Intro: Shaky Slinky Clock
You have to sneak up on this clock, hanging on the end of a slinky. If it sees you coming, it gets the shakes.
Using a Roberval balance arrangement (arms in the center), it doesn't matter where I place weights as long as the left and right side have a total equal weight. Torque on the upright rod does change depending on where the weights are placed.
The clock, hanging on the slinky should be easy enough to read--but it's a slinky; it needs to bounce. To make things a little more lively, I added a PIR module to detect anyone approaching from the front. This operates a relay which turns on a shaker motor and gets the slinky moving.
The moving slinky/clock upsets my delicate balance on the arms. Rather than the traditional solution of more weight on the left, longer base on the right, guy wire on the left (I try to break traditional thinking sometimes), I decided to turn on a fan on the left. The blade "pulls" the system to the left--countering some of the wild flinging on the right. I know, it's a waste of energy, but I wanted to try the concept.
Drill holes in a battery powered clock mechanism and thread wire (I use magnet wire) through the holes.
Tie the slinky to the clock with the wires.
Put a piece of tubing (bright colored rubber eyeglass holder) on the hour hand. Throw the minute hand away; this clock is not for people who watch minutes.
Attach a one inch square (4 feet long) piece of aluminum tubing to the acrylic base using aluminum angle and small bolts. My acrylic base is about six inches by 12 inches with the pole mounted on the left end toward the back.
Using four six inch by 1 inch by 1/4 inch pieces of acrylic and a few nuts and bolts, build the Roberval arrangement at the top of the pole.
Drill holes near the end of the three foot long (by 1 1/4 inch by 1/4 inch plexiglass "right" arm). These holes should match the shaker motor (I scavenged the shaker from a K Mart Halloween decoration).
Mount the shaker motor.
Secure the slinky at the end of the arm by drilling a hole through the acrylic and wiring the slinky to the arm.
Run wires from the shaker to the center arm--securing them with packaging tape.
Mount the motor and propeller on the left side using aluminum tape or duct tape. Run wires to the center pole. The propeller should pull to the left when active.
Add weights on the left side that equal the weight of the right arm, shaker, slinky and clock.
Using double sided tape, attach the two battery supplies to the back side of the upright pole.
Build the circuit described in step one and stick it to the front side of the pole (there is adhesive on the back of the prototype board).
Set the time.
Stand back and admire your clock--before you install the batteries. After the batteries are installed, it should be fairly difficult to sneak in close enough to read the time without the clock having a serious case of "shakes."