My wife, Annelle, and I discovered this "artist made" climbing bear toy at the artists' shop (an interesting place to look around and talk to the artists) in Murphy, North Carolina.
This hand made bear (signed and dated by the artist--costs $12.00 in the shop) is operated by alternately pulling the left and right ropes--then releasing the ropes to let the bear fall. I wanted to add this toy to Santa's Shop (Christmas window display placed in local store window), so the automation project was born.
Step 1: Parts
First, you need a climbing bear. This is an old folk toy design and similar versions are found in many cultures of the world. This particular toy was hand made by Phil Baerreis in North Carolina.
Climbing Bear--Gallery 26 (http://www.gallery26.org) Murphy, NC about $12.00 plus shipping
(2) Servo motors --Hitec hs311 or similar
(1) Arduino Uno
(4) AA batteries and battery holder
Ten inches of wood 1" x 2"
2-56 x 1 1/4 machine screws and nuts
3d printed parts
Mount a 5 inch long 1" x 2" wood piece into the base support and secure to the base.
Fasten the servo motor to the 1" x 2" using 2-56 screws and nuts.
Add a second motor, eight inches away from the first (measured center of 1" x 2" to center of second 1" x 2").
Add arms to servo motors.
Where to tie the knots and mount the bear is a "fiddeley" thing, depending on your situation. To climb, the left and right ropes must always be in tension (if one gets loose, the bear will slip on that side).
When I had everything working on a test rig, I knew that the "real setup" would have to be adjustable--or I would be forever reworking the knots that hold the bear. My heavy duty plastic screw (with a slot for the rope) can go up or down a couple of inches to adjust for rope tension.
This is my Arduino sketch to control the servo motors (wire according to the schematic in step #1).
The numbers in the sketch work for my situation, but they will have to be adjusted to fit your servo position and knot length.
The base and the top have to be secured because some tension is required on the ropes.
After each "pull" of a servo motor, I allowed a bit of "rest" time so that the ropes would not swing wildly (and possibly turn around).
At the top of the climb, I held the bear for a couple of seconds before releasing the ropes and letting him fall to the base.