there was a british single-speed freewheel that would do this - basically, it was a freewheel that had these pins that you could engage remotely (via cable) which would lock the 2 pieces together to make it a fixed "cog".
ive ridden a bike with one, and it seemed to work reasonably well, but frankly, felt a little sketchy. engaging the locking pins felt a little dodgy. i certainly wouldnt trust it for any heavy usage. the trick is how to smoothly engage the locking mechanism.
for the life of me, though, i cant remember the manufacturers name...
-joel
>Has any manufacturer ever constructed a combination fixed rear hub
>that can also turn into a freewheeling single speed rear hub with
>handlebar type activation? This goes back to a conversation with a
>local that supported the value of such an animal. You would have the
>efficiency of a fixed, but at a moment's touch you could also
>freewheel down a hill or freewheel in traffic making caliper brakes
>easier to judge. I thought that such a device might have been
>designed at one time or another due to how simple it would have been
>to engineer, but I could not recall a discussion of it in any book
>or forum.
>
>Garth Libre in Miami Fl.
>_______________________________________________
--
joel metz : magpie@blackbirdsf.org : http://www.blackbirdsf.org/
bike messengers worldwide : ifbma : http://www.messengers.org/
portland, oregon
==
i know what innocence looks like - and it wasn't there,
after she got that bicycle...