Steam trains: what is the 'choo-choo' sound?

Question

What is the thing called that makes the 'choo-choo' sound on steam trains? What is it's purpose?

Answer 1

TO BREAK THE MONOTONY OF THE 'CHUGA CHUGA' SOUND!

Answer 2

Train whistle, (originally referred to as a steam trumpet), is an audible signaling device on a train, locomotive, or the like, which produces a loud sound to warn that a train is approaching, and to communicate with rail workers. During the era of steam locomotives, the whistles were steam whistles, arranged to play a minor seventh chord.

Answer 3

Hoghead has the best answer here, the extra ten(10) points should go to him.

Answer 4

Vented steam from the drive wheel pistons.

Purpose - to allow the piston to return to the closed position.

Answer 5

Sounds like the US Chime whistle, which is several small whistles in a single casing, a few of these were fitted to UK locos, like 3 or 4 pre WW2 and post war BR Standard Locos were fitted with these until problems with excessive whistling prompted  a change to a boring Caledonion Hooter.

Answer 6

Good question.  

The sound comes from the "smoke box".  This is a portion of a steam engine's boiler at the front which has the main steam pipes to the cylinders, the exhaust pipes from the cylinders and the smoke stack.

The "chuff chuff" sound is produced when the cylinders exhaust their steam.  In addition, the flues from the firebox travel the length of the boiler and exhaust the smoke from whatever fuel they were burning.  The exhaust from the cylinders created "draft" at the smoke box which in turn moved air through the flues, helping the fireman maintain a hot fire.  The fireman had a "blower" as a way to get more draft while starting, when the exhaust steam is not strong or long enough for proper draft.

There were a class of engines that had three cylinders (the third was under the boiler connected to a cam on the No. 1 driver) that had a distinct off-beat rhythm.  On the SP, these were called "stutter decks".

There were also a series of different articulated locomotives with two (or more) engines under one boiler. Sometimes they would run "in sync", other times not, producing a-rhythmic sounds.

Then there were the "Climax", "Shay" and "Heisler" type steam engines that were gear driven by two or three cylinders.  Low geared for logging operations, they sounded like they were going a hundred miles an hour while plodding along at nine or ten.

Thanks for asking.

Answer 7

It's a huge whistle attatched to the steam collum. It's the equivilent to a modern day train blowing the horn.

Answer 8

The exhaust steam from the cylinders goes to a common pipe which discharges through the funnel. The release of steam is - obviously - intermittent and produces a 'choo' each time. More exhausts, more choos.

The steam is vented via a funnel having a waisted shape and a vent which blows through it. This produces a vacuum to pull air through the firebox and boiler tubes to make the fire burn well and give good heat transfer in the boiler.

It also dumps part burnt fuel, ash and steam containing cylinder lubricant into the atmosphere. They were and are awfully dirty!

RoyS

Answer 9

The choo choo, is a result of the piston(s) moving back and forth from the steam building up and releasing during the exhaust stroke.

Answer 10

large amounts of steam being released in short bursts

Answer 11

The choo is the whistle.  The chug are the pistons.  That clack is the shaft(s) changing direction as they drive the wheels.  All noticably absent on electric commuter trains.

Answer 12

It is the steam whistle it has the same purpose as a horn on a car

Answer 13

It is the exhaust from the pistons. there are two, one on each side for each set of drive wheels. They exhaust once for each stroke  The two sides are 90 degrees out of phase so there are four power strokes or chugs for each revolution of the wheels.  Some of the exhaust helps to  induce draft and make the fire hotter and blow the smoke out the stack.