All true - but by 1802 cylinder casting (and boring, which was the harder part - early steam engine cylinders were fined to round by hand..) was a much more mature technology (many of the improvements in casting and boring, of course, having been driven by the more demanding specifications for cannon..). It's be fair to say that by 1800 high-quality iron casting of even large cylinders was something that could be done by - at a rough guess -
10+ firms around the UK. Fabrication of large wrought-iron plate structures was at a much earlier stage of development, though things were to change fast in the next 10 years or so.
That's really nitpicking on the terminology. Displacing something by admitting another fluid (or gas, or vapour) is often referred to as "flushing"..
There were various methods of operating valves automatically from a fairly early stage, but most of them seem to have required coughing up patent royalties. Provided someone cheap (or free..) could be found to operate the valves manually, that was often a better deal for the owner of the engine. A typical arrangement seems to have been for the child of someone working elsewhere in the operation to to the job, either for a /very/ small wage or as part of their father's employment terms. One such childhood valve-operator was George Stephenson.
By the early 1800s operation via strikers (pins on the rods of the engine flipping the valve across) seems to have become the normal method of operation, though presumably a few manually-operated engines would still remain. In the locomotive context, valves operated by strikers can be seen on the two surviving Wylam machines - and in operation on the replica at Beamish:
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that the valves would always need to be worked manually to start the engine or after reversing it. This could be difficult, particulary on a locomotive at night (Jem Stephenson was said to be the only man who could reverse 'Locomotion' on his own at night, though Mike Satow reckoned he could do it with the replica)
The clack valve is - essentially - a non-return valve to stop boiler steam getting back into the feed system, nyet? Presumably the pumps used in early locomotives had non-return valves in them (well, they must have, being intended to push water one way...), but it's clear from Marshall's comments ("hot water entered from the leaking of the valves, causing them (the pumps) to be filled with steam") that they didn't work well enough to keep the pumps at their duty. Given the materials available at the time, it's easy to see how this happened - and given that until then most applications requiring continuous working[1] had been the domain of low-pressure engines, with Trevithick-type[2] high-pressure engines restricted to more intermittent tasks[3] where the boiler could be topped up after each burst of work (pressure having dropped then, anyway..), it's easy to see how the problem hadn't been encountered before. The valves had worked well enough for low- pressure (and stationary!) boilers, after all (actually, the battering taken by the machinery in an unsprung locomotive on short - 3'-4' rails - can't have helped the functioning of the pump valves at all!).
Essentially, if they could have made a really good clack valve, they'd not have had the problem with the pumps locking and the pet-c*ck wouldn't have been needed. As materials available meant they couldn't, the pet-c*ck was a real breakthrough in producing a locomotive which could run more than a very short distance between extended (and madly hazardous!) stops.
vacuum.http://en.wikipedia.org/wiki/Atmospheric_engine>>>> >> FFS! Don't believe _anything_ on Wikipedia!
"Flushing" is generally the deliberate rather than consequential purging of a substance from somewhere. If you are referring to the animation at the top of the above Wonkypaedia article then no such process is shown but if any does take place then it will (except at startup) be "expired" steam that is flushed rather than air.
Opening a valve to admit steam to the cylinder seems deliberate enough to me.
It's fairly clear from his own writings that Mr Savery was of the same opinion:
"Then skrew in the faid pipes again as tight as possible. Then lightthe fire at B No.1. When the water in L boyles, the handle of the regulator mark'd Z, must be thrust from you as far as it will go, which makes all the steam rifting from the water in L, pass with irriftible force through O No.1 into P No.1 pushing out all the air before it, through the clack R No.1 making a noise as it goes."
'The Miner's Friend, or, An Engine To Raise Water By Fire', Thomas Savery, S. Crouch, 1702, available on-line at:
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me, that implies a very deliberate use of the steam to flush out the air in the working vessel..
That device looks distinctly different to the one in the Wikipaedia article. Rather than using a piston it seems to use alternative positive and negative pressure (relative to atmosphere) in a vessel with valves arranged so that water is sucked in from below then discharged up to the surface. As often occurs, older descriptions can be somewhat simplistic; the purpose is clearly to propel water while any propulsion of air is consequential to some being present but not necessary for the ongoing process.
