[Eternal Student (OP)]

Hi.

    I was looking through some of the old Feynman lectures and came across this section which attempts to explain what makes a gyroscope start to precess instead of falling.   Just to be clear, it does not suggest this is what sustains precession, just what starts it.   You have a situation with a spinning gyro supported on a pedestal at the centre and you are holding the (soon to be) free end stationary with your hand until it is suddenly released.

gyro.JPG (28.45 kB . 583x312 - viewed 478 times)

This is what the lecture states:
     Some people like to say that when one exerts a torque on a gyroscope, it turns and it precesses, and that the torque produces the precession. ........it does not fall under the action of gravity, but moves sidewise instead!  .....( but ).........
    .....The gyro actually does fall, as we would expect. But as soon as it falls, it is then turning, and if this turning were to continue, a torque would be required. In the absence of a torque in this direction, the gyro begins to “fall” in the direction opposite that of the missing force.....

[End of section 20-3,  "Rotation in Space", Feynman lectures.
https://www.feynmanlectures.caltech.edu/I_20.html ]

      I can't be the only one who finds the idea of a "missing force" a bit odd.   To say that things accelerate in the direction of a net force is one thing,   to say that they would accelerate in the opposite direction to a missing force is much harder to live with.
     There's a computer on my desk and it is missing a force to move it left but it does not accelerate to the right.

    Anyway, is this explanation with "missing force" still popular?   At the moment I'm inclined not to recommend that explanation.   Maybe Feynman tried to oversimplify and has ended up with something that isn't all that usefull for understanding?   i.d.k.   I do note that he has quotation marks around "fall" as if he was just making an analogy to objects falling when they are missing a force to support them. 

Best Wishes.

LATE EDITING:  Fixed various spelling errors.   Title changed from "in the direction" to "in opposition to" etc.