Claimed to produce over-unity...
Bob Neal

The original idea of the ambient air heat engine was published by Nikola Tesla in 1900. But Tesla had not worked out what the best "working fluid" for the system would be.

After years of experimentation, Bob Neal filed for a US Patent in 1934 for an engine/compressor unit that ran continuously from a tank of compressed air. The engine produced excess mechanical energy while keeping its own compressed air tank full at all times.

When the Patent Office informed Bob Neal that his patent claim would be denied because it was a perpetual motion machine, he built a miniature working model, put it in a suitcase, and flew to Washington DC. He plopped the engine down on the patent commissioner's desk, turned it on, and requested that he be granted his patent on the basis that the engine worked. His request was granted in 1936 with the issuing of US Patent #2030759.

Sometime after the patent issued, Bob Neal was visited by some German officials who requested that he share his secret with them. Their request was not granted. Shortly thereafter, Bob Neal's daughter was kidnapped, and once again the German's requested that he share his secret with them. As the story goes, Neal took his working models apart and scattered the pieces around the countryside. He informed the Nazis that he was through with the engine forever, and requested that they return his daughter, which they did.

A more probable scenario suggests that Neal traded the secret of the engine to the Germans to secure his daughter's release, and then abandon any further work on it for the future safety of his family.

World War 2 was well underway in Europe, and the Germans were agressively procurring any advanced technologies they could find. Toward the end of the war, the Germans perfected their pulsejet propusion system, which was probably inspired by Bob Neal's patent, since it uses the same ideas as the mysterious equalizer that allows low pressure air into his air tank. Of course, the Germans used their pulsejets to power their V-1 cruise missles to shower London with bombs.

Bob Neal's breakthrough technology lay dormant for decades until Scott Robertson dug everything up again and built his astonishing website detailing the rich history of compressed air technology and the legacy of the ambient air heat engine demonstrated by Bob Neal in the 1930's.

Before you lose your perspective on this, a compressed air engine that runs from a tank that keeps itself at full pressure all of the time is NOT a perpetual motion machine. It is a HEAT ENGINE that runs by the extraction of heat from the ambient air, which was put there by the SUN.


Bob Neal and other compressed air inventors
July 05, 2011

I want to recommend US Patent 2030759 by Bob Neal "Compression Unit".

It is a unique way of compressing air using resonance in the compressor discharge pipe (like water hammer but in air) to do the compressing in the pipe and in the tank instead of in the compressor.  Water hammer or I should say resonance is the only method I know of that has been shown to work for getting over-unity, like the steam generators invented by Joe Griggs and Carl Schaefer and the air heater invented by Eugene Frenette.  Except other compressed air tricks which I'll discuss another time.  Air is the most natural source of free energy because it's heated by the sun 24/7.

This has been worked on by a machinist who was in communication with me for three years.  His results were very good but his machine was not built strongly enough so he moved on to work on a simpler device of his own.  Bob Neal's patent is in the public domain.

The Neal compressor has 7 pistons for each engine piston.  The 7 compressor cylinders are evenly spaced around the crank cycle so the "problem" of vibration in the discharge air is made "worse" by having so many cylinders.  In this case worse is better.

The engine piston is in phase so that while a standing wave in the compressor discharge pipe is pulsing air into an equalizer space in the pipe defined by 2 check valves, simultaneously in the tank the pulse of air leaving for the engine is communicated to the equalizer tail pipe which is an open-ended pipe that blasts squirts of air from the equalizer into the tank.  The tail pipe amplifies pulsations in the tank to produce a strong rarefaction wave that pulls at the air coming into the tank while the pressure wave at the intake to the equalizer hammers at the door.

The compressor has to be as strong as any compressor in order to compress air to 100 psi normally like any compressor.  By that time it has to reach the right rpm to trigger resonance in the discharge pipe.  When that happens a standing wave is set up in the pipe between compressor and tank so the compressor stops running hot and compression takes place in the equalizer instead, in the middle of the tank.  The compressor resists only atmospheric pressure, it is just an air mover and pulsation generator.

So not only is all compression heat conserved, but the only work the compressor has to do is to generate a wave of the right frequency and keep the air moving.  Neal's patent calls for putting air into a 200 psi tank with a single stage compressor running cool..."impossible" but my machinist friend proved it.

There is much more to say but I'll let it go at that for now.

Pneumatic Options Research Library
September 30, 2013

Nova Neal Compression Engine

Involving a self-sustaining, heat-exchange, air compressor

Compiled by Sterling D. Allan

On September 26, I met with David Yurth, who is the Director of Science & Technology at Nova Institute of Technology in Salt Lake City. He and his wife treated my wife and me to lunch, then took us to their home where David showed me a few videos of some technologies his group is pursuing, which he'll allow me to talk about later.

