To take care of chainline & tension on bikes with vertical dropouts?

The answer is no, though there will be plenty of reading-impaired people who will suggest you the ENO eccentric.

Having used an eccentric hub from the abovementioned company (of course, it's not a cassette hub), and having disassembled it to correct a bug introduced during fabrication, I have to say that it's a bad idea. The ENO hubs are shiny but badly fabricated (high tolerances) with cheap and crappy bearings. Hugely overpriced.
It would be much better if you would just change the dropouts to horizontal or track, if you are so attached to that frame.

Oh well, That's what I thought but was hoping someone would chime in with some little-known company from Slovenia or somewhere that made one.
Damn tensioner & spacers.

Are you talking about the cassette spacers? Don't you like them?

for sure if I went SS I'd use a freehub.

Well I don't necessarily want a cassette hub. I just wanted a hub that would correct both the chainline and tension on a bike with vertical dropouts and a track crank. If there was one....

A freehub with spacers allows for very easy chainline adjustment, that's true, but with a bit of patience you can adjust chainline also with a SS/track hub.

But I would STRONGLY DISCOURAGE you from trying to use a vertical dropout bike for SS/FG. You're doing too many compromises for no good reason. Either get a frame with track/horizontal dropouts, or replace your current dropouts - and then USE ANY DAMN WHEEL YOU LIKE.

Yeah, I am planning on using one. Was just hoping for one that also fixed tension. I guess I was dreaming.

Yes absolutely, but the OP said "damn tensioners and spacers", hence my surprise.

Well, Horizontal dropouts would be nice but that's the bike I have. I bought a new Cyclocross bike and decided to convert my old 1993 Giant Iguana into a SS townie bike. I already stripped and repainted the frame, so I am not cutting and welding the dropouts at this point. Just ain't gonna happen.
That said, a cassette hub with spacers will give me exact chainline and half links/ magic gear will hopefully get me close on tension- otherwise a singleator...
And then I can still use any damn wheel I like. I was just hoping for an all-in-one solution.

I misread

Magic gears don't work. They work for the first 50-100 Km, and then your chain will be hopelessly loose. And that's if the magic gear thing was done right. If it was not, your chain will be hopelessly loose at 0 Km.

But, it's good that you do understand the importance of being able to use any damn wheel you like. Flexibility is often underrated.

would you like to try the sheldon method?

use a hub with hollow axles, one that works with a QR, and chop the axle so that it sits flush with the lock nuts.
now, instead of the axle sitting in the dropout, you have the skewer sitting in the dropout, giving you more room to work with.

and if that doesn't give you enough room, which it should, then you can file some slots into the dropout if the dropout has enough material.

be sure to use a shimano or campagnolo skewer.

For singlespeed, chain tension isn't as big a deal. I think you'll be OK. Get a cassette hub and a couple of used cassettes. That way you'll have a number of cogs to choose from and plenty of spacers. Try and find a magic gear from those. The chain will become slightly more slack after a year or so, but it shouldn't be a big deal. If you had a couple chainrings to try (was your crank originally a double?) that would help. I'd start with the small ring and the 13T or 14T cog.

Yeah, That's what I was going to do. It isn't going to be a fixie.. just for riding around my town, to the supermarket etc. And if the chain does get too loose I'll bolt on a tensioner until maybe it eventually gets loose enough to fit another half-link. I'd really rather not have a tensioner though. It sucks to finally remove that clunky dérailleur just put something on that looks just like a dérailleur again.

Also, Thanks AEO,
I read about Sheldon's skewer method, but to be honest I would still be nervous about that. I'm afraid I would end up on that "MS paint your mishaps" thread..

And, wroomroomopps, Of course magic gears work. It's bloody magic, mate.

Hahah! Ok, well, talk to you in a week or two.

Take a pic of your bike before and after - for maximum effect (read: shame & disappointment).

Careful. You might find some people are overly-sensitive.

well, if you're building a wheel with the ENO hub, said wheel would not have any dish so chainline tweaking would be applied at the chainring/bb...

You're mostly right. You can do a bit of tweaking by adding a spacer before threading on the freewheel onto the hub, but that will get you only a mm or two. Which makes the OPs need for a freehub all the more understandable.