Clapper height tonal variation

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Re: Clapper height tonal variation

Postby JohnGouwens on Thu May 02, 2013 6:46 am

Go hear some of their work and you'll hear how silly that claim is. Their more recent work has all been with iron clappers (Glendale, Ohio, Berea College, Brigham Young University, Ball State University, La Porte). The bronze clappers make an ugly, clangy sound!
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Re: Clapper height tonal variation

Postby TerryMcGee on Sat May 04, 2013 12:32 am

Heh heh, so the web-site is probably lagging behind the reality.

Now, it's interesting to contemplate what would make a difference between clapper materials. I can see a few possible issues:

Density. Not a lot in it. Cast Iron given as 6800 to 7800 Kg/m3 (where water is 1000). Steel 7850. Bronze 7400-8900. Manganese Bronze 8359. Casting brass 8400. You'd think those small differences could be made up by adjustment to size.

Elasticity. A bit more variation. Cast Iron 13.4. Brasses and bronzes in the range 14 to 17. Steels up closer to 30.

Do we know if anyone has ever analysed for a difference in sound from different clapper materials?

Hmmm, broader question - is there a bibliography of research papers on carillon and related bell topics anywhere? If not, why not? (he added menacingly....)

I'm still wondering what those Bathurst strikers are made of and if that is part of the reason for the harsh tone. It appears welded and galvanised, suggesting perhaps mild steel.
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Re: Clapper height tonal variation

Postby JohnGouwens on Sat May 04, 2013 2:18 am

Well, I'm a musician with some technical smarts, but I'm certainly no metallurgist or engineer. I know that some bellfounders have at least tried different materials with clappers. For sure, Taylor at one time tried brass clappers (I know this from very old correspondence with them) and they had found that the iron held its shape longer. Of course, a problem here is that there are variations on all of these. I know that Brinell hardness tests are used in determining the suitability of a material, and that it is desirable to have a surface that is ductile (bendable, flexible) but with less tendency to form a permanent impression. Forgive the gaps in my knowledge on this, but I'm just not trained as a scientist. I therefore am not sure how the Brinell Hardness number translates in practical terms. Gideon is in a far better position to explain that, though I am certainly skeptical about his claim of the superiority of manganese bronze. I don't doubt that manganese brass is less likely to oxidize, but it is a simple matter to brush, prime, and paint the iron, so where's the problem. I care about two things:

1) Having a metal that is strong enough to excite the bell into vibration, while soft enough to allow that compression of the clapper contact point (which you have measured) to occur, giving the advantages of that very slightly longer clapper contact needed for the same mellower sound you achieve on freshly-re-shaped clappers.

2) Once the above criteria are met, having a metal that is as resistant as possible to permanent damage to its shape, either though a tendency to wear off under use or to compress and harden.

Now, having said that, the original adjustable clappers for bells 1-24 were actually some form of brass or bronze. We have never seen documentation about what exactly was used, nor have we attempted to have a metallurgist analyze them. The majority of those have been replaced with new cast iron clapper balls, but for practical as well as budget reasons, they were not all replaced at once. Taylor made the new clapper balls, and followed my request to have a raised ridge at the contact area, making easier to keep the contact area small. (It stands to reason that this would also allow somewhat greater temporary deformation, allowing the clapper to stay there longer. We made the iron clappers to the same diameter as the originals (measured by hand - by me), but made them "taller" so as to add some mass. Even so, consistently, the new iron clappers, being of a less dense material, were lighter in weight. I weighed them as I replaced them. The clappers I replaced were all clappers where I was having to turn them too often, as the bells were tending to sound harsh consistently, and I was running out of places to turn on the originals. In all cases, the new clappers brought better, more tractable tonal results, even though the weight of the new clapper balls was smaller. The trouble is, we therefore have some confounded variables. The new clappers were cast iron, though they were then turned in a lathe to obtain the desired shape, and sliced above and below. (The original castings were spherical, as I understand it.) The new clappers have the contact point ridges, while the original ones do not, so while my own experience has shown clearly that the replacement clappers we put in get superior results compared to the originals, the test is surely not scientific enough to be totally conclusive. I do know that the "naval bronze" clappers Verdin used to use - until they went over to iron clappers in about 1991 for Glendale, Ohio, did not hold their shape very well, and went rather quickly from a gentle sound with brand new clappers to a harsh, metallic sound thereafter, usually within just a couple of years. I believe in going with the most time-proven solution, which for me has been cast iron, though it must be heat treated to obtain the necessary ductility (pliability).
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Re: Clapper height tonal variation

Postby Gideon Bodden on Sat May 04, 2013 11:25 pm

JohnGouwens wrote:What???? You're advocating a return to manganese brass such as Eijsbouts used in the 1970s? I cannot agree with that! It has surely been by now established that annealed cast iron clappers produce a far more agreeable sound.

