Can anyone identify this horn?

[Anonymous]

http://incolor.inetnebr.com/diecastgalore/Trainz/strange_horn.jpg

Hi all: Can anyone out there identify the brand & model of the air horn used by both Great Northern & CB & Q on their U-boats? It is a goofy looking thing, has a big box where the power chambers or manifold would normally be. The link is to a pic of the horn, on a BN unit. Any help appreciated.!

 

[ndbprr]

This is a guess.  I suspect the airlines were susceptible to freezing and thus no horn. It looks to me like a sheet metal housing installed by the railroad to keep the airlines warm enough to keep them from freezing so they can use the horn.  It is an old joke that anything that runs on air comes with a line in the instructions stating, "The customer will supply clean dry plant air".  This puts the onus on the user when the mositure, oil or dirt plugs things up.  Nobody has found a way to make clean dry plant air including railroads.