I've found a few posts on the Early Rail forum...here's a sampling...
" Joe,
I can recommend Page 469 of "The American Railroad Freight Car" John
H. White, Jr., Johns Hopkins University Press.
Tom"
With regard to a wreck on the Colorado Midland...
" Another one upside down with FOX trucks, so probably NYC something or
other" (that was 1903)
Another
" I did a drawing of an Santa Fe (GC&SF) box car that had Fox trucks with
outside hung brakes. This car ended up in M-of-W service and then
became living quarters for track workers at Allensworth CA."
I also found a post mentioning a New England road using flat cars with Fox trucks into the 1970s, although it appears their era was 1890-1910. It was the primary truck of the PRR for 1890-1905
Here's a couple more posts:
" wrote: I have seen pictures of two types of Fox trucks, one with only
coil springs over the journal, and the other with coil springs above
the journals and leaf springs sticking out of the center of the side
frame. I would presume that the latter were to allow some equalizing
function.
The Fox trucks with the blank side panels between the journals have
the truck bolster plate rigidly fastened to the side to side transoms.
The Fox trucks with the leaf springs sticking out the hole in the
center of the sides have a "floating" truck bolster. That is to say,
the truck bolster that directly contacts the underside of the car then
sits on those leaf springs. The bottom of the leaf springs are then
mounted to a plate on the bottom of each side frame. What holds the
bolster in place are the side transoms and straps across the top of
the transoms to keep it (the truck bolster) from popping up when
removed from the car.
This arrangement probably provides a limited amount of side to side
flexibility and some extra cushion and a much improved ride but no
direct equalization per se as one would get using levers and so on as
in a passenger truck.
Actually, from what I've read, neither the Fox nor the various types
of arch bar trucks provided true equalization. However, the sloppy
tolerances and inherent flex in the metal bars of the arch bar design
provided a "practical level" of equalization far superior to the Fox.
Hence the Fox truck was prome to develop stress cracks on the
relatively rough US roadbed which led to its going out of favor.
Bob M."
and
" Yes, Fox Patent trucks would still be in use in 1910. They also lasted on
non revenue cars until those cars were scrapped or sold to logging lines, etc.
The East Branch & Linloln RR in New Hampshire bought old flat cars from the
B&M that had Fox trucks and they were used until the 1970's, on their line,
carrying pulpwood. I thought that I posted a pic of one of these cars."