Yup, some older "wooden" coasters, like Coney Island's Cyclone, use steel supports.
It's still a "wood" coaster because it's the same laminated wood track with steel rail contruction on top of those steel beams.
Heck, LOTS of wood coasters use steel in key parts. Even Thunderbolt at Kennywood has at least one I-beam (where they cut into the structure to allow Phantom to pass under it)
It's apparently more expensive to build, but easier and cheaper to maintain long-term.
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--Greg
http://www.pobox.com/~gregleg/