Editing Steam engine (section)

=== Rotary steam engines ===
It is possible to use a mechanism based on a [[pistonless rotary engine]] such as the [[Wankel engine]] in place of the cylinders and [[valve gear]] of a conventional reciprocating steam engine. Many such engines have been designed, from the time of James Watt to the present day, but relatively few were actually built and even fewer went into quantity production; see link at bottom of article for more details. The major problem is the difficulty of sealing the rotors to make them steam-tight in the face of wear and [[thermal expansion]]; the resulting leakage made them very inefficient. Lack of expansive working, or any means of control of the [[cutoff (steam engine)|cutoff]], is also a serious problem with many such designs.{{citation needed|date=January 2013}}

By the 1840s, it was clear that the concept had inherent problems and rotary engines were treated with some derision in the technical press. However, the arrival of electricity on the scene, and the obvious advantages of driving a dynamo directly from a high-speed engine, led to something of a revival in interest in the 1880s and 1890s, and a few designs had some limited success.{{citation needed|date=January 2013}}.

Of the few designs that were manufactured in quantity, those of the Hult Brothers Rotary Steam Engine Company of Stockholm, Sweden, and the spherical engine of [[Beauchamp Tower]] are notable. Tower's engines were used by the [[Great Eastern Railway]] to drive lighting dynamos on their locomotives, and by the [[British Admiralty|Admiralty]] for driving dynamos on board the ships of the [[Royal Navy]]. They were eventually replaced in these niche applications by steam turbines.{{citation needed|date=January 2013}}

[[File:Aeolipile illustration.png|thumb|upright|alt=Line drawing of a sphere suspended between two uprights forming a horizontal axis. Two right-angle jet arms at the circumference expel steam that has been produced by boiling water in a closed vessel under the two uprights, which are hollow and let steam flow into the interior of the sphere.|An [[aeolipile]] rotates due to the steam escaping from the arms. No practical use was made of this effect.{{Citation needed|date=July 2020}}]]