This hub does indeed require a special freewheel. It was made by Regina and utilized a splined gear that fit over a matching splined hub. This gear was the achilles heal of the bivalent system. There were many complaints of the fine teeth of the spline actually stripping out, causing the freewheel to spin. If you happen to find a freewwheel be sure to check the spline teeth for wear. If you're lucky, you'll find a good one.
Ken denny Boston
>From: "David Goerndt" <email@example.com>
>Subject: [CR]Bivalent hubs
>Date: Sat, 17 Feb 2001 10:23:32 -0500
>I had a question about Cinelli's Bivalent hubs. Does using these hubs
>require a special freewheel or will generic freewheels work?