Where can I buy this movement?

Aha! Thanks! ...Jim Thompson

Use a radio control servo to move the hands of the clock. More:

Not at all what you'd want, but for a while Freightliner was (and may still be) making it's gauges with really lightweight stepper motors. On power up you just drive it backward against the pin long enough that it'll always get there, then start counting pulses for where it "should" be.

It's clearly not analog-friendly.

Google for 360 degree servo. For example: However, don't bother buying a continuous rotation servo as any RC servo can be modified for 360 degree rotation: The only thing preventing the servo from going all the way around is a plastic stop or metal pin in the gearing, which can easily be removed.

The pot doesn't read 360 degrees -- it's more in the neighborhood of 270 or a bit more.

Most modern servos can be made to go over 90 degrees just by feeding a pulse train that varies by more than 1ms (1 to 2ms is nominal), but how much so depends on the servo. For analog servos, response will be sluggish but power consumption will be reduced by increasing the frame rate (60Hz is nominal, but you can go down considerably).

...or one that goes to '11'.

a basic clock motor, disc on drive shaft, offset drive pin in disc for a reciprocating action and cam with sloping and sharp drop off to be used for a distance senseor to measure position.

actually, the drive can directly spin the needle and you have the disc with the ramp cam in it for the distance magnetic sensor.

These sensors can be gotten cheap from automationDirection and they output near 0..10 volts with supply voltage of 12.. 30Vdc. ect

For 360 degree rotation, the pot is set at midrange and the drive shaft to the pot is disconnected. See the YouTube video above.

Here's another instructional video: which uses two fixed resistors to replace the pot.

I have no clue what's inside the 360 degree servos offered by Sparkfun and Adafruit.

The instructables.com instructions above are wrong. The pot has to be disarmed.

Most servos that I've seen work for 180 degree rotation, with zero being 90 degrees. I don't understand what you're suggesting, but it's easy enough to try (later).

Er... why go to so much trouble? If you have a 180 degree movement, just connect it to the shaft with a 2:3 gear ratio (or sprocket ratio with a chain or timing belt). It's good procedure not to direct-couple the motor anyhow.

There must be 1000+ ways to build a clock. If this were my headache, I would use a clock escapement which drives a shaft, which drives the minute hand. Wrapped around the shaft is a nylon rope, and a heavy weight. No pendulum. A 60 second clock oscillator causes the escapement to release which moves the minute hand forward exactly one minute. Add a 12:1 gear reduction for the hour hand. Why do it this way? Because it's a "conversation piece" and might get the grand brats interested in technology. Extra credit for adding a 2nd clock face in the back, and having the hands go backwards.

Might as well take advantage of Arizona's natural resource, sand:

Yes, you could do it but it would be a mite tedious compared to using a cheapie $2 pre-built 8-bit micro on a board such as an Arduino.

something like a 12-bit counter and a couple flip-flops to generate the quadrature outputs, and some logic to generate the reset pulses to run it backwards up against the stop once in a while, then drive it forwards to the desired angle.

voltmeter. I don't know what the drive method they use is- could be a moving coil movement or a stepper or an air core movement. Whatever it is you could just dissect the movement, borrow the electronics within and dlive it with 0-18V or whatever.

Both options are in the sub-$20 range. A good real analog 270 degree meter movement (eg. aviation type) would probably cost $100.

--sp

Another option- air core movement driven by analog quadrature current.

One type available on the used market was used in the BMW E38 chassis instrument cluster and they cost around $25-$35. This listing erroneously calls it a stepper:

BMW's instrument clusters mount the motors through a PCB.

Driver- LM1819 NOS (they're obsolete now) maybe $10. CS8190 in SMT package maybe $5.

--sp

Interesting! Is that a spring in the photo? ...Jim Thompson

Yes. It's not necessary for the functionality, the angle the pointer assumes is atan(ix/iy) where ix is the current through the sin coil and iy is the current through the cos coil.

The herrspring returns the pointer to the CCW stop when power is removed rather than having it flop whichever way.

--sp

OK. That looks like the solution to my problem. Thanks! ...Jim Thompson