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From: John Nagle on 27 Feb 2010 15:11
(Changed title, trimmed irrelevant groups.)

D Yuniskis wrote:

> Now, I am much more fascinated by electro-mechanical *mechanisms*.
> I have been working on a kinetic "sculpture" to act as a timepiece
> in the back yard. A tribute to Rube Goldberg -- with the exception
> that it must run *continuously* (most of his contraptions were
> "one-shot" devices). But, in order to keep *good* time, I need
> to "close the loop". Doing so without being noticed means
> using some "non-discrete" device that you can control. I.e.,
> something like a liquid whose rate of flow can be varied without
> a critical observer being able to *easily* determine that this
> is happening. Living in the DSw poses a problem using water as
> it evaporates too fast (replenishing it from the domestic water
> supply would be "cheating" :< ). I also need to locate some
> larger solar panels so the device has no connection to the electric
> utility.

Look into shape-memory alloy wire. See

"http://www.amazon.com/gp/product/B000FMUEGI"

Run a current through that, and it contracts slightly. Not much.
Then obtain or build a pendulum clock, and use the shape-memory
wire to change the supported length of the pendulum. You'll
only get 1-2% change, but that's all you need to fine-tune
the thing.

John Nagle
From: Rob Gaddi on 27 Feb 2010 15:05
On Sat, 27 Feb 2010 12:11:32 -0800
John Nagle <nagle(a)animats.com> wrote:

> (Changed title, trimmed irrelevant groups.)
>
> D Yuniskis wrote:
>
> > Now, I am much more fascinated by electro-mechanical *mechanisms*.
> > I have been working on a kinetic "sculpture" to act as a timepiece
> > in the back yard. A tribute to Rube Goldberg -- with the exception
> > that it must run *continuously* (most of his contraptions were
> > "one-shot" devices). But, in order to keep *good* time, I need
> > to "close the loop". Doing so without being noticed means
> > using some "non-discrete" device that you can control. I.e.,
> > something like a liquid whose rate of flow can be varied without
> > a critical observer being able to *easily* determine that this
> > is happening. Living in the DSw poses a problem using water as
> > it evaporates too fast (replenishing it from the domestic water
> > supply would be "cheating" :< ). I also need to locate some
> > larger solar panels so the device has no connection to the electric
> > utility.
>
> Look into shape-memory alloy wire. See
>
> "http://www.amazon.com/gp/product/B000FMUEGI"
>
> Run a current through that, and it contracts slightly. Not much.
> Then obtain or build a pendulum clock, and use the shape-memory
> wire to change the supported length of the pendulum. You'll
> only get 1-2% change, but that's all you need to fine-tune
> the thing.
>
> John Nagle

Muscle wire's a pain to work with. In free air you wind up needing to
run a pretty decent amount of current to replace the heat you lose to
natural convection. Even more so if you've got a breeze.

How about the pendulum drives a small DC motor/generator? That lets
you both monitor the frequency and give it little kicks to keep it
on course. With good bearings it shouldn't take much energy to
overcome the losses.

--
Rob Gaddi, Highland Technology
Email address is currently out of order
From: D Yuniskis on 27 Feb 2010 17:59
Hi John,

John Nagle wrote:
> (Changed title, trimmed irrelevant groups.)
>
> D Yuniskis wrote:
>
>> Now, I am much more fascinated by electro-mechanical *mechanisms*.
>> I have been working on a kinetic "sculpture" to act as a timepiece
>> in the back yard. A tribute to Rube Goldberg -- with the exception
>> that it must run *continuously* (most of his contraptions were
>> "one-shot" devices). But, in order to keep *good* time, I need
>> to "close the loop". Doing so without being noticed means
>> using some "non-discrete" device that you can control. I.e.,
>> something like a liquid whose rate of flow can be varied without
>> a critical observer being able to *easily* determine that this
>> is happening. Living in the DSw poses a problem using water as
>> it evaporates too fast (replenishing it from the domestic water
>> supply would be "cheating" :< ). I also need to locate some
>> larger solar panels so the device has no connection to the electric
>> utility.
>
> Look into shape-memory alloy wire. See
>
> "http://www.amazon.com/gp/product/B000FMUEGI"
>
> Run a current through that, and it contracts slightly. Not much.
> Then obtain or build a pendulum clock, and use the shape-memory
> wire to change the supported length of the pendulum. You'll
> only get 1-2% change, but that's all you need to fine-tune
> the thing.

The appeal/beauty of using something like a water source
is that folks don't see "discrete motion" in it -- though
recognize that it *is* moving.

E.g., a gear turning is less "magical" than water flowing.
Especially as adjusting the flow rate can be virtually
imperceptible. Anything that moves quickly (perceptibly)
defeats the purpose. If, OTOH, you look at something...
then look at it again 5 minutes later and have to *work*
to figure out what has changed (and *how*), then you're
never quite sure that it actually *did* change.

I.e., someone would have to invest a fair bit of effort to
figure out:
1) that it does move
2) that it moves predictably
3) that it is a timepiece
4) *how* to tell the time based on that

It would be impossible (impractical) to hide the fact that there
is a pump recirculating the water. But, it's relatively easy to
hide the feedback loop so it appears (to mere mortals) to be
"magic" :>

For example, I use a pocketwatch as a compass and always
confuse the hell out of observers trying to deduce the "trick"
from the 10 second observation. Leave people with puzzles to solve
so it makes the experience more memorable. :>
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