Interviews with Bill Truitt

(first written from telephone notes in 1986, most recently augmented in April 2010
Bill Truitt died in 1989)

After more than six years of collecting information on compressed air and air cars, I sat down with my files to start putting a book together. In going through what I thought at the time was the a vast array of research findings in my collection, I ran into some flyers that a friend had sent me, which described the work of Willard "Bill" Truitt of McKees Rocks, Pennsylvania. Bill Truitt was a retired designer and builder of race cars. He had also invented a flamethrower and a wind-indicator for artillery during World War II, and had a career in radio broadcasting.

I had first heard of Bill Truitt's Pneumatic Electric Air Car when I read a book on alternative cars, Auto Engines of Tomorrow by Harris Edward Dark, a technical writer. H. E. Dark included a paragraph on Truitt's air car towards the end of his book, but said nothing about how far the car could go between fill-ups. I always assumed that, since the car used electric pumps to make its fuel or part of its fuel, it would only be able to go a few miles before running out of air. This is what an engineer would tell you on first thought, and most engineers would refuse to give it a second thought. One time I had gotten Bill’s phone number from Information but never called him. I saw no reason to research designs based on hope that perpetual motion might be found in compressed air. For years I'd been looking for practical ways to increase the efficiency of compressed air used in motors, and ignored any theory or claim that seemed to contradict the accepted laws of thermodynamics.

So on March 30, 1986, when I decided to go ahead and call Bill Truitt, in case I had anything to learn from him, I almost forgot to have a pencil along for taking notes. When Bill started talking about his sixty-six years of off-and-on experimentation with air cars, I was surprised to find myself writing as fast as I could, trying to get every concept down, and wondering why I even cared about recording what I thought had to be exaggerations.

But as Bill continued to spontaneously reel off what sounded like a description of a real machine, I felt more and more strongly that I wasn't talking to a con man. There was no pushy come-on, nothing for sale. He openly admitted that his air car did what engineers thought to be impossible, and I felt he was trying to inform me if I wanted to learn, but he wasn't trying to convince me of anything. He urged me to call him regularly, build something small first, and he would talk me through the tough spots. Unfortunately I only called him twice, and that is my fault. He was very courteous at all times and although he was considered a colorful character in McKees Rocks, he was not a liar or a con man.

The only time I thought Bill 's answers ware vague was when I asked about the laws of physics. His explanation of "how he got around the Law" was that his system comprised three separate units—engine, compressor and electrical charging system—whose separateness somehow made possible the anomaly of a car filling its own tanks on the fly. I didn’t understand his separateness principle at the time, but after many years of trying to devise a self-filling air tank I would guess that he meant the car was easy to design and build without a lot of engineering because the main component categories within the design functioned independently of each other. For example, by not putting his air engine and his main compressor on the same crankshaft, he ended up having a lot of flexibility. One component could be adjusted for speed or some other parameter without throwing everything else off. Wanting to combine every known advantge into one Rube Goldbergesque component is a beginner’s mistake, the wanna-be inventor’s ego trip. Bill had three main systems that didn’t depend on each other’s characteristics in order to function properly. Bill’s “keep ‘em separate” principle has been very instructive for me.

Another explanation Truitt offered was that "it isn't horsepower", though he didn't know what else to call It. He responded positively to my suggestion that maybe It was torque, since air cars—like steam cars—transmit torque more effectively than gas cars, and therefore can get more out of an engine that is smaller in terms of its power rating. However the highly advantageous torque characteristic of air engines isn’t enough to explain self-filling air tanks.

Another place Truitt indicated I could look for explanations was in his leakproof valve, without which he said the car couldn't work. After all these years I still don’t know what to make of Truitt's valve. He sent me a picture of an ordinary spool valve, a control valve on an engine cylinder. But his statement that his secret valve "works like a heart" tells me that it might be some kind of two-stage pump that injects pulses of air into a circuit of moving fluid. This makes me think of Bob Neal’s equalizer valve, a double check valve. The heart is a double check valve, with flexible chamber walls that themselves do the pumping.

