This article is from the Scientific Skepticism FAQ, by Paul Johnson Paul@treetop.demon.co.uk with numerous contributions by others.
Gyroscopes (or gyros) are a favorite of "lift" machine inventors
because many people have come across them and they behave rather
oddly. However there is nothing all that mysterious about the
behaviour of gyros. You can use Newtonian physics to explain them.
Briefly, if you imagine a bit of metal on the edge of a spinning gyro,
then to turn the gyro you have to stop the bit of metal moving in its
current direction and start it moving in another direction. To do
this when it is moving fast you have to push it rather hard. Nothing
about this makes the thing get any lighter (in fact to be pedantic,
the gyro gets very slightly heavier when it spins, in accordance with
Einstein's theory of relativity.)
 
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