On 27/07/2011 09:20, Andy Breen wrote:
OK. Hypothesis. The Wylam engines and the Killingworth engines
operated on short runs - 2-3 miles maximum. Could it be that
for such short runs the practice was to put a certain amount
of water in the boiler at the start (one known from experience
to be 'what she went well with'), then top up again at the end
of the run?

Sounds a practical answer.

On the S&D (Locomotion) the runs were much longer, so something
was needed to allow the crew to check boiler levels en route
- thus the two try-cocks.
Presumably something better still was thought necessary for the
higher speeds and longer continuous runs that Rocket and her kin
would have to do, so the gauge-glass was introduced (there may
also have been worries about the multi-tube boiler being more
vunerable to water level issues).
I still can't figure out why Rocket has the two try-cocks at the
chimney end and only one at the back, though...

If she had a gauge glass from nearly new perhaps the single try-cock at
the back was an auxiliary fitting. The two at the front may have been
there for maintainence purposes (a quick check of the water level when
filling up at the start of the day or something.

--
Graeme Wall
This account not read, substitute trains for rail.
Railway Miscellany at www.greywall.demon.co.uk/rail