If you look into the compressor he used, a three-stage compressor pump 13-1/2 inches square, and the power required to run it fast enough to fill up three welding cylinders in 14 minutes to 5000 psi (as per Truitt’s claim), this kind of task cannot be done by two car batteries! It might take a dozen car batteries to run such a compressor. So it’s likely that the valve did something to lower the resistance of the tank air so that the compressor could run fast without having the normal amount of work to do. Remember, it’s the ambient heat entering the system that provides the pool of thermal energy for all this work to take place.

Bob Neal’s equalizer and the “heart like a valve” that Bill Truitt would not describe further led me into an unusual research finding. Another air car inventor had said he got his idea for the self-filling air tank or whatever he did from the famous pilot Charles A Lindbergh who was forced to invent something mid-flight to solve a fuel reserve problem. I haven’t found the reference to this event yet, but while looking for it I learned that one of Lindbergh’s obsessive interests was a glass pump he invented for the culture of living tissue. The device would hold a liver or heart or whatever in a chamber which would be supplied with fresh nutrient fluid through its artery by pulsations of compressed air. The device was called an “artificial heart” by the press, and it included another chamber comprising two check valves that was called an “equalizer”.

Another interesting device I’ve learned about is the pulse fuel pump. This device has liquid fuel on one side of a diaphragm and pulsations from the engine’s crankcase or intake manifold on the other. Two check valves in the fuel line on either side of the pump create a positive flow in one direction with no other power than the existing pulse from elsewhere in the system.

As for Bill Truitt’s pairs of hydraulic air pumps, I ignored that hint till recently because I wished he had not used hydraulic anything! I have finally seen the light and tried to learn what kind of pump this is, and I can’t find any such thing on the market. Sure there are lots of patents, but is there one you can buy? I don’t know yet. Other air car inventors have hinted at some anomaly in the difference between air and hydraulics that opens a door to super-efficiency if you combine them. Especially Jerry Coren of Bronson, Florida who claims outright that there is an overunity effect of some kind. Other inventors that thought highly of combining hydraulics and pneumatics included Kevin Brainard, Samuel David Todd, and others.

So I thought about it, and I think there’s a real advantage to pumping air into a tank with hydraulic pressure. I don’t see any overunity in it, but for cars it might be very helpful in keeping the equipment compact and adding flexibility. The notion is this. Air is compressible, hydraulic fluid is incompressible. The next thought is this. Piston rods are heavy and more or less breakable. Imagine pushing an air piston with fluid pressure instead. If the hydraulic piston and the air piston are on a common shaft, the hydraulic piston could probably be the diameter of the rod only, because higher pressures are common in hydraulics so the smaller piston will push with the same force as a larger air piston at pressures commonly used in pneumatics.

But the main idea is this. When the compressor piston is being pushed by hydraulic pressure, its resistance through the first ¾ or so of the stroke is constantly increasing. To a piston rod that means increasing, uneven stress; to hydraulic fluid it would, in my opinion, actually work in favor of getting the compression stroke done. I’m saying that, for the sake of brainstorming only, it seems like increased resistance in the air cylinder would push back on the hydraulic cylinder. Hydraulic fluid is incompressible, so any push on it that succeeded it moving the piston backward should cause the hydraulic pressure to tend to go up. I wouldn’t say this amounts to overunity because that would be against the law, and anyway, the air will not succeed in pushing the piston backward. But what it means is that a hydraulic push on an air cylinder should be absolutely invincible and very flexible compared to doing the same thing with a crankshaft and a piston rod. I have nothing against piston rods, it’s the associated bearings, guides, lubrication and especially the crankshaft that we could all live without. So in spite of my not liking hydraulic fluid, I do like the idea of a hydraulic air pump.

