Talk:Cornish engine

message: I have removed the word "sough" from the article, and replaced it with "adit". They are basically the same thing, however "sough" is a colloquial term specific to the Derbyshire lead mining district that never made it to mainstream modern mining terminology. Adit is more universal and is the standard term in Cornwall.--▫Bad▫harlick♠ 23:28, 21 October 2009 (UTC)
replies: text: To my mind they are not synonyms: a sough is a drainage level; an adit is a horizontal access route.  The term is perhaps most evident in Derbyshire, but by no measn confined to it, for example it was used in Black Country coal mining befoire 1600.  Peterkingiron (talk) 20:03, 22 October 2009 (UTC)
thread_title: Removed word

message: After reading this article I am still not sure what distinguishes a Cornish engine from other beam engines. Globbet (talk) 21:47, 13 May 2010 (UTC)
replies: text: It doesn't explain it at all and needs expansion. Try reading Hill's "Power from Steam" if you're in a hurry for it. Andy Dingley (talk) 23:11, 13 May 2010 (UTC)
replies: text: My understanding is that a "Cornish engine" is one that works on the "Cornish cycle".  This means that steam is first admitted above the piston and drives it down (assisted by the vacuum below the piston).  As the piston comes up again, the steam goes through a transfer port and fills the lower part of the cylinder.  The valve to the condenser then opens, creating a vacuum in the lower part of the cylinder, and the cycle starts again.  The steam is therefore used twice - first above the piston to provide pressure and then below the piston to create vacuum. The engine is, however, single acting because both forces are in the same direction. Biscuittin (talk) 20:31, 6 July 2010 (UTC)
thread_title:  Definition 

message: Does anyone know which was the last Cornish engine to be erected?  I've got refs for it being both Dorothea Quarry and also Hodbarrow mine, in the Lakes. Both are just into the 20th century. Possibly Dorothea was the last new build, Hodbarrow was the later re-erection of an older engine from elsewhere?  Andy Dingley (talk) 07:36, 20 June 2012 (UTC)
thread_title:  Last Cornish engine? 

message: Per this change https://en.wikipedia.org/w/index.php?title=Cornish_engine&type=revision&diff=724202180&oldid=722386777
Why does it now say, "The principal advance of the Cornish engine was its increase in efficiency due the use of higher temperature steam made possible by a boilers capable of withstanding pressure." ? Rather than the previous,  "[...] its increase in efficiency due to expansive working of the steam. "
Firstly this is unclear. An advantage compared to what? Compared to a condensing Watt engine, or compared to a Trevithick high pressure expansive engine?   Secondly the added idea (unsourced of course) that the Cornish advantage was from some increased temperature and pressure, when these engines were actually working at lower pressures (and yet greater efficiency) than most contemporaries.
Further issues are the loss of "A Cornish engine pumps by a falling weight that is lifted by the engine." - this was a crucial change contemporary with the Cornish engine, made possible by the switch from bucket pumps to plunger pumps.
Also changing "Trevithick's early "puffer" engines discharged steam into the atmosphere. This differed from the Watt steam engine, which used low pressure steam and so depended in part on the creation of a vacuum when the steam was condensed." to "This differed from the Watt steam engine, which moved the condensing from the cylinder to a condenser separated from the cylinder;" is seriously misleading, as it implies that Watt's changes were to the Trevithick engine, and involved improving Trevithicks's condenser (Trevithick was of course later and non-condensing).
Also change "duty" to efficiency is wrong - far too simplistic, and it also makes no sense when a value of 50 million is still quoted. What's an efficiency of 50 million? 
Also, why the change (also at Watt steam engine) from UK to US spelling? Andy Dingley (talk) 20:42, 7 June 2016 (UTC)
replies: text: The Cornish engine was a compound engine, which is why it was more efficient.  This engine was probably developed as a way to boost capacity of an existing Watt or Newcomen engine by adding high pressure engine and reusing it's exhaust or alternately  starting with a high pressure engine and adding a Watt engine.  The following are my notes from Hunter's Steam Power
In 1830 naval engineers witnessed trials of Cornish engines achieving 6 times the dusy of Boulton and Watt.Small, horizontal non-condensing engines added as supplementary power connected to the main drive and exhausting to existing low pressure engines (Truchers) “more widely used was adding a vertical high pressure cylinder beneath Cornish engine’s beam, exhausting to the cylinder of an existing Boulton and Watt engine.Trevithick high pressure engine ran side by side with a Cornish engine for a number of years with equal duty.  High pressure engine cost much less.Some Cornish engines economy was less than 2 pounds of coal per hp-hr and Cornish engines with steam jackets typically used <2.5 lb coal per hp-hr Phmoreno (talk) 21:34, 7 June 2016 (UTC)
thread_title:  Accuracy of recent changes 

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message: I believe Jonathan Hornblower around 1781, developed almost the same engine type, but because Watt patented most of the technology in 1778 or so, he couldn't sell it. In 1800 or so patents expired, and in 1804 the Cornish engine was basically a revival of the Hornblower design.  2A02:168:F609:0:5F8:C25A:2F16:ECD5 (talk) 11:42, 26 June 2019 (UTC)
thread_title:  Pre-developements and history, and Watt and Bulton patents