Originally Posted by
rnt654
I'm interested in making a expanding seat post. what would be better cause I've seen a couple online like this one
http://www.flickr.com/photos/kirkohly/5325360365/ 
It doesn't need to be as fancy it could be a seat post without a build in clamp. If you have some pictures and some directions in would really appreciate it.
my gut instinct is to say the sliding type quill that you linked to in a previous post would be better, but that is an unqualified statement with no evidence to back it up. Of course, the expanding type will be easier to fabricate. I have no pictures as I have never built one. If you have any experience running a metal lathe I can write up a procedure that will make you an expander plug. Then again, if you had access to a lathe this whole thing would be trivial because the part is so simple.
If you have a correctly sized seat post already, and a set of calipers, you can head to a local machine shop and have them make a tapered plug. This may cost much more than you spent on the frame so be warned. I may be headed into the university machine shop in the next few weeks to make some parts for a project at work. If you can get me the inner diameter and outer diameter of a properly sized seat post I will see if I can dig up some scrap stock and make the part when I get there.