On Mon, 25 Jul 2011 19:40:31 +0000, Andy Breen wrote:
On Mon, 25 Jul 2011 11:54:33 -0700, harry wrote:
On Jul 25, 10:53Â*am, Andy Dingley wrote:
On Jul 25, 6:27Â*am, harry wrote:
No-one in their right mind is going to lose sight of the water
level.
A wise idea - mostly because it's very hard to tell if a gauge glass
is full of water or steam, once you've lost sight of the level -
especially on the LMS, where the gauge cocks were linked to a single
handle, so you couldn't blow one at a time.
If you look at a guage glass it has diagonal stripes behind it.
If the glass is full of water they are refracted to the horizontal as
seen through te sight glass.
If the glass is full of steam, they remain diagonal. So you know
whether the water level is above or below the glass.
snip..
There are three cocks to every guage glass. Steam side and water side
to isolate the fitting if the glass breaks and drain to blow down each
leg separately so as to prevent blockages and rings forming on the
glass. There are min. two gauge glasses on ever boiler for redundancy/
camparison reasons
They are all fitted with safety glasses too.
So - what would be the recommended operating method for an early
locomotive with no gauge glasses (and no feed pump - Middleton, early
Chapman engines - or one which might or might not work - Trevithick,
Wylam, Killingworth..)?
Illustration: there's a picture of the preserved 'Locomotion' at
Darlington North Road taken in July 2008, showing the back of the
boiler (fire-hole end) and what I'm pretty sure is the driving side
of the engine. As you can see - no gauge glass, neither for fireman
nor driver (the feed pump and pet-cock to bleed the pump are low on
the back of the boiler, out of shot in this). There is a drain-cock on
the back of the boiler which I would guess was used to estimate water level
- if all you get out is water the level is too high, if all that comes out
is steam it's too low, if you get a sputtering mix it's right?
I need to go back to the texts and see if anyone mentions how it was used,
but if you have any ideas from experience of more recent boilers it'd be
much appreciated.
http://users.aber.ac.uk/azb/images/locomotion.jpg
Locomotion, as it survives, seems to have an original (or at least early)
boiler shell, and its condition is essentially that after an early restoration
to running-on-rails status after retirement as a stationary engine in 1850.
It seems likely that it was working without a gauge glass of any sort when it
ceased work (plausible, given what's known of practice at the time).
The 1845 Derwent locomotive, as preserved, has a gauge glass, but it looks
very much like one crudely retro-fitted:
http://users.aber.ac.uk/azb/images/derwent.jpg
Given that Derwent was working regularly until 1898, and was restored to run
under its own steam in 1925, retro-fitting of a gauge glass somewhere in
its later life is very likely.
--
From the Model M of Andy Breen, speaking only for himself