Yes, I am advocating a return to manganese brass such as Eijsbouts used in the 1960's until about 1990. The reason: the hardness of a specific alloy of manganese brass (with exactly 0.5 % aluminum) can be regulated very exactly, while it does not become much hardened at the strike spot. Cast iron is a terrible material for bell clappers because it is very difficult to get the right hardness, and even if the cast metal itself has the correct hardness, it hardens excessively at the strike spot.
In past centuries blacksmiths would hammer clappers of wrought iron, and there are many very old examples around over here that prove that they used a sort of iron that would have fabulous properties for serving as bell clappers, but unfortunately that type of forgable iron is no longer available on the market.
I really do have a lot of hands-on experience with clappers and clapper materials, John, while you don't.
And then, you keep mixing up different materials. Brass isn't bronze. Bronze is not to be used for clappers.
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Re: Clapper height tonal variation

Postby FrancesNewell on Sun May 05, 2013 12:24 am

Are any of these different combinations of metals noticeably more or less sensitive to changes in weather, such ad extreme heat or cold or excessive humidity?
I wonder if the hardness is affected and therefore the quality of sound?
In an earlier discussion, I asked about temperature changing the bells' pitches, but wouldn't temperature and humidity changes also affect the clappers?
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Re: Clapper height tonal variation

Postby JohnGouwens on Sun May 05, 2013 4:49 pm

I'll have to defer to the others to comment on that, as I've made it all too obvious I'm not a scientist! I do know that I've never heard of the weather changes altering the behavior in a noticeable way, though it stands to reason that in colder weather, clapper density and flexibility would be a bit different.
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Re: Clapper height tonal variation

Postby TerryMcGee on Sun May 05, 2013 10:57 pm

So it sounds like there are at least two issues that would need to be tested in any comparison of clapper materials:
- the initial sound quality, and
- the rate of degradation of sound quality

That second one rather rules out a simple test, as you would need to set up a repetitive bonger, capable of delivering say 100, 1000, 10,000 and 100,000 bongs. That doesn't present any real problem, but I suspect my neighbours might complain well before we hit 100. You'd probably need to keep swapping the clapper materials too in case, by the end of the first set of 10,000 bongs, the bell had changed a little in character, tilting the playing field. That all probably suggests that no-one has conducted really rigorous testings of clapper materials, unless they have their own research facility or have formed an alliance with a university. Do we know of such facilities or alliances?

And do we know why Eijsbouts gave up brass?

Incidentally, we did a calculation which showed that the Canberra Carillon had probably carried out about a quarter of a billion bongs in its 40 year life. Assuming for the moment that each bell received the same number of bells, that suggests about 110,000 bongs per annum. Obviously the more popular bells would receive many more than that. No wonder the clappers get flattened.
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Re: Clapper height tonal variation

Postby JohnGouwens on Sun May 05, 2013 11:16 pm

Replaceable clapper balls offer the easiest way to field test without those dramatic measures. Putting a couple of trial clappers in the middle of the third octave (likely to get the most repetitive use) with fresh iron clappers, and maybe three each of any alternative material would do it. Not as scientific, but after a year of regular use, one could make determinations about how they wore. Tests with each material fresh would still be worthwhile.
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Re: Clapper height tonal variation

Postby TerryMcGee on Sun May 05, 2013 11:28 pm

Frances, on the face of it, there doesn't seem to be much in the nature of metals that would change significantly with normal weather variation. But I've certainly heard claims that the weather has an impact on carillon sound. I wonder if it's more to do with the acoustic properties of the air, rather than the metals?

It would be interesting to see if carillonists agree that a particular weather condition produced the same effect. That would give us somewhere to look for what is causing that effect.
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Re: Clapper height tonal variation

Postby TerryMcGee on Sun May 05, 2013 11:33 pm

JohnGouwens wrote:Replaceable clapper balls offer the easiest way to field test without those dramatic measures. Putting a couple of trial clappers in the middle of the third octave (likely to get the most repetitive use) with fresh iron clappers, and maybe three each of any alternative material would do it. Not as scientific, but after a year of regular use, one could make determinations about how they wore. Tests with each material fresh would still be worthwhile.


Yep. As long as the initial sound quality didn't vary so much as to make the instrument sound silly!

It would be possible to attach a counter to keep track of the number of times each bell had been rung. That wouldn't account for piano and forte, but it would be reasonable to assume that would average out. So, yes, it would be possible to do reasonably rigorous testing without a formal lab setup.
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