Yes. Newcomen's engine was essentially a combination of ideas from Papin (piston-in-cylinder) and Savery (use of condensation of steam to create a vacuum to raise water). The working principles, in terms of the use of steam to expel the air from the working vessel and then condensation to provide the working force, however, were the same as Newcomen's machine - a fact recognised by Newcomen himself, as he conceded that his machine was covered by Savery's patent (the small number of Newcomen engines installed before the expiry of Savery's patent was a result of this - the patent royalties made them even more expensive).
The text clearly shows that Savery understood that his engine worked by replacing the air in the working vessel with steam which could then be condensed to create a vacuum, with the latter being used to raise water (exactly the same principle as was adopted to a cylinder/piston and separate boiler by Newcomen).
Maintaining otherwise shows a disregard for primary evidence which surprises me in your case (I'd expect it from Michael, or Bruce in recent years, but not you).
Lower than you think. The beam was usually raised just by the weight of the pump on the other end; the purpose of the steam was just to push the air out. Then the condensation led to a partial vacuum, and the air pressure does all the real work.
You guys really must go to Crofton Beam Engines. When they are in steam, of course!
More assistive than providing 50% or so of the power output, though.
I did think of mentioning the use of condensers to assist the efficiency and output of stationary and marine HP machinery, including turbines, but decided not to as there seemed to be enough confusion about the workings of simple pistons machinery...
The Murray/Blenkinsop machines, one of which was exported to Germany (and another one built there). Both the German examples had cast boilers, as did at least the first pair of machines at Middleton. At least one of the later Middleton machines had a wrought iron boiler. I'm not sure if there is any evidence one way or another for the ones used at Coxlodge, and the Nant-y-Glo machine is distinctly obscure.
Pearce contends that Locomotion underwent a flue tube collapse - much less dramatic - and the boiler barrel explosion was another locomotive of the initial 5 built.
The Brunton machine used at Crich certainly seems to have had a cast boiler. The second(?) one may well have done so before being reboilered.
The Bye paper makes it quite clear that the first three machines at Middleton (at least) had cast boilers. The fourth one differed in a number of ways and /may/ have had a wrought-iron boiler, but this cannot be confirmed from surviving information. The machines built for the Orrell Colliery at Wigan did have wrought boilers. Nothing known either way about the Nant-y-Glo machine, and the later Kenton and Coxlodge machines, at least, differed in dimensions from the Leeds engines (and perhaps also in construction?) - Bye, ER2; Guy, ER1 (Coxlodge only).
The Blenkinsop machine built in Berlin for the ironworks at Chorzow had a cast boiler - made in two halves and bolted together (details in Dusseldorf archive). The second - also Berlin-built - machine of the same type, for Saarland, also had a cast boiler (Clarke, ER1). No details are given for the Blenkinsop machine built for Leige.
Not from the beginning. The Winfield/Steele 'Gateshead' engine of 1805 had a cast boiler, as did Hedley's first machine of 1812-13 ('Black Billy', built on the manually-operated test chassis). To quote Hedley: "An engine was then constructed, the boiler was of cast iron" (William Hedley, letter to the Newcastle press on 10 December 1836, cited in Crompton, ER2). The later 2-cylinder engines had wrought iron boilers.
Chapman seems to have used wrought iron boilers from the outset. That would include the Whitehaven machine of 1812, though the putative Swainson 'Trevithick' of 1808 may have used a cast boiler - if it existed!
I made a mistake here. The Crich machine is described by Guy (ER1) as having a wrought iron boiler. Given that Brunton made a great point of the novel construction of this boiler (claimed to be safe to 400-500 psi) it is reasonable to assume that the Newbottle machine, in both original and modified form, used a wrought iron boiler too.
Stephenson was pretty good at covering the traces of his first two(?) - unsatisfactory and probably derivative - geared-drive engines, but in view of the parallels between these machines and Chapman's work wrought iron is likely. 1814 seems late for a cast iron boiler in a British-built locomotive anyway.
Indeed so. Some low pressure turbine casings include a special explosion vent comprising a thin metal sheet normally sucked onto a mesh frame, with a sharp spike poised above it. If pressure becomes positive, the metal bulges and is pierced by the spike to vent to atmosphere. I remember working on the control relays which, as vacuum fell, opened the turbine hall roof vents, so that the anticipated blast didn't take all the windows out.
time to time. My recollection is that they were built as Watt engines (negligible boiler pressure) but converted to work on the "Cornish Cycle" (using Trevithick's strong steam) later-ish in life.
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