stone wrote:

I want to make a pipe pole with larger diameter pipe
on the bottom and with a smaller diameter on top.

Is there a way to weld something like this together?

The only way I could think of was to have the smaller
diameter pipe run the entire length and use some sort
of bushing at both ends of the larger diameter. Making
the welds there.

No sliding, right? Then why not just slide the smaller pole into
the larger pole for as long as you figure you need to, and weld up
a lap joint right around the smaller pipe at the joint? Ideally,
you can find some pipe that just barely doesn't fit into the larger
size (e.g. 3/4" pipe that won't quite fit into 1" pipe, both sch 40)
and you can grind a flat on the 3/4" pipe to fit over the weld and
make it just go in, then it will be pretty tight. If you got a 3/4"
pipe to go in say 6" then it won't be any less resistant to crumpling
in cantilever than it would be if it were completely inside the bigger
pipe. (This just from intuition) - GWE