I've got a number of frames hanging in the garage and was wondering if I could do something like the Rivendell Quickbeam. The QB uses a road double crank with a cog to give you two speeds; four if you flip the rear wheel.

I wondered how good the chainline was with that setup; probably good enough or Rivendell would've not put it on the market.

Then I see the Surly Dingle cogs and thought; what if I used one of those with a road double crank and gave myself four possible gears without even flipping the rear wheel.

I am thinking of using a Sugino RD crank with a 48 outer ring and either 46 or 44 inside ring. Then putting a 17-19 or 17-20 Dingle on the rear wheel. Going inner ring to inner cog or outer ring to outer cog should still give me a straight chainline but what about outer ring to inner cog or vice versa?

I think chainlength/dropout length is a bigger issue than chainline

Forget chainline issues. You dropouts won't be long enough to handle the difference if you cross chain.

Trial and error.
Go for it. Post pictures.

Trial and error is my middle name. So be it!

Pictures will follow.

I don't think you'd actually use a Dingle / Double Crank set up for spur of the moment changes, like riding along and suddenly thinking "Gee, maybe I'll stop and go from big/small to small/big".

The Dingle is sized so the jump is on the order of a 1/4" change in chain length if I remember correctly.

If your riding in a scenario where you'd actually contemplate that radical a change, say on tour, then carrying a chain-breaker isn't an unrealistic expectation. Or an entire chain sized appropriately.

Well, if you use the dingle and a double to give yourself two different gears, you might be able to keep the chainline acceptable. For example, if you're using the 17t/21t dingle, try using 50 and 46 tooth chainrings in front. This setup would keep the same number of teeth engaged at any given time, meaning you wouldn't need to use a different length chain or move the wheel in the droouts. Am I right about this? I think I am. This way, you could have a gear for climbing or for riding into headwinds (46x21) and a gear for descending or riding on long flats (50x17). Now that I look at those ratios, that spacing seems a little wide, but you get the idea.

Yeah, if you keep the tooth count the same, the rear hub doesn't move. I've got a Sugino RD with a 48T ring so I bought a 44T ring, some new chainring bolts, 9-speed chain, and a 17-19 dingle. The 48-17 ~ to 42-15 that I'm used to and the 44-19 would be low enough to climb lots of stuff or carry a heavy load. I'll throw something else on the other side of the hub.

My Raleigh Sprite has some long dropouts but the Paramount has even longer ones. I think it'll be the Sprite that gets the nod. I think the C & V forum would kill me if I built a fixie out of the 1970 Paramount.

Pics coming soon.

Bump from the past. Any updates with pics?