The reason I don’t like hydraulic fluid is that every drop of it that’s ever sold will find its way back to the earth where it came from. So why not leave the petroleum in the ground, if at all possible, instead of getting it dirty and then dripping it back on the ground anyway?

An engineer told me that water is the best hydraulic fluid, but only if it is perfectly clean. Moving around inside erodable machinery the water will not stay clean long, but it might be worth a try. In the field of irrigation there is a very large machine, half the length of a cornfield, called the “pivot system”. This is a big long pipe connected with a swivel fitting to the well, which is at the center of the pipeline’s radial sweep. The sections of the pipe are each supported on steel frameworks mounted on wheels, and the wheels move very slowly so that the entire pipe pivots around the well and covers the whole field with water in one slow revolution. The work of making the wheels turn is done by a water motor, one for each set of wheels. So the pumped water that irrigates the field also makes the huge apparatus rotate around in a bumpy, muddy cornfield. The hydraulic pressure is so great that if one set of wheels gets stuck in the mud and the farmer tries to override the safety “off for trouble” feature by holding his thumb on the ON button, the water motors will bend the huge pipe and tear it in half.

So hydraulic power can be silently unstoppable, depending on the situation, and I think we should look seriously at using it to compress air. This might have been part of Truitt’s secret.

The other clue Bill gave me in response to my annoying repetitious requests for lawful explanations was that the key was in how once the wheels are going, you have the whole momentum of the car to tap into. Once again, a statement I didn’t appreciate at the time, but have since come to respect as enlightening to a certain degree.

It makes us take a closer look at what makes a car roll and what makes a car stop. I’ve gone into detail on that in Compressed Air Power Secrets, but here I’ll just mention that Detroit has us completely bamboozled with hundreds of horsepower, to the point that we have forgotten our instinct about wheels, which is that they make it easy to move heavy things. My main point here is that any heavy thing that is pushed to make it start and then continues for a ways under its own momentum is like a flywheel: its motion or kinetic energy is a way of storing work that has already been done. Bill was adamant that there was an advantage to the fact that “the car was already moving” and I could tell that he was trying to get through to me about something. Another air car inventor came right out and said that his system would not work in a stationary application. And air car inventor Obid M Smith came right out and said that a car is running on momentum almost half the time! So you see, it’s not so much about overunity or proving science wrong, as it is not taking for granted that things have to be done as the status quo would have us continue to do things. Everything has to be questioned and looked at upside-down and backwards.

Bill Truitt said that his system was easy enough to design once he learned how air worked. How does air work? It’s about energy. Is this “pressure energy” we’re talking about? No, pressure is not energy. Air compressors convert work into heat, and air engines convert heat into work. Even that simple statement, if literally interpreted, would throw a roomful of engineers into a tizzy of denial, but the math doesn’t deny it and the textbooks prove it: compressed air power is heat energy manipulated through time. I believe there is a strong likelihood that compression heat must be conserved in order to make a system go overunity. Bill’s air tanks were lined with cork to conserve heat. At elbows in piping, where the air would encounter a pressure loss, Bill wrapped the pipe with an electric heating pad. He mentioned this more than once, it seemed to be important to him. Why are there so many companies these days doing consulting on how to make your compressed air installation run more efficiently? Because the difference between air used stupidly and air used smartly is big. Not we just need to up the effort and use air ingeniously.

Inventor Obid M Smith also said that he had a way of keeping his system at a more or less constant temperature. Think about it. Instead of trying to capture compression heat, which isn’t easy, isn’t there some way to prevent high temperatures to begin with? I didn’t say prevent compression heat, that’s impossible; I said prevent high temperatures. I haven’t gotten this research underway yet, but compressed air is a refrigerant. If the air is 10 degrees below zero when it enters the compressor, its temperature when it comes out of the compressor is going to be that much less and that much less likely to escape. The only reason heat escapes from the system when air is compressed is that the high differential of ambient temperature and compressor temperature makes the heat flow fast into the cooler surroundings. Some say that this is how Leroy Rogers’ 4-cycle air engine worked.

