Seeing the original Accutron again damn near brought tears to my eyes. Back in the 60s my Dad bought one and he would sit in front of his SX42 that he bought in 1946 or 47 and exclaim "Dead balls on with WWV"! I miss him.

My dad was not that keen on me buying the watch initially. He considered it a frivolous purchase. However, once he had a chance to see how accurate it was, he bought himself the more conservative model.

I too would check it against WWV and was always impressed at how accurate it was.

hgmjr

 

Jewelers had a small fixture that they laid the watch on and it picked up the fork frequency and compared it to a standard.

I remember that calibration machine. Every so often I would go to the jeweler where I bought the watch and he would let me watch as he checked the accuracy.

hgmjr

 

Getting way off topic here, but...

My Granddad was really keen on having his timepieces set accurately. Every day at the same time, he would tune in to the WWV signal, set his wristwatch, and then go around the house with a notepad on a clipboard to record the variances of the various timepieces from the WWV time signal. After he'd accumulated enough data, he would adjust the clocks a bit to try to make them more accurate.

In the mid-1970s, I bought an inexpensive Timex watch ($12, I think) that had a quartz oscillator and an LED display. You had to push in the stem to view the time. It was accurate to within a few seconds a month. My Granddad was amazed by it. I had that watch for years; had to replace the band a few times, and the battery every couple of years. My wife bought a newer watch for me, but it was a mechanical self-wound watch. It drove me nuts that it would gain or lose a minute or more per month.

Anyway, trying to get back on topic - it seems to me that there are possibilities for a more interesting display if free-running oscillators were used to drive a voice coil, rather than a pair of tuning forks.

We haven't heard back from our OP for a while. Wonder if they're still around?

 

Anyway, trying to get back on topic - it seems to me that there are possibilities for a more interesting display if free-running oscillators were used to drive a voice coil, rather than a pair of tuning forks.

I totally concur. Think about the versatility.

 

I think I am the one that sent this thread off-topic. My intent was to show that exciting a tuning fork magnetically was indeed a doable thing. That said, I would tend to favor the speaker approach. I wonder if a mirror attached to spinning motor shaft would yield an acceptable perturbation. I'm not entirely certain of the end results that the OP is after.

hgmjr

 

I think I am the one that sent this thread off-topic. My intent was to show that exciting a tuning fork magnetically was indeed a doable thing.

Stuff happens, and it was all interesting I took it WAY OT though, so I needed to nudge it back towards our OP's topic.

That said, I would tend to favor the speaker approach.

That would indeed be a very versatile and inexpensive approach.
But as our OP is an artist, and we do not as yet have any feedback from them as how aesthetically important the tuning forks are to their design, I feel that some kind of feedback from them is needed.

I wonder if a mirror attached to spinning motor shaft would yield an acceptable perturbation. I'm not entirely certain of the end results that the OP is after.

It's my understanding that they were using the tuning forks to deflect a laser light beam in order to display Lissajous patterns; likely on some (at least) partially reflective surface.

I dissected an old HP LaserJet printer a few years ago. The laser scanner assembly used a stepper motor with a triangularly shaped mirror holder on it's shaft. The laser's beam was gated by the onboard electronics to "zap" the drum in a dot pattern so that the zapped areas would pick up toner; a raster scan type arrangement.

If our OP wanted to do a raster scan type thing, a rotating mirror would be a good option.

 

Would it be possible to take a motor with a rare-earth magnetic attached to the shaft or perhaps a series of magnets attached to a disk on the shaft to be spun in proximity of the tuning fork and excite it into oscillation mechanically? Of course this would only work if the tuning fork is ferrous.

hgmjr

 

I do believe that tuning forks are made of ferrous material. However, thinking more about it ... a motor, even rotating at low RPM might be kind of hazardous out on public display. For example, let's say some little girl with long hair was bending over it, and got her hair entangled in the motor shaft.

With a voice coil, the surfaces would hardly moving at all, yet still produce a useful output.

 

I do believe that tuning forks are made of ferrous material. However, thinking more about it ... a motor, even rotating at low RPM might be kind of hazardous out on public display. For example, let's say some little girl with long hair was bending over it, and got her hair entangled in the motor shaft.

With a voice coil, the surfaces would hardly moving at all, yet still produce a useful output.

That's a valid concern. This being a public display then safety should take a front row seat in the design process.

hgmjr

 

Something really simple might be to mount a tuning fork standing up on an enclosed box that contained a solenoid controlled by a timer. At some interval (from perhaps 1/2 second to several seconds) the solenoid is energized to give the inside of the box top a whack, or the shaft (handle) of the tuning fork a whack.

This would be much more simple to construct than attempting to build a resonant excitation system, and the display would change every time the fork got a whack, particularly if each fork's solenoid was driven by a different timer.

 

Correct me if I'm wrong, but if one tine of the fork is excited with the output of an amplifier and the other tine supplies the input to the amplifier, wouldn't the loop become self resonant at the fork frequency? Proper transducers would be required.

 

Correct me if I'm wrong, but if one tine of the fork is excited with the output of an amplifier and the other tine supplies the input to the amplifier, wouldn't the loop become self resonant at the fork frequency? Proper transducers would be required.

That sounds like a reasonable description of physics of the tuning fork to me.

hgmjr

 

Correct me if I'm wrong, but if one tine of the fork is excited with the output of an amplifier and the other tine supplies the input to the amplifier, wouldn't the loop become self resonant at the fork frequency? Proper transducers would be required.

Yes, but that's a problem; you wouldn't be able to attach anything to the tuning fork in the "U" section without changing it's resonant frequency. Also, having coils, wires, and other things hanging out there would be aesthetically unappealing.

However, it might be possible to pick up the tuning fork resonance from a platform it's mounted on, and feed that back - all the electronics out of sight in a box that serves as it's base. That would make it a bit more mysterious, too.