Eric Laithwaite: New Scientist: Eric Laithwaite Defies Newton (14.Nov.1974)

The Professor of Heavy Electrical Engineering at Imperial College London, Eric Laithwaite, highly successful inventor of the linear motor, has entered the sacrosanct domain of the mechanical engineers. And he says "they need me". Last Friday as the piece de resistance of his evening discourse at the Royal Institution he demonstrated a machine that, he claimed, violated gravity and produced lift without any external reaction.

The machine is pictured here in action on a kitchen spring balance, just as he demonstrated it. The machine uses two precessing tops whose precession (slow motion of the axis of rotation about a vertical axis under the action of gravity) is assisted by the motor at the bottom. This makes the tops rise. The tops are restrained from rising by a track like a big dipper, and as the tops follow the track the whole machine jogs up and down. Professor Laithwaite contends that there is more jog up than jog down.

Laithwaite began his discourse with a series of entertainments from his work on electromagnetic levitation, draing applause and laughter from his evening dressed audience like a good juggler, and throwing in his usual flamboyant claims. All this was to prove Don Quixote’s phrase "all things are possible". Then he moved into h=gyros (mmore exactly, tops).

Tops are certainly fascinating. They fascinated the Victorians and the Edwardians after them, and many a Newtonian treatise has been written about their motion. They are used with great precision in gyroscopes in ships, submarines, aeroplanes and rockets, so there must be some understanding of their motion. But Laithwaite contended that the familiar precessing top that can be bought in the toyshop, being of a different design (not supported through its center of gravity), is not properly described by Newton’s laws of motion.

He drew the curtain covering the blackboard to reveal a modification of Newton’s second law (in an inertial frame) that bears the same relation to the usual equation as does the equation for the voltage on a resistance, capacitance and inductance to Ohm’s law.

In practical terms he had four main contentions about gyroscopic precession. First, he believes that the angular momentum of precession (about a vertical axis) is created out of nothing, so that angular momentum is not conserved about that axis in direct contradiction of Newton’s mechanics; second, he believes the precession is not accompanied by any centrifugal force (the force you feel if you swing a bucket around in the garden); third, he contended that it requires no force to stop the precession; and fourth that if the precession is speeded up, the tops (which certainly rise) do so without there being any consequent downward reaction.

It is my opinion that none of these contentions was proved by the experiments Laithwaite performed at the Royal Institution during his discourse. Perhaps he will be able to do more precise experiments which will bear him out, but until he does so his case remains at least unproven. To take just one example --- and the most spectacular --- his anti-gravity machine weighed to within half a pound of the upper limit of the scales (where there was a mechanical stop). So even if the reaction on the scales was reduced during one part of the machine’s cycle (and it indeed went down 5 pounds out of its total 20), the reaction would not have shown on the scales if it had gone above 20 pounds on the least of the cycle. The needle in fact swung violently between its upper limit and 15 pounds.

You have probably got the impression by now that I am skeptical of Eric Laithwaite’s views on the gyro. You would be right. I believe he has got it wrong by changing fields too quickly and jumping to conclusions --- or else we are all being taken for a marvelous ride! Yet he said in his discourse that his "life had led up to this moment", and he appeared to be extremely serious about his views.

If indeed he is not joking he is beginning to bear a strong and sad resemblance to one of his heroes, Don Quixote. A giant (figuratively and physically), he is gentle (he is an expert on butterflies) and has all Don Quixote’s lovable but arrogant naivity. This time he has tilted at windmills.

Newton's Point of View

Newton, though long dead, can still give us his views through his equations of motion. The first point he might make about Laithwaite’s experiments is that they involved "fast" tops. These are tops that have far more kinetic energy in the gravitational field (weight times distance the center of gravity of the top can move). Such tops have a deceptively simple motion that can confuse generalization to slow tops.

One example of this is the question of the "creation" of angular momentum about a vertical axis when the top begins to precess. In fact the top, when released from a stationary horizontal position, falls vertically until has a component of its own high internal angular momentum along the vertical --- just enough to compensate for the angular moentum of precession. This fall (which indetail is a damped out nutation) is hardly noticeable in a fast top but is obvious in a slow one. Hence the creation of the angular momentum of precession.

A similar remark applies to the centrifugal force of precession; if a top is fast the centrifugal force is only a small fraction of the weight of the top, so it is hardly noticeable. For a slow top the force becomes more important as the precession speeds up, and this is one of the contributions to the falling over of a toy top on its support as it slows down.

Next, according to our old friend Newton, a force is certainly needed to stop a precessing top, albeit a small one. The exact motion of the top after it has been stopped depends on the details of its previous motion. So in both the case of the centrifugal force and stopping the precession there is a simple test by which Newton’s and Laithwaite’s contentions can be distinguished.

Finally there is the question of the reactionless rise of an assisted, precessing top. Laithwaite agrees that the exact amount of energy needed to lift the top must be introduced by twisting its vertical support, so there is no gaining something for nothing on that score. Newton would argue that no vertical reaction was necessary anyway once the top started upwards (just as no extra reaction is necessary on a crane when it is steadily lifting its load). And to test the contention that the machine gets lighter, Newton would ask Laithwaite to measure the impulse (force times time of action), not the force itself. Such sophistication is beyond a set of kitchen scales.

New Scientist (14 Nov. 1974)
"Eric Laithwaite Defies Newton"
Robert Walgate
Mirrored From: REXRESEARCH