The primary reason for the meeting was to discuss open sourcing the Nova Neal Compression Engine. I shot a video of him giving a brief introduction, which I've transcribed for the sake of those of you who visit our site through translation services.

In preface, let me say that while I respect David and his team at Nova for open sourcing this, and they seem to be a very bright group, I have a hard time believing this design will work. I don't see any way that it harnesses the wheelwork of nature, unless it is a heat pump or something like that, pulling heat from the environment.

Official Websites - This PESWiki page is the official page for this open source project.
David's organization website.



In 1936, an inventor by the name of Robert Neal obtained a patent from the US Patent Office for an engine whose medium of exchange was compressed air, which was self-sustaining once it got started.

The patent application was initially denied because "perpetual motion" was a category of application that the patent office had decided they would not respond to. So, as the story goes, Mr. Neal packed up his engine, took it to Washington [D.C.], put it on the desk of the patent commissioner, turned it on, and demonstrated it, after which, he got his patent.

The story about what happened to the engine is a matter of record. Eventually, because of interference from people who wanted his engine and who kidnapped his daughter as a way of compelling him to relinquish it, he agreed that he would disassemble the engine and distribute the parts and not make it any more.

In the 75 years since that happened, to the best of our knowledge, no one has succeeded in either identifying the specific set of principles that made it work, or recapitulating the engine or in a newer or similar kind of design.

After about 10 years of research on this process, we know how his engine worked, and we understand the principles that are involved. And [with what] we have available today, with 21st century technologies and materials, [we have the ability] to operationalize what he created with much cruder materials a long time ago.

The engine operates as a heat exchanger. There is nothing exotic about it.

What happens in his engine is this. Two secrets made it possible for him in his design to build a self-sustaining heat-exchange, air-compressor engine.

1) He developed a valve that enabled him to put low-pressure air into a high-pressure tank.

2) He designed his engine in such a way that the first air that went in was re-compressed to a higher pressure, and the tank he accumulated the pressure in was designed and put so that he could retain the heat of recompression.

What that meant was, based on the calculations that we have developed today, 100 psi air input into his engine at 20 ft3/minute was translated into a much higher pressure that allowed him to tap the same input volume, but at a self-amplified pressure that was 8-12 times higher than the original input value.

It's just as simple as that.

So, what we've done is put together an abstract that details the principles that make it work, a partial list of components that are needed in order to build one today, and the sources for the pieces that made his engine unique.

Essentially what happens is that we take a tank of about 100 gallons. The tank is a serious piece of business. You have to make sure, when you're operating at pressures that are in excess of 1100-1200 psi that you haven't short-cut anything on your tank. One end of the tank (the dome) has to be detachable, because the recompression equipment goes inside the tank, and has to be contained in it, in order for low pressure air to be input into an internally-held air-booster while the heat of compression is retained inside the tank.

So, [you can get] a Haskell Boster, or a booster made by Eaton, or other manufacturers -- ubiquitously available on the Internet, they use them on the Space Station, you can buy them in a quantity of one, for anywhere from $2500 to $5000. These are typically the kinds of devices that are used to take air pressure from a conventional single- or double-cylinder compressor, and convert that into 4000 psi pressure in scuba tanks.

We're just going to put one of those inside the [larger] tank; seal it up; make sure that the tubing and the piping is pressure-rated, so it isn't collapsed under the internal pressure of the [larger] tank.

Once that is put together and engineered, then you have a compressor on the outside of the larger tank, which is driven by an electric or gasoline-powered engine, and connected by a slip-clutch of some kind, so that once the engine becomes operational from the [internal] tank, you can disconnect the [external] compressor from the extrinsically-powered unit, and drive it by an air-powered engine, which takes the air off the [internal] tank, out through the dome.

We've specified an [Angelo] DiPietro Engine, [which we] like because it has a rotating cylinder, it operates with very high torque and very high efficiency at a relatively low consumption rate. So, at something on the order of 18 - 20 ft3 / minute, the DiPietro Engine, powered by a tank that is compressed at 800 - 1100 psi will enable that little engine to drive two things simultaneously.

1) The first thing it will do is drive the external compressor so it is continuously recompressing the [internal] tank; but you have 40-45% of the work potential provided by the pressure in the [inside] tank left over to perform other kinds of work.

2) So the DiPietro Engine can also be attached to a compressor, or an alternator, or a generator, or a pump, or anything that requires shaft-driven torque in order to perform work function.

