On Sat, 16 Jul 2011 11:12:48 -0700, harry wrote:

On Jul 16, 1:07Â*pm, Andy Breen wrote:
On Sat, 16 Jul 2011 02:33:21 -0700, Andy Dingley wrote:
On Jul 16, 10:24Â*am, Guy Gorton wrote:

Then again, early stationary engines normally ran at a maximum
of about 3 or 4 psi.

That seems very low.

No, this was the sort of pressure used. Early boiler feedwater wasn't
pumped in, it was fed by a gravity cistern up in the rafters of the
engine shed (it was raised here by the pumping engine itself).

but, as stated, Trevithick used much higher pressures - not least
because his engines did most of their work via steam pressure, not
vacuum)

Filling locomotive boilers against ~50psi pressures in the earlies was
a problem.

chomp

Even after the pet-cock came in and allowed the boiler to be refilled
while the engine was working, hot feed from a kettle to the feed-tank
seems to have been the norm until the bigger and more efficient boilers
introduced by Hackworth (1827 on Royal George) and Stephenson
(1828-1829) came in.

There's a thought on operation: fill the boiler, wait until you have
pressure. Now tie the safety valve hard down, get moving. At the end of
it, release the valve, blow down the boiler and gravity-feed with
boiling water. All with a cast boiler. The Middleton machines worked
like that for over 20 years..


I think some early locomotive had a hand pump for feedwater. Modified
village well pump sort of thing.

They did, but there were still problems with the pump locking. To quote:
"..an incurable defect in the feed-pumps of locomotive engines, for the
pumps could not be made to keep in action, as they were fixed close to
the boiler, and hot water entering from the leaking of the valves, causing
them to be filled with steam instead of water at each stroke; thus preventing
them forcing any water into the boiler.." (W.P. Marshall, writing in 1849
"under the direction of Robert Stephenson", and cite don p.310 of Andy Guy's
paper in Early Railways 4)

The pet-cock, introduced - apparently by George Stephenson - in about 1815
(I mis-recalled above, when I said about 1820) allowed the pump to fill the
boiler without pressure having to be blown down (though pumps were still
regarded as "precarious" as late as 1857 - Templeton)

--
From the Model M of Andy Breen, speaking only for himself