Scott Robertson is an expert in the field of air cars, that is cars that run on compressed air. His website can be found at http://www.aircaraccess.com.

Ken, webmaster of About Facts Net. http://aboutfacts.net Webmaster@aboutfacts.net

The following interview was conducted by email, because it was impractical to do it by phone for several reasons. To hear the interview you can use the Robo Reader device. Cars that run on air are all the talk right now, with a company in India talking about exporting them to the U.S. next year.

Ken:

Would you please tell my audience your background.

Scott Robertson:

My dad was a soil conservationist for the USDA, inspired by his living through the Dust Bowl, which was caused by bad farming practices. I wanted to be a hippie when I grew up, but he talked me into trying piano tuning instead. I had a hobby of ripping pianos apart and trying to fix them,so he sent me to tech school and I was a piano technician on and off until 1997. I traveled around and worked lots of odd jobs and chose air car research as my career, even though it didn’t pay me anything. I really wanted to save the world, but have since given up that goal.

Ken:

Please tell us how you got interested in air cars.

Scott Robertson:

When I was 13, I rebuilt my parents’ player piano. That is a piano that plays by itself, and it runs on air. It is an air powered computer from the early 1900s. They were the predecessor of the phonographs and radios, as the most popular form of family entertainment, back when Americans still liked to sing. The coded tape in a player piano is a roll of paper with holes punched in it, and it is turned by an air motor with bellows for pistons. That little motor is very powerful, and that’s how I got the idea for air cars.

Ken:

Would you tell us exactly what an air car is?

Scott Robertson:

An air car is any car that runs on a pressure differential, with air the preferred fluid since it’s readily available almost everywhere on earth. You can also run air cars on nitrogen, and you can use suction or a combination of suction and pressure. You can use compressed fluids like compressed air or you can use cryogenic fluids like liquid nitrogen or liquid air, which expand when warmed up and drive the same kind of engine—an expansion engine—that a compressed fluid will operate.

But in general when people say “air car”, they’re talking about a car that carries tanks on board with compressed air in them. Straight air cars are either standard—they stop at air stations to refuel—or self-fueling, which use compressors on board to extend the range of the car and supposedly can keep their own tanks full, based on the fact that our atmosphere is heated by the sun 24/7 and the real fuel of the air engine is heat.

The expansion engine is the same kind of engine that used to run steam cars and steam locomotives. It is ideal for cars since it has maximum climbing and starting torque at low engine speeds, unlike the Internal Combustion (IC) engine which needs high rpms to get any torque.

Ken:

I have read that an ordinary car engine can be made to run on compressed air. Is this true and if so, is it practical?

Scott Robertson:

I met a man in 1980 who used to do it in 1949 with a friend. He said they drove their cars from coast to coast, but had problems due to their lack of engineering ability. Their last air car blew a piston out the top of the engine, out through the hood, and up into the sky, and they never saw it again.

Scott Robertson:

The IC engine is already a compressed air engine and compressor combined, with a little gasoline or diesel squirted in to ruin its performance and create a lot of jobs and a class of billionaires. It definitely increases the gross national product to squirt gasoline into air engines and then start it on fire. With the emphasis on “gross”.

A man named Leroy K. Rogers of Ft. Myers, Florida has built air cars and has a patent on his 4-cycle air engine conversion. He wanted to put out a conversion kit, but got cold feet for various reasons. Mainly, he became sought after by so many people that his home life was ruined. He said the auto makers pooled their money and offered him a billion dollars for his invention, but he refused to sell it to them because he was afraid they just wanted to shelve it, to hide it from the world.

Is it practical? Air engines can be very small for their output, depending on the type, although the more efficient varieties are bigger. Maybe that is something to take advantage of. I think it would be better to use the IC engine as a compressor and put a little air turbine on it in place of the starter motor, put a stronger flywheel gear on, and do it that way. A little air turbine can run a car. The existing clutch could be used to unload the motor for starting and climbing, and re-engaged to use the compressor as a tank warmer for regenerative braking, coasting downhills, or wherever you have extra power to make it go. They use air turbines as starter motors on big jet engines. But they’re not very efficient until they get up to speed, so maybe instead the IC engine could be both engine and compressor. Lee Rogers solved that by making his air engine 4-cycle. The engine itself compresses some of its own air on every fourth stroke, with an added supercharger and also maybe a small high pressure compressor that puts out about 600 psi. I’m telling you this from memory and of course, he has his secrets which I wouldn’t know.

