On Jul 15, 2:12*pm, Andy Breen wrote:

Except there were. Only in the early days, I'd admit, but the first
commercially successful locomotives (and the first locomotives to
be built as more than prototypes, and the first exported..) had
cast-iron boilers.

Which ones? Most of Trevithick's had cast iron shells (still with a
wrought iron endplate), but I can't think of any others, or of any
"first exports" (which one?) that were cast iron. Certainly the
Tyneside builders were using wrought iron from the outset - although
they still managed to have boiler explosions, including Locomotion
itself.

There is some possibility that Brunton's Mechanical Traveller (the one
with the walking legs) was built with a cast boiler, but it had been
fitted with a wrought iron boiler just before it was destroyed by a
boiler explosion.