Question about firing a steam locomotive

The black smoke is from incomplete combustion. On coal fired engines, a shovel or auger has just loaded some coal in the firebox. On oil fired engines, the fireman may have just thrown in a shovel of sand to clean the flues. I'm sure Jack and Melvin can write a whole book about it.

I am no expert. When I seen a clean stack in photos, the loco is usually running at speed on level ground, and I think the valve gear is set to cut off so the valve is only open for a small part of the stroke. This uses less steam, so less fuel needed to make steam, so less smoke. When you see photos of helper engines on the hill, they are usually pouring out smoke and often barely moving. In this case, the valves are open for the full stroke.  That means they are using way more steam, so more fuel needed to burn to make more, so more smoke.

The fireman has to make enough steam for the job at hand, keep water over the crown sheet, and conserve fuel to the degree possible.

Others who know more can correct and amplify

Interesting responses so far. Guess I'll wait awhile and see how this all pans out.

"Shovel all the coal in, gotta keep her rollin".

@Hot Water posted:

Interesting responses so far. Guess I'll wait awhile and see how this all pans out.

LOL,  looking forward to it.

There is a difference between smoke and steam exhaust I think.     In cold weather a steamer often put a plume of billowing white steam exhaust -    I think when you have black smoke,it is incomplete combustion.    I have also read that opening the fire door to throw in some coal would cause incomplete combustion.

I have a somewhat related question maybe somebody could help me with. On the New York Central Hudson that Lionel made famous, or is it the other way around, there is an “Auxiliary Smoke Stack”.   It is smaller and in front of the traditional smoke stack.  What is the auxiliary smoke stack for?  

@prrjim posted:

There is a difference between smoke and steam exhaust I think.     In cold weather a steamer often put a plume of billowing white steam exhaust -    I think when you have black smoke,it is incomplete combustion.    I have also read that opening the fire door to throw in some coal would cause incomplete combustion.

When a clean hydro carbon, maybe coal or oil,  is burned and there is perfect combustion, the product of that combustion is heat, CO2, and water (as either steam or water vapor, depending on the temperature).  In cold weather that water maybe seen as a white cloud coming out of the stack.  This no different than what is seen at an automobile’s exhaust in cold weather.  

@David Johnston posted:

I have a somewhat related question maybe somebody could help me with. On the New York Central Hudson that Lionel made famous, or is it the other way around, there is an “Auxiliary Smoke Stack”.   It is smaller and in front of the traditional smoke stack.  What is the auxiliary smoke stack for?  

The J1e’s at the beginning, used a Coffin feed water heater,….the Coffin type used exhaust steam to heat feedwater,…( all feedwater heaters used exhaust to heat the water be it open or closed type, .Coffin is a closed type ) …the piping forms an arch inside the smoke box door,…the small stack is used to vent steam that is not condensed, …

Pat

Thanks, great information.

@harmonyards posted:

The J1e’s at the beginning, used a Coffin feed water heater,….the Coffin type used exhaust steam to heat feedwater,…( all feedwater heaters used exhaust to heat the water be it open or closed type, .Coffin is a closed type ) …the piping forms an arch inside the smoke box door,…the small stack is used to vent steam that is not condensed, …

Pat

I think you will find that that "small stack" is for the booster exhaust.

@Hot Water posted:

I think you will find that that "small stack" is for the booster exhaust.

You’re correct Jack, ….that is the booster exhaust, …the vent pipe for the feedwater is a smaller pipe,…

Pat

I realize there is a reason for it, but why was the trailing truck exhaust piped all the way to the front of the boiler, instead of below the cab?

@Chuck Sartor posted:

I realize there is a reason for it, but why was the trailing truck exhaust piped all the way to the front of the boiler, instead of below the cab?

You mean you want all that noise AND steam exhausted right below the cab?????

Isn't that where the blowdown outlet usually is? And it would only be for a short time while the booster is engaged. I would think a lot less piping to the front of the engine.

