Hi folks,

During the later 70s I built a six speed commuter bike using an SA three speed hub with two sprockets. It worked well for my environment at the time, but I was in the relatively flat Silicon Valley and considerably younger. I currently live in Salem, Oregon which is hilly, but no steep climbs. My current townie is a 2004 Giant Iguana 1 X 9 with an 11-32 cassette and a 42 tooth chainring. It is equipped with a rigid fork and runs 700C wheels with disc brakes and 32mm tires. This setup is OK for most of my riding, but I could use some lower gears. The seat stays have brackets for linear brakes which I may have to retro fit for the initial install.

The co-op where I volunteer frequently gets IGH wheels. Most of these are 3-5 speed hubs. Once in a while we will get a wheel with a 7 or 8 speed hub. My idea is to use a Sturmey-Archer 5 speed hub with two sprockets for 10 speed gearing. Research indicates this can be done with a pair of “dished” sprockets. It also says that three and five speed sprockets are interchangeable, but there are a few cautions and disclaimers. I haven’t done a spreadsheet to check the gearing and would like inputs from other members who have done this or something similar.

Thanks & regards,

Van

AKA: Senior Ryder 00

It has always seemed to me that when you combine derailleurs with an internally-geared hub (IGH), you get the worst of both worlds. Derailleurs are vulnerable to bending and breaking and need more frequent maintenance. IGHs are heavy and expensive. You may have a plan to mitigate the cost. Rigging up these two cogs might be a technical challenge, but that can be fun and rewarding. If you want it to be durable, I suggest you get one of those ugly derailleur guards that prevent the bending-in of the derailleur/hanger. They work, and you want a heavy duty bike, right?

Another consideration is that IGHs are not rated for the high torque that you make when you gear them very low. You can probably get away with it, though.

You might also look for a FSA two speed IG crank. It did what you want to do. Of course mine failed and I didn’t know enough to figure it out but I loved the idea.

Sounds like a fun idea ?

I have a Sturmey RK3 in the shed I keep thinking I should do something mad with .
OLN is 135mm which narrows up the frames I can use it in .

(bold above) My feelings exactly. Which is why I don't like the mix on a Brompton, but then, it needs that long-arm derailleur to take up chain slack when folding.

To the OP, what is your goal? Full chainguard (that a front derailleur would preclude)? Does the frame have horizontal dropouts for chain/belt tensioning? Going full IGH would allow full chainguard, plus belt drive if you desire, a big plus for an all-weather commuter. If you want 2 sprockets with an IGH, find a Brompton hub (BWR, Brompton Wide Range) so equipped, but be aware it's intended to be geared for 16"/349 wheels, but you may remedy that with chainring choice, possibly sprockets, more limited I think. Or just go front and rear derailleur, or these days, wide 1X cassette, which is super easy to do on large wheels; It's small wheels where there becomes more limitation on really large cogs, though you can still get into the low 40s on 20"/406 wheels. With larger wheels, you can easily go 11-50+ teeth on the cassette, and with the appropriate chainring, gets you plenty of range for a commuter, I think that is both your easiest and cheapest solution, and quite a common setup. My townie is 21 gear inches lowest gear, enough for all but heavy touring with long and steep hills. My high is 85, don't need higher, so about ~400% range, I think minimum unless you live in flatland. (You've currently got just under 300%.) More than that is gravy, which you can easily get with wide 1X cassette, and rear derailleur "slope" designed for it.

If this is the ugly thing, of which you speak, then I could not agree more. Works better than nothing, does add weight and hurts my eyes...

As much as I love IGH builds, in this case I’d swap in a 38t chainring and call it a day.

What about a double front ring, mech, and a tensioner at the back?

The six speed SA hybrid is reliable as any bike geartrain out thres. Yes, it has a derialleur, as do most bikes and it is as vulnerable to damage as any other bike out there. It is not really any bigger liability than just a plain Jane deraileur bike. My concern, and it is a small one is that you will end up with three shifters. That can gets a bit confuing, but that is not a deal killer as far as I'm concerned.

The other suggestion of having a double (or even triple) chaninring expands your gear range and gets you into the same three or even four shifter delemma. When I first built my hybrid SA bike I had it set up with dished SA cogs in the rear, the Sturmey-Archer AW three-speed and a double chainring in the front. I ended up going to a single chainring in the front because of having to deal with three shifters and trying to figure out the shifting pattern. But I live on Long Island, NY. I am not facing big hills so six speeds and two shifters worked out for me. You may find a pattern that works and you get used to. And you are dealing with more hills than me.

Here is my ultra reliable, and old time index shifting S-A hybrid six speed moved to a different frame than my original build in 1980.

I can think of two production bikes that have a multi-speed freewheel on an internally geared hub.
Bike Friday and Bike-E.
I think B-F did it for easier folding and setup, and B-E for less floppy chain running past you to manage.
Had the Sram equipped Bike-E, and it worked but was more entertaining than amazing.

