Compressed-Air Road Vehicles

FIRST STEPS
The first compressed-air vehicle I have found so far was devised by Bompas, a patent for a locomotive being taken out in England in 1828. There were two storage tanks between the frames, with conventional cylinders and cranks. It is not clear if it was actually built. (Knight, 1880)

The first recorded compressed-air vehicle in France was built by the Frenchmen Andraud and Tessie of Motay in 1838. A car ran on a test track at Chaillot on the 9th July 1840, and worked well, but the idea was not pursued further.

Left: The Parsey compressed-air locomotive of 1847 The reservoir A was filled with air "compressed to as great an extent as was compatible with safety" which fed chamber B, kept at engine pressure by automatic reducing valve C. Pipe D fed the double-acting engine E. At F is the air recharge valve, and G is the safety valve. The locomotive was intended for coal-mine work, but again it is not clear if it was actually built.

In 1848 Barin von Rathlen constructed a vehicle which was reported to have been driven from Putney to Wandsworth (London) at 10 to 12 mph.

At the end of 1855, a constructor called Julienne ran some sort of vehicle at Saint-Denis in France, driven by air at 25 atmospheres. (350 psi)

THE MÉKARSKI SYSTEM

COMPRESSED AIR TRAMS IN GREAT BRITAIN

Compressed-air trams were tried in East London, Wantage, the Vale of Clyde, Liverpool and Chester. Various designs were used. None of the trials lasted long; the cost of operation proved excessive.

The Wantage experiments used two Mékarski-type trams built by the Compressed Air Engine Co Ltd, of 19 St Swithins Lane, London EC. The air was preheated by some sort of bouillotte, which raised its temperature to 312 degF, doubling its volume. Compressing plant costing Ł2000 was installed at Wantage Town tram terminus. A single-acting compressor pressurised six large air receivers to 450psi. Recharging a tram took 15 minutes. Quite why it took that long to fill the compressed air tanks is not easy to understand- for me anyway.

The range of the compressed-air trams was barely sufficient for a round trip. Matters were not eased by the 1:47 gradient at the end of the route, when the air pressure was at its lowest. The first compressed-air journey was made on Thursday evening, 5th August 1880

Mr. G. Stevenson, the line's engineer, estimated that the compressor used about 24 cwt of coal per day, but on such a sparse service this was far too high, as steam locos would only use 5 cwt per day.

COMPRESSED AIR TRAMS IN AMERICA

These articles are taken from the journal Manufacturer and Builder:

Street Cars Run by Motive Power

Manufacturer and Builder / Volume 10, Issue 5, May 1878

"The Second Avenue Railroad of New York city, has one of the Pneumatic Tramway Engine Company's cars. Upon each platform is a steel lever, by means of which the car can be started, stopped or its direction reversed. The car is of the same general model as that of ordinary street cars. It has six tubular air receivers situated under the floor of the car. The air is compressed by an engine which is standing at the side of the depot, and is introduced by a rubber hose into these receivers. That air passes through an engine situated between the axles, and propels the car."

"The car lately ran from 63d to 95th street and back in about 20 minutes, with two or three stoppages. It is claimed for the car thus inspected that it can be stopped more readily than the horse cars, and that its rate of speed can be increased to 30 miles per hour, while it can make 9 miles per hour and still not appear to go faster than the horse cars. The car which was run is only a model, and it takes about four hours to charge its receivers with air, but machinery has been ordered which will perform the work in less than a minute."

"One of these air engines, it is said, can easily draw a whole train of ordinary street cars. A company composed of 25 capitalists has been formed to manufacture cars upon the above model. It has already received an order for five from the Second Avenue Company. These will be used on the upper part of the Second Avenue route."

Compressed Air Locomotives in New York City

From Manufacturer and Builder / Volume 11, Issue 11, November 1879

"The Third avenue horse railroad has now in operation one small locomotive, which is used instead of a span of horses to propel one of their ordinary cars. The machinery is partially on the front platform and partially below the bottom of the car and under the side seats, which will accommodate about half the number of passengers that the car will hold. The propelling power is compressed air, which is stored up at the depot up-town by a stationary engine, and tapped by the car from its reservoir at every trip, the capacity of the reservoir in the car being sufficient to contain compressed air enough for a down and up trip."

