Steam Whistles

Trains Magazine General Discussion
1

I hope this topic does not come up too often but, how do steam whistles work? Does any one have any diagrams of one? Thanks!![8D]

2

Steam whistles work just like organ pipes - but since the mass and pressure of steam are much greater than that of air a whistle is louder. A simple whistle has a closed tube with a lipped slot in one side. When steam is admitted to the tube, it first pressurizes the tube slightly. Then the steam starts to escape through the slot - lowering the pressure. The alternating increase and decrease in pressure results in resonation – which is the sound the whistle makes. Using tubes of different lengths and adjusting the slope of the lip tune the whistle to different pitches (tones).

dd

3

Have a look at
http://www.whistleman.com/html/whistle_terms.html

4

And, by the way, they did not all sound the same, different railways had different whistles,as did each locomotive in some cases. and if you listened carefully each engineer had is own style.

5

The wooden “train whistles” you can buy at souvenier shops and train shows work exactly the same as the real deal. Obviously the real ones aren’t wood, and use steam (or air, in some cases) for the airflow, but all of the physical principles are the same. If you 've got enough wind, you can make one of the wooden one “talk,” too.

6

Thanks everyone! I am going to try to build one just for fun.[:D]

7

Here’s how I understand it:
Steam is admitted to a cupped bowl. Above this bowl is a bell made out of copper or brass, with a slight gap separating the bottom of the bell from the top of the bowl. Steam escaping through this slot sets up a different pressure on the outside of the bell than the inside, and in turn causes the vibration of air molecules which are perceived as sound. The frequency of the vibrations and therefore the pitch of the sound is determined by both the length and the diameter of bell.

8

there was a “how to built it” article in Model Railroader many years ago

dd