Subject:
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Re: More Thomas Engines: James
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Newsgroups:
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lugnet.trains
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Date:
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Tue, 17 Oct 2000 18:25:26 GMT
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Viewed:
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1950 times
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> > More simple than that - J2 is refering to the steam dome. He's just • confused -
> > not like *that* is anything new!! ;-)
>
> Yes, I was referring to the steam dome, whose function I thought was for super
> heating the steam. I think I may have my vocabulary wrong, but I think I'm • still
> half right (not a half wit;)
OK, quick steam lesson: Unless your name is Abner Doble, you want to put heat
INTO the steam to superheat it :) Best place to do so, is in the flues, or
across the back of the firebox (even better!).
Typical steam engines have smokebox temperatures that are quite bearable by
humans. The temp at the smokebox should NOT get high enough to burn paint
off. If it does, you have flues/tubes that are too big for the boiler (we've
made this mistake with the Live Steamers). However, if you make them too
small, then you strangle the fire (which is a worse mistake, because then you
have a 1000 hrs work boat anchor for a small boat!).
If you pass the steam through a pipe that goes across the back of the fire, it
will pick up heat. This heat will add to the steam's heat. By keeping the
same pressure as the boiler (because it is open at one end to the boiler), and
increasing the temperature, you increase the Energy within the steam to make
it hotter than the steam in the boiler. This is superheating. Works great!
Now, steam domes: From my little handy Thomas the Tank Engine book, James is
based on a N series mogul (2-6-0 built by Woolwich Arsenal, fitted with super
heat from new). Domes are used to rase the collection point of the steam above
the water surface. UK domes were typically small because of low overhead
clearances. If a dome is not fitted, then what will be fitted instead is a dry
pipe, which is a pipe that runs the length of the boiler at the top, fitted
with a large number of small diameter holes. They both help to dry the steam
out before it reaches the superheater (which you want, otherwise you can get
all kinds of weird things happening). Some locos had the superheater after the
throttle, some before. If the superheater is after the throttle, and a slug of
water goes through, then you can end up with the situation that 'Blue Peter"
ran into in about 1995, where you have a uncontrolled slip by a slug of water
passing into the superheater, and then evaporating. Even if you close the
throttle, you still do nothing until the water has boiled.
(BR paid in the order of 100,000 pounds to repair the damage that was done, the
engine needed completly new motion parts, because they all bent, and it was the
BR train driver who was responsible)(BR=British Rail, now no more)
James
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Message has 1 Reply:
 | | Re: More Thomas Engines: James
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| James Powell wrote: <snip the informative lesson on steam which mostly went over my head> (...) The Thomas the Tank Engine website says James is based on a "Hughes Class 28 2-6-0 Superheated tender engine". I'm not too familiar with foreign steam; (...) (24 years ago, 18-Oct-00, to lugnet.trains)
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Message is in Reply To:
| | Re: More Thomas Engines: James
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| (...) Yes, I was referring to the steam dome, whose function I thought was for super heating the steam. I think I may have my vocabulary wrong, but I think I'm still half right (not a half wit;) -John (...) (24 years ago, 17-Oct-00, to lugnet.trains)
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