Hello! I need help

[AWindyDay]

Hi to everyone!

I don't really know much about trains, but I'm writing a story (probably get this a lot in here, huh?) and trains play a big part in it. One of my protagonists is basically on a train travelling for half their story.

I'm hoping to learn what I need here, but to be honest I don't understand most of what's in here haha. I feel dumb just from reading the threads.
It would be really helpful if someone answered this question for me: what kind of replaceable parts does a 19th century~ train need to work?

Looking forward to learn more! Thanks everyone!

[boilersuit]

I think we need a bit more to go on here, AWindyDay! Obviously there are many thousands of component parts to any train. Trying to read between the lines, are you asking if there are parts can easily be removed from a train to stop it running?

[D.O.G.F.A.N.]

Have a look at Riley & Son (e) web page and in particular to the work carried out on loco 44871 in years gone by.Gives an idea of what goes on in a restoration project.Although this was the 20th century I imagine the same applied to the period you are looking at.
Stuart

[Grosvenor]

The first question that needs an answer is do you mean a train or the locomotive. Following on from that do you mean normally replaced on shed or at overhaul. For a train the most likely components are brake blocks. For a locomotive brake blocks and firebars come to mind as things that can easily be replaced on shed when the loco is stopped and out of steam.
Almost all parts of a Victorian train or locomotive could be replaced but very few needed replacement between visits to the works. Other components could be reworked while the loco was stopped. Axle boxes and bearings could be re-metalled on shed and firetubes in the boiler could also be replaced. The only thing that I can think of that could be replaced while running would be the water level gauge glass.
To provide a more comprehensive answer a little more info is needed.

[AWindyDay]

Thank you everyone for your helpful answers! This community seems really nice!

The kind of train I'm thinking of is a cargo train used to transport all kinds of goods, not sure if it's a train or a locomotive.
The parts I was talking about are ones that can be replaced (for example in the engine) if they stop working, when the train is stopped. Not sure if this is very helpful in better understanding my vision.

I think you've given me something to work with! Thank you all again for sharing you knowledge with me!