Steam Engines - What Is Happening?

[LoudTrain]

To some of you, I bet this will be pretty basic!

I have 2 questions about some things I saw recently watching YouTubes of steam engines in operation:

(1) The train will be in motion, and a nominal amount of gray smoke will be coming out the smokestack. Then, all of a sudden, there will be this brief burst (like a cannon shot, lasting 1-2 seconds) of thick black smoke. Then it will return to the gray smoke. Sometimes it happens again in about 45-60 seconds. What is this?

(2) I saw one of the big Pennsy engines (I think it was a 0-4-4-0) starting up. The rear 2 drive axles were going at normal speed. But the front 2 axles were spinning very fast. What was happening here? Did the rear axles have better traction? Was there more steam to the front cylinders?

Thanks in advance!

-- Russ Schwartz

 

[TweetsieDude]

For your fisrt question, i really can't answer unless i saw what the engine was doing. Do you know what kind of fuel it was burning? If it was burning oil, i was assume the fire had gone out and was relit. if it was burning coal or wood, the flues may have had something in them being cleared, or the locomotive was using more tractive effort.

#2, your fisrt guess was right. The wheels spinning had more traction than the other set.

I can't garuntee my fisrt answer may be right.

Rock On!
Dusten

 

[jadebullet]

#1) The fireman shoveled some more coal on, and started to increase the heat of the fire for more pressure, and thus, more tractive effort.

#2) That's a duplex for you. With the exception of the Q2 which had anti slip measures installed, the PRR duplexes tended to slip constantly. What you are seeing is the front driving axels having too much power, and not enough grip. Thus, they started spinning. Slippage happens to any type of steamer though. If you listen to a steamer going up grade, you can sometimes hear the chugging increase dramatically, then reduce. This is due to slipping, and is really not good for the engine.

BTW, could I have a link to the PRR video. Duplexes are an interest of mine.

 

[barn700]

1) Often loco drivers would create excessive smoke for the photographers of course, it was truely frowned upon by the Railroad Companies, as it indicates inefficiency of the loco and the driver/engineer. What you describe is probably a clearing of flues with a steam jet. So dont take YouTube vids too seriously, it is probably the engineer showing off a bit.

2) Correct, spinning wheels were a problem with many locos, especially icy/wet tracks hence sanders to give more grip when needed.

On my Erie Triplex model (which has 3 sets of drivers) the rear drivers were loaded heavy at start (they were under a heavy tender) but as fuel was used up the rear drivers used to spin a lot. The model reasonably depicts reality, where different drivers would slip depending on accelleration, this happened on the real Erie Triplex and led to their downfall.

All of my articulated locos act this way in various amounts, and the steam sounds, linked to the drivers, goes in and out of synch, most pleasing to hear a true artic going round a curve where the drivers are going different distances. In Trainz this sound is quite well depicted in TS2010 of course.

 

[LoudTrain]

Thanks!

Thanks, all, for your answers to my 2 questions!

-- Russ