The reason this apparatus works is because the air that is put into the [inside] tank at 100 psi as the initial value, without the use of any external, extrinsic, mechanical or electrical power is driven through the internal re-compressor, which operates by cams. That's what allows you to put low pressure into a tank that's re-pressurizing it to about 800 psi. By retaining the heat of compression, the 800 pounds-per-square-inch pressure coming out of the re-compressor is further amplified so that you have a compressed tank at 1100 - 1200 psi at whatever the ambient temperature is inside the tank.

[By email, David elaborated: It continues to work because air is constantly being withdrawn and replaced. When the work function potential is withdrawn the pressure is reduced along with the volume. When the external air motor drives the compressor, it regenerates the heat and pressure in a continuous operational cycle. It is not static – it runs all the time, working to find a homeostatic balance.]

If you paint that tank black, and sit it out in the sunshine, you'll get an incremental amplification of between 25 and 40% in addition to the retained thermal value that is retained from the compression.

[Correction: The 100 gallon tank is going to have maximally 2 square meters of collecting sunshine surface. The Sun gives about 1.5 kilowatt per m2. So even if it would collect all of the sun energy it would increase efficiency by few percent -- not 25-40%.]

So, this engine would cost between $7500 and $10000 to build, using ubiquitously-available, off-the-shelf materials; and will generate around 45-48 kilowatts of power, continuous. [That is in self-looped mode, with no external input to maintain it.]

When you put this thing together, you should have a good heating, ventilating, and air-conditioning or refrigeration guy help you make sure that your connections and your tubing, and the other interstitial pieces of your apparatus are going to be able to withstand the pressures, so you don't introduce leaks and other kinds of anomalies into the system.

We're releasing this information. We've done the calculations, we've tested all the pieces; we're in process of building a demonstration engine now. We hope to be able to bring that with us to the next TeslaTech Convention in Albuquerque in 2014.

We're open sourcing this design. The reason I'm doing that is because I want the design to be in the world. I don't own it. I didn't create it. I understand it. And I'm willing to share it with anybody that wants to build it, with absolutely no charge, and no strings attached.

If you want this information, it's ubiquitously available. Sterling is going to publish on the PESWiki site. You go there and download it. If you want to correspond with me about what to do and how to make it work, I'd be more than happy to entertain your calls or your inquiries.

There are no fees. There are no charges. There are no strings attached. If you build it, you own it. And more power to you.

Post by tommy
Jul 5, 2013

Here is what I see with Neal's storage tank. The inlet pipe is smaller area than the tank and is located one-half the distance of the tank length. The tank itself is a pipe shape. The tank's f1 has a p node at center. IMO the tank f1 should match the arriving pulses rate from the equalizer. This creates a for-sure p node at the tank center, which is also the inlet pipe's open end. The tank outlet pipe (towards motor) is small area compared to the tank area and the outlet pipe is at 90 degrees to the tank pipe axis. The outlet pipe is at the tank's f1 p antinode which is a location of very low wave velocity, v. The tank's f1 p will only leak out slightly towards the outlet pipe because the outlet pipe's area is so very much smaller than the tank's pipe area. Any v coupling will be small also because the outlet pipe is at 90 degrees to the f1 v flow inside the tank. If f1 is 175 Hz, then tank inside length would be about 38 inches, if inside was 48 inches, that would be about 140 Hz.

If you take Neal's figure 3 and assume the crank pin where the piston arm connects is a one inch diameter, then you will get a certain scale. Now if you make the assumption that the lower figure 6 is drawn to one-half that same scale, then the inside length of the storage tank is 39 inches, approx. This equals a wavelength for f1 of exactly 2.0 meters which is what we saw earlier with the other pipes in his figures. That is an f1 of about 175 Hz. On Neal's other pages figures, we also saw where the scales of each drawing was an even multiple of the other figures scales. This makes sense for a draftsman to do when drawing.

For further study of this sort of tank arrangement, see 2936041 and 4570745.

The next step is to work on the pulse timing diagrams from a few weeks ago, and add more detail with the tank and downstream of the equalizer. Need to figure out how the main pipe responds to open vs closed equalizer valves and that will take some drawing time to figure it out.

Uncle Buddy
Jul 7, 2013
I spent a couple hours with the paper. The most important term seems to be "transmission loss" which just means sound x goes in and sound less than x comes out. Peaks on the graph are in decibels (vertical axis) and at different frequencies (horizontal axis). Regularity of peaks across the "frequency domain" (horizontal axis of the graph) indicate harmonics, and the peaks seem to occur at odd harmonics. So maximum effectiveness of the muffler is at odd harmonics. That indicates that quarter-wavelength resonation is occurring inside the muffler. Which means that sound is being trapped inside the muffler due to reflection of waves at open ends of pipes.

