I am going to post three of my Harriman ten wheelers. I have four, all in 17/64 scale. The first is a T-31, with 69" drivers and a tiny heart pump motor in the firebox. It can pull maybe four cars. The other three are tender drive, and they can pull anything they can hook to. You can see the narrow firebox quite well in all my photos - ten wheelers in general are not well suited to in-boiler motors. You should see what PSC had to do with their gorgeous, but fragile, T-28.
I may have the SP designations wrong - now and then I look them up - but T-28 is a 63" drivered all purpose locomotive, and some had Walschaerts gear, but not all. The archetype is Varney's HO ten-wheeler, which is sort of Harriman, but with a wider firebox. Herewith:
