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RE: Church bells

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1. The basic problem is one of an assembly of parts (the bell, the support/pivot shaft, and counter weight) that must have a center of gravity located at some TBD distance on the bell-side of the pivot. This distance will determine the ease of pivoting the bell from its neutral downward position. But further, the polar moment of inertia of the assembly about the pivot axis will determine the pendulum swing period of the bell assembly when it is rung. For example, a small counter weight at a large distance from the pivot axis will result in a long period whereas a heavy counter weight at a small distance from the pivot axis will result in a short period. The proper period is a matter of church bell aesthetics. So the problem must be looked at as an oscillating pendulum with parameters of polar moment of inertia and the restoring force based on CG location.
2. Welding sounds OK but preheating the bell to avoid potential thermal distortion and/or cracking would be advisable. Post weld stress relief would also be advised.

Steve Smith, P.E.
Systems Stress
(425) 294-7681
M/S 02-56


> ----------
> From: 	Alex C. Nacionales[SMTP:anacio(--nospam--at)skyinet.net]
> Reply To: 	seaint(--nospam--at)seaint.org
> Sent: 	Wednesday, January 27, 1999 12:40 PM
> To: 	seaint(--nospam--at)seaint.org
> Subject: 	Church bells
> 
> 
> I am reconstructing several bells in old church  here. The bells
> are about 1000 lbs. The bells have bullet holes about 1
> inch in diameter and the concrete counterweights were destroyed.
> 
> Problem
> 
> 1. How heavy should the counterweights be so that the bells will stay
> upright when at rest and swing 45 deg. on each side with a minimum push.
> 
> 2. How to repair the holes to improve the bell tones. The bell metal is a 
> mixture of copper and tin. I am planning of welding it using 
> electrodes with matching base metal.
> 
> I will appreciate any help from you.
> 
> Alex C. Nacionales, C.E.
> Iloilo City, Philippines 
> 
> 
>