Monster Pete

I just rigged up a simple modification to my commuter which others might find of interest. I swapped the 19t sprocket+spacers on my AG hub for 21t and 18t sprockets, back-to-back. A rear derailleur from my parts box shifts between sprockets, controlled by a 1970s stem shifter, mounted on the left handlebar.

This combination of sprockets and hub gives perfect half-step gearing. It retains the ability to shift the 3-speed when stationary, while allowing you to fine-tune a slightly higher or lower gear- I've often found I need to be somewhere between 2nd and 3rd gear. With 3/32" chain, the spacing is a little too wide but works, so one dished and one flat sprocket may work better, or alternatively 1/8" chain if you can find a derailleur it will run through.

FBinNY 

This was a very common arrangement in the fifties and sixties, but had gone out of fashion. There used to be a 3 sprocket adapter which fit directly onto the hub's driver. What probably speed it's demise is the progression from 4 or 5 sprockets on derailleur systems to the now current 9,10 or 11.

The advantages are as you indicated, but the drawback is that you lose some of the benefits of IGH like a single loop chain without a tension arm.

The only thing that counts is that it works for you, as apparently it does.

Monster Pete

Yeah I only really tried this out as an experiment. I think on the whole a 5 or 6-speed freewheel and rear derailleur would probably be of more practical use. It is a convenient way to add a bit more range to an existing 3-speed bike though.

FBinNY 

Actually one of the nicest benefits is the half steps between an AW hubs large steps. IMO the perfect gearing for most city riding is a fairly narrow range with steps of 10% or less.

I use a vintage super narrow SA AC three speed with steps of about 6.6%, and it's perfect for the slight adjustments needed on basically flat terrain.

FlatTop

It is a pretty neat idea. And on a cycle that must run a chain tensioner (vertical dropouts) there is less of a downside.

HillRider

Flat terrain? What's that?

zukahn1 

Very cool old school shifting set up. I haven't 3x2 steup on bike someone actually road since I was a kid. This setup is great for flat terrain. I suspect it might have some minor issues if you need to shift going up or down steeper grades on hilly terrian.

fietsbob

once you have a chain tensioner, to wrap up the slack,
you can use a double chainring to the same purpose .
but since the front is bigger, a tooth change is a smaller %
so makes getting the half step % more precise.


Back in my kid days I had a 3x3x3 27 'speed' I put together.
it got a machined solid steel 3 cog piece ... 16,19,22T , I think .
got a cotter fitted triple crank, back in the day [JFK was still breathing]

a 3x2x2 might be a worthy experiment.. Alloy parts, an improvement..

Airburst

This is pretty much the setup I have on my old Raleigh, only I've used an old friction thumbshifter. How much space is there left over on the driver with the dual sprockets on yours? The circlip on mine doesn't quite seat properly because of the extra thickness of the sprockets, do you have the same issue?

tcs

In "Teach Yourself Cycling" (1953), Reginald C. Shaw suggested 19T & 22T cogs combined with a 46T chainwheel as another good combination (of course with the ubiquitous AW and 26 x 1 3/8 wheels).

mikeybikes

I might have to try this. I have 17T, 20T and 22T cogs. All 3/32". I could play with this...

Monster Pete

I'd like to do an IGH+FD setup sometime. It would certainly be easier to rig the cables with only one going to the rear. The downside is that it's more difficult to incorporate a chainguard, whereas mine has enough width to accomodate the difference in chainline for two sprockets.

@Airburst- by just using the sprockets with no spacer, they are actually slightly loose on the driver, but using one spacer the circlip won't fit. Ideally I need a thinner spacer to go between the sprocket and circlip, or between one flat and one dished sprocket.

@fietsbob- I recall seeing somewhere here a setup involving a half-stepped AW hub, coupled to a double chainring which half-stepped those six gears. This way you'd use the hub for large ratio changes, the RD for fine adjustments, and the FD for even finer adjustment. Seemed like a logical layout with nice closely-spaced gears.

Airburst

The new drivers must be shorter than the old ones, mine is a new Taiwanese hub, not a UK-made one. I'm going to modify a pair of Shimano Hyperglide sprockets for mine with a grinder, as I think that'll work out at thinner, and should shift better to boot. I assume you're using an old british hub?

Monster Pete

Yeah I have an AG from 1979 and an AW from 1989, and this setup works on both.

cycle_maven

@Airburst- That's what I did for my dual-drive. Ground down a couple of Shimano 7-speed cassette sprockets so they only had 3 tabs, and ground the 3 tabs down to nearly half-round. With a spacer from the same cassette, they fit perfectly on the hub body with no slack, and the circlip lodged in its groove perfectly as well. The hyperglide shifted perfectly- especially since I used adjacent sprockets (15 and 17) from the cassette, and kept the orientation with respect to each other.

Monster Pete

If you are able to modify the sprockets like this, I'd say this is definately the way to go. The advantage over SA-type sprockets is that you have a much larger selection available, as well as the shifting ramps on the sprockets themselves. Plain sprockets shift ok but nothing like as well as a partial cassette would.

cycle_maven

Here's a photo mid-grind: