On Jul 21, 2:51*pm, Andy Breen wrote:
On Fri, 15 Jul 2011 15:17:08 +0100, John Williamson wrote:
As far as I know, locomotives all had wrought iron boiler barrels from
the earliest days, with stationary engines using cast iron for parts of
theirs. Then again, early stationary engines normally ran at a maximum
of about 3 or 4 psi.

This set me off thinking and doing some reading up, and that's prompted
a couple of ideas..

Pre-1815 locomotives seem to divide pretty evenly between those with
cast iron and wrought iron boilers (with quite a few undetermined..).

* denotes locomotives built by well-established foundaries or engine-builders
with foundaries, # engines built by local workshops (e.g. colliery workshops)

Cast:
1802-03 Richardson Coalbrookdale machine (completion doubtful)*
1804 Trevithick Pen-y-Darren machine*
1805 Trevithick/Steele/Whinfield Gateshead machine*
1808 Trevithick Catch-Me-Who-Can*
1812-14 Blenkinsop/Murray machines at Middleton (first 3, certainly)*
1813 Hedley 'Black Billy' at Wylam# (boiler*)
1814-15 Blenkinsop/Murray machines in Prussia*

Wrought:
1813 Brunton engine at Crich*
1814 Blenkinsop/Murray machines at Wigan (built by Daglish, Haigh Foundary)*?
1814-16 Chapman Whitehaven locomotive#
1814 Chapman Wallsend locomotive#
1814-16 Hedley 2-cyl locomotives at Wylam#
1815 Stephenson locomotives (chain-coupled)#
1814-15 Brunton locomotive at Newbottle #?

Plus a lot of 'uncatagorised', though the only one of those built by
a major foundary seems to be the 1813 Chapman chain engine for Heaton,
built by Butterley.

With the exception of the Brunton engine at Crich and the Wigan Blenkinsops
(by Butterley and Haigh Foundary respectively), the wrought iron boilers
seem to mainly be the products of local workshops. The only country-built
machine that used a cast boiler was the first Wylam engine ('Black Billy')
- and that boiler was bought in (along with much of the machinery).

Hypothesis: in the early days of locomotive building cast iron was the
preferred material for boilers, but only a limited number of companies
could manufacture such large and complex items. As larger wrought iron
plates became available it became easier for colliery workshops and smaller
local foundaries to build boilers from wrought iron, avoiding buying in
large and expensive items from outside.
The emergence of George Stephenson as the dominant figure in railway practice
from 1816 established the use of wrought iron boilers (as in the Stephenson
standard locomotive) as the norm.

The hypothesis seems to fit available evidence, and oddly I've not seen it
suggested before. Have I missed anything obvious (e.g. actual costings..)..
Thoughts/comments welcome..

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

You would still need some means of bending and forming flanges etc in
the plate.