The basic configuration is a smaller tube going into a bigger cylinder and another smaller tube coming out the far end of the big cylinder. The paper deals with different ways in which those smaller tubes have the effect of quarter-wave resonators. The idealization of a quarter-wave resonator is a tube with one closed end and one open end. Waves enter the open end and due to reflection characteristics, wave energy gets trapped in the tube.

As for Tommy's suggestion that it applies to Neal, I assume he's drawing a parallel with the pipe entering the tank and dumping air through the equalizer. The configuration will act like a muffler, not destroying acoustic energy but capturing it and holding it hostage so its energy can be directed to a good cause. In this sense, we might see the equalizer or double check valve as an energy trap in the end of a pipe; the important part might be the open end going into a much larger pipe; but I didn't study it enough yet to say too much. It looks like the author is saying that the end corrections on the open ends act as quarter wave resonators in themselves, independent of the tubes they extend from. If so, then that is new information to me so I might choose that part to get excited about. New information always tempts me to get excited; "this could be the missing link," the thing that made previous understandings incomplete. That's what I'm going to look at first when I go back to the paper for a second grazing.

End corrections. When waves bounce off an open end and go back into the tube, they in fact actually bounce off a place slightly beyond the open end. The difference between where the end of the pipe is and where the reflection is, is the end correction. The real wavelength is then different from the theoretical wavelength which is based on the real tube length. So I thought I read in this paper that the extended length beyond the end of the pipe literally functions as a quarter wavelength resonator; an energy trap where standing waves form. Wavelength of frequencies trapped can be extrapolated from length of the extension or end correction beyond the end of the pipe. I'm going to take another look at the paper, as this is news to me, maybe big news.

Also, while pulsations leaving the tank for the engine represent acoustic energy, I guess we're saying that the bulk of this acoustic energy remains in the tank due to reflection at the open end of the pipe leaving the tank.

That's a very general feeling for how I think the article relates to Neal.

Read more:

Compressor unit
USP 2030759


The invention relates to a compressor construction, and more particularly to a combination fluid operated engine and compressor. The primary object of the invention is the provision of a compressor of this character, wherein there is arranged an automatically counter balanced crank shaft and...


The invention relates to a compressor construction, and more particularly to a combination fluid operated engine and compressor.

The primary object of the invention is the provision of a compressor of this character, wherein there is arranged an automatically counter balanced crank shaft and fluid equalizers within a storage tank, which makes it possible for the said engine to operate on constant reserve tank .0 pressure so as to actuate additional equipment, the pistons for the engine being also automatically balanced and suspended when the said engine is in operation.

Another object of the invention is the proviS5 sion of an engine of this character, wherein the same is operated from air under pressure, the said air being supplied by compressors, these being in bank with the engine construction.

A further object of the invention is the provision of an engine of this character, wherein the same is of novel construction, as the engine proper and the compressors are operated from the same crank shaft which is of the automatically balanced type, so that high efficiency is attained. A still further object of the invention is the provision of an engine of this character, which is comparatively simple in construction, thoroughly reliable and efficient in its operation, strong, durable, and inexpensive to manufacture. With these and other objects in view the invention consists in the features of construction, combination and arrangement of parts as will be hereinafter more fully described, illustrated in the accompanying drawings, which disclose the preferred embodiment of the invention, and pointed out in the claim hereunto appended.

In the accompanying drawings:

Figure 1 is a perspective view of the engine constructed in accordance with the invention.

Figure 2 is a vertical transverse sectional view through the compressor part of the engine.

Figure 3 is a vertical sectional view through the power part of the engine.

Figure 4 is a detail elevation of the crank shaft of the engine.

Figure 5 is an enlarged sectional view through one of the electric heaters for the engine.

Figure 6 is a vertical longitudinal sectional view through the air storage tank including the equalizer.


Similar reference characters indicate corresponding parts throughout the several views in the drawings.

Referring to the drawings in detail the engine in its entirety comprises a cylinder block 10 having formed therein the series of compressor cylinders II and the power cylinders 12, respectively, the block 10 being of the V-type and closing the upper ends of said cylinders are the removable heads 13 and 14, respectively, which are secured in place by head bolts 15, as is conventional. Beneath the block 10 is the crank case 16, which at opposite sides carries the detachable plates 17, these being held in place by fasteners 18 and such plates are seated so as to be leak proof. The block 10 is chambered to provide a water jacket 19 about the cylinders, while at the forward end of the said block are water pumps 20 circulating water through the inlet pipe 21. which leads into the jacket and letting said water out therefrom through the outlet pipe 22 leading from said water jacket. Next to the pumps 20 is a fan 23 operated from a belt 24 which also drives the pumps.

