This stabilizer can be used succesfully with moderately long exposures and moderately long focal lengths.
Needed: 2 discarded harddisks (HDs)
Some old discarded computer, or parts
The part in the old computer which holds floppies en HDs at a 90 degree angle...
A woden box or plywood etc..
A hand grip
One or two strips of aluminum
A camera screw
3 or 4 car USB phone chargers
A 12 V power source (lead acid cell, a discarded NiCd cell, or (rechargeable) batteries)
Some rubber washers and a piece of inner tire
Costs: something between E 0.00 and E 50.00 (my costs: E 15.-)
Time to build:a few days, including some shopping...
Tools: Simple hand tools, drill, soldering gear.
Update: look at my single Gyro stabilizer: www.instructables.com/id/Single-HD-Gyro-Image-stabilizer/
Step 1: How it works
Most hard disks spin at 5400, 7200 or 10.000 RPM. The rotating parts have a considerable mass, and are very well centered and balanced. Old HDs with storage space below ca. 10 Gb can be obtained very cheaply, or even for free.
The spinning HDs working as gyroscopes in the horizontal and vertical plane (X and Y) can almost completely prevent motion blur.
When a long exposure, or tele picture is taken by hand, motion blur occurs in a combination of horizontal and vertical (X and Y axis) shaking; not so much in the back and forth (Z axis) direction.
The spinning mass in the HDs steadies the camera.