One advantage of a 4-cycle air engine is that it's compression heat will be used immediately. That’s a big deal, because the normal compressor gives away literally all of it's work as heat, which all dissipates. That is the compressed air industry’s big secret. I don’t know who told them to keep silent about it, but don’t all the big industrial sectors work together?

Ken:

How popular has the air car become in areas where it has been out?

Scott Robertson:

In 1907 Charles B. Hodges patented a 2-stage air engine, which expanded the same air in two consecutive pistons. Between the two stages, a heat exchanger warmed the air, expanding the air supply by absorbing heat from the environment. This is possible, because compressed air gets cold when it expands so an air engine is part of a refrigeration cycle, or a heat pump cycle, by drawing free heat into itself from the surrounding air.

The compound air engine was used all over the coal mining areas back east in the US, then in Europe it was improved. They used three expansion stages, three successive pistons, each expanding the same air, with free heat expanding the air supply before all three stages. I read in a technical journal that there were 624 of these three-stage air engines being used in one coal field alone in Germany. By extrapolation then I would guess there might have been thousands of these things all told, in mining operations in Europe. Air is very safe in coal mines where there are explosive gases, so you don’t want a hot engine or one that sparks.

At their top operating conditions these engines increased their range 60% with the addition of ambient heat.

During WWII all trace of these engines disappeared from the textbooks and the term “air engine” was no longer used in textbooks.

But before the war the Germans had developed a hybrid compressed air-diesel locomotive engine, not a little mine shuttle, but a big full-sized 1200 horsepower locomotive. It used an air engine to run the wheels and a diesel engine to run the compressor. The hot water used to cool the diesel engine was injected directly into the air engine cylinders along with the compressed air, and the result was a 26% savings over a straight diesel’s fuel cost. That was in 1931.

But the first air car advocate I know of (aside from the father of modern physics, James Clerk Maxwell) was General Herman Haupt. He threw his influence and technical writing ability behind the move to advance the air engine in the 1890s. Before that, he was President Lincoln’s railroad chief during the Civil War. He wrote a book comparing the various alternatives, since it was not yet clear that the IC engine or electric car was going to be taken seriously. But the air engine was finished. It is such a simple thing, there are thousands of configurations that could be made to work, so there is plenty of room for competition and Gen. Haupt was convinced based on his experience as a civil engineer, that air was the way to go.

He supported a project to run air powered passenger trolleys in New York City and there was a huge air station put up, a 1000 hp compressor that filled a two story building. The compressor was run by steam engines and I believe they used hot water exhausted by the steam engines to fill hot water tanks aboard the air cars, when they stopped to refuel. The key to air cars is to add heat. It is 7 times cheaper to heat existing compressed air than it is to compress more air, in regards to the gain that can be had either way.

There were three different inventors who got their air cars into the technical journals regularly during the 1890s. First was Mekarski, then Hardie (championed by Gen. Haupt) then Hoadley & Knight. The problem with compressed air is it’s too simple, safe, clean, and quiet. Almost unamerican! The big industrial people went with the highest profit maker, maybe assuming that petroleum was here to stay. It’s hard to sell air when we’re surrounded by it and anyone can buy an air compressor.

I have to mention that like gas cars, the air car can be refueled in a minute or two. Not directly from a compressor, but from a big high pressure tank that is kept full by a huge compressor. So if there is a short range, say 50 miles between fill ups, then it’s not that big of a deal to stop and fuel up.

Ken:

The air car has only made it into the news in the US, in the last couple of months. How long has it been around?

Scott Robertson:

The air car has been in the news occasionally a lot in recent years, maybe for ten years or more, because an inventor in France, Guy Negre, has been getting a lot of publicity selling franchises for air car factories based on his patents. He is an auto professional and has put air cars on the map again after years of silence, while petroleum had its way. The first time I searched the Internet for “air cars”, I only got 15 hits. Guy Negre changed all that.

