Peter Davey Heater

[CompuTutor]

Maybe some pics to study too ?

[CompuTutor]

(Limit 10 pics per post...)

[zuvrick]

Sorry for coming into this so late.

I have read through some o fthe posts on pages 1-5 and some of the last 3.

I didn't see anyone mention these acoustic issues.

The size of the bells will have no relationship to their bell-resonant frequency. The frequency is determined by the thickness of metal, modulus of elasticity and Poisson's Ratio, which vary with differing alloys. Also any work hardening induced in the stamping, pressing or metal spinning methods to make such a shape change the modulus of elasticity.

The other very important fact is that the velocity of sound is also part of the equation. When a bell in air is struck it will have a certain pitch or frequency, but when it is immersed in water the resonant frequency will be lowered. You can test this by immersing any wind chime bar or tube, or any bell in water after it has been struck. You'll hear the pitch slide downward (glissando in music).

My trusty handbook for this info is Music, Physics and Engineering by Harry F? Olson, my copy was published in 1968 or so (been dragging it around for 43 years). I have played a lot with metal instruments, and witnessed the building of a bronze Javanese gong that takes to days of hot and cold forging to make it sound musical. These use Beta Bronze, a special intermetallic compound and not really an alloy, of tin and copper. But that's another story.

I have a sneaking hunch that any tuned resonance by Davey was done in air and has no relation to the bell resonance in water.

Another factor is possible the resonance of the cavity formed, but that is hard to measure.

I would think that the easiest way to prove or disprove resonance in this is to supply a variable frequency power signal. Take an amplifier and and use a 220V primary and 12-24V secondary transformer, connect it backwards to step up the ampliier output to 100-250 volts and then vary the frequency around 40-150 Hz while measuring the current and temperature rise.

Zuvrick from Indonesia

[Paul-R]

The size of the bells will have no relationship to their bell-resonant frequency.

This is not true.

The factors that you mention in your next paragraph will have a bearing, but if the diameter of the bell is doubled, all else remaining constant, do you imagine it will not change the resonant frequency?

[MasterPlaster]

Here is a study on water cavitation that is great source of info:

http://www.dtic.mil/dtic/tr/fulltext/u2/a031182.pdf