I've wanted to build an automatic slinky machine for years, but the custom width/length belt left me stumped--until now. You can make your own custom belt using cardboard and tape; it really works!

Supplies

Cardboard

1" wide Gorilla tape (any sticky, strong duct tape)

Glue

30" Velcro

Misc. 3mm screws

1/2" plywood--12" x 15"

Servo motor (without end stops)

Slinky

(3) Snowmobile bearings

3d printed parts

(8) 1/2" wood screws

DC power supply variable (5 volt to 10 volt, 1/2 amp)

Step 1:

Let's start with the belt. Cut (22) 4" x 1" pieces of cardboard. Place them in a straight line, space between each piece, so that the total equals 30".

Step 2:

Add tape on one side, then the other. Create a "belt" by taping the inside together, then the outside. I used about 6" of tape to overlap the joined spot.

Step 3:

Print the 3d pieces. The cylinders take about 8 hours each, so this portion is not fast.

Step 4:

For a metal gear drive motor, easy to attach via servo horn, I modified a "no stop" servo motor.

Start by removing the four screws in the bottom of the case.

Step 5:

Next, cut the two wires from the circuit board that go to the motor.

Step 6:

Cut the three wires from the circuit board to the potentiometer. Remove the circuit board.

Step 7:

Take the two wires from the motor and solder extender leads.

Step 8:

Push the solder connection joints into the cavity of the servo motor housing.

Step 9:

Screw the bottom cover back into place. Set this aside for the moment.

Step 10:

On one of the pulleys, apply tape to match the tape position on the belt you made earlier. This provides a bit more friction for the drive pulley (the 3d printed pulley is somewhat slippery).

Step 11:

Secure an axle to one end of the driven (no tape) pulley.

Step 12:

Add the other axle using 3mm screws.

Step 13:

Press snowmobile bearings in the bearing holders.

Step 14:

Press a bearing in the tall bearing holder.

Step 15:

Secure the motor to the motor bracket using 3mm screws.

Step 16:

Attach an axle to the drive pulley.

Step 17:

Secure the servo horn to the motor axle using 3mm screws.

Step 18:

Attach the servo motor to the motor axle using the servo screw (there is a hole in the axle so that a screwdriver will fit).

Step 19:

Attach the motor axle to the drive pulley using 3mm screws.

Step 20:

Paint the plywood (if desired) and attach the bearing and motor holders using wood screws. Be certain that the belt is reasonably tight (depress less than 1/2 " midway between pulleys).

Step 21:

Add velcro to the belt--it's just a bit too slippery for the slinky without the help.

Step 22:

Make two side supports. The lower piece of cardboard is about 2 1/2" x 3 1/2". The upright piece is 3 1/2" x 7". Glue together at a 90 degree angle--I used 1" x 2" wood scraps to firm up the angle.

Step 23:

Glue 4" x 13" cardboard (at an angle) to the upright cardboard supports. These side walls must not touch anything that moves.

Step 24:

In an ideal world, the pulley will rise 13 units for 33 units of horizontal length. I didn't get this correct, so my 1" Gorilla tape under the foot of the system makes this work.

Step 25:

I turn the motor on (about 8 volts in my example--around 200 mA) and set the slinky on the bottom of the belt. As the slinky moves toward the top, I lift the upper part of the slinky and pull it downward. Two or three tries and you'll get the hang of it.

Usually it will run a minute or so until it runs off the bottom or top (feedback and stable acrylic walls might enhance the run time).

Enjoy :)

Introduction: Slinky Machine