Many months ago (OK, it was probably well over a year ago) I posted an inquiry about a self-securing, or expander seat post for a frame that has no binder ears or clamp area. The frameset, although it bears the names Schwinn and Paramount, is completely off topic I think (Aluminum), even though I bought it at the Cirque auction in about 2004 or 2005. But the solution that we created is potentially helpful to others with any similar but on-topic frame. In addition, before creating what was needed, we happened to find a previously modified Nuovo Record post, which is 100% on-topic.
Well now, I have finally taken photos to document both self-securing seat posts, and posted them to Wool Jersey for education and the greater good: <http://www.wooljersey.com/gallery/fujifish1/VintStuf/Parts/Campagnolo/Exp andSeatPost/>
The Nuovo Record post: In photo 2, you can clearly see vertically sliced sections of aluminum tube (perhaps taken from another post) that are held together by spring clips ... kinda similar to the Campagnolo bar end shifter internals. At the bottom of this, there appears to be the nut side of some misc. quick release skewer, acting as an expander "cone", like in a stem.
In photo 3, you can see that a hole was drilled through the side of the post, in order to install an Allen head driven, internal cam. Neat and clean, I'd say.
In photo 4, you can see the other side of the cam bolt, secured by a nut. Thus, the cam hole passes laterally, all the way through the shaft. To install, simply insert post, and rotate the cam bolt to the "tight" position. The "cone" pulls up, and spreads the aluminum pieces into the inner walls of the post shaft.
The off-topic seatpost: Although we found the cool Campag piece just described, it does not fit the seat tube in question, so we had to get creative, and this is perhaps something that can be done for an on-topic bike. We took cues from the Record post to get started, but did not employ the cam mechanism, opting for the easier to make top nut design.
In photo 2, you can see the bottom of the black post, with opposing slits cut through it with a hack saw (only one, rough looking slit is visible). There, you can also see two nuts tightened to one another just below an actual stem expander cone. Not visible is another bolt or two tightened in the same way, just above the cone, in order to hold it all fast in place on a threaded rod that passes through the post. Finally, you can just see the edge of a "reducer insert", that narrows the ID of the post enough for the cone to work properly. We were lucky to find that one particular old stem quill, happened to fit perfectly and snug inside the seatpost shaft. The stem quill was cut long enough so that we could cut expansion slits into it too. We cleaned the parts very thoroughly of all grease and dirt, applied some glue, and shoved the stem quill into the seatpost shaft, making sure that the slits lined up, IIRC.
In photos 3 & 4, you can see the securing nut at the top of the seatpost. We drilled a hole there in order to have the threaded rod come through.
To install, insert the shaft onto the seat tube, and tighten the top nut to draw up the cone, until secure. The pieces fit so well together, that we think the glue will be enough, especially as it seemed the ID of the post grew a bit narrower as the stem quill went in, making it more difficult to get it in the last bit. If the internals slide, we will just add a set screw somewhere near the bottom of the post, and file off to flush. The limitation to our design, is that in removal, it will likely be necessary to first remove the saddle, in order to hit the cone out of position, just like removing a quill stem. Installation will be easier though, as a wrench can do the tightening while the saddle is mounted.
I hope I wasn't too wordy, and that this will be helpful to others in the future...
Ciao,
Mark Agree
Southfield MI USA