The design is really simple: on both sides of a telescopic extension pole sit a fixture that can pan and tilt, using two hinges. The fixtures are identical, except for the camera mount.
The fixtures are connected to each other by 3 pieces of wire. The resulting effect is that if you move one fixture, the other fixture copies the exact movements.
The range of motion is about +/- 45 degrees left&right and up and down. As there are no pulleys or complex lever systems, the motion is pretty smooth. The hinges need some more work, they tend to stick a little and make some noise. I'll remove some material to make it smoother.
Here is the crane itself:
And here is some footage I shot with it
Step 1: Stuff you'll need
- A telescopic extension pole. These things can be used for painting, changing bulbs, etc. I got a 16 ft one at OSH for $40. That's the most expensive part of this crane. I'm sure you can find a cheaper one if you shop around.
- About 2 feet of 1x1 inch square aluminum tubing (OSH, around $10)
- this is where it gets fuzzy: various pieces of aluminum (I had these lying around) and wood.
- 60 feet of nylon rope
- various screws, bolts. (screw to mount camera is 1/4")
The most critical thing in the desing is the double-hinge that allows for pan and tilt. A ball joint is less preferable, since that will also allow the fixtures to rotate around the axis parallel to the extension pole.
When building the double-hinge, make sure that the rotating axes are as close together as possible. You'll have to make some smart trade-off's there: bring them really close together and you might limit the range of motion. If you have them far apart, the tension in the wires will change with varying angles. This can be overcome by adding a spring or rubber band in one of the wires.
I'll might post a detailed how-to-build list, but as you can see, it's pretty simple. I built it in a single afternoon...
The pole flexes quite a bit if extended fully, but that doesn't seem to be a problem. Getting smooth motion and aiming the camera will require some more practice.