Sounds made by idling steam locomotive

[GP-9_Man11786]

This summer, my wife and I rode the Durango & Silverton. Upon arrival at Silverton, we went to take a picture of the locomotive, a K-36 2-8-2. I noticed the locomotive making a kind of drumbeat sound at regular intervals. It went in kind of 1-2-3-4--pause--1-2-3-4 beat. Does anybody know what this sound was?

[Rader Sidetrack]

You may have been listening to the steam-driven air compressor. Here's one example:

Image linked from: 

http://www.billcaid.com/2010/HogHunting20100323/Part29/Part29.html

[switch7frg]

GP-9MAN11786;   if that was a cool sound, wait untill you are standing beside the beast looking intently at the pipes and  wondering what they are for and then the safety valve pops off ~~~ hoo hoo  cheap thrill.

[tree68]

Sounds like the air compressor.  Depending on how the exhaust is plumbed, you may have also heard a soft exhaust "chuff" at the same time. 

How often the air compressor cycles is dependent on how well the train holds air.  Odds are if you were in earshot when the brakes were released, and thus recharging, you'd have heard it working much harder.

[selector]

If it was a double "thoom-click, thoom-click', or a muffled thump followed by a metallic sound, it was definitely the pumps.  However, in many cases, the pumps are surprisingly quiet except for their exhaust which sounds like a rhythmic panting sound.  The Pennsy K4's were like that...pant-pant, pant-pant...

[Deggesty]

switch7frg

GP-9MAN11786;   if that was a cool sound, wait untill you are standing beside the beast looking intently at the pipes and  wondering what they are for and then the safety valve pops off ~~~ hoo hoo  cheap thrill.

Or, you are in a trainshed and a car is uncoupled with the anglecock open on the car that is to be left. My first experience with that was about sixty years ago, in Atlanta's Terminal Station.

[tomikawaTT]

Japanese steam used the same Westinghouse cross-compressors as shown in the photo above.  The also had a massive single-cylinder water pump that had a drawn-out shhhh-THUMP sound when operating.  The turbogenerators were well-maintained and almost silent.

I recall being in the Haijima station in the '60s.  There was a C58 class 2-6-2 standing alone, almost dead silent, waiting for a catenary motor to arrive with its train.  Then the safeties lifted...

I have been to Niagara Falls, and I'll state that the steam escaping through those brass inverted trumpets was louder than half the water that rains on the North American continent falling off a cliff...

Chuck

[aegrotatio]

Here's a video of the air compressor.

http://www.youtube.com/watch?v=X-9dPuFf8XU