Go Gravity Go!

Henri Giffard's Airship, 1852

The first human to fly in a controllable machine was Henri Giffard, inventor of the boiler injector. He beat the Wright Brothers by 50 years. His boiler injector was considered an impossible perpetual motion machine some decades after it was already in commercial use.

Still Impossible After All These Years?

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...by injection, not compression; air is compressed by mixing with air already in the tank; energy comes from the ambient heat of the atmosphere constantly replenished by the sun.  Original patent granted to Bob Neal in 1936.

Not perpetual motion. This is a heat pump. Heat pumps can make more energy available than they use; this is established science and doesn't challenge the laws of thermodynamics; it happens every day with ordinary heat pumps. Efficiency is not over 100%; the C.O.P. (coefficient of performance) is over-unity.

Textbooks explain that all work of compression is lost as heat. So where does the energy come from that is conveyed by compressed air? It is ambient heat from the sun. It was already there before the air was compressed. Heat pushes pistons; pressure only indicates how much the air can expand. Heat is energy; pressure is only a component of energy that can be measured easily.

The concept below is one of hundreds of ideas by Scott Robertson to achieve what Bob Neal claimed in his patent. The injector concept was first suggested by the famous civil engineer and civil war general Herman Haupt in 1893, to increase the range of air cars between fill-ups.

injector system for self-filling air tank by Scott Robertson
Inject air into full tank instead of compressing it into tank.


  1. Roots blower, a low pressure, high volume rotary compressor provides oil-less air.
  2. Air engine, two-stage engine shown, uses air in two consecutive cylinders with ambient heat absorbed by fins.
  3. Jet drive compressor, two stage compressor shown, boosts existing pressure of tank air to supply jet drive; compression heat stays in tank to increase air temperature while being conserved for system use.
  4. Two-stage series of check valve units; five valves per unit (two shown) ensure porting for intake of enough low pressure air to keep the tank full and then some.
  5. Toroidal (donut-shaped) cavity, or vortex diode, prevents backflow of compressed air into low pressure zone.
  6. Jet drive supplies high pressure jet to create low pressure zone at check valve discharge.
  7. Tank pre-filled by external compressor.
  8. Ambient air (normal atmosphere) pre-heated by the sun.
  9. Low pressure zone at check valve discharge allows low pressure air to enter high pressure tank.


This is not perpetual motion. The energy used by all compressed air motors can and should come from the sun. Engineers can do their jobs (which is to design air motors for portability and convenience, not for efficiency) without knowing that all compressor work is lost as dissipated heat, so this vital information has been left out of textbooks for many decades to keep people from asking questions.

The air in the pre-filled tank represents enough energy to start and run every device on the car, and then some.The trick is to manipulate this energy through knowledgeable design so that it is not dissipated any more than necessary, in order to keep the tank full. The real trick is "Maxwell's Demon," which I have decided is the Bernoulli Effect: air pressure can be converted into air velocity (jet drive), so that in the localized absence of pressure (low pressure zone inside tank) the high velocity jet can induce low pressure air (continuous source of solar energy) into the tank without wasting a lot of energy compressing it to get it in. Because of air's internal energy (heat that is there before the air is compressed), the power needed to generate compressed air is uniquely unrelated to the power available from the compressed air thus created. This gives the appearance of perpetual motion, but is not; it is a heat-pumping process. Like many existing commercial heat pumps, this system can provide more energy than it consumes; that is, its C.O.P. (coefficient of performance) is greater than one.

Advantages of the devices shown:

Roots Blower (1) has no reciprocating (back-and-forth) parts so operates more efficiently than a piston compressor. It only works for low pressure applications. Its task it to provide a positive, solid push of solar-heat-laden atmosphere into the check valve unit which traps it for induction into the low pressure zone in the tank.

In-Tank Booster Compressor (3) heats and pressurizes tank air above tank pressure to create a positive, higher pressure jet of air that induces low pressure air into the high pressure tank. Since it is located inside the tank, the heat it generates stays within the system and becomes additional fuel for the air engine. With adequate measures taken to conserve its compression heat, the booster compressor operates almost for free, in terms of its net energy use.

Low Pressure Zone (9), Jet Drive (6), and Vortex Diode (5) work together to manipulate the high pressure air in the tank to step aside and let large quantities of low pressure air into the tank.  The net effect is that the tank pressure will continuously go up, and a separate port (not shown) will have to be provided to vent air for use in other equipment such as to run a car, a pump, a generator, or air tools.

If you think you know how Neal's tank worked — or if you want to know what others think — join this new forum now!