Prof. Laithwaite's Gyroscope Experiments Part III

A subjective loss of weight

I have been discussing the strange phenomenon of the apparent lack of weight that an experimenter feels when he first force-precesses, then lifts a heavy spinning gyroscope. When Professor Laithwaite did this, he described the gyroscope as "light as a feather." In the Australian replication, the comment was "it feels incredibly light as I do that."

Although as I have pointed out, these experiments could have been better instrumented to gain much better data, let's assume for now that the orthodox conclusion of no weight loss of the experimenter plus gyroscope, throughout the lifting experiment, is correct. Can that possibly be reconciled with the loss of weight felt subjectively at the experimenter's hand?

Unorthodox explanations

The "falling-away" laboratory frame will have some influence, but I doubt that it could fully explain this phenomenon. I think we are forced to look for unorthodox explanations. One possibility is that the gyroscope is somehow transferring its weight back not just as far as the experimenter's hand, but instead to his elbow joint, or even his shoulder joint — which does not rise as the gyroscope rises.

I would be quite skeptical about that idea, except that there seems to be some support for it in one of Professor Laithwaite's experiments.

The "double-joint" experiment — background

On two separate occasions, Professor Laithwaite was invited by the Royal Institution to give the "Christmas Lecture" a.k.a. the "Faraday Lecture", traditionally a very prestigious event. His first lecture in 1966, on electromagnetic devices, was well-received. His second lecture in 1974, on gyroscopes, was so controversial that for the first and only time ever the Royal Institution refused to publish it. It was subsequently published independently as Engineer Through The Looking-Glass.

[Reference: Engineer Through The Looking-Glass, E. R. Laithwaite, ISBN-10: 0563129794]

One of the experiments performed in this lecture (the "double-joint" experiment) is shown, with the gyro non-spinning at first, in the sketch below from page 51 of this book:—

Fig. 4.14 The double-joint experiment — initial state

Prof. Laithwaite says:—

"...First the system is balanced by means of the adjustable weight about the tower pivot, as shown in Fig. 4.14, with the stationary gyro and bearing ring hanging freely from the second pivot. The wheel is then spun and raised until the whole gyro axle is horizontal and from this position it is released. If the spinning wheel succeeds in transferring its weight to the second pivot by precession, the bearing ring and piece of spindle up to the second point are 'dead-weight', and must surely cause the gyro to precess about the vertical tower pivot whilst adopting an attitude as shown in Fig. 4.15.

Fig. 4.15

What did happen was that the gyro end raised itself to the position shown in Plate 4.11, whilst precessing about the vertical tower axis in the expected direction. There appeared to be no ordinary explanation for this but it reaffirmed my belief, which I first expressed in a Friday evening Discourse at the Royal Institution on 8 November 1974, that a gyro exhibited phenomena that were not to be found in any other mechanical object, and could well be worthy of a study at a level not hitherto attempted..."

Plate 4.11 The double-joint experiment — final state

I'll do some further study of the "double-joint" experiment myself, next time.