Ten speed fixie?

[Cooper Dogbert allstar]

So I am torn between how much i love riding fixie and how physically exerting it is to haul ass. This brought me to an idea of taking a ten speed cassette and some how disengaging it's free wheel, making it a fixed cassette. My question is: is this possible, if so how can i do this?

[nfmisso]

not possible because you need some sort of gear change / tensioning system like a derailleur which would get wrapped up (major disaster) with a fixie.

It MIGHT be possible with an internal gear hub......

[DaveM]

3 speed fixed hub:
http://www.sturmey-archer.com/products/hubs/cid/3/id/47

To answer your specific question. It is probably possible to "lock" the ratchet in the freehub, but it won't work. If you tried to put back force on the pedals the chain would either slip off the cassette or cause havoc with your derailleur. For a fix to work like a fix, the chain can't have a spring type tensioner (i.e. derailleur), but you do need that for multi-speed drivetrains.