It’s just something to think about.

The components I describe below are the ones Bill used in one or more of the three vehicles he converted to run on compressed air.

His first air car, which he built in 1920, had started life as a Stanley Steamer, and Bill gave it an air engine made from a motorcycle engine. He also converted a Buick Skylark and a Rolls-Royce. Though all of these cars were self-fueling to some degree, his designs improved over the years till held gotten it "pretty well whipped" from 1974-1980.

For an engine, Bill recommends a two- or three-cylinder refrigeration compressor from a large refrigerator truck. He replaced the steel piston rings with neoprene rings, which he said would last 60,000-80,000 miles. I tried this, converting a compressor to an engine, and had a machinist make new grooves on the pistons for big neoprene O-rings. The rings never gave me any problem.

Bill said his engine could be installed in 35 minutes. The special valve could be changed in 30 minutes. The engine ran on 86-125 psi. The car was so fast it was scary to drive; Bill once had it up to 136 mph. (Remember he had been in the race car business.) It was extremely powerful and accelerated too quickly for someone used to driving gasoline cars, so Bill put a limiter on it so it couldn't go over 55 mph. The engine drove the axle through a turbine clutch, a hydraulic drive invented by a friend of his that slips at speeds up to 300 rpm. I think this was a fluid coupling, which works like a torque converter. A closed housing containing hydraulic fluid has two fanlike rotors in it which face each other but do not touch. The input shaft turns one rotor, and after it gets above the slipping speed, the hydraulic fluid turns the other rotor which turns the output shaft. It gave his car perfectly smooth starting so the high torque available from the air engine wouldn’t alarm the driver.

Top engine speed was about 1200 rpm. The engine used air non-expansively, that is, the air entered the cylinder throughout almost the whole piston stroke and still had pressure in it when it was exhausted, like a commercial air motor. When I asked him why he didn’t use a closed cycle or expansion air engine, he said it wasn’t necessary. This is the “work smart early” principle in which you must not go into energy debt with an expensive, conventional air compressing machine and then expect a real nifty air engine to pull you out of the poorhouse at the last minute so you can achieve overunity. The best air engine for cars is non-expansive because it is very small and extremely torquey, but without a special way to compress the air such a thing would be much too wasteful. A good compromise is partial expansion, but for every bit of expansion you have to make your engine bigger to get the same amount of power, so there are diminishing returns involved in expansion engines for a vehicle as small as a car.

The engine did not idle. It went right in front of the differential. The compressor was the heart of the machine. It went under the bood where the gas engine had once been. It was run by a 24 volt DC motor which got its power from two 12 volt car batteries which were charged by two automotive alternators, which were run by pulleys from the engine shaft. The compressor was three-stage, capable of pumping the car's three "acetylene-sized" tanks up to 5000 psi in 14 minutes, but in practice it was used to fill them to only 2000 psi. I’m pretty sure this performance from a 13-1/2 inch square compressor would be impossible if he hadn’t altered the compressor cycle or augmented it in some secret way. His valve probably had something to do with it.

A pressure switch would turn the compressor on when the pressure in the tanks got down to 1000, 1250, or 1500 psi, depending on terrain. In hillier driving, the compressor came on more often, with the pressure switch set to maintain a higher minimum tank pressure. The Mako compressor he used cost him about $1600 at the time (1970s). It ran at about half the speed of the engine, and only about a tenth of the time the car was running.

