[Bell Historians] Diameters

[Carl S Zimmerman]

At 19:16 +0100 2005/08/12, George Dawson wrote:
>I usually find that the inside and outside edges are very close together.
>GAD
>
>> Give the shape of a bell's lip, I'm not sure how you could measure it
>> on the inside! Edge of lip to edge of lip is the usual proceedure.
>>
> > R

A lot depends on what profile and molding technique the bellfounder 
used. I've seen bells with distinct inside and outside edges as 
George indicates, but if it's an angular profile (German or 
German/Hispanic) then the inner "edge" might be quite far from the 
outer edge. On the other hand, some profiles have a continuous inner 
curve such that there is no "inside edge" at all.

Diameter at the rim is a very useful measurement when comparing bells 
from the same foundry, but not so useful when comparing bells from 
different foundries. (The same holds true for weight.) Again it's 
down to profiles.

A measurement that should be more consistent across founders and 
profiles would be the interior diameter at the strikepoint of the 
clapper. But that's not easy to measure reliably.

Ultimately, of course, to describe a bell completely one would need a 
complete tracing of the exterior and interior profiles, together with 
a complete audio analysis of all the measurable partial tones. I 
imagine that this is the sort of thing that André Lehr and the 
Eijsbouts foundry have done in order to be able to design by computer 
an exact match to any existing set of bells. Perhaps other foundries 
have done similar work, as well.

Lacking those tools, the rest of us make do with a few simple 
measurements like diameters and weights (over which we quibble 
endlessly :-)).

Carl