The first air car plans were in the 1880s. They wanted to put a lightweight bullet car in an airtight subway tunnel, engineless, and have it pushed along by a large volume of low pressure air. It was New York City’s first subway, though it didn’t catch on since it wasn’t practical. Then they thought of a third-rail concept, where the air supply runs along the track and a flexible pipe thing reaches down from the engine car to take its air supply out of the pipe continuously. They didn’t have the materials back then to make the seals work, but the Aeromovel company now has a similar air powered train in daily use in a couple places around the world, I think it’s Jakarta and Brazil.

It was during the oil crisis .of the the 1970s—when the US reached its peak oil supply and started down the other side—that people got serious about air again. Air car builder Bill Truitt of McKees Rocks, Pa., had built his first air car with his father in 1920, and in the 1970s he perfected his design with his third air car. He drove it two or three thousand miles without a fill up, since it had on board compressors, and he knew the secret by then. He got a lot of unwanted attention, people sneaking around his garage, accosting him with offers, etc. and he finally gave his design to the US Army and NASA.

Truitt would not divulge the real secret that he used to keep his tanks full but it certainly involved upgrading ambient heat into a usable form: compressed air. Heat pumps can heat a house in the middle of winter, supplying heat that exists (unknowable to our senses) in cold winter air, by concentrating it into an upgraded form, to heat a house. The heat pump uses three times less electrical energy to do this than the heat energy they supply. That’s why Bill Truitt and Lee Rogers and others have to stop. It’s too good to be true and having that kind of secret makes them too popular and/or too unpopular with all the wrong people.

Ken:

I have heard that the modern theory of compressed air powering a vehicle has been known for at least 30 years. Is this true and if so why haven't we heard of air cars before this?

Scott Robertson:

I guess I’ve been harping on that theme already.

Ken:

Do you think that the big oil companies have prevented companies like Ford and General Motors from coming out with their own air car?

Scott Robertson:

I’m not a student of industrial history, but my guess is that the big oil companies and the big car companies are the best of friends at a deep level. I don’t believe in conspiracy theory, I believe that people get together to plan successful competition against their industrial enemies. So I believe in conspiracy as the nature of economic reality. Success is always a team effort and competition is all about vanquishing an enemy.

Ford has been involved with research and development on a hybrid air car invented by a professor from UCLA. I don’t know how that’s coming along.

Ken:

Besides the fuel being cheaper, after all it uses compressed air, is the car cheaper to build and sell than a typical gasoline powered car and if so, why?

Scott Robertson:

Yes, because it’s the simplest possible engine. Forget about the carburetor, cooling system, frequent oil changes (because it runs cold, not hot). You can use two big cylinders instead of a bunch of little ones, and run the engine slow instead of fast so it lasts longer and has less parts. The air engine was perfected back when gas engines and electric motors were not sure things. You could drive air cars all day despite their short range because a fill-up only takes a few minutes.

Compressed air can be free with the only cost the purchase and maintenance of the equipment. There have been windmill-powered air stations and in Grass Valley, CA you can see a big Pelton Wheel, that’s a water-wheel, that ran a 1000 horsepower compressor supplying two of the biggest gold mines in the world with all their ventilation and tool air.

Before 1900, compressed air was piped all over Paris, France as a standard utility, like we have natural gas now. They had air powered trolleys and big outdoor clocks on street corners, run by air.

Ken:

Recently a news item came out that stated that the air car was not only coming to America in 2009, but it would be a six passenger and have about 100 miles range and run at 95 miles per hour Do you think that this is true?

Scott Robertson:

Please send me that news item and I’ll add it to my collection. No, I hadn’t heard it, but it could happen. I collected every word I heard or could find in a library about air cars for over 25 years, because of Guy Negre the Internet became full of information itself, then I retired from air car research and went back to my first love, which is grammar and linguistic study. I’m no engineer, I love to do research and think. I was not well-suited for actually building things, though I still wish I was.

Ken:

One thing baffles me. Why must the car be refilled with compressed air? Why can't a compressor be built into the vehicle and keep the air tank full?

Scott Robertson:

This is a can of worms but I’m famous for opening cans of worms.

Standard engineering practice says that you can’t create energy and you can’t re-use the same energy to do the same thing. These are the laws of thermodynamics and they are correct. When you devise a plan to create energy, that is a perpetual motion machine of the first kind, because it defies the first law of thermodynamics and it can’t be done. Only God can create energy and to my knowledge he stopped when he stopped. You’ll have to ask Einstein for the details.

