This is the third of a number of posts pertaining to the progress of my 21M.299 (The Social Lives of Instruments) final project, The Springboard.
The springs have arrived!
The spring constant corresponds to the stiffness of the spring, or how difficult it is to extend and how much tension there is at a given extension. Tension typically corresponds to pitch- when you tune a guitar, the pitch increases as the tension increases. This translates to springs as well; too stiff of a spring and it would vibrate very little (and at high frequency). However if the spring is too slinky then it will vibrate far too much and too slowly to be useful. These springs are around a foot long at rest and have low constants at less than .25 lbs/inch.
To check the feasibility of the instrument, I first needed a way of mounting and testing the springs with the bow. To do this, I bought hardware (screws and nuts) to attach one end of the spring to the (eventual) sound board. The other end will be stretched to a series of J-hooks that will act as crude tuners. Since I don’t have the instrument body yet, I improvised by attaching one end of the spring to a hook in my closet and pulling the spring taught to 3x its length by the screw attached to the other end (as shown in the above photo). I then played the spring using my other hand with the bow.
The same technique was used as in my previous experiment playing the lamp’s springs. Stretching the spring matched the lamp’s results, where the timbre became clearer at longer lengths and no noticeable affect on pitch. The spring produced the clearest tone when played close to the ends, which is good news and means that the instrument can be guitar-like physically (i.e. a resonating body with a neck). The empty space of the closet also amplified the tone. I also did not have the same problem I had with the lamp spring, where the pitch would change along the bow’s length. I repeated this test for the four pictured springs- the top three worked best and offered different pitches and timbre, however the bottom spring was too massive and stiff to create a usable tone.
To experiment with controlling pitch, I bent the taught spring around the closet’s wooden door’s edge. This shortened the effective length of spring, increasing the pitch. It seems that the pitch of a spring corresponds more to amount of vibrating mass rather than the amount of tension or length. This also had the affect of causing the closet to resonate with the spring, greatly amplifying the sound. A resonating chamber would definitely be worth adding to the instrument prototype.
I then experimented with using the closet door’s metal handle as a sort of fret. This worked as well as the wooden door’s edge, but also introduced more higher harmonics, resulting in a brighter tone. This leaves my decision of fretted vs unfretted as one of taste. For ease of prototype construction, it will likely remain unfretted. Another possibility is movable frets of some sort.
The next step will be to decide which and how many springs I would like in this instrument, and to design a body that features a resonating chamber and is long enough to keep the springs under sufficient tension. Stay tuned!