- #1
guyburns
- 42
- 10
Background
I'm doing an AV about a friend who died 3 years ago. In his spare time he made hundreds of tiny, what he called "Worlds", sculpted out of copper, brass, aluminium, ranging from 1cm to 3cm across, hollow. They don't weigh much. I've set up a rig to film them rotating at 1 RPM. About a dozen of them will be used between chapters in the AV, 10-15 seconds, like a planet filling the screen. See attachment.
Rig Construction (see attachment)
I attached a thread to the centre of the second hand on an analog clock, from which hangs a spring. I chose the spring so I can easily attach new "Worlds" to the hook at the bottom of the spring. The spring does not act as a spring (as far as I can see).
Each "World" has its own thread, super glued to the top, with a loop at the other end which I connect to the spring's hook. The thread is the thinnest I could find – 0.18mm.
Resonance
The problem is – some of the "Worlds" resonate. They speed up and slow down, some even go into reverse. I thought: "Aha – I'll attach a long pole to the bottom of the spring, to act like those long poles used by high-wire artists. That'll add angular momentum, reduce wobbles, resonance, and generally smooth things out".
I made three "poles" out of thin, 1mm solder, 10, 15 and 20 cm across. I also fitted a straw as part of the testing (see attachment), thinking: this won't add much mass, but a lot of air resistance. But still, if I fit all four 'poles' in turn, there are resonances in some of the "Worlds".
Questions
Q1: Is there some catch-all solution to stopping resonance? Or will I have to tailor each 'pole' to each "World"?
Q2: I wait at least 5 minutes to allow resonances to die down, but some seem to persist. If I wait long enough, will resonance dissipate?
Q3: Any suggestions on other techniques to reduce resonance.
I'm doing an AV about a friend who died 3 years ago. In his spare time he made hundreds of tiny, what he called "Worlds", sculpted out of copper, brass, aluminium, ranging from 1cm to 3cm across, hollow. They don't weigh much. I've set up a rig to film them rotating at 1 RPM. About a dozen of them will be used between chapters in the AV, 10-15 seconds, like a planet filling the screen. See attachment.
Rig Construction (see attachment)
I attached a thread to the centre of the second hand on an analog clock, from which hangs a spring. I chose the spring so I can easily attach new "Worlds" to the hook at the bottom of the spring. The spring does not act as a spring (as far as I can see).
Each "World" has its own thread, super glued to the top, with a loop at the other end which I connect to the spring's hook. The thread is the thinnest I could find – 0.18mm.
Resonance
The problem is – some of the "Worlds" resonate. They speed up and slow down, some even go into reverse. I thought: "Aha – I'll attach a long pole to the bottom of the spring, to act like those long poles used by high-wire artists. That'll add angular momentum, reduce wobbles, resonance, and generally smooth things out".
I made three "poles" out of thin, 1mm solder, 10, 15 and 20 cm across. I also fitted a straw as part of the testing (see attachment), thinking: this won't add much mass, but a lot of air resistance. But still, if I fit all four 'poles' in turn, there are resonances in some of the "Worlds".
Questions
Q1: Is there some catch-all solution to stopping resonance? Or will I have to tailor each 'pole' to each "World"?
Q2: I wait at least 5 minutes to allow resonances to die down, but some seem to persist. If I wait long enough, will resonance dissipate?
Q3: Any suggestions on other techniques to reduce resonance.