A design that attempts to re-use the same energy over and over to run a machine is a perpetual motion machine of the second kind, it can’t be done. Perpetual motion is impossible but it is very attractive to amateur thinkers, idea people who don’t have a technical background. It is because of the propensity for unrealistic idealists to want the impossible that engineering as a whole has developed a zero-tolerance attitude toward anything that seems to be providing its own source of energy, and understandably so. Any engineer who presents his company with a perpetual motion scheme is going to find himself flipping burgers before he knows what hit him. It doesn’t pay to push the envelope in that particular direction.

I already mentioned heat pumps. They heat a house with three units of energy—heat energy from the surrounding atmosphere—while they only consume one unit of electrical energy. This is ordinary business, it is not in violation of any law, you buy it at Home Depot. It works because the heat is put in the atmosphere by the sun all day and all night. The atmosphere weighs four quadrillion tons and if it wasn’t heated by the sun, it would fall to the earth as snow. A heat pump is a “cycle”, that is a tricky design that makes something special happen, like the “Otto cycle” that runs the IC engine against all odds, or the “Diesel cycle” that does something similar. The heat pump cycle collects energy by creating a very cold spot that absorbs heat from the surrounding air even during winter. Absolute zero is 460 degrees below zero Fahrenheit so there’s a lot of heat in the air that we don’t feel because our skin temperature is about 92 degrees F.

The air engine expands air, and expanding gases push a piston, because they convert heat into the mechanical energy of the moving piston. Pressure is the measure of air’s ability to expand due to a difference between its own pressure and the pressure of the atmosphere. Pressure is not energy. Heat is the energy source of an air car. The typical air compressor is a “cycle”, that is, a trick used to get air into a tank so we can use its energy later by letting it expand. We make the mistake of assuming that the air compression cycle we know is the only way of getting air into a tank, and that is like assuming that the earth is flat. Sure it’s flat downtown, but back off a ways, get some perspective, and it’s round.

Asking the status quo world of engineering and industry to rethink its approach to compressed air is like Galileo telling us that the earth revolves around the sun; he was imprisoned for it. Or Columbus saying the earth was round. He was right, by the way. But a prophet is not welcome in his own land, according to the Bible. The self-fueling air engine, if it works, does so by using ambient heat in a tricky cycle of some kind that is in effect a heat pump. But getting a professional engineer or any other technically trained person involved in working on an idea like that is nearly impossible.

That in spite of the fact that engineers are generally taught little or nothing about compressed air in school. And try finding a textbook on the topic, one that starts with the thermodynamic basics and builds to a general theory of how and why air engines work. For that matter, try finding a textbook that even uses the term “air engine”. It will be dated around 1930 or earlier.

Ken:

Is there any reason for a car that runs on compressed air to be structurally less strong than a traditional car?

Scott Robertson:

No. Because of the short range, maybe 40 or 50 miles for the standard air car with no on board compressor, people want to build the whole thing out of plastic so it will be lighter and go farther. This is based on misguided thinking. You can’t be driving something like that on the road when something big and heavy comes along, it’s not safe.

You have to have a way of heating the air so the car will be powerful and go farther.

On the other hand, the American dream we know (which is an aberration of history because of the “petroleum vacation” we’ve all been on for the past very few generations) apparently includes this myth that we have to go fast and we have to go far. I live in the Philippines and guess what? The need to go fast and far ain’t absolute. People will relearn new expectations as needed. Here I pay seven pesos for a ride in a sidecar powered by an old worn-out motorcycle engine. There are seats for six but it fits maybe fifteen people because Filipinos like to share their space. A motorcycle pulling a sidecar with a couple people, a pig, a couple of chickens, a couple bags of rice, some babies, and a couple bunches of bananas, doesn’t go fast. And the gas tank is small, it has to be refilled several times a day. Gasoline is sold in used liter bottles that started life as Coca Cola bottles. Usually a half liter of gas is bought at a time.

That is reality for most of the world. When petroleum runs out, these folks will go back to wagons pulled by horses and water buffalo, with nary a whimper. But I wouldn’t want to be living in the US when the petroleum runs out.

Ken:

If air cars become popular, do you foresee the price of compressed air going up?

