Rotary Steam Engines: Contemporary Comments.

Updated: 13 May 2008
Engineering added
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John Russell Scott Portrait
Left: John Scott Russell (1808-1882)

Russell wrote an extended criticism of the rotary engine concept called "Fallacies of the rotary steam engine" which was printed in Mechanics Magazine for April 1838, starting on p192.

He was born near Glasgow in 1808. He graduated from the University of Glasgow in 1825, and moved to Edinburgh University where he taught mathematics and natural philosophy. In 1834, while conducting experiments on the design of canal boats, he discovered the soliton. (external link)
Russell moved to London in 1844. He worked on the design of ships, becoming a director of a shipbuilding company. Isambard Kingdom Brunel who made him a partner in building the Great Eastern, but there were problems; Russell was in financial difficulties and the two men disagreed on aspects of the design and construction. (The Great Eastern was eventually launched in 1858) He was expelled from the Institute of Civil Engineers for some questionable arms deals during the American Civil War.

Russell was a great scientist but a mediocre businessman and his reputation suffered from his disputes and financial irregularities. He died a relatively poor man in 1882.

John Scott Russell's main criticisms of rotary engines were:

  • The Crank Fallacy; in other words, the error of advocating rotary engines because they avoided an entirely imaginary problem with cranks and connecting rods. It appears to have been believed by some people that because the connecting rod was not always acting at right-angles to the crank, the loss of mechanical advantage meant a loss of power. For example Thomas Masterman, the patentee of a rotary engine in the form of a steam wheel, claimed that the usual crank system absorbed half the power available in the steam supplied. This is obvious nonsense, because if the crank system had somehow been absorbing power, it would have eventually got red-hot. John Scott Russell devoted pages of deeply tedious analysis to proving that there was no power loss.
  • Greater bulk; in other words a rotary engine of the same power as a reciprocating engine would be bulkier because the steam at the inner parts of the engine worked with less mechanical advantage upon the rotor.
  • Uneven wear; the outer parts of the engine moved at a greater linear velocity than the inner sections, wearing faster and considerably complicating the task of keeping the seals steam-tight.
The crank fallacy in particular, was subjected to an almost interminable examination. Strangely, he barely mentioned the main problem- the sealing difficulties inherent in the geometry of most rotary engines. The closest he got was to say:

"There are other defects to which this species of engine is particularily liable- to vacuities and losses at the valves and passages- to irregular action, and collisions and shocks from the action of the parts upon one another..."

Clearly in the last part of that quote he is thinking of the dreadful whack-a-butment designs where the moving parts hammered into each as the engine rotated. The first of many sad examples was The Watt Engine.


Scientific American text
Left: This commentary on rotary steam engines appeared in Scientific American in June 1847.

Even at this relatively early date, there appears to be considerable cynicism about the concept.
The bit at the end about "the excess of centre speed" is wholly opaque to me.


George Stephenson Portrait
Left: George Stephenson (1781-1848)

Below are presented extracts from the minutes of a General Meeting of the Institute of Engineers on 26 July 1848; at this period more than 50 patents for rotary engines had been taken out. While several of the participants appear to come from the pages of Terry Pratchett, this is not actually the case. These are the real names.

THE PRESIDENT is none other than George Stephenson.

MR ONION then stated that his engine* had been working for some weeks at the Derby station, by permission of Mr Kirtley, the Locomotive Superintendant of the Midland Railway; and during that trial, experiments with his and another engine had proved that his effected a material saving in fuel.

THE PRESIDENT said that it appeared to him to be impossible that such could be the case. The engine might have answered at one trial, but it might fail at the next; and one trial was by no means a sufficent proof.

MR SLATE observed that there was one important desideratum which he desired to see obtained in the Rotary Engine- namely, some method of packing tightly. That had never yet been found. He had paid much attention to the Rotary Engine, and had seen approaches made to an efficient system of packing, but none had been so perfect as to render the rotary principle equal to the crank. Mr Onion had told them his engine was more simply packed than the common engine.

MR ONION said that Mr Scott Russell**, who had written on and patented several Rotary Engines, confessed to him that he (Mr Onion) had succeeded in overcoming difficulties which had hitherto been found to be insurmountable, such as making his engine steam-tight, and also in doing away with the usual noise*** of the Rotary Engine.

MR JOSEPH MILLER said that one great advantage of the Rotary Engine, supposing it to be thoroughly efficient, was the small space which it occupied... He had never yet seen a Rotary Engine rendered sufficiently tight, but he would not go the length of saying that it could not be done.
As a practical man, however, he saw great difficulties in the way. He had never seen a Rotary Engine which remained tight for any length of time; and he should as soon expect to discover the perpetual motion as to make one which would.

On being referred to, Mr HENRY ROBINSON said that the government had a Rotary Engine (Lord Dundonald's engine) working in the Portsmouth dockyard for the last seven years. Mr Onion claimed the credit of being the first who had ever suceeded in packing efficiently, but it was only the same as he (Mr Robinson) had been in the habit of using for years... If Mr Onion would call upon him in London, he would show him an engine similar to his own, and packed in the very same way. It was one that was applied to a locomotive, commonly known as the "Jim Crow" engine- from its having been painted black...
All that he (Mr Robinson) was prepared to say about the engine (Lord Dundonald's) was that it had hitherto done the work which it was intended to do.

