Courtesy of John Breen one of the most ingenious supports I've Seen John's description...

"Gentlemen, Statement of the problem:

The large diameter duct system is designed to use waste heat (1200 degrees C) by routing it through a turbo expander which turns an electric generator. Obviously the turbo expander is strain sensitive and cannot accomodate much loading at high temperatures. The inlet duct to the turbo expander is stainless steel - 1670 mm OD with 30 mm wall thickness horizontal run with large isolation valves (very rigid duct and the system relies upon expansion joints (hinges and gimbals)for flexibility). The duct entering the turbo expander inlet has two of the very heavy isolation valves nearby and must be supported but it cannot be supported on a roller from below because the radial growth of the duct would cause too high a moment on the expander. So, the heavy duct must be supported at its centerline while also accomodating the axial thermal growth. The duct must be allowed to move axially BUT it cannot change elevation as it moves with expansion - it cannot use rod hangers attached to trunnions at the centerline because it would move up as it expands horizontally.

The solution, the duct is supported at the centerline by a precision cam. The cam pivots on a shaft supported by pillow block bearings. As the duct moves horizontally, it moves the cam. The cam is designed such that the distance from the centerline of the pivot shaft to the moving support point increases exactly enough to keep the centerline of the duct at the same elevation as the duct moves with horizontal expansion. Elegant!

Regards, John "