This is an archive of past discussions about Newcomen atmospheric engine. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.
As I recall, this steam engine was known as the Danemorra Fire and Air Machine. I once read a very old book in the MIT library that referred to it as such, and used the information to build models of the steam engine. They worked like a charm!
In revising the article, I have eliminated a number of statements, which seemed to be wrong, not being in accord with the authorative work by Rolt and Allen. I hope that I have avoiding introducing the results of original research. The article as I found it seemed ambiguous as to who invented the jet of water for condensing the steam; I am not sure that the present statement on this is quite correct. If you disasgree with statements that I have made, please argue out the issue here, citing your authority. Peterkingiron10:54, 29 November 2006 (UTC)
Animation
I have problems with the animation. The basic principle is clear enough (although it could still be slowed down), however there is no indication as to how the condensed water is drawn off before fresh steam is admitted. — It's spirited away "just like that there"! From contemporary drawings (and the second one in this article) it can be seen that there was a drain pipe from the cylinder bottom leading to a low-level tank (hot well?). Again from contemporary drawings it can be seen that the boiler did not rest on thick brick peripheral walls but on a small ledge which means that hot gases could flow round the sides of the small cylindrical part, consequently the heating surface was greater than just the concave bottom of the "pan" as shown here.--John of Paris08:50, 8 March 2007 (UTC)
The condensate might run back into the boiler when the value was opened, but most diagrams of engines in Rolt & Allen do have the pipe in question. However they do not make clear whether this was opened automatically at the end of the power stroke, or was opened manually by the engineer when needed. Peterkingiron21:47, 10 March 2007 (UTC)
My understanding is that the remains of the condensate was driven out through a one-way valve by the action of the admission of the steam. This valve was caled a 'snifter' after the noise that it made. I suspect that it was a simple spring release ball valve, the spring being equal to the steam pressure. Perhaps someone can enlighten us.
Much simpler than you imagine. I visited the Dudley replica on a steam day a couple of weeks ago, but was unable to get a good look at the snifting valve; however I was told it is a simple leather flap closed as you say by steam pressure at admission. You can see in the photo the plugman, Mike Dunn purging the air from the cylinder before starting the engine by the simple expedient of pushing the flap down with a brick. Your "simple spring release ball valve" is simple to make today but far beyond the technical possibilities of 1712. The snifter is the funnel-shaped object soldered onto the lead drain pipe leading from the bottom of the cylinder to the hot well. Above Mike is a fall pipe draining the excess of water used to seal the piston; the small branch leading into the snifting valve provides another water seal with its own overflow also going on down to the hot well. I have put a short report on my recent visits to this and other engines in the talk:steam engine.--John of Paris09:39, 6 May 2007 (UTC)
Correction Sorry, I may have been wrong about the leather flap. According to David Hulse (see ref. in article), the snifting valve is believed to have taken the form of a conical brass poppet valve maintained in place by its own weight carefully calculated to keep constant steam pressure The snifting valve's job as far as I can gather was to ensure the immediate release of the vacuum on admission of the next charge of steam and to make sure that the cylinder was uniformly filled with steam. This still does not explain Mike's use of the brick that appears to be bearing down on something to release trapped air as he said. I shall enquire further about this.--John of Paris10:39, 8 May 2007 (UTC)
Worcester & Savery
I am afraid that the previous description of Savery's engine was factually incorrect and I have just altered it. Referring to [1], there can be no doubt that the engine used alternately both the vacuum effect and steam pressure. As for Worcester, it seems difficult to make out what this engine was actually like: the drawing reproduced by Thurston was copied from that given by Dirk which seems to be the latter's own hypothetical drawing based on Worcester's description. This is worth following up, but would perhaps be more pertinent to the Steam engine article than the present one. Also the statement that Savery introduced the water spray appears to be pure speculation, but I have not touched it yet.--John of Paris14:08, 5 September 2007 (UTC)
The view from across the pond
Congratulations, this is an excellent article. I always love those little animations and to me they are what makes on-line encyclopaedias so different from the paper versions. As to the pronunciation of Newcomen, we Brits would pronounce it with equal stress on all the syllables, but of course our pronunciation of "new" is somewhat different from the American one, so we would say nyew-cum-un.The last syllable sounding like "urn" but slightly shorter. I suppose it's like the "en" sound in the American "gotten" Richerman17:43, 26 September 2007 (UTC)
Thermal Efficiency
I have seen opinions that the efficiency of a Newcomen engine was about 1%, a Watt about 3%, & steam engines in the late nineteenth century about 10%.