A member having spoken of Beale's Rotary Engine, THE PRESIDENT stated that he had been concerned in having a trial made of that engine, in a steam boat intended to carry passengers only half a mile, to Yarmouth; but when the engine was put to work he could not make the boat move forward, and so the experiment failed. He managed to get the boat to sea, and it cost him and his party £40 to bring her back again.
As to Lord Dundonald's engine, he was invited, on one occasion, to see it tried on the London & Manchester railway; but he refused to go, because he was convinced that a failure would be the result; and so it was, for the engine could not be made to draw a train of empty carriages.

Not much enthusiasm for the concept here. Clearly sealing was a major problem.

* The only Onion engine I am aware of was Onion's steam wheel, which destroyed itself in a quite unique way after its first trial. It appears that a different rotary engine is being discussed here.

** This is John Scott Russell, mathematician, engineer, and discoverer of the soliton. See above for more on his views on rotary engines.

*** This hitherto enigmatic passage probably refers to the sort of rotary engines that struck their own internal parts as they rotated. For another example see The Chapman Engine which was reported to sound like a tilt-hammer in operation.


"It cannot be said that any one of the multitude of rotatory engines yet tried has been completely successful; nevertheless we are by no means of opinion that a good rotatory engine will never be discovered, but, on the contrary, believe that the reciprocating engine will yet be superseded by a rotary contrivance of a far simpler kind than any one now contemplates."

From A Treatise on The Steam Engine in Its Application to Mines,Mills, steam navigation and Railways by the Artizan Society, ed John Bourne, pub 1853 Longmans

Some prescient words from John Bourne, anticipating the steam turbine.


Franz Reuleaux portrait
Left: Franz Reuleaux (1829-1905)

Reuleaux came from a family of machine builders in Liège, Belgium. The family moved to Aachen in West Prussia, and he studied philosophy, mathematics and mechanics at the Universities of Berlin and Bonn. He published several books on machine design and kinematics. He was one of the few authors to write in any depth on rotary steam engines.

In his book "The Kinematics of Machinery", which was published in English in 1876, and is considered the foundation of scientific kinematics, Reuleaux deals with many rotary steam engine designs from a strictly theoretical standpoint; the phrase "Reuleaux says..." will be found scattered throughout my pages on rotary steam engines. The main purpose of the book was not the study of steam engines, but to popularise a notation he had invented for describing mechanisms. (Charles Babbage invented a notation with the same purpose) Some of the diagrams in these pages retain the Reuleaux notation describing the engine, from which it can be seen to be somewhat opaque. So far I have found no evidence it was ever widely adopted.

Reuleaux says, at the start of Chapter 9 of his book:

"Such a multitude of arrangements have been devised- and are still being devised- for the carrying out of one and the same purpose, that it appears almost impossible for a single individual to reduce them all to order, or even find out their existence. The irrestible tendency towards the invention of "rotary" steam-engines has contributed greatly to increase the number of these arrangements. This tendency has given us many useless, or apparently useless, machines, and has been the means of wasting much thought and capital. Would-be inventors have again and again been warned of it, but the warnings do not seem to have had any effect."


Left: From Design And Work, 24 Jan 1880 p91

These letters are obviously in answer to a query about the practicality of rotary steam engines. The opinions are, as usual, not very positive. I have not so far found the original query.

Left: From Design And Work, 31 Jan 1880 p115

Design And Work is a journal I have only just discovered, and at the moment it is a bit of a mystery. It appears to be identical in format and approach to English Mechanic, which was active around 1900.

As we have seen, the phrase "rotary steam engine" covers a very wide variation in construction. The British journal Engineering thought that was part of the problem, saying in 1939.

"It is probable that it is this very variety that has been the curse of the postive acting rotary. For an inventor, finding by experiment that his first scheme was faulty, was less likely to persist with it and by steady minor alteration to improve it than to turn his attention to another variety, and experience further disappointment. By contrast the attention of succeeding generations of engineers has been continuously concentrated for a century and a half on pistons, connecting rod and crank mechanism so that as a result of persistent minor improvement it can today be so constructed as to run at speeds which the first users would have regarded as fantastic."

Possibly the unknown author was thinking of Cochrane or Galloway; almost all would-be inventors seem to have stopped at one design. He also ignores the fact that the rotary engine has geometrical problems that are inherent, and will not yield to dogged detail development.
An interesting question is why Engineering should be concerning itself with rotary engines as late as 1939. One would have thought that at that time there would have been more important things to think about; we must be grateful that no-one tried to fit the Hawker Hurricane with a rotary steam engine.

Engineering went on to further misplace the plot:

"Much more complicated mechanisms have been made reliable as the result of the unremitting efforts of engineers striving towards a single end... and we see no reason why similar efforts directed towards perfecting the rotary should not yield equally encouraging results."

I don't buy this, and I don't see what technology the author is referring to. If a bit of machinery is unreliable and ineffective, no-one is going to wait generations for a practical version to come along. Newcomen's pumping engines were slow and horribly inefficient by later standards, but they could do the job of keeping a mine clear of water with acceptable economy, and so could be sold to hard-headed mine owners. If it had taken generations to come up with something commercially viable, nobody would have bothered.
Another point is that the Wankel rotary internal combustion engine has received an enormous amount of development, but remains deeply flawed.

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