Working within the cylinders II are the reciprocating pistons 25, their rods 26 being slidable through packing glands 27 and fixed to crossheads 28, which are slidably mounted upon guides 29 secured within the crank case 16 to opposite side walls thereof. These crossheads 28 are fitted with wrist pins 30 pivotally connecting therewith the connecting rods 31 which by the bearings 32 are engaged with their cranks 33 of a counter balanced crank shaft 34, which is mounted in supports 35 arranged in the crank case IS, the shaft being supplied with the required bearings 36.

The inner ends of the cylinders 11 are fitted with inner end heads 37, which are provided with air intake ports 38, these being fitted with spring ball inlet checks 39, the air having admission through passages 40 opening exteriorly of the block 10. The glands 27 are associated with the heads 37.

The heads 13 and 31 are provided with the compressed air outlets 41 and 42, respectively, these being fitted with spring ball checks 43, the heads 13 being also provided with the central air inlets 44, which are fitted with spring checks 45.

By couplings 46 are attached to the air outlets 41 and 42 the outlet feed pipes 47 and 48, respectively, these leading to a main conduit 49 located in the center channel 50 in said block 10.

At the rear end of the block 10 and on the shaft 34 is the fly wheel 51, this being of conventional type.

Working within the cylinders 12 are pistons 52, their rods 53 sliding through packing glands 54 and fixed in crossheads 55 slidably mounted upon guides 56 which are secured within the crank case 18 at opposite side walls thereof. The crossheads 55 carry wrist pins 57 connecting therewith connecting rods 58, these being engaged by bearings 59 with their respective cranks 60 of the crank shaft 34, the inner ends of the cylinders 12 being also closed by inner heads 61 with which are associated the glands 54.

On the cylinders 12 are slide valve chests 62 in which are the slide valves 63, these being operated by throw rods 64 actuated by cams 65 and such valves controlling the air admission and exhaust of air to and from the cylinders 12 through the ports 66 and 67, and these valves 63 are provided with the ports 68 for the delivery of air under pressure from the inlet passages 69 common to a lead 70 from a compressed air storage tank 71.

The bottom of the crank case 16 is fitted with a removable plate 72 which is secured in place by fasteners 73, and when this plate is removed access can be had to the crank shaft 34 and the bearings for the engine, as well as other parts within said crank case, as should be obvious.

Leading into the cylinders 11 are the passages 14 of a lubricating system (not shown).

The storage tank i7 for the compressed air includes therein a double check discharge nozzle 75, this being supported by a member 76 and leading to this equalizer is an air inlet pipe 77 which has the communication 78 with the chamber 79 formed by said tank. In the equalizer 75 are the spaced spring ball checks 80 and 81, respectively, one being for the inlet side and the other for the exhaust or outlet side of said equalizer. This pipe 77 is connected with the main conduit 49, while a pipe 82 is connected with the leads 70, the tank being also fitted with an automatic relief valve 83 of any approved type.

About the pipes 70 for the passages 69 are the electric heating units 84 which are for the purpose of heating the air under pressure above a freezing temperature when delivered from the tank 71'to the cylinders 12.

Supported on the block 10 is an electric generator 85 which is driven from the shaft 34 through a belt 24 and this generator is included in an electric circuit which also has the heaters 84 so that these will operate from current furnished by said generator.

The storage tank 71 with the equalizer is so constructed that it is possible to pump air into the said tank with a tank pressure of two hundred pounds, while the compressors are only pumping against fifteen pounds or atmospheric pressure. Outside air pressure source can be coupled with the tank to augment that pressure derived from the cylinders II of the engine.

What is claimed is: In a structure of the kind described, a V-shaped cylinder block provided with upwardly divergent cylinders, end heads fitted to said cylinders at opposite ends thereof, each head having valved inlets and outlets, a main outlet lead between the cylinders of the block for a storage tank and having lateral branches to the outlets at the inner sides of said heads, one inlet being located at the center of each head at the outer ends of said cylinders while the remaining inlets are at the outer sides of the heads at the inner ends of said cylinders, a substantially V-shaped crank case fitted to the block beneath the cylinders, a counterbalanced crank shaft journaled in the crank case, pistons operating in the cylinders and having rods extended into the crank case, crosshead guides fitted to the sides of said case interiorly thereof, crossheads connecting the rods with the guides and slidable on the same and connecting rods operated by the crank shaft and pivoted to the crossheads for reciprocation of the pistons.