"It appears to give satisfaction so far, and if this continues, it will afford great relief to the horses, which, when used on street cars, suffer much from the continual stopping and starting connected with this mode of travel. The Society for the Prevention of Cruelty to Animals will, we hope, encourage this new enterprise."

Revival of the Use of Compressed Air as a Motive Power
By Dr. P. H. Van Der Weyde

From Manufacturer and Builder / Volume 26, Issue 12, December 1894

"Lately an important problem has again been brought to public notice -- namely, the propulsion of street cars by means of compressed air, carried on the car itself."

"The solution of the problem requires the execution of two kinds of contrivances -- first, a reservoir strong enough to withstand considerable pressure, and, secondly, a motor machine to be put in operation by this pressure. The reservoir is by preference made in the form of cylinders, of say one or two feet in diameter, so that they can be placed under the seats of the car, and of a length sufficient to utilize all the space afforded. The motor is best placed under the floor of the car, now a common method in the electric trolley cars, while the regulating devices are on both platforms where the motorman performs his duty."

"It is evident that this system offers peculiar advantages, especially by reason of its apparent simplicity. The cylinders containing the compressed air -- the motive power -- are charged at the station and need no further attention, as is the case with locomotive boilers, where the chances of safety depend on the engineer and stoker. All the heavy machinery used for the production of the primary power is stationary, and no power is wasted to move it about as in the case of the locomotive, the only weight to be transported is the motor and the cylinders containing the compressed air. Summing up the advantages, they are:"

1. No dead weight of coal or fuel on board.

2. No dead weight of water, boiler, furnace, and other material which has to he stabled, the real primary motor, which is a stationary structure of large dimensions, and therefore economical, as the economy increases at a very large ratio as the engines are increased in size.

3. The compression of air is going on continually in the reservoirs, and is always connected with the gauges, so as to insure safety.

"The first application of this principle was seen some six or eight years ago at the Harlem station of the Second Avenue Railroad. It was intended for the propulsion of trains, and the compressed air reservoirs consisted of two huge cylinders placed horizontally, with a space between, through which the engineer could see the forward track while standing on the motor, and having the train of cars behind."

"A few years later I saw some interesting experiments of thie same character at the Delamater works, where pipes were laid to quite a distance from the works, and at which pipes the cylinders could take up new supplies of compressed air without going back to the supply station."

"A syndicate has been formed to introduce this system of street transportation, so that we will have another additional method in practice."

THE HARTLEY AIR-POWERED TRICYCLE

Left: A Compressed-Air Tricycle for mail delivery. Nothing is currently known beyond the information in the New York Times article. No US patent appears to have been taken out by either Hartley or Stoll. If the compressed-air-tank was installed "under the handle bars" this seems to indicate it wasn't very large, and it seems surprising that such a tricycle could cover thirty-three miles. Perhaps in reality it couldn't. Thanks to Bill Levine for bringing this to my attention.

THE PNEUMATIC CARRIAGE COMPANY

Left: The Pneumatic Carriage Companie's compressed air car: 1898 The Pneumatic Carriage Company of New York City developed a car that ran on compressed air. The air is believed to have been stored in a steel cylinder running the length of the lower body; the storage pressure is not currently known.

From The Horseless Age for October 1898:

"In 1895, the Pneumatic Carriage Company was organized under the laws of West Virginia, with an authorized capital of $5,000,000, and with offices at 253 Broadway, New York. The organizers had been conducting experiments with compressed air motors for street railway service for several years, and naturally turned toward the motor vehicle when it received its first impetus in America. The president and manager of the company is A. H. Hoadley, who has been in charge of the experiments at the works of the American Wheelock Engine Company, Worcester, Mass.

