Found this pic recently.
Any idea what kind of trucks these are? Never seen before.

Those look like Allied Full Cushion trucks of the sort used on troop sleepers: viewtopic.php?p=324964#p324964
I have no idea why they are on that boxcar, but I also don't know their origin story or why they were favored for troop sleepers.

I believe several railroads had boxcars with these trucks for express service on passenger trains.

While I don't see a 2nd dangling hose, there is a 2nd air pipe which could be for a passenger train's communicating whistle.

Those are Type 66 Allied Full Cushion trucks on CB&Q XM-32 boxcar 30050. The first one hundred of these cars were built in the "Q"'s Havelock, NE, shops in Nov and Dec 1940. 30000 - 30049 were also equipped with steam and signal lines for passenger service. The second fifty cars were not equipped with steam and signal lines. A later run of the same type of car, 31000 - 31099, also came "shod" with the same trucks and all one hundred of those cars carried steam and signal lines. The ones equipped for passenger service were painted Pullman green as opposed to mineral red for the freight only cars. After WWII, the CB&Q purchased a number of former Army kitchen cars/troop sleepers which were converted for headend service on passenger trains and the 150 boxcars were stripped of their steam and signal lines and repainted into red during 1947-48. All two hundred cars retained the Type 66 trucks until they were outlawed and were mostly replaced with Type 65 or 67 trucks.

Boxcars were common on M&E trains -- which were often among the physically fastest trains operated on particular railroads.

The Allied Full Cushion was an attempt to combine the advantages of the wing-box (see the "Napoleon Hat" passenger trucks) principle of individually-sprung low-mass primary springing, and the use of a swing-hanger bolster for better lateral control, with the constructional advantages of a three-piece freight truck. As I recall, the 'Achilles heel' of the design was in the castings between the bolster and sideframes; they were prone to cracking with age, which was impossible to detect without disassembling the truck, and when they failed they would promptly release the sideframe from the bolster, resulting in lozenging and prompt derailment with no advance warning.

The principal 'riding advantage' of the trucks when sprung for freight load was probably in the lateral compliance (compared to pre-Chrysler/Symington 'high speed' three-piece trucks). This reminds me of when a college roommate (who was trying to impress us with his worldliness in 'riding the rods' as a teenager) said he couldn't understand what the big deal about those Hydra-Cushion boxcars was: he thought they rode no better than any other kind of boxcar...

Additional info on this type of truck from a while back.

http://www.rypn.org/forums/viewtopic.php?f=1&t=22665

JR

Interesting, I've always wondered why Allied Full Cushion trucks were used on troop sleepers, it seems fairly obvious that those one-piece cast sideframes would have problems. Why not use the very sturdy standard two-axle passenger trucks such as REA used on their express boxcars instead? I can only guess that whoever made Allied Full Cushion trucks had good salesmen.