Need 3-speed conversion advice
 

This story begins with a broken spoke and a gift certificate, and ends with a wild hair.

The 1971 International that I built up over the winter snapped a rear spoke a few days ago. After looking the other spokes over I figured I'd just rebuild the wheel: nice Araya rims and super nice Omas hubs - seemed to me like a worthwhile thing to do. My wife is a big fan of Groupon and had bought one for an LBS that I occasionally visit. I don't really need anything at the moment and it's only valid for a limited time so I figured I'd use it and have them rebuild the wheel. So I stop in this morning to drop it off ... and they totally freak. NO WAY this wheel is worth the rebuild: Is that a 27" rim, for pete's sake? And oh my gosh, it's got a friggin' FREEWHEEL! Long story short, they tell me it's not possible and that the rim will just go completely haywire once the spokes are sprung; it's a lost cause. I smile, walk out fuming because I know better. Guess I'll have to do it myself and then drop by in a few days to show them the impossible wheel.

But on the way home I get to thinking (always a dangerous thing.) I remember that I've got a nearly new set of CR-18 700c wheels, with the rear laced to a Sturmey-Archer S-RF3 hub (this is the version with no coaster brake.) I've got big, cushy 38's on the wheels too. As I drive, I get to thinking about various 3-speed configurations I might try - which leads me to the wild hair: What if I leave the triple installed in the front? That effectively creates a nine speed - three in the rear x three in the front. (I haven't done the math to see how the gear spread actually looks, btw... I'm just cogitating at the moment.) Has anyone built this configuration? How did it work for you? I'd need to use a chain tensioner, which I haven't used before. Can anyone recommend one that would work with this configuration? Or is this just silly? School me, please.

You could make it work, but you'd need a chain tensioner (or derailleur) in the back to take up the chain slack as you shift gears in the front.

I do think the big issue would be gear redundancy since a Sturmey AW has a normal 1:1 second gear with a 25% high and 25% low on each side. The 3 cog SA adapters for a rear derailleur typically had close ratios to help fill in the rather large jumps in the IGH. My instincts are telling me that's not how a front triple would roll out.

Too tired to do the math and I'll leave for the more adept geeks on the forum.

Edit I guess you could just use a claw derailleur set static in position under the rear cog without a cable?

Yes, that was my question: if anyone had a specific chain tensioner to recommend. Would any model do the job?

I would just put on a big-ish front chainring. 42-46T, Easy chain adjustment, no springs or derailers. I think a triple on the fornt would require a rediculous amount of extra chain to accommodate the large step from 30t-52t thats 1 links(22 half links) that would need to be hanging there if you were in the granny.

I think pretty much any rear derailleur would do the trick once you locked it in place via the limit screws -- the tooth difference for most triples is 20-23 teeth, well within the capacity of most "road" derailleurs. :thumb:

EDIT: I would definitely crunch some numbers on Sheldon's gear calculator or www.gear-calculator.com before ordering any parts. Some sort of faux half-step would be nice for breaking up the gaps between AW ratios...

Yeah, crunch some numbers!

Off the top of my head, when you put two cogs on an AW you want them 3 teeth apart, so something like 20 and 23 is good. That splits the hub gears nicely. If you did the same rat-io in front, so 40 and 46 for example, you would get the same effect. Do that jump again, so 40 46 52 and you would double two gears and add one more. Mostly you would just add confusion. The best chain tensioner for this purpose is a rear derailleur. But really, the best thing to do is to use two cogs on the hub. This is easy and indeed much simpler than what you propose. Either way you need a rear derailleur, so why bother with a front one?

These are good points, and thanks for the input, btw. I've been thinking about it today and reached pretty much the same conclusions myself. Very likely I'll wind up going with a 1x2 to yield six speeds (for the reasons you've already made) or even simpler still, just going with the single in back/single in front and going with the tried and true straight 3-speed. I'm sometimes really good at making a simple thing much more complicated than it absolutely needs to be!

I built a 6-speed bike using an SA hub on a Schwinn Super Sport. I used the Huret rear derailer locked with the limit screws to manage chain tension.

High was ridiculous. I could only use it going down really steep hills and a couple of times got the bike going so fast I feared for my life- the frame had an oscillation ability in the front end at really high speed. OTOH low was really nice. The jumps between gears was more than I wanted. If I were to do it again it would likely be with a single chainwheel, maybe 42 teeth, and a couple of gears in the rear.

It was that bike though that got me sold on IGHs. I built up several bikes using the (then) Sachs 7-speed hub. With that hub I never worried about additional front sprockets and it did fit on the older frames that I used. The Alfines and the Rolhoff are a different matter.

I wound up going with a 42/19 configuration. With 700 x 38 tires that puts the "normal" (1.0) gear at 60.4 gear inches and the low (.75) at 45.3; the high (1.33) is 80.5 gear inches. My "normal" ride gear on the Boulder is 61.2 and I spend probably 98% of the time in that gear; occasionally I need a lower gear for a steep hill and the low gear I use on my big ring is 45.9 gear inches (I almost never use the small front ring.) The long and short of it is that those gears almost perfect match the two gears that get used on my main rider. I wish I'd done a little cypherin' up front!

And with that, you're not far from the stock gearing on a lot of English 3-speeds! :thumb: (Mine is 46/18, for 50/66/88 with the 26" wheels.)

I've gotta agree with rhm that if you were going to use an RD, you might as well do your shifting there, too. I'd call it a "1x2x3" to really mess with people. ;)

Indeed. Make sure you use the old-style dished cogs as you need only place them back to back to get clearance between the cogs. If you use the modern undished cogs, you'll need a spacer between them.