Converting to Single Speed - Chain Tension

I'm considering converting a geared cross bike to a single speed.  The main hurtle is keeping the chain tensioned correctly.  Bikes with gears have vertical dropouts, which lock the wheel in one place (this is a very good thing).  The chain tension is maintained by a derailleur.

However, when dealing with a single speed, there is no derailleur, so you need a way to keep the chain tight.  In theory, you could get the right chainring/cog size combination such that you could adjust the chain length to the nearest link and have it work perfectly.  In reality, that will never happen.

I was just writing a summary of all the solutions I had (thus far), when I came across the Single Speed FAQ at mtbr.com.  There's no need to reinvent the wheel; you can go straight to this section to review all the chain tension solutions out there.

My favorite:  The Ghost Chainring!  See that extra chainring?  It's wedged in the chain to keep the tension nice and tight.  The top of the chain, of course, moves at the same speed as the bottom, so in theory, it will stay in place.  I've got to try that one.

But really, if you want to do it right, horizontal dropouts are the way to go.  Actually, you want "track ends," which are the type of dropouts you'll see on a track bike. For a retrofit, this would require some welding.  I wouldn't do it with an aluminum frame, but it's doable with steel. This pictorial at 63xc.com sums up what is required.  A frame builder could do this for you, to.  Probably a good idea!

Once you get your chain tension solution figured out, the other biggie to deal with is the rear wheel.  I'll cover that one later.  I've done a lot of that already in converting bikes to fixed gears, so I need to take some pictures in the garage.