The Liquid Engines

Gallery opened June 2012

Updated: 21 July 2017

Another new Malone engine
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This page was previously called The Malone Liquid Engine. Now it has become clear that Malone was not the only worker in the field, it has been renamed.

Virtually all prime-mover engines work with gases (such as hot-air engines) or gas and liquid. (such as steam engines) There have also been solid-expansion engines based on the expansion of solid material. But in one unique case, liquid alone was used; the expansion of water when heated under high pressure was used to drive a piston.


The first attempt at a liquid expansion engine so far discovered is that of Edward Thuemmler of Little Rock, Arkansas. See US patent 226,570.

Left: Thuemmler's liquid engine: 1880

A is a conventional furnace for heating the working liquid. B is a cooling tank for the liquid. C is an annular-piston engine. Thuemmler was planning to use lard, olive-oil, or cotton-seed oil as his working liquid.

D and E are spring-loaded pistons designed to act as hydraulic accumulators, to protect against water-hammer, or in this case, oil-hammer.

Thuemmler did not confine himself to liquid engines; in October 1880 he was granted US patent No 233,125 for an improved hot-air engine. Nothing else has been discovered about him and it may be concluded that his liquid engine was never built and in general his engines did not prosper.

From US patent 226,570

Left: Thuemmler's liquid engine: 1880

The liquid is controlled by a conventional slide-valve. The annular piston in the middle has a greater area than the plunger, so that incoming liquid pushes out-going liquid back into the heating furnace. Or so the patent says, anyway.

From US patent 226,570


John Fox Jenkins Malone is undoubtedly the foremost exponent of liquid expansion engines; is the only person jnown to have actually built engines and conducted tests on them. The only book I know of on Malone is John Fox Jenkins Malone: The Liquid Stirling Engine by Robert Sier, published by L A Mair in 2008. (ISBN 978-0-9526417-2-8) Robert Sier is a well-known author on hot air engines. The book includes a foreword by Ray Malone, the son of J F J Malone, and father of John Malone.

Malone's first experimental engine appears to have been built at some time before 1925, and is known as the 'First Small Engine'. The only information on it is some vague references in Malone's 1931 paper before the Royal Society of Arts. It used mercury as a working fluid; Malone commented on the high cost of mercury but not its toxicity.

The Malone engine was a modification of the Stirling cycle, using water as the working fluid instead of gas; heated and cooled with regeneration as devised by Stirling. The engine needed to operate at high pressures to get a reasonable power density. Unfortunately the work of Malone between 1920 and 1931, was scantily reported and much has subsequently disappeared. But... see the blueprints reproduced below; however be warned that it is doubtful if they refer to a liquid expansion engine.

Left: Malone's first large liquid engine: 1928?

Behold the Malone liquid engine: Malone's first 50 hp large vertical prototype engine was completed in 1925, and used a coal-fired boiler to indirectly heat high pressure water sealed inside a cylinder. The power cylinder is at the top of the assembly; piston diameter was of the order of 5/8 inch. The heavy high-pressure connection and pipework to this cylinder were necessary to deal with the high pressures involved. The actual pressure used in this engine is not currently known, but Malone said he had used up to 1000 atmospheres (14,696 psi) in his experiments on the properties of liquids; that is some serious pressure. Malone wrote that extensive experiments were carried out with this engine between 1925 and 1927. Note its enormous size, with scale given by the man on the right, and a very heavy flywheel considering the modest power output.

According to Malone, this engine had eighty regenerator tubes (believed to be situated to the right of the actual engine in the photograph, connected by the upper pipe) and two power cylinders. It appears to be a vertically-opposed engine with one cylinder above and one below the crosshead.

In the bottom right corner the photograph is marked 'The Engineer', which was one of the foremost British engineering journals of the day. This suggests it was taken from an original article and one might hope that if the article was found a better reproduction might be obtained. The Museum Staff have searched diligently, but there appears to be no online archive of The Engineer for the relevant period. If any one has access to it a scan would be much appreciated.

Left: Malone's small horizontal liquid engine: 1927

It is not currently clear if this is the same engine as the First Small Engine referred to above.

The engine and flywheel are clearly on the left; it is believed that the regenerator tubes are in the centre and the furnace on the right. Malone did all his heating with coal or coke.

Left: Malone's second large liquid engine: 1931

Malone's second vertical engine, demonstrated in 1931, also gave 50 hp but in a much more compact format. It was alleged that in independent testing the design showed an astounding efficiency of 27%, the figure referred to below.

According to Malone the engine had 20 regenerator tubes housed in the central vertical structure. It had two power cylinders, arranged vertically-opposed as in the first large engine above.

Malone experimented on the the thermal-expansion coefficients and compressibilities of a range of liquids, including mercury, liquid carbon dioxide, liquid sulphur dioxide, and various hydrocarbons. However he, no doubt wisely, choose water as the operating fluid for most of his liquid engines.

