell Mountain. One day this engine was ordered to the shops. An engineer named Damon Hicks started up the hill with the ailing jack. When he entered the tunnel a cylinder packing was blowing. Before he got half way through it went out, enveloping him in a swirl of steam. To complete his discomfiture, the drivers started to spin and he couldn’t find the throttle for the ghostly “soup.” The pusher slipped down. Damon tried to start, but the old mill just danced. She was out of sand – the very life-blood of an engine in a tunnel. The other hogger had used it helping on the mountain during the night.

When Hicks finally got her out, and wiped his sweating face and hands with the waste he had to breathe in, every inch of skin came off. He was out of service several months, and still feels the effects of his experience under Braswell Mountain.

This ear-trumpet effect decorated the head-end of the Boston & Lowell’s “Eagle”, back in 1870. Strictly speaking, it was a spark arrester, not a smoke deflector.
The R.G.&S. Tunnel is another product of Southern Railway ingenuity. In order not to impede his movements, the Fireman’s hood is equipped with a longer air hose connected at the rear.

Again. On March 18, 1918, George W. Green was firing the 251, the lead e

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Posted by spikejones52002 on Monday, December 18, 2006 6:26 AM


The only reason for the smoke hood or deflectors were to prevent the force of the exhaust from destroying the roof of the tunnel.

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Posted by spikejones52002 on Monday, December 18, 2006 6:34 AM

Greetings Again:

I hope this answeres the first part of your query.

many Steam and some diesel will die from lack of oxygen in long or incorrectly designed tunnels.

In these problem tunnels they placed mid and end engines to push the front ones through.

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Posted by PBenham on Monday, December 18, 2006 3:45 PM

That article was really interesting. Imagine trying to get modern day railroaders to accept what their grandfathers and great grandfathers had to put up with.

Also, we see why Southern bought FTs as early as the WPB let them do so!


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