Scott Robertson:

If left to the industrialists, of course they’ll try to monopolize it and to some extent they will succeed, since the backyard mechanic has been marginalized and turned into a speed freak on welfare in our country. However air has the power to give itself to us because it is always there when we need it, so I would hope to see the rebirth of the backyard mechanic, people building their own air cars, doing their own conversions, recycling the broken down hulks that litter our cities, towns, and farms. If the American spirit hasn’t been completely broken by the consumerist mentality, then there’s a chance that we’ll get off our sofa, turn off the TV, and go back to taking care of ourselves. In that event, those who work together for the common good can have their own neighborhood air stations and cooperatives and never mind what the billionaires want to charge us for the stuff.

Ken:

Will a car like this need air that is under so much pressure that we can't supply it with one of those compressors that plug into an electrical socket?

Scott Robertson:

Yes or no, depending on the type of air car. A standard air car that needs to stop for fill-ups will have high pressure tanks, 3000-4000 psi, so it can hopefully go several dozen miles between fill ups On the other hand, the idea of a self-fueling design, if it is possible, is to bring down the size and pressure of the tanks so there’s room for lots of people in the car, dogs and cats and kids and TVs or whatever people carry in their cars these days. DVD players, I don’t know, I haven’t driven a car in three years.

The little shop compressor you buy at Sears puts out maybe 120 psi tops. An air engine can run on that, but probably will rather run on 140-160 or even up to 400-500 psi depending on the design. You need three-, four-, or five-stage compressors to get high pressure air economically, because of the extra time the compressing takes with more opportunity for cooling.

Ken:

Do you think that the car will have a special fitting on it that will preclude us from filling it at home?

Scott Robertson:

If so, your friendly neighborhood backyard mechanic will help you yank it off.

Ken:

I heard that the car company producing the car in India is working on a way to increase the volume of air so that the tanks would take the car further, is this true if you know?

Scott Robertson:

I don’t know. Tata Motors is the biggest car company in India and has struck a deal with Guy Negre to produce his cars. Nobody has made it to the market with his car yet, but like I said he has put air cars on the map again (the Internet at least) so we should be grateful to him for that.

The problem with air is that it weighs more than we think, so if you carry enough air to go 200 miles between fill ups, the air itself might weigh a ton. So you have to concentrate on a way of reducing the air consumption of the engine instead of increasing the pressure and size of the tanks. That and also to find a way of replenishing or partially replenishing the tanks, at least with regenerative braking if nothing else. An air car with no braking compressor is only half an air car. You can’t stop any car with brakes alone unless you want to replace your brake linings ten times a year. We all use compression braking, big trucks use it a lot.

The air car has the distinct and unique advantage of working better in stop and go driving. That was proven on the streets of New York City over 100 years ago. The Hardie locomotives used the air engine as a compressor when stopping, slowing down, or going down hills, resulting in a tank of hot air instead of a tank of cold air. As air pressure goes down, the air gets continuously colder, and you really need to do something about that. Heat doesn’t weigh a thing and it doesn’t take up much space, last time I checked. You have to stop thinking of air as something you keep in a tank, and start thinking of it as something you can’t get away from; it’s everywhere. Take it, use it, give it back unchanged. That’s the air car principle. The smaller the tanks, and the lower the pressure, the more success the air car will see.

I have to cover the concepts of hybrids and closed cycles.

Hybrid air cars store gasoline and run an IC engine which runs the compressor. The IC engine runs at its optimal speed so the gas burns more cleanly and efficiently, and air is used at what it does best, starting the car and keeping it going. Getting gas cars to do that is really a problem, because they’re smelly, foul things that just want to blow themselves up, not purr smoothly down the street. The best we can do with them is run IC engines at one speed all the time in a hybrid.

Closed-cycle air engines put the exhaust of the air engine back into a compressor before it loses its last bit of pressure, and re-compress it. The advantage is smaller equipment, since the air going into the compressor is already “small”, that is in a compressed state, therefore the compressor is also smaller for a given amount of atmosphere being compressed. The disadvantage is that it’s a hot system, so how do you take advantage of a cold spot in the cycle to absorb ambient heat?

But everyone should learn in kindergarten—as General Haupt informs us in his book—that adding 100 psi to a pound of air is cheaper at an already elevated pressure than to do the same thing from atmospheric pressure. That is because less heating takes place if the air is already somewhat compressed. So less work is necessary to compress it some more.