||About bells’ quality
ABOUT BELL FOUNDING’S QUALITY
Bell’s sound is one of the most important criteria of its process quality. What shall we pay attention to, when ordering bells and their receiving?
1) Bell’s ringing should be calm, without “croaking” and strong beats, which tell about founding’s defects, bell’s wrong shape and asymmetric allocation of its mass.
2) If high tones are quickly disappearing (so called “cluster” sounding) after a beat (especially with large bells) and only rumble remains (i.e. only undertone’s sounding), this means that the alloy is of low quality or the founding is porous, friable and has internal defects.
3) One of the most important quality’s criteria is the time of sounding. It should at least 5 seconds for little (over-toll) bells, at least 10 seconds for middle (under-toll) bells and at least 20 seconds for large (toll) bells, at 1 meter distance. Otherwise it’s a defect in founding or presence of flaw in the bell.
4) If you compare the main tone – undertone (i.e. the lowest and the longest overtone) of different bells of the same weight, but from different producers, you’ll see that it varies to several half-tones. Unfortunately, nowadays some bell-founders and their dealers advertise their bells as sounding lower, then others (e.g. comparing with bells of "Pyatkov and Co" partnership association in Kamensk-Uralsky), that’s why they proclaim rhetorically: why should you buy larger bells with the same tone? In fact, it’s black advertising for such misfortune-producers, as the practice shows that bells of lower tones sound worse and flaw quicker.
What’ the matter here? The answer to this question is given in Hladney’s formula of bells’ conformity.
where: F – is sounding’s wave frequency, T – thickness, D – diameter, E – elastic modulus (Young’s modulus), p – material’s solidity (specific gravity).
Bells’ certification, held by Bells' Centre, shows that practically everyone of our bell-founders use the same basic data for Russian profile, including thickness-cut diameter ratio (1/14), and Olovyanishnikov’s method of creating profile. That’s why, comparing sounding of the bells, familiar in size, you needn't use thickness-diameter ratio.
As for specific gravity, it varies only a little and tells about brass and stannary balance and presence of secondary impurities.
The last is elastic modulus E, which tells firstly about founding’s quality (if it is dense or fozy, if it’s porous or has some defects in form of flaws). It can also determine if the alloy was produced rightly - it should contain 80% of brass and 20% of stannary (with ± 2-3 % variance of this balance) and the amount of impurities not more than 2-3%.
Some bell-founders are not improving founding’s quality (i.e. rising elasticity) to lessen the probability of their products' split, but specially lessen the concentration of stannary, increasing material’ ductility, but the fact is that the sound looses its power, becomes less harmonious, pitch level lessens.
At last, there’s only one conclusion to be made – while material’s elasticity is high, the quality of its founding is better, persistence for beating is larger and its mode is higher.
Taking to consideration that v Å / ð is sound’s speed in metal, we have decided to check Hladney’s formula and conclusion made, measuring sound’s speed in bell's bronze for the bells of the same size (about 40 poods in weight) from different producers. We should keep in mind that maximal sound’s speed in bronze with high concentration of stannary is ~ 4750 mps). Undertones’ meanings are real, measured during the process of certification.
||Sound’s speed (mps)
|"Pyatkov and Co” partnership association,
|H, small octave
||4550 - 4650
||G-sharp, small octave
||4450 – 4550
||G, small octave
||4350 – 4450
Tutaev, Yaroslavl region
|F-sharp, small octave
||4250 – 4350
As you see, our conclusions were right. So, if you are offered to buy bells of the same size and weight, but having different meanings of the main tone - undertone, what bell would you choose from the point founding’s quality? Right you are, the bell, which has the highest undertone!