I am thinking of designing a motorized lathe tool which would consist
of a router with a long shaft attachment...say 3-4 feet long. My idea
would be to weld up a fixture from pipe and flanges that would have
recesses for bearings at both ends for an inner spinning shaft, bolt it
to the router on its faceplate, and put a second router chuck at the
working end.

I find that cutting large burls down to round, especially the huge ones
with irregular surfaces, is really time consuming with a chain saw, and
it's often very hard to determine where the smallest circle that takes
me down to existing surfaces will be.

Furthermore, when I'm working with really really large pieces on
outboard, it's very scary and slow to hog out the inside of a gnarly
piece of olive or carob which has irregular surface and natural edge,
and it's nearly impossible to hog out the inside of a huge bowl with a
chainsaw. I can only really take off small bits that way. I think a
light cut with a router bit will be cleaner and faster and safer.

Has anyone here done something like this already?