On Fri, 15 Jul 2011 12:19:13 -0700, Andy Dingley wrote:

On Jul 15, 2:39Â*pm, Andy Breen wrote:

As did the Murray/Blenkinsop machines at Middleton (and elsewhere!)

There's a well-known period illustration of a Blenkinsop machine showing
a boiler that's clearly riveted from plates.

Yep. Just checked in the ER procs., and there seems to have been a change in
boiler construction between the first two and later engines at Middleton.
The first engines there certainly had cast boilers (from both illustrations
and contemporary descriptions).

and, IIRC, the Gateshead "Trevithick" and its immediate descendent, the
Wylam 'Black Billy'.

Puffing Billy & Wylam Dilly survived a long time, along with their
wrought iron boilers. I don't know which you mean by the "Gateshead
Trevithick", but none of the Gateshead-built locos have any evidence for
using cast iron.

The 1808 machine ordered(?) by Wylam but never delivered and subsequently
used to drive the foundery blower. Black Billy was the 1813 Wylam machine
- single cylinder and flywheel, possibly built on the 1812/13 test chassis.
Puffing Billy and Wylam Dilly came in 1814, after Black Billy had been
working more or less unsatisfactorily for a while.
Checking the ER procs. suggests that Black Billy may also have had a
wrought iron boiler, so the date for suitable boiler plates becoming
available may be more like 1812-13 than 1813-14.


Presumably plates of a
suitable size got cheap enough somewhere between 1812-13 and 1814-15..

Price didn't change significantly - although everything, and especially
provender or iron goods, became cheaper after Napoleon, hence the number
of cast iron bridges dated 1816. What did happen is that ironmasters
could make _bigger_ plates, allowing the introduction in the mid-1830s
of the "long plate" boiler. This had plates long enough that a whole
boiler barrel could be made of four parallel staves, without the need
for either endwise joints or else very short barrels (as Stephenson used
with Rocket & later).



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