16 years ago
seen before: actually two. There was a short train of gondolas filled
with bundles of ties, obviously for a tie-replacement project, pulled by
a hi-rail big-rig tractor. I'd seen hi-rail pickups, but not big ones
like this. With the fore and aft "training wheels", this thing was
essentially a 2-6-2 locomotive, with 3 big ol' tires on each side riding
on the rails.
The other interesting thing was the tie picker-upper. Not sure exactly
what to call it: it straddled a gondola (or more than one--read on), and
was otherwise a standard maneuverable loader with a claw to pick up the
tie bundles. But the really kewl thing was that this thing could
actually "walk" itself from one car to the next, using a
cleverly-designed double frame; the two sections of the frame could be
independently attached to the side of the car or not, and they slid past
each other as well as riding up or down. (The outside anchors on one
frame were labeled "W" and the inside ones labeled "C".) When I first
saw it it was halfway on one car and halfway on another, and I got to
see the guy move it, kind of like a crab, onto one car.
I was going to say that this could be an interesting modeling project,
but it sounds more like something you'd expect to find readymade from
Kibri or similar. Although maybe you could adapt a Cat?