The first carriage built by the company, illustrated herewith, was completed in November, 1896. It has seating accommodations for six passengers, weighs 2700 pounds, and will run 20 miles over ordinary good roads on one charge. A grade of 20 per cent is claimed to be surmountable. The wooden wheels are 30 and 42 inches respectively, and pneumatics of 4 inches diameter render riding as easy as possible. The motor, of the reciprocating type, weighs 400 pounds and operates at 350 revolutions, when the carriage is making 15 miles an hour. Ordinary compensating gear and hub steering are employed. In order to heat and expand the air before it enters the motor, it is surcharged with hot water, carried in the vehicle in a separate tank and kept at a temperature of 400 degrees Fahrenheit. Five pounds of water are required for each mile traversed. All the above machinery is spring-supported, to relieve it from the shocks of the road.

This carriage has been tested for the past year or more in the streets of Worcester and Washington, DC"

This account positively bristles with impracticalities. Note the very limited range, and the need to carry around a tank of hot water to heat the air; if five pounds of hot water were expended per mile, and the range was 20 miles, the contents of the full tank would have weighed 100 pounds. The engine appears to have been extraordinarily heavy at 400 pounds.

Note that the hot water was stored at 400 degF. The normal boiling point of water is 212 degF, so clearly it was stored under pressure. In fact, under considerable pressure, because water boils at 400 degF at about 230 psi- a greater pressure than that used in most steam boilers of the day. The water tank would have to withstand this pressure, so it would have to be a lot stronger and heavier than a simple tank. This clumsy and potentially dangerous setup seems to indicate that the Pneumatic Carriage Company had considerable difficulty in storing enough energy to heat the air, even for the very limited range that was claimed.

Therefore "filling up" would be quite a business. You would need a filling station that not only had a supply of compressed air (which I suspect was at considerable pressure- the later Mekarski system stored air at 60 atmospheres = 840 psi) but also a constantly-hot steam boiler working at an unusually high pressure. And with a 20-mile range you would need an awful lot of filling stations. You can see why this idea did not take off.

The following news item provides a little more information:

"A Compressed Air Carriage. Nov 1896"

"For some time past experiments in compressed air motors have been conducted at the factory of the American Wbeelock Engine Company, Worcester. Mass. These experiments have been very exhaustive, covering the application of compressed air motors to both track and road vehicles. To gather data for tbe latter class of vehicles, the Pneumatic Carriage Company, which is the name of the company working in this particular line, have just completed a two-seated carriage, which was publically exhibited in a procession held on Flag Day, Oct. 31, through the streets of Worcester, although close inspection was not allowed, inasmuch as tbe present vehicle is merely experimental and the company are not yet prepared to furnish specific information. President Hoadley states, however, that the experiments will be continued until a thoroughly satisfactory model is obtained, when steps will be taken to introduce compressed air vehicles for public service in cities."

"The Pneumatic Carriage Company has New York offices at 3S3 Broadway, connected with those of the American Wbeelock Engine Company."

THE AIRMOBILE COMPRESSED-AIR CAR

Left: Drawing of the Airmobile from above: 1914 Two engineers, C R Harris and Rutherford G. Goldman (who as an artillery artificer in the Spanish-American War, earned a medal for heroism), applied for a patent for a rotary fluid-brake in September 1911; US patent 1,127,237 was granted in February 1915. This brake appears to have been some sort of radial air compressor, though this is currently speculative.

From this grew the idea of a compressed-air propelled car called the Airmobile. The historical record is rather vague, but it appears that by 1914 Harris and Goldman were preparing to produce a car that had four-wheel rotary air-brakes which also functioned as air-motors, and also two air storage cylinders and an engine-compressor combination. The engine was claimed to be a “frictionless rotary engine fueled by crude oil” a description that rather undermines one's confidence. It is not clear if this was rotary engine in the Wankel sense, or a misdescribed radial engine. The air compressor is also described in the drawing as "frictionless". Oh really?

Given the relatively small amount of air storage provided, the whole compressor/air-motor system is just a very cumbersome and inefficent transmission system. It appears that all the heat generated by air compression was simply thrown away. To add to the complications, the suspension was partly by pressurised air-cushions, with their own air reservoir; see extreme left of drawing. In the drawing above the air-motors on each wheel are shown as no larger than an ordinary hub, and I doubt if this was realistic. Having four motors rather than one central motor much increases the complexity, and presumably also the unsprung weight. No means of preventing the air-motors from icing up is visible.