There has to be some significance to the fact that he never let the pressure go below 1000 to 1500 psi. The secret valve might have been driven by high pressure air straight out of the tank—not regulated down to the low pressure that the engine used—and who knows exactly what it was used for, but the point is that if it was used to do any work at all, that is more than a typical regulator system would allow for. Here are some possibilities. A short spurt of high pressure air could have been used as a refrigerant to both raise the pressure and lower the temperature of incoming air before it was compressed. There could have been some kind of mixing going on. The high pressure air could have been used in any sensible way, we will probably never know. Jets aimed at each other can generate high temperatures—just get busy and dream it up, we aren’t really trying to figure out exactly what these inventors did, we are just letting them inspire us.

In my interview with air car builder George Heaton, he had made a point to mention that his car had tanks at two levels of pressure: a storage tank at about 1000 psi, and a drive tank at a lower pressure. On the other hand, Bill said, “It’s all high pressure.” Oddly enough, he never mentioned a low pressure tank. Either there wasn’t one, or it was so essential that it was secret and he didn’t want to talk about it. What if it was a big heat exchanger? Does he have any grandchildren out there who can try to get these questions answered? Or maybe the US Army will send me a set of plans so I can sleep better at night.

Truitt used several small worm-drive hydraulic air pumps. These pumps were easy to replace, as they slid onto a shaft run by the differential’s ring gear. These pumps put air “directly into the main tanks” at all times while the car was running. More pumps were required in mountainous terrain, the maximum being 10-12. Because it seems unlikely to me that these pumps could put air into 1000 psi tanks, some possibilities are suggested: maybe the pumps were so strongly built that the hydraulic power literally pushed the air all the way into the tanks, either in one stage, or else maybe the pumps were two stages or the pairs of pumps were used in a series somehow. In mountainous terrain he had to keep a higher pressure in the tanks, which is itself a clue, but it might just be because air has less power per volume at higher elevations. The pumps apparently came in pairs, I don’t know what he meant by that. At that time I didn’t know what questions to ask. The pairing might have been referring to a hydraulic pump and air pump in each unit. Or it might have been a two-stage system, run very slowly by means of the worm gear, to get up to tank pressure. Or even more radical: maybe the hydraulic air pumps were just hydraulic pumps, all piped into a central reservoir, and the power taken out of there to operate the compressor hydraulically. With the electrical kicking on only when needed. That is actually my newest idea.

Still more possibilities: the secret valve was used to get low pressure into high. Or the high pressure air refrigerated the air being compressed. There are so many details known about Truitt’s design, but so many unknown, that we can only get frustrated trying to guess what he did. The point is to use his information as a springboard to your own unique design.

When I asked if I could visit him in McKees Rocks, Bill changed the subject and started talking about harrassment he’d gotten from the powers that be, including oil companies and car makers. He said the Japanese car companies had sent spies to accost his friends and try to get his secrets out of them. The U.S. car companies had his phone tapped. Finally to stop this harrassment he sold the car and the right to make the car to the U.S. Army and NASA, for a 0.1% royalty for himself or his heirs. The Army has built air powered tanks, jeeps and a helicopter using Truitt's designs. The helicopter was only able to get 50 feet off the ground. Bill said the Army generals who are working to develop air powered weaponry have decided that the public isn't ready for cars that have an unlimited range between fill-ups with no cost for fuel. He thought it would hurt the auto and oil companies too much if air cars were introduced now, and wanted to give the U.S. automakers a chance to catch up with Japan so Japan wouldn’t corner the air car market. He dreamed of a future where we could have Chrysler air cars, Ford air cars, etc. Bill was satisfied to let the revelation of his secrets happen at the government's pace. The Army was supposed to build a model air car for the automakers to copy. He’s told me in writing and over the phone, when I asked for the whole truth, "The rest is Top Secret."

When Bill Truitt was about 17 years old, he built his first air car with his father's help. His father owned a service station in Huntington, West Virginia where they lived at the time. When the car worked, Bill's father asked him to keep it quiet, because it might hurt business if word got out. Although there have been times when he was getting sacks full of mail wanting to know about air cars, somehow Bill did what all air car inventors have done, and took his secret with him to the grave.

Scott Robertson