Figuring out the development of the various gear combinations is a decent amount of work

most likely a number of near overlaps

I had a superb 3x4 hybrid transmission on an old Armstrong 3-speed. A neighbor gave me a wheel with a 14-16-18-20 cogset, and when I started playing around with it, I happily noted that the hub clicked when I twisted the cogs clockwise. The gear ratios worked out superbly, with overlaps at the top and bottom of the middle internal range, which worked out well with the double shifts. With a 40T chainring and 26" wheels, I had 39 to 99 gear-inches. One could always put a double up front, something like 40-28, which would take the bottom ratio down to 27 gear-inches..

You need my Cyclo Benelux 3-speed conversion set (new in box!) for your hub. Keep it weird.

I think about it probabilistically: random events happen, so the longer you go, the more likely a given mishap is to occur. But surely, bending the derailleur in is more likely than bending it out. I observe that they do get bent in through various means such as laying the bike down on its right side, being hit in a self-closing door, and having something collide into it. When I was a shop mechanic I saw it a lot, and the customers were unaware of what had hit their bikes. If I ever take a long tour, I will install one of those ugly things, and I'll probably install a dork disc as well. These things work, and I do not want a bent derailleur or hanger when I'm far from home.

Sounds like a Sheldon Brown kind of thing to do.

I don't have an answer to Senior Ryder's original question, but I will drop an observation about the 2 speed derailleurs on Bromptons.

I have a 2014 Brompton that I bought new and ride fairly regularly on short errands. I can't recall the gears ever needing adjustment except the one time that I brushed against a curb and the plastic derailleur basically exploded. I was not even able to find all the pieces. The derailleurs do the job as long as you don't abuse them, but they cannot withstand any kind of impact. Fortunately there's a Brompton dealer close by and the replacement was pretty cheap. Having discovered they are disposable I bought two.

Sheldon Brown gear calc, or gear-calculator.com, provided either has the specs for the IGH, you just select it and enter the other stuff.

S-A wide range 3-speeds always had 3:4, 1:1, and 4:3 ratios, so just multiply your regular wheel diameter * chainring teeth / cog teeth gear-inch number by 0.75, 1.0, and 1.33.

Crazier winter project, from Capo of Vienna Austria: the eis bike

I made a similar arrangement which I installed on my mountain bike. It was devilishly difficult to ride without the stabilizing gyroscopic influence of a spinning front wheel. Basically, I couldn't climb any sort of hill once my speed dropped too much. However, the steel edges of the ski gave almost unlimited cornering grip on hard packed snow

Surely the co-op has triple cranksets and FD's in abundance. Just return to stock, essentially.

It would also be really easy to turn it into an 11-speed, which would have exactly the same ratios as you have now but two more downshifts. But I wouldn't guess those parts are in the bins.

Thanks for the feedback. It was the type of information that I was looking for, the good, the bad & the ugly. Now, I'll do some calculations on the options. As I said in the initial post, this was one of my "wild Hair" ideas.
Cheers,
Van

I beg to differ! In he Seventies, I built a similar commuting bike, but I used the Cyclo Benelux triple cog conversion on a Sturmey Archer AW hub. It had nine speeds essential widening he range of the Three speed. What I liked about the system was the ability to instantly shift into a lower gear at a complete stand still. How many times has someone been forced to make a quick and decisive stop to avert some catastrophe! If one was on a hill or in less than ideal road conditions, starting in the higher gear could be a problem. With that delicious “click” down shift, one could scoot right along! I will grant you it’s heavier than a derailleur system, but also gave the rider three gears that were unaffected by snow or grit or cold. As for the “limited” torque rating in lower gears it probably doesn’t matter for most riders in the normal range of elevation.
Then there’s that ever so cool esoteric quality of the hybrid gearing system…. Sunrace Sturmey currently makes a three speed hub that is splined to accept an eight speed cassette. Further more, Brompton had a proprietary version of the system the OP describes. Two cogs on a three speed SA hub with their unique derailleur. I have a long delayed project that uses one of these triple cogs on a SA five speed hub with drum brakes. If I could ever find a place and time to just respray the frame……..

I think the shifting-while-stopped feature of IGHs is overrated, except for city and rental bikes used by less experienced riders. I'm almost never at a stoplight overgeared, because with a gripshift on right and front brake on left, it only takes a second to downshift, even in a hard stop. On the rare times when I had to stop on an uphill climb without first downshifting, I get on the bike, do a sharp turn to downhill, downshift, turn back around to climb the hill.

I'll agree with elcraft and disagree with Duragrouch. Shifting while stopped is valuable. I'm experienced, so I almost always remember to shift down when coming to a stop, but not everyone can, and even experienced cyclists can't all the time. I can also shift my derailleur while stopped by lifting the rear wheel behind me and pedaling and shifting, but it's tricky and not nearly as convenient as with an IGH.