A clapper stay is used to clamp the clapper in its mid position in order to to silence a bell, typically for silent practice. The clapper stay comprises a wooden spar that fits snugly across the diameter of the bell at about the level of the sound bow, with a means to clamp it to the shank of the clapper close to its ball. The examples shown here were made using 45mm x 70mm planed softwood but these dimensions are not critical.
Ideally, the spar should be as long as possible to just fit above (when the bell is down) the clapper ball. The ends of the spar are cut at an angle to match approximately the slope of the bell at the point where the spar contacts the bell. It is probably easiest to get the length and the angle of the ends of the spar right by trial and error, making the spar too long and then trimming it to get a good fit. If making a set of clapper stays to fit several bells, start with a mid sized bell so that if a spar is cut to long or too short it may be suitable for one of the other bells.
A common problem with clapper stays is that they do not grip the clapper shank well enough to avoid them slipping, allowing the whole assembly to become loose. And this in turn can allow the bell to sound, albeit quietly, as the clapper stay rattles against the sound bow. If the faces of the clapper stay that grip the clapper shaft are rounded to match the diameter of the clapper shaft, they can be difficult to make accurately enough to avoid having just two points of contact. This design uses three points of contact between the clapper stay and the clapper shaft, rather like the jaws of a three jaw chuck (on an electric drill for example). So, even after some wear or ‘bedding in’ the clapper stay can still be tightened retaining three points of contact. One of the three points of contact is the side of the spar whilst the other two are provided by having a vee-shaped notch in the clamping bar.
Another common problem with other clapper stay designs results from the clamping force being applied by tightening a nut (commonly a wing nut). The nut can be over tightened, causing damage to the clapper stay, or it can come loose in use. And the nut can be dropped whilst attempting to fit or remove the clapper stay. Fitting a clapper stay while the bell is up is generally thought to be too dangerous, but just imagine trying to retrieve a wing nut that has fallen inside the bell – this is the stuff of nightmares…
This design uses a Velcro® type hook-and-loop cinch strap instead of a nut and bolt, and the strap is tacked to the spar so there are no loose parts that can accidentally fall off during fitting or removal.
To do this, make a disc shaped template with a diameter equal to that of the clapper shank. It is probably easiest to measure the circumference of the clapper shank e.g. by wrapping a tape measure or a length of string around the shank, and dividing by π (≈ 3.14) to get the diameter. The disc template can then be cut out from card, or you might be lucky enough to find a coin or large washer that is near enough the right size. Use the disc template to draw a circle on the clamping bar as shown.
Then use a set square to construct an equilateral triangle (with 60° corners) around the circle.
The bottom of the triangle should be truncated as shown to avoid weakening the clamping bar unnecessarily.
Then cut out the truncated vee-shaped notch...
... and check again with the disc template as shown.
Attach the clamping bar to the spar with a hinge (I have used a cranked knuckle back-flap hinge which works well).
In the example shown I have used 25mm wide by 75cm long Benri-Strap. This can be tacked to the spar to avoid losing it.
It is safest to do this with the bell down but if this is not possible for any reason, and if there is safe access, it is possible to fit the clapper stay with the bell up as shown here, and there are no loose parts that could fall into the bell.
3rd May 2023.
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