Technical Advice - Door
The tubular bells of long bell chimes can be the source of a variety of problems.
The bells are very simple in concept-- just long thin-wall tubes, cut to special lengths for tuning, plugged at one end with some sort of hanger attached. In some cases the plugs provide the base for the hanger. In all cases, the plug serves to provide substance where the plunger strikes, which is essential to achieve good tone, volume and resonance. It is very important that the bell hanger loop is the correct length so that the plunger strikes the bell directly in the plugged region. Some of the patents for bell construction refer to the plug as an “anvil”, which perhaps provides appropriate imagery for its acoustic function.
The tubular bells can have a couple of problems. Most significantly, cracks at the ends. Many older bells have a crack of up to 2” long at the plug end. The cause of this is clear: the snug press fit of the plug inside the tube (which is absolutely essential) is snug beyond what the tube can take, so it cracks. Often the cracks are visible only upon close inspection, so are of little cosmetic consequence; unfortunately they can cause tonal problems. In the worst cases they can cause the bell tone to have a buzzing character and perhaps slightly affect volume. The crack may have less effect on tone if the bell is placed so that the crack is away from where the plunger strikes. The only reasonable repair that I know of is to cut off the cracked portion and reset the plug in the newly shortened tube. Each bell needs to be shorted an equal amount to maintain relative tuning between each bell.
I occasionally get a question about fitting a long bell chime into a niche that isn’t quite long enough. I usually advise that a more modest 2 or 3-bell chime with shorter tubes would be the best answer… but then I found this notation in some NuTone literature from 1949:
FOR SPECIAL SERVICE-- If you have any special problems (such as shortening of tubes for small niches, apartment house installation, etc.) write giving full details to NuTone Inc., Cincinnati, 27 OHIO, U.S.A.
So there you have it, you could actually get NuTone factory customized lengths. Retuning with sophisticated equipment was probably not a big deal- but can be dicey to get as set of 4 notes tuned right by ear- so I generally avoid doing it. Changing length and retuning a simple 2-note set is relatively easy as there is a lot of latitude for what ding-dong sounds like.
Another issue with old bells is cosmetic. Most every set of vintage bells suffers from discoloration- overall or localized dark and dull areas or spots of tarnish under the clear coat. Given that it is under the coating, there is no simple remedy, and even if you could spot polish the blemishes, they would never match the original radial brushed finish. I have developed a technique to totally refinish the bell to original appearance. I spin polish the entire length of the bell. My method involves making a tapered mandrel sized to fit into the open end of the bell. I chuck the mandrel into an electric drill and spin the bell while firmly holding fine sandpaper against the bell. The old finish and whatever tarnish is sanded off, and a new radial spun brushed finish is created- just like the original. This must be done with gloved hands, as any hand oils will cause irregular tarnish spots. Once an even appearance is achieved, the bell must immediately be clear coated to avoid fingerprints and tarnishing, unless of course you would prefer to leave the brass bare to age to a natural dark color.
Metal polishing is one of the tasks that you can generally get someone local to do for you. However, all the bell polishing that I've seen done by others is either a general bright unbrushed finish or brushed in a lengthwise direction. This does not result in the shimmer of the original radial brushed style that most vintage chimes had.
But the really tough problem with bells is that they have a nasty habit of going AWOL. A chime without bells is like... well, sorta quiet. There are a limited number of solutions. Last I checked, new bells can be ordered from NuTone/Broan for about $120, but if so, some improvisation required to add your own hanger loops for correct length for you application. Alternatives? Buy another whole chime and scavenge the bells. Or make new bells from scratch. Tuning by ear is unbelievably difficult, so best to model after known lengths of an existing set of bells. Getting the correct spin brushed look is covered above. Beyond that there is devising an end plug and hanger loop of correct length. There is just a whole lot to making bells, and while I do it for my new chimes and for restorations it is complicated and expensive. I can supply bells in sets of 2, 3, or 4.
Occasionally I get a question about replacing a single missing bell from a multi-bell set. This is probably not a viable thing to do. Exact alloy, diameter, and wall thickness combine to make the attributes that affect tuning, which is determined by length once the other characteristics are set. So not only is it really difficult to tune the replacement bell, it is likely to end up being a length that looks out of synch with the set. Otherwise there are cosmetic concerns; all bells in the set would need to be re-polished and refinished to look similar. Replacing all bells is what I recommend.