The 25 December 1916 issue of “The Automobile Journal” published a section titled “Novel Power Plants” (page 21) in which the following appeared on page 26:

“Features of the New Airmobile. “THE Rotary Products Company, Los Angeles, Cal., has adapted the rotary principle of generating power from gasoline and storing It as compressed air by driving an air compressor, designed on lines similar to the engine, and In turn piping the air to rotary air motors attached to each of the four wheels. This Is probably the most unique Idea In motor car propulsion that has been presented this year. “Its practicability rested with the perfection of the rotary principle which Involved largely the question of maintaining the necessary pressures In the explosive chambers which heretofore has been impossible because of leakage. The maker of this motor, however, claims that leakage has been negatived and that the engine can be run at low speed and produce high pressures, whereas formerly rotary engines were run at high speed and only produced low pressures. “A further and Interesting fact about the mechanism Is that It Is applicable not only as a rotary gasoline engine, but as an efficient air compressor, an air motor or can be adapted as a clutch or brake. The rotary engine is used to drive a rotary air compressor, both machines being hung on cross members in the forward part of the chassis. The air Is stored In tanks and piped to the four wheels, which are operated by individual air motors, or as brakes. “By this method of generating and transmitting the power the maker claims to have obtained not only a frictionless drive, but to have eliminated crank and camshafts, flywheel, clutch, transmission, levers and friction brakes; reduced weight and cost of construction and incidentally have adapted a set of air cushions which supplement the springs and reduce the vibration to a minimum.”

A somewhat less than perceptive account.

No production vehicles resembling the drawing above were ever produced, and it appears that the idea was abandoned sometime around 1916.

THE ROY J MEYERS COMPRESSED-AIR CAR

Left: The Roy J Meyers Air car: 1932 This car was not so much a practical proposition as a perpetual-motion fraud. The text says air is heated electrically until it reaches 200 psi. It then powers the motor and is 'recovered and drawn into a compressing chamber, where it is heated again and returned to the tank.' This sounds like a hot-air engine, with the energy supplied by that electrical heating. The electricity is suppplied by a battery and generator- so what powers the generator? It would have to be a sizable petrol engine to supply all the power continuously, in which case the compressed air is just acting as an inefficent transmission system. However I have a deep suspicion that the generator was connected to the air motor, to give a good old-fashioned perpetual motion machine. How else to interpret 'not one cent of cost to the driver for fuel'? The question is not clarified by the four big cylinders on the back of the car. These are described as 'fuel tanks' in the caption to the illustration, while in the illustration itself they are clearly labelled 'compressed air tanks' which is exactly what they look like. I suggest that the real power source was air stored in these tanks, which would be sufficent for short demonstrations but certainly not for journeys of 500 miles. Roy J Meyers had a colourful history, which included a 3-1/2 year sentence in the Arizona state prison at Florence; what for does not seem to have been recorded. While there he claimed to have invented an 'Absorber' which could extract electricity from the air and give free power. This appears to have been around 1912. He planned to build a 200-foot Absorber that would power the city of Phoenix; unsurprisingly it was never built. Meyers has become an icon for those seeking free energy. See viewzone.com, and also aircaraccess.com for some of his rivals, but he was clearly at best deluded, and more probably a con man. 3-1/2 years for confidence trickery sounds about right. The six-cylinder radial engine is interesting; note the small intake manifold and the large exhaust manifold. This article appeared in Modern Mechanix for Jan 1932.