A kg of coal has a heat of combustion of 27MJ. At 3.6MJ per KWhr, & a thermal efficiency of 1%, we need 13 kg of coal per hour to get a kilowatt of mechanical power. --DavidErskine02121.217.147.99 (talk) 04:15, 8 February 2009 (UTC)
Sawing wood
The up and down movement of a Newcomen engine could have been used to saw wood, a saw fitted to a vertical segment instead of a pump. Workers could have held a log against the saw.& offcuts burned in the firebox. I know that wood offcuts were valuable for kitchen stoves in the days before electricity & gas, & sawdust was valuable to absorb spills, so perhaps using Newcomen engines to saw wood was not economic. --DavidErskine02121.217.147.99 (talk) 04:21, 8 February 2009 (UTC)
The duty cycle of an atmospheric engine was such as to run at about 10 - 12 strokes per minute. At this speed, a carpenter would need to be especially patient for his wood! Besides, in practice, the size and cost of an engine would have meant that such use was prohibitively expensive.
With the right design, a carpenter sets up the Newcomen saw, and is then free to do something else. There would need to be some way of mechanically pressing the log against the saw, or a boy could look after it. Sawing all day by hand is heavy, tedious work. --DavidErskine121.217.147.99 (talk) 03:33, 15 February 2009 (UTC)
In theory, it would be possible, but as EdJogg says very slow. In practice, it did not happen. The Newcomen engine was hardly used outisde Britain, and saw mills were hardly used there. There were windmill-powered saw mills in Holland, and the machinery could have been powered by watermills, but when I researched them a few years ago, I was unable to find any in Britian earlieer than blockmaking machinery, supplying blocks to Portsmouth dockyard in about the 1770s. This is perhpas because Britain had such a low area of woodland, and much of it was needed to fuel the iron industry. Your comment makes an interesting speculation, but leads nowhere. Peterkingiron (talk) 17:16, 15 February 2009 (UTC)
Driving canal barges
I can see a Newcomen engine driving a canal barge. In the days before the crank, the to and fro movement of the engine could push a flat wood plate, which folds on the return stroke. A narrow boat, or canal barge, was usually pulled by one horse, so I envisage a 1 kilowatt Newcomen. Pehaps it would have used too much coal. --DavidErskine02 121.217.147.99 (talk) 04:26, 8 February 2009 (UTC)
I can't really see how your proposed mechanism would work, but I would guess you are expecting it to work in a horizontal mode. Coal use would have been only one problem: the sheer size and weight would have precluded use on the canals. According to Maurice Kelly, one of Newcomen's first machines was a 'small' one, at a height of 7 1/2 feet. Even if it was possible to float such a device, it would never have gone under the bridges. EdJogg (talk) 16:16, 8 February 2009 (UTC)
The problem ultimately is that Newcomen engines were too slow to drive machinery, and too heavy to move themselves easily. Your proposal might theoretically to possible, but it did not happen. I do not think we can have WP cluttered with 1000s of counterfactual might-have-beens. Peterkingiron (talk) 22:30, 8 February 2009 (UTC)
If you have references from authors who investigated such limitations it would not be unreasonable to incorporate what was appropriate into the article text.
Coal was freely available in collieries, as the article says, but it does have an opportunity cost, and the heavy consumption of coal by Newcomens would have been a concern to the mine owners. Then again, no pumping of water, no mine. Newcomens were also used in metal mines, so it was presumably economic to transport coal, to keep the engine running and the mine going. I understand that low grade coal, of little value, was used to fire Newcomens, but such coal could also have been used to fire coking ovens, turning better coal to coke, of higher value. --DavidErskine02 121.217.147.99 (talk) 04:38, 8 February 2009 (UTC)
The problem was that many non-ferrous metal mines were in areas where coal was scarce. In coalfields, your argument does apply, meaning that many mine-owners continued using the less efficient Newcomen engine until the patetn on the Watt engine expired. Peterkingiron (talk) 22:33, 8 February 2009 (UTC)
Preserved specimens?
A list of preserved 18th century Newcomen engines (in Museums I'd presume) would be a very nice addition if somebody has one. -- 92.230.20.192 (talk) 12:02, 26 April 2009 (UTC)
Please no edit warring on this. I happen to favour Wolverhampton's priority, but a legitimate histroical argument can be made for either. Articles setting out the case for each have just been published in International Journal for the history of Engineering and Technology 72(2) (2009). This issue is disputed by reputable historians; adding the views reported by journalists adds noting to this. I have therefore removed the citation of Express and Star (a local evening newspaper), which does not rank as a WP:RS, at least not when a better source is available. The journal cited was formerly called Transactions of Newcomen Society. Peterkingiron (talk) 21:23, 17 August 2009 (UTC)
