I have now added the front of the boiler, and started texturing and detailing the mechanical parts.
I’ve done a bit more work on this. More boiler panels have been added, along with some details along the side. I had to lower the boiler a touch and change the diameter as it goes further back.
How do you decide about number of poles on round objects? I notice that at least one conrod end is hexagonal, were they designed like that or are you saving verts for bevels?
BTW looks great!
It depends on the size/importance of the object really. I’ll normall try setting to low poly e.g. 12 verts, then add sub-surf if it bothers me as I progress (in fact the hexagonal part I think you’re refering to - I’ve already add sub-surf too). I may have to turn off the sub-surf modifier on some objects when it comes to rendering later though, if the poly count gets too high
An Classic i like it 
5/5
Nice work so far, keep it up
Arrgh, I was going to model a train (Flying Scotsman) but after looking at this, I’m not sure I can get anywhere near this level of detail and quality. Great work so far. You’re getting to the point where you can see the light at the end of the tunnel (and it IS a train). Can’t wait to see the finished result.