> The keys vibrate on the gurdy I'm building when I > bow the string quickly. I thought I made the keys fit > pretty snug but I'm guessing not enough.. I took some > thin clear plastic styrene sheet and glued it to the > edge's of the keys to give it a better fit but I'm > still getting the vibrating. > > Any thoughts on why this is happening? I'm thinking > I'm going to have to make a new key box... Thanks, Seth >
I don't always trust that all my email gets through, but it seems to me that no one has replied to your question, Seth, so I'll stir the pot. The basic point first: I see that you specify that it only happens when you crank fast. Sorry if this seems a simple answer that you've already considered, but sometimes, if the tangents are too close to the melody string(s), faster cranking can make the string's amplitude great enough that the vibrating string can strike the tangents at or near the octave keys. Are you sure that this "rattling" of the string against the tangents isn't what you're hearing? Perhaps not, which leads me to the more complicated issue: Note that I said "no one has replied to your question," rather than, "no one has answered your question." It sure would be great if there was a simple answer to vibration problems, but based on my experience and that of others who have shared it, it's just as likely that your problem isn't simply one of keys that fit too loosely. I have seen some instruments with very loose, worn keys that don't present any problem at all, and I've seen (and built!) others with very precisely fit keys that make a horrible racket! The problem, it seems, is often that the instrument ends up with a natural resonant frequency that makes everything loose (keys, in this case) rattle. It may be just one note on the melody strings, or it may end up being a combination of different octaves sounding together or even two unison notes not quite in tune. On one lute-back G/C hurdy-gurdy I made (which was made on the same forms and intended to be exactly like others I've made), the open melody strings caused the keys to rattle with particular quality that can only be described as a dull roar! If I tuned the strings slightly off a true G (by A440 standards)in either direction, the rattle was silenced. What did I do? I chose not to follow some advice I got: "Just re-string it to D/G"! I noticed that in this case the rattle changed depending on where I grasped or put pressure on the keybox: I was lucky enough to find that by adding bits of extra mass in a couple of places out of sight beneath the keys inside the keybox, I was able to change the way the keybox absorbs the vibrations and squashed the noise. If this resonance is your trouble, then the problem becomes: once you complete a hurdy-gurdy, how do you change this resonating frequency so that your keys don't rattle? Maybe *looser* fitting keys are the answer? Lighter weight keys? Heavier keys? I sure would like to hear more about whether anyone else has successfully tackled this problem... ~ Matt
