They’re fairly cheap. They’re plentiful. And they’re simply a bit too big to look good on R-1 and R-2 curves.
The Bachmann “Big Hauler” 4-6-0 is probably the most common US outline locomotive in the LS hobby. The later drives are fairly sturdy. But the size simply overwhelms many smaller layouts. However, with some work, combining it with readily available NoS (new old stock) Delton c-16 parts off ‘the Bay’, it can be remade into a rather good looking Mogul for much less than the cost of a ratty used LGB one!
I had a 5th generation one from a set. It had nearly no run time, but it got dropped… twice. The second time was a tumble from a high shelf - destroying the cab and breaking off many detail parts. Thus it became a perfect candidate for a bash… too good to junk, but too messed up to repair.
The first step was to take off the superstructure… lots of screws, some not in very obvious places. This is also a good time to remove any details that you may wish to re-use (like the gauge cluster, sand dome, bell and headlight). Snack size baggies are great for keeping track of the tiny fiddly bits, while pill bottles work great for screws. Removing the rods, monkey motion (Walshaerts gear) and crosshead guides at this time is a good idea as well - to help prevent damage to them.
The next step makes a big mess, so don’t try it in the livingroom! A reinforced cutoff disc in a dremel is probably about the best way to cut away the lower boiler parts cast into the chassis. You need to shorten it quite a bit to look right with the smaller boiler and cab. I took an inch off the rear overhang. It’s just plastic, air and the sound switch board there. I then relocated the cylinders rearward and shortened the pilot a bunch. I used Marine (UV resistant) Goop and a several of the salvaged screws to reassemble everything at the length I wanted. I also used some plastic pipe (3/4") to make the cylinders appear larger.