Left: The Roy J Meyers Air car: 1932 This photo gives a good view of the six-cylinder radial engine. So far as I can see there are no fins on the cylinders to combat icing. From Popular Science for Jan 1932, p58

Left: Roy J Meyers patent: 1926 It did not take the Museum staff long to track down two patents by Meyers. The first (US 1,550,833 of 1925) is a bizarre brake that has its friction surfaces immersed in oil. The second patent (US 1,608,802 of 1926) is more to the point; it is called 'Fluid Pressure Generator' and is clearly the technology- if it might so be called- on which the Meyers car was based. The operation is thus. Electricity from battery g heats the wires 10 inside pressure chamber A, and the air around them expands and rushes through the Giffard injector 23, pumping air into pressure chamber B. From here it passes to A through check-valve 8, keeping the pressure up despite air being drawn off at 46 to run the car. Items 31 and 32 are air reservoirs (the ones on the back of the Meyers car) and 33 is an air compressor to get the whole business started. What drives that is not stated. Yes, it's a good old-fashioned perpetual motion machine of the First Kind, and how it got past the US patent examiners I do not know. The Giffard injector, invented by the remarkable Henri Giffard, is a perfectly respectable device. It uses the pressure of a steam boiler to force in fresh water, naturally against the same steam pressure. This sounds impossible but it is not- the secret is that part of the steam condenses in the water being injected, using energy, and this makes it all thermodynamically possible. Nonetheless the operation appears paradoxical, and in the early days there were many who refused to accept it could work. This paradox caught the eye of free-energy enthusiasts, who convinced themselves that this could work with an air tank. Compressed air from the tank would be fed to an injector, which would stuff that air, plus more entrained from the atmosphere, back into the tank. This is impossible, because no condensation occurs, and there is also the little matter of the Law of Conservation of Energy. It would be a bizarre universe in which this could work; presumably the air pressure would increase without limit, or at any rate until the tank burst.

CONTEMPORARY COMPRESSED-AIR CARS

THE PEUGEOT HYBRID-AIR SCHEME

Left: Peugeot: 2013 This project used a car with a conventional petrol engine, plus regenerative energy storage in the form of compressed nitrogen. The project was begun in great secrecy in 2010, and a car was supposed to be in production by 2016. The basic idea of the Hybrid Air car was to make an efficient hybrid vehicle that did not have to carry around a great weight of batteries. The main power came from a conventional petrol engine, coloured red in the illustrations. Instead, on braking or slowing down a hydraulic pump/motor (coloured green) pumped oil to compress nitrogen stored in a four-foot long gas cylinder, with a maximum working pressure of 3600 psi. When the stored power was needed for acceleration the compressed gas pushed the oil back through the pump acting as a motor. The middle illustration shows the oil/nitrogen reservoir in the centre of the car. The extra green tank at the right holds a reserve of hydraulic oil. In 2015 it was announced that the project had been put on indefinite hold. Why? Here are my thoughts: There is a lot of extra weight to carry around; the hydraulic pump/motor, the nitrogen cylinder, and the charge of oil. In particular, a gas cylinder that can safely withstand 3600 psi, even in an accident, is going to be heavy. There is a lot of extra stuff to go wrong. The amount of energy that can be practically stored, even at 3600 psi, is small. Perhaps I'm missing the point, but I would have thought a few back-of-an-envelope calculations would have shown this wasn't a practical project right at the start. Image & info from the Observer 24 Mar 2013, p18

Left: Computer rendering of the Peugeot car: 2013 This shows that the oil reserve tank at the back is actually quite big. Its shape and colour suggest that it is under the same pressure as the central cylinder. More expense!

THE ZPM AIR CAR SCHEME

OTHER COMPRESSED-AIR VEHICLES

MODEL COMPRESSED-AIR VEHICLES

This intriguing kit was spotted in the gift shop of the Science Museum in Milan. It is a very fine science museum, though for obvious historical reasons they do bang on a bit about Leonardo da Vinci. My view is that anyone can design a helicopter that does not work. Working solely from the picture, the engine seems to be two very simple single-acting cylinders (to avoid dead-centre problems) driving a common crankshaft in the upper forward part of the grey chassis. There are then at least two stages of reduction gearing in the drive to the rear axle. How the crankshaft connects with the first spur gear (with the green segments) is unclear. The info on the back of the box (see below) says there is a pump-up bar, a pressure gauge and a safety valve, none of which are visble. The round thing at the back of the air reservoir appears to be the on/off valve. I have no idea what pressure is used or how far this thing will run. Author's photo. Milano May 2018.

The information on the back of the box. The text under the reflection is 'NO BATTERY'. Author's photo. Milano May 2018.

EXTERNAL LINKS