Looking for info re: retarder brake systems for rail

[tomikawaTT]

There is a patented system (US Pat. 3938646) for spraying a 10/1 water-oil emulsion on the car wheels to (allegedly) quiet the squeal of the retarder with negligible effect on brake action.  Whether any railroad has actually installed this gizmo, deponent saith not.

Chuck

[theothersiberia]

As noted in the subject I am trying to gather information about the retarders used to control cars on gravity humps. It would seem to me there may be new technology "out there" that could quiet the resonance of these breaks during operations. Any input, direction or advice on how to locate information about any new technology or current manufacturers of retarder systems would be appreciated! Thanks in advance. Joe