Early locomotives and "rebuilt as"

I’ve been reading some history books with very early locomotives, and
the phrase “rebuilt as” gets used some.

Here’s a very early example that makes me want to ask something. I
read that Robert Fulton, a 0-4-0 from Britain got rebuilt as John Bull
4-2-0. When I look at the pictures, these are two very different
looking machines!

In a typical case of 19th century “rebuilt as”, what usually got
saved? How did the work get done in the shop? – I mean – was it
all drawn up and signed off (like today) or did some guys with torches
and mallets just go to work?

Sort of puts me in mind of great-grandfathers’ hatchet. Been in this
family for 175 years. Has had 5 new handles and 2 new heads.

John

Same idea as the hatchet. Often it is the boiler that is used in the new rebuilt locomotive. At one point, Canadian Pacific had a number of 3-truck shays for, well, something in the mountains. After a while they decided that the shays were inappropriate and the boilers were used to build the first of the 2-10-0 decapods.

Further examples: Reading T-1’s were rebuilt from 2-8-0’s and any number of IC Paducah rebuilds in the steam era got new wheel arrangements.

NYC&HR 999 was rebuilt with 70" drivers replacing the 86" drivers and was later re-boilered.

I believe in locomotive construction, the frame is considered the locomotive, so if engine 100 came into the shop and had a boiler from another engine put on it, and a new cab, and a new tender, it would still come out as engine 100.

Great Northern 1355 is currently displayed in nonoperating condition in Sioux City Iowa. It is a Baldwin product, delivered by them in 1909 as a 4-6-0. Due to increasing train weights the GN rebuilt all of their locomotives of this class with new boilers and larger fireboxes in their St Paul shops in the 1920’s. They emerged from the rebuild as 4-6-2’s.