The following description is taken from Time magazine for Monday, 3rd August 1931:


"By surrounding two cylinders with high pressure boilers, by filling the boiler coils with water and then sealing them hermetically, Engineer J. F. J. Malone of Newcastle-on-Tyne, England has made an effective heat engine. Last week he demonstrated it.

"A furnace heats the base of one boiler-cylinder to 900°F. (688° above water's normal boiling point). The superheated water expands (but cannot change to steam because it is too closely confined) and pushes a piston at the far end of this cylinder. Cold water or air, applied against the piston end of the boiler, cools the confined water sufficiently to make it contract and suck the piston back to its original position. The external cold water or air is shut off, the cooled water in the boiler coils passes into the second cylinder, and newly heated water comes from the furnace to push the piston of the first cylinder again. Thus heat energy carried by the water changes to mechanical energy in that piston.
"The cooled water which left the first cylinder for the second is still much above the boiling point. It carries a certain amount of heat energy which it transfers to the second piston upon its being cooled and contracted a second time.
"After the second cooling the confined water returns to the furnace for reheating to 900°. The circulation of the water through the coils of the two cylinders is on the same principle as the circulation of water through the radiators of a residential hot-water heating system. Heated water rises from the furnace; cold water drops to the furnace.

"Claimed thermal efficiency of the Malone engine is 27%. Superheated steam locomotives are 8% efficient; steam marine engines 14.7%; gasoline engines 26%,; Diesels 47%. Once filled the Malone engine needs no more water for long periods of time."

This describes what is essentially a Stirling-cycle hot-air engine with the air replaced by water, which is kept under such high pressure that it cannot boil even at the high temperatures used.

There seems to have been little contemporary interest in the idea, and Malone appears to have abandoned work on his liquid engine in the mid 1930's, turning his attention to a regenerative gas machine. To this end he formed the The New Engine Company Limited.

Left: John Malone: date unknown

John Fox Jenkins Malone was born in Wallsend on Tyne, England in 1880. He served at sea with the merchant marine for fourteen years, during which period he was apparently wounded seventeen times in Arab and Latin-American wars. Having no doubt got fed up with this, he abandoned the sea and founded the Sentinel Instrument Company in 1912, and later the Fox Instrument Company. He died on the 16th of June, 1959. This photograph appears to have been taken when he was in the merchant marine.


John Malone was granted US Patent 1,487,664 for a 'Heat Engine'in March 1924. At the time he was living in Newcastle-On-Tyne, England.

Left: Malone US patent No 1,487,664: 1924

This diagram from the patent shows the general idea of Malone's liquid engine. A liquid (in the patent Malone recommends either mercury or an alloy of mercury and lead) is moved from a cold area to a hot area, where it expands and does work. It is moved by a displacer and passes through a porous regenerator 25 made of 'fine wires', to conserve heat and so improve efficiency; this is a liquid version of a Stirling hot-air engine.

Here the heating is done by gas jets at A and the cooling by water-tank B.

Left: Malone engine: 1931

This drawing was part of a paper read by Malone before the Royal Society of Arts in 1931.

It is not believed to represent any engine actually built.

The principle is the same as for the US patent drawing above, though there are now separate power and displacement cylinders. The working fluid is moved between the heating area at the right and the water-cooling area at the left by the displacer piston, its ends labelled 'cold dummy' and 'hot dummy'. The porous regenerator is labelled 'T-D-pile'; T-D stood for 'ThermoDynamic'.


In August 2015 I was contacted by John Malone, the grandson of JFJ Malone. He pointed out that not all the Malone material was lost, and he had a set of blueprints for one of the engines, apparently dated between 1929 and 1931. With his permission I am going to publish them here.

According to Sier, Malone abandoned development of his liquid engine in the early 1930's, and instead set up 'The New Engine Company Ltd' to develop a new external-combustion marine engine; this company is unknown to Google although there is a contemporay company of the same name which has no apparent connection. No details of this later engine are known, and I suggest that these blueprints may be all that remains of that engine. The fragmentary information on the drawings suggests that it may have been some sort of compound hot-air engine operating at high pressure.

Left: Malone blueprint No 2

The HP & LP coolers. From this it appears that compound operation of some kind was planned.

Left: Malone blueprint No 5

This is Sheet 1 of Blueprint 5. (I think) It shows the HP and LP compressors and engines. Once more it appears that compound operation was planned.

The valve gear was driven from the crankshaft by bevel gears; see the shaft at extreme right.

Left: Malone blueprint No 5, sheet 2

The valve gear is shown as driven by the inclined shaft at top left.

Left: Malone drawing No 5, sheet 2

This shows the valve-gear in close-up. The gear at extreme left, driven by the worm below it, presumably adjusts some aspect of the valve timing.

Left: Malone drawing No ??

This appears to show a flue-gas preheater for the combustion air to the furnace, but there are several references to high pressure and low pressure air pipes, which is strange. From the size of the air pipes they could not possibly supply the air required by a furnace. All very puzzling.

