Re: Singing pipes

[George Spagna <gspagna@rmc.edu>]

At 10:53 PM 3/18/97 -0800, Leigh Palmer wrote:

> These are called "Rijke tubes". The gauze is optimally placed one quarter
> of the length from the bottom of the tube. The ones I've made are also of
> 50 mm diameter glass, with about 3 mm spaced brass wire gauze. I've made
> quite a few of these and have kept a set which is tuned to a major triad
> plus the octave. They are deafening!


> I cannot explain simply (or otherwise) how these tubes work. Brian
> Pippard (former Cavendish Professor of Physics at Cambridge) and I had a
> go at trying to understand them during his visit to Simon Fraser thirty
> years ago. After he left we continued a correspondence about them, and
> he believed that he did understand them, but I was incapable of
> understanding his explanation, which was nonmathematical. I saw quite a
> bit of Brian during my stay in Cambridge a couple of years ago, but I
> didn't renew the discussion. Brian told me that schoolboys in Britain
> had made drainpipes sing by shoving lighted newspapers up into them from
> below. I was unable to duplicate the feat, even with his help. He had
> never done it himself.

Yes  -  we don't use a wire mesh or a newspaper, rather insert a Meeker
burner into the pipe.  We have a set of oversized cardboard mailing tubes,
and one large carpet roller which shakes the building when we fire it off!

In the last century these flame-driven singing tubes were referred to as
"Chemical Harmonicas".  Toepler, the same guy who invented Schlieren
projection, did a stroboscopic study of the shapes assumed by the flames
within these pipes  -  (Ann. Phys. 128 (1866)), which I came across while
doing a study of another "standing wave" demo, the Rubens Flame tube.

> What can be said confidently is that the tubes are powered by convection.
> When mine are laid over sideways they become utterly silent. After being
> left that way for ten seconds or so I can turn them vertical and they
> sing loudly again, seemingly with no energy source. It is quite a
> dramatic effect.                  ^^^^^^^^^^^^^^^^

                                   Except, presumably, the hot wire mesh.

> I, too, would like to know how these things work.
>
> Leigh

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