Guy Yinon

I'm thinking about online buying a frame that utilizes adjustable rohloff oem dropouts (aka sliding dropouts).
I'm not thinking about buying a Rohloff hub but might consider alfine hub or even better, a dingle speed.
The adjustable distance that the dropouts can move looks quite small ...I'm not sure that its less than 1cm.
Can it still use single speed hub w/o tensioner?

Andrew R Stewart 

Generally just over a 1/2" of adjustment is needed as that's what the chain length units are. (Assuming a 1/2" pitch is being used which nearly all chain driven bike have these days). There's no reason why an additional chain tensioner can't be used as long as there's no back pedal applied feature (coaster brake as example). I can't remember an adjustable dropout not having at least this range as to have less would be a poor design (excepting when an additional tension changing element like an eccentric BB). If you're running a belt instead of a chain then there's other needs and limits too. Andy

grumpus

You only need a little over 1/4" axle movement if you don't mind using a half link in the chain. I wonder how much tension a ghost ring supports, without the hub it would normally be mounted on - I guess it depends on your choice of chainring.

Andrew R Stewart 

And if it fits around the chainstay... I ran a ghost ring on our tandem's timing chain for a short time but it would "walk out" and fall to the road if we tried to push really hard, there was so much twisting to the frame. Andy

grumpus

Surprising, my assumption would have been that the timing chain is the least demanding place to put a ghost ring. It will remain a fun useful thing that I might try one day.