Yup ... (2) chainring and (1) cog.
"Why?" ... just to have one.
... nah, it gives me the ability to have a SS with a granny gear as well. One of the main places I ride ... some of the climbs are a bit too steep for the typical SS gearing (at least for me) ... that's were the granny gear comes in.
A Paul's Melvin rear tensioner. (bolts onto you derailleur hanger) ... Invalid Link Removed
It's made to retrofit multi-speed frames to singlecogs. It's made to be used for a SS or (2x1) (since it allows for a 20T difference).
I know about the tensioners, I have one on my Retrotec(vertical dropouts)- I was unaware they were capable of taking up enough slack to run multiple rings. On that note, I'm guessing you'll run a garden-variety front derailleur & shifter..?
Lastly- just to be picky- a 2/3x1 is not really a SS, now is it?

Again- no disrespect meant- ride what you like, I just like talking bike(s).

