self-filling air tank graphic

Self-Filling Air Tank Company?

When it costs a barrel of oil to produce a barrel of oil, how long do you think it will take for the Big Boys to figure out how to do what they are calling impossible today?

U.S. PATENT NO. 2,030,759
patented February 11, 1936

Bob Neal tank and equalizer

Bob Neal had a surprise for the world. A revolutionary cheap way to keep an air tank full, using some of the energy in the tank to get more air in. This instead of the usual brute force method of pushing air in against the resistance of the pressure in the tank. Neal's claim was essentially an air engine running its own compressor, but unlike many inventors making similar claims, Neal had a patent in spite of Washington's best efforts to keep him from from getting one. Neal's compression unit was not only built and tested, he took it to the patent office in Washington D.C. when they kept trying to turn him down. They called it a "round robin" system, a perpetual motion machine. The person who got Neal an audience in Washington was Neal's fellow Arkansan, Garrett Whiteside, the "97th senator." Whiteside got his nickname by knowing more about Washington than some congressmen. According to the New York Times, July 4, 1947, Whiteside's distinctions included:

This page is dedicated to Bob Neal and his son Floyd for being bold enough to take a self-sustaining air engine to Washington D.C. instead of giving up when the patent office tried to make it impossible. Because of the trouble that Bob Neal went to, we have evidence that the self-filling air tank is real. Since they didn't want to give him a patent anyway, any failure of his working model to measure up would have certainly resulted in a final refusal. But the patent was granted.

It has been suggested that this patent might be complete as is. It probably isn't, but it might be very close. The only discrepancy I know of for sure is that Floyd remembers that the "double check valve discharge nozzle" or "equalizer"—or else the pipe leading up to it—had a long tapered shape "like an extremely skinny long plumb bob". The patent doesn't show this, and there's no telling how much the patent doesn't show.

I have some simple but unusual theories about why and how Neal's compression unit works. I have not made these ideas public yet. Others are working to prove that Neal was for real, and other than to say that the equalizer effect certainly is not a figment of Bob Neal's imagination, I am not at liberty to discuss other workers' results. Other than that, acoustic power still sounds like a likely way to go, for example, operating on the principle of the hydraulic ram. That is a self-powered water pump, well known for over 100 years, in which the power of falling water interacts with a double check valve unit that uses the energy of the falling water to pump some of itself back up hill. The major differences between Neal's patent description and a ram pump are:

It is notable that the hydraulic ram also contains an air chamber, and compression of the air in the chamber by the water entering the device is what actually pumps the water uphill. (I have since been told that the air chamber isn't that essential but haven't had time to research it yet.)

As for how Neal's patent could have worked without major elements added or left out, here is the basic idea.

The main difference between his compressor and conventional compressors is not the equalizer—the double check valve in the tank—but the compressor configuration itself. The patent shows what is essentially a 28-cylinder compressor, although Neal ended up also using only half that many cylinders and still had plenty of air going into the tank when he used the device to operate an engine lathe. But why 28 or 14 cylinders? Most compressors use as few cylinders as possible.

Neal's cylinders are evenly spaced around the crankshaft and the engine cylinder is on the same shaft. In this way, not only is the usual compression load divided into small bites, but the wave going out of the tank has the same fundamental frequency as the wave coming in, and is an exact in-phase harmonic of that wave. So the air going into the tank is going to have an acoustical hammering effect at the closed end of the intake pipe where the check valves are. It seems logical that high pressures would build up at that point. It's a fact that acoustic effects are accentuated or "tuned" in motorcycle tailpipes by using the right length and shape of tapered exhaust pipe. This is used to supercharge fresh atmosphere into the hot cylinder by fully blasting out or scavenging the spent gases when the exhaust valve opens. Tuning to optimize the Kadenacy effect causes an instantaneous mass exit of the exhaust gases, so the cylinder is emptied well and a suction is produced which helps the cylinder fill more completely on the intake stroke. This vastly increases the power of the 2-stroke engine.

Based on what I've read about acoustic power devices, only the peak of the pressure pulse in Neal's hammering intake pipe will make it across the first check valve into the equalizer chamber between the two valves. This will result in pressure building up in the space between the check valves until suddenly in a blast, the contents of that space will enter the tank en masse, leaving behind a depression or low pressure zone for a split second that will help induce the next spurt of air.

There is no reason to doubt this is possible. There are water pumps such as the Fluidyne and the ABCO by Roy Phillips which use only heat between two check valves to pump water in this way. I once had a toy boat with a coil of aluminum tubing on deck, and both ends of the coil in the water at the back of the boat. If you fill the tube with water so there is no air in it, put the boat in the water and light a candle under the coil of tubing, the boat will take off across the water sounding like a machine gun due to alternate outwards blasts of steam and inward intake of fresh water. The person who makes these boats lives in Oregon and is acquainted with a physicist who is an expert on pulsejets. Similar boats can be seen on You Tube.

My advice to anyone who gets hooked on the Neal Tank concept is to build a small model of exactly what the patent shows, and try it, before trying to design improvements. That is the path I wish I had taken in 1988 when my work on the equalization engine was interrupted by my discovery of this groundbreaking patent by Bob Neal.

I can't help but add an insight derived from discussing this with so many people over the years. If you don't know what parts comprise a compressor installation, this might not mean anything to you, but the answer would be easy to find online. Here goes. Essentially, the equalizer is an unloader. Now if you expect it to act as an unloader, then to see the desired effect you had better put it under a load, right? For years I tinkered with this, but never got my equipment matched to where the air motor had enough power to really make the compressor do anything but burp a few times. This is where I fell short in my experimentation.

In short, if you don't build it, it won't work! See you at the forum .


Floyd Neal interview, page 1 Floyd Neal interview, page 2 Floyd Neal interview, page 3 Floyd Neal interview, page 4 Floyd Neal interview, page 5
Bob Neal's US Patent 2030759 for Compression Unit, page 1
Bob Neal's US Patent 2030759 for Compression Unit, page 2
Bob Neal's US Patent 2030759 for Compression Unit, page 3
Bob Neal's US Patent 2030759 for Compression Unit, page 4
Bob Neal's US Patent 2030759 for Compression Unit, page 5 pulsejet engine
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