Professor Laithwaite's Gyroscope Experiments Part I

Before leaving the topic of gyroscopes, I want to comment on a forty-year-old experimental result that I must admit I still don't understand well. With modern technology it could probably be resolved easily enough, but I won't be holding my breath waiting for that to happen!

Videos

The experiment is shown in these videos:—

The first video shows Eric R. Laithwaite, Emeritus Professor of Heavy Electrical Engineering at Imperial College, London, force-precessing, then easily lifting a heavy, spinning gyroscope weighing 40 pounds. The second video shows an Australian replication of this experiment, again with a gyroscope weighing 40 pounds.

1975 — A space odyssey

Professor Laithwaite's experiment in the video above is a repeat (with a heavier gyro) of the experiment he did and wrote up in his article "1975 — A space odyssey" in Electrical Review, 28 March/4 April 1975, p398.

In the image above from that article, Professor Laithwaite is resisting forces that should be 24 pounds vertically plus 17 pounds horizontally with only the little finger of his right hand. He says:—

"Fig. 5 shows me supporting an 18 lb wheel revolving at 2,000 rev/min on a 6 lb shaft, 22 in long on my little finger with my arm fully extended towards the camera. It is not posed; it is an action shot and I am rotating at about 1 revolution in 2 seconds about a vertical axis, dragging the gyro around faster than its natural precession speed under gravity. The wheel is rising quite rapidly (about 3 ft vertically in half a revolution of me). What is most dramatic is my ability under this forced precession to lift the other end of the rod also. Had the gyro merely transferred its mass to its first point, i.e. my finger, I could not have supported 24 lb at arm's length, let alone accelerated it upwards. Had there been the usual centrifugal force it would have been Mrω²/g, which with M = 18 lb, r = 3 ft and ω = π rad/s, works out at about 17 lb, the shaft would certainly have been snatched from my finger. Photographs, of course, can be faked, but anyone can repeat the experiment for themselves." 

The important part

I have added the emphasis on what is the most important and difficult-to-explain part of this experiment. There would seem to be only two possible explanations, both very unlikely: either Prof. Laithwaite was much stronger than anyone realised, including himself, or else the gyroscope was exerting much less downwards force than its natural weight (and also less than expected centrifugal force) at the point where its axle was being held.

I'll look at some experiments and modelling of this, next time.