More on the Perpetual Motion Machine

MOTHER EARTH NEWS readers share their feedback on the gravity perpetual motion machine article featured in issue NO. 33.
By Nicholas Rosa
November/December 1975
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The trouble with this and all similar "unbalanced wheel" perpetual motion machines is that they eventually run down because of bearing friction at the hub, air friction on the wheel itself, and other losses.

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MOTHER EARTH NEWS readers share their interpretation of the gravity perpetual motion machine article featured in issue NO. 33, and provide their own ideas about the success or failure of the perpetual motion system.

Feedback on the Perpetual Motion Machine


MOTHER EARTH NEWS readers shouldn't invest workshop time or material resources on the "gravity perpetual motion machine" suggested by Rainbow Atma in MOTHER EARTH NEWS NO. 33. This device, sketched on page 144 of that issue, is a sort of hollow wheel divided into pie-wedge compartments, each holding a ball weight which is free to roll toward the center or the rim. As Rainbow said, the idea is an old one . . . and it doesn't really work.

The trouble with this and all similar "unbalanced wheel" perpetual motion machines is that they eventually run down because of bearing friction at the hub, air friction on the wheel itself, and other losses. (To explain those last factors would require my writing a complete lecture on energy physics, which might get a bit tedious for all concerned.) The same thing happens in all machines, and there's no magical reason why this particular design should be exempt.

"Working" models of the unbalanced wheel have been built, and they appear to operate all right . . . provided that the observer doesn't hang around long enough to see them run down, or doesn't make a series of strobe-light tachometer readings that would detect the steady loss of rpm. The fact is that friction always catches up in the end.

The "perpetual motion" wheel spins because of the impetus given it by the person or device that set it in motion. Like any other well-balanced rotor on good bearings (wheel, motor armature, gyroscope rotor, whatever), it can go on spinning a heck of a long time on its inertia. Even an antique foot-powered grindstone, with its primitive bearings and its many friction-prone linkages, takes a good while to quit once you have it up to any speed at all.

"Aha!" say fans of this and similar designs. "You just called the perpetual motion wheel a 'well-balanced rotor' . . . but the whole point of the gadget is that it's an unbalanced rotor. There's more 'weight' on one side than the other, and therefore gravity will keep pulling harder on that side, and therefore the machine will continue to run. Right?"

Not so. Each ball in this machine exerts what engineers and physicists call a "moment of force". If you regard all moments of force on the "downward" side of the wheel as "positive", all the moments on the "upward" side are "negative". The negative moments of force, added up, equal the sum of the positive moments. The result is zero.

It follows that the situation is the same as with an ordinary roller-skate wheel you've set spinning with a twirl of your finger. All the moments of force in that rotor add up to zero, too . . . that is, if you have a nicely balanced wheel. (One in poor adjustment vibrates itself to a stop rather quickly.)

Now then. For fun, let's suppose that we somehow managed to maintain a slight dynamic imbalance in the perpetual motion wheel . . . so that gravity affected the machine's sides differently and supplied just enough energy to overcome all the frictional forces. Then the wheel should keep spinning "forever", no? Yes. Of course. In fact, we could expect it to start rotating by itself if we so much as breathed on it. But what good would it be?

MOTHER's children are seeking, presumably, a useful device, an energy supply . . . not a curiosity for the local museum of gee-whiz "science". The rotor I've described has no such potential. The moment we tried to take power out of our spinning wheel — by hooking it up to the cream separator or the 12-volt generator or whatever — the apparatus would slow down and then come to a stop . . . because we'd be putting a load on that machine, thus introducing additional frictional, viscous, and other drag forces. The load would act just as it would on a Pelton wheel, a diesel engine, or a steam turbine: it would consume power, tend to decelerate the "engine", and require an additional energy input to keep speed up and prevent the whole system from grinding to a halt.

YOU CAN'T GET SOMETHING FOR NOTHING. This "ecological" principle — first discovered through physics experiments — governs everything in the universe, and, is the unbeatable rule which promoters of so-called perpetual motion machines try to evade. They demand more energy "out" than energy "in" (the same thing as more power out than power in, since power is simply energy per unit of time). To put it another way, they demand what engineers justly deride as "an efficiency greater than 100%". They demand, in short, something for nothing.

As even Mr. Atma admitted, the concept of the unbalanced wheel is quite old . . . yet the machine hasn't rolled anywhere yet, because it can't. My advice is, "Stick to waterwheels and windmills and solar power and methane engines, and forget perpetual motion."


In MOTHER NO. 33, Rainbow Atma described an overbalanced "perpetual motion" wheel he saw in a museum and added that he'd "heard lots of reasons why it shouldn't work".

For the benefit of Mr. Atma and any of MOTHER EARTH NEWS readers who — in common with about 92% of our population — had no physics course in school, I'd like to expand on that comment. There aren't "lots of reasons" why the machine "shouldn't" work, there's just one reason why it won't work: the principle of conservation of energy (or energy plus mass, after Einstein). This concept was fully developed in the nineteenth century, beginning with James P. Joule and ending with Clausius, and is rendered in the vernacular as "There ain't no such thing as a free lunch".

You see, Mr. Atma, gravity is not a "free" source of energy. An object raised above a reference level (the floor, the ground, etc.), does indeed have "potential" energy . . . but it took exactly that amount of energy to lift the article in the first place. So — apart from waterfalls and tidal forces and ocean wave action and sunlight and radioactivity and wind — no source of energy can be called "free".

Sorry, Rainbow, but neither you nor anyone else can brainstorm the old perpetual motion wheel into an electrical — or mechanical — power generator. In fact, even unloaded, your wheel won't run very long . . . at most, a few hours. (Magnet arrangements won't work either.) Once again: To get energy out of the machine, you have to put energy in.

MOTHER's readers might more profitably work on the principal idea exhibited by the "atmos" clock, which runs by virtue of small changes in atmospheric pressure. It seems entirely possible that such a structure could be scaled up enough to produce usable forces.

You might also look into the interesting mechanical "motors" which can be made from stretched rubber bands alternately heated by the sun (free energy!) and cooled by water. Or the famous toy called the "drinking bird" could perhaps be increased in size to give appreciable forces . . . again with the aid of the sun's heat. (See MOTHER EARTH NEWS NO. 22, page 9, for Steve Baer's ingenious application of this idea. — MOTHER.) 

In case you're wondering about my qualifications, I have a bachelor's degree with a major in physics, worked 20 years in geophysics and electronic engineering, and have taught physics for 13 years now. I'm hoping that the information I've given here will save MOTHER's readers a good deal of frustration. Admittedly, "new" principles are discovered from time to time . . . but they don't necessarily override older knowledge. Newton's laws still apply today in everyday life, and no fresh finding is likely to make the gravity wheel work.


R. Atma's letters and drawings (MOTHER EARTH NEWS NO. 31, page 124, and NO. 33, page 144) left out a few factors which are important to the perpetual motion wheel. You must consider not only the number and location of the balls, but also the leverage arm, its angle, and the momentum (or speed and direction) of each weight. Most essential is the fact that — because you can't shield the machine from gravity — each ball weighs the same no matter where it is in the device.

However, if magnetism — which is easily shielded — is substituted for gravity, Mr. Atma won't have to give up his dreams.

In fact, anyone can use magnets to propel a car or heat and light a home. If you'd like to see a description of a permanent magnet prime mover (non-thermodynamic), send 50 cents to the Commissioner of Patents, Washington, D.C. and ask for patent number 3,879,622.

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