@Chuck Sartor posted:

Isn't that where the blowdown outlet usually is? And it would only be for a short time while the booster is engaged. I would think a lot less piping to the front of the engine.

Blow down is not exhaust Chuck, ….Jack is correct, and I stand corrected too,….the smaller pipe is the booster exhaust, the Coffin vent pipe is much smaller, and not often molded, especially on die cast models,…having the exhaust under the cab would be noisy as all get out, ….although used to start a train moving, the booster would make a lot of racket with the exhaust exiting under the cab, and the crew wouldn’t be able to hear a thing….

Pat

@Chuck Sartor posted:

Isn't that where the blowdown outlet usually is?

No.

And it would only be for a short time while the booster is engaged.

The booster was primarily used for starting heavy trains, but was also used on steep grades, which could require usage for a half hour or more. I can personally remember one VERY long case of using the booster on 4449 while working the American Freedom Train on the long main line grade southbound on the Southern Ray, out of Danville, Va. We spent almost an hour at 9 to 10 MPH at full throttle and booster engaged. The sound was deafening, even with the booster exhaust piped forward into the smokebox (into the exhaust stand)

I would think a lot less piping to the front of the engine.

Piping was not a design issue with steam locomotives. Keeping all that steam exhaust & noise away from the operating cab was of far greater concern.

Okay. So the technical reason it was piped to the front of the engine was to eliminate the noise and steam?  Did one road have it piped to the tender? (I'm thinking NYC Niagara?)

What would keep the smoke box from drawing air in the auxiliary smoke stack when the booster was not being used?

@Chuck Sartor posted:

Okay. So the technical reason it was piped to the front of the engine was to eliminate the noise and steam?  Did one road have it piped to the tender? (I'm thinking NYC Niagara?)

No, not the exhaust from the booster. That would require yet another flexible connection assembly between the engine and tender, which would need to be disassembled ever 90 days for the ICC (now FRA) mandated quarterly inspection. Every quarterly inspection requires the tender to be separated from the engine, and the drawbars hammer-tested for cracks.

@David Johnston posted:

What would keep the smoke box from drawing air in the auxiliary smoke stack when the booster was not being used?

That "auxiliary smoke stack" was ONLY for the exhaust steam from the booster, thus had no "connection" into the smokebox. In other words, if the booster was NOT being used, nothing ever came out of that smaller stack.

Got it. Thanks.

Great topic. Always wondered what that little thing was next to the stack.

With our little oil burner just south west of Raleigh, I always strove for a “gray haze.” A light bit of exhaust you could easily see through. You didn’t want to blot out the sun with a dense black plume… although on occasion this was necessary. And yes, running a scoop or two of sand through the tubes to scour the soot off of them dirtied up the stack a bit.

Rich has told me that depending on weather conditions, that would result in seeing more or less exhaust. This was his answer to my question on black smoke. I think I asked that over two years or so ago.

@Dave NYC Hudson PRR K4 posted:

Rich has told me that depending on weather conditions, that would result in seeing more or less exhaust. This was his answer to my question on black smoke. I think I asked that over two years or so ago.

Actually, depending on the ambient temperature & humidity, the most common "visible exhaust" is mostly water vapor from the condensed steam exhaust. It doesn't really matter whether the locomotive is a coal burner or oil burner, most of what is seen from the exhaust stack is water vapor. Now, on a really hot day, with very low humidity, then there is nothing exiting the exhaust stack, when a locomotive is being properly fired.

@Hot Water posted:

Actually, depending on the ambient temperature & humidity, the most common "visible exhaust" is mostly water vapor from the condensed steam exhaust. It doesn't really matter whether the locomotive is a coal burner or oil burner, most of what is seen from the exhaust stack is water vapor. Now, on a really hot day, with very low humidity, then there is nothing exiting the exhaust stack, when a locomotive is being properly fired.

Yeah, that's what he said.