Left: Malone drawing No ??

Here we learn that the engine (or maybe just the drawings for it) were Contract No 912. But who with?

Left: Malone drawing No 37/1

This drawing does not seem to fit with the others. Apart from it not being a blueprint, it appears to show an engine with conventionally sized cylinders rather than tiny ones adapted to liquids. Close examination shows the cylinders labelled as 'LP expansion', 'LP compression', 'HP expansion', and 'HP compression'. This perhaps suggests a compound 2-stroke Diesel engine that is nothing to do with the liquid engine.

The text bottom right, under 'ENGINE ARRANGEMENT' claims 1525 indicated horsepower at 60 rpm. There is also a reference to a voyage consumption of 10 tons of coal per day. This engine was clearly meant for marine applications, driving a ship of significant size.

As we have seen, Malone was not the first to think of a liquid expansion engine; but he does appear to have been the first to actually build one, to measure its performance, and to develop it.


Malone had those who came after him in the liquid engine business. So far there is no evidence that they built their engines.

Left: Westcott's liquid engine system: 1962

William B Westcott Jr, of Cleveland Heights, Ohio,took out US Patent 3,055,170 for a LIQUID THERMAL ENGINE in September 1962. The working fluid was intended to be 'hydraulic fluid identified by the military specification MIL-O-5606, (1950) approved by the U.S. Air Force and Navy Departments'. Wescott says this reaches a pressure of 50,000 psi when compressed by about 10%.

In the diagram 74 is a heater for the liquid and 11 is a heat exchanger to cool it. 19 is an accumulator to stabilise the pressure in the system. The engine has plunger-type pistons apparently about an inch in diameter.

The patent is long and complicated, but comes down to the same heating/cooling cycle as Malone; however Malone's work is not referenced or mentioned.

Putting 'Wescott liquid thermal engine' into Google brings up an earlier Wescott patent (US 2,963,853 of 1960, Liquid Cycle Heat Engine) but nothing else at all, from which I am inclined to conclude that nothing was ever built and the idea went nowhere.

Left: Westcott's liquid engine, Side elevation: 1962

It was an oscillating-cylinder engine. The cylinder 29 (which does not look as if it is built to withstand huge pressure) pivots on pin 23.

From US Patent 3,055,170

Left: Westcott's liquid engine, top view: 1962

This drawing reveals that the projected engine had a single cylinder. The timing gear 62 drives camshaft 63 which operates two spool valves that control the flow of liquid into and out of the cylinder.

From US Patent 3,055,170

These earlier US patents were cited in Wescott's 1962 patent:

13 Apr 1880
'Thermo-Dynamic Engine'
Boulton & Perrett
20 Jan 1885
9 June 1903
26 Jan 1904
9 July 1912
22 Aug 1922
31 May 1949
31 Mar 1953
17 June 1958


Interest in the Malone cycle disappeared for decades but then revived; in the 1970's John C Wheatley, then a physics professor at the University of California resumed the study of liquid-based engines, with the intention of building heat pumps and refigerators rather than prime movers. He chose propylene as the working fluid. Propylene C3H8 is the 3-carbon analogue of ethylene; it is sometimes called propene, or methyl ethylene. The boiling point is -48 degC, and it is usually stored as a liquid under pressure. Its advantage for this work is that liquid propylene can be raised in temperature by 9 degC if compressed to 2500 psi, a straightforward process.

This work resulted in US patent 4,353,218 granted on 12 Oct 1982.


In 1992 the Los Alamos group was working on refrigeration cycles based on Malone's work. One version was built by Dr Swift, using liquid carbon dioxide at 2000 psi as the working fluid.


Interest in liquid expansion continues. Brian Hageman of Phoenix Arizona was granted US patent 5,899,967 in May 1999, and US patent 5,916,140 in June 1999. Both patent are titled HYDRAULIC ENGINE POWERED BY INTRODUCTION AND REMOVAL OF HEAT FROM A WORKING FLUID but while they are very similiar they are not identical documents. What the point of this was I do not know.

Both patent cite the Westcott Liquid Engine. (see above)

Left: Hageman's liquid engine: 1999

The Hageman engine has small-diameter pistons driving a heavy crankshaft. The working fluid in the cylinder communicates with a flask 177 that is alternately heated and cooled by fluids (water is suggested) controlled by the valve assemblies 166, 168. This seems to be no advance on the Malone system, and in fact a step back as it has no regenerator to improve the efficiency.

Working fluids suggested include freons, liquid argon, liquid nitrogen, liquid oxygen, ethane, ethylene, liquid hydrogen, liquid helium, and liquified natural gas. Liquid hydrogen as a working fluid? This list suggests either an extremely versatile engine or a patentee who has very little idea of what he is talking about. Freon R12 is specifically mentioned, and that was banned in developed countries in 1996, long before the patents were granted; noting that and also the general tone of the patents, I'm going with the second option.

From US Patent 5,899,967

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