jonwvara 

I've heard that Sturmey-Archer recommends that the input gearing of their hubs should not be lower than 2:1, i.e. 48-24, 46-23, or whatever. Otherwise, excessive torque (I guess) can supposedly damage the internal gearing. In other words, since 2:1 translates to about 52-54 inches (depending on wheel size), and low gear on an AW hub is .75, the lowest gear one can/should ever go with an AW is somewhere around 40 inches.

I've always found that sort of questionable. I've been riding happily around for years on an AW hub with 48-28 gearing (there's also a derailleur and a 23-tooth cog) which translates, I think, to about a 35-inch low. I'm now about to build up a wheel for another bike that will have a 40-28 low, which is just a hair under 30 inches with a 27 inch wheel, I think.

Given the conservatism of engineers, I would not expect that to be a problem. I can just about believe that a very big rider could damage the gearing by standing hard on the pedals and hammering uphill. That's not how I ride. But I'm curious about experiences that others may have had. Does anyone have a real-world account--first-hand or otherwise--of an SA hub that was damaged by gearing it too low? Or is this one of those awful things that can supposedly happen but never actually does?

tatfiend 

No personal experience but I have read of such damage occuring from bicycle mechanics postings here even with supposedly acceptable input ratios. If you are a spinner then I would not expect a problem but a strong or heavy masher can apparently have problems. One member who runs an IGH ebike has reported destroying both SA and SRAM hubs due to excessive input torque. Rohloff and NuVinci hubs have survived on the same bike. SA 3 speeds are cheap enough so even if problems develop the financial hit is not too bad.

Currently only SRAM, Rohloff and NuVinci list minimum input ratios. The older Sturmey Archer England documentation available on the Sturmey Archer Heritage web site lists a 2 to 1 minimum input ratio for all of their older hubs that I have downloaded information on.

Unless you are limited for some reason why not use a hub with more gears and a wider range in order to provide the wanted low gear and a more reasonable high gear? Unless a very special purpose bike the high seems to be excessively low.

jtgotsjets

Just curious, what do you use this bike for that requires such a low gear ratio? It seems like you'd spin out at frustratingly slow speeds even for just cruising.

Some sort of IGH mountain bike? Bike polo? Maybe I've been spending too much time without coasting, but I am having trouble wrapping my brain around a practical use for gearing 2:1 and then having an even lower gear.

sciencemonster

I have toured on my 3 speed, and even just riding around, you need to be able to climb a hill once in a while. 30 inches isn't that low.

You make it sound like a three speed is only good for going to the store. Get with it! There are mountains to conquer!

jonwvara 

Well, that's my feeling also. And for me it's a lot more than "once in a while." I live in the Vermont mountains, and every ride I take ends with a grind up 3/4 of a mile of ten percent grade (on a dirt road) to my house. It's just no fun to grind up it in anything higher than 30 inches. My attitude toward SA gearing is to figure out what you NEED for a low, and then live with whatever that gives you for a high. I don't find lack of a gear higher than 75-80 to be a big deal--it doesn't cost you many miles at the end of a day. Pedaling downhill means you go fast for a short time, but has little effect on your average speed, in my experience. Your average speed--I should say MY average speed--seems to depend mostly on how fast I go UP hills. I have no problem with coasting down.

tcs

Over-torque is real: long, long ago I even over-torqued a freewheel - spun the sucker into pieces. (Say what? It was an Italian freewheel mounted on a tandem. Through the lens of the intervening decades, duh.)

I'm loathe to make a recommendation that would ultimately cause someone's equipment to fail, but a sacred IGH input ratio? Equally for your 82 year old grandmother and world champion sprinters? Seems rather simple minded.

Best,
tcs

noglider 

It depends on the rider. I had a large customer who would break spokes and the pawls in his AW hub. I don't think I could ever do that if I tried. I'm just not that big or strong. And I think most people aren't, either.

I think long-legged people can apply more torque than everyone else. He was at least 6'4". I'm 5'9" and short-legged.

tatfiend 

I worked in reliability engineering for years and general practice is to specify things at a level where 99%+ of users will not have a problem. It cuts way down on warranty repairs or replacements. I suspect that it was also SA's practice and is that of the makers who still specify minimum IGH input ratios. The problem is to know how much you can exceed their recommendations without problems and the only way to find that out is to try it and see if you break something. If you do then you have gone too far for your individual use.

SA 3 speeds seemed to last practically forever with the almost 3 to 1 input ratios fitted to the old British 3speed roadsters. A lot of people felt that they were overgeared for most riders.

Mr IGH

I've never seen one damaged internally. I expect they are much tougher than most think. The minimum input gear is just a guide. If the engine's power (the rider) isn't included, then the limit is just a guide. Fresh guts can be had on the 'bay for $10, I wouldn't worry.

bikamper

Myself, I take those input ratios with a grain of salt. I've run an Alfine with a 34-18 for the past year without a problem and have a 28" low. I also have been running a Sram S7 with a 31" inch low for 2 years. I think the lowest I run a Sturmey 3 speed at is in the high 40s and that's only because I want high around 72". Old Raleighs are geared too high anyway.

Mr IGH

That's what I run on my winter bike. On my MTB's Alfine I'm running 32/23 with no issues and I'm riding at ~230lbs with full kit.

rhm

I would think the chainring/cog ratio would be just one of many factors that one has to take into account when judging what kind of torque the hub can handle. In its classic application (e.g. Raleigh Sports) wheel size and crank arm length were standardized at 26" and 6.5" respectively, effectively taking these factors out of the equation (though of course smaller wheels were used occasionally, e.g. Moulton, Raleigh RSW 16, &c). Even so, the amount of weight being applied to the crank arm, and the amount of weight being pulled, must also represent big variables that could wreak havoc when certain limits are exceeded. Therefore I suppose the engineers specified the 2:1 ratio assuming standard 26" wheels and 6.5" cranks arms and the heaviest rider they could imagine. Since that was the 1930's, I doubt they were thinking of riders over, say, 250 lbs and total load (rider + bicycle + cargo) much over 300 lbs.

I have often wondered why it is that today, when riders generally favor lower gears and higher rpms, they also favor longer crank arms. I would think lower gears and higher rpms are a movement in one direction, while longer crank arms are just the opposite. Perhaps on older bikes the crank arms were were deliberately kept relatively short out of concern over over-torquing the hub?

But since you asked about actual experience, I must admit I have none to offer. I haven't tried running a ratio lower than 2:1 with any IGH, and I gear the AW higher than most. On Long Island, where I do a lot of AW riding (including touring!) I found 46/22 low enough. In NJ I ride some good hills, but there I have an FW hub that gives a sufficiently low gear even with 46/21 gearing. On my Nexus 8 and NuVinci equipped bikes a 2:1 ratio (38/19 and 44/22 respectively) has got me up every hill I've tried. My Rohloff equipped tandem is geared 40/15 which lets me crawl up hills at 4 mph if necessary (and it often is).

rhenning

Back in the early/mid 1980s I built a real low budget mountain bike from an AW and an Astabula cranked Schwinn frame with a 36 tooth front sprocket and a 22 tooth rear. You could climb almost anything with in it but the teeth on the planet gears broke very often. Sometimes taking teeth off and sometimes splitting the gear/gears in half. Way more toque load than the planets were designed for. Roger

cyqlist

I used this setup for touring from 1983 until the late 1990's, with a small chainring of 21 teeth and large rear cog of 21 teeth on a Sturmey Archer AW hub for a 20" low gear:


I did have a few failures early on, broken teeth on planet pinions, and a couple of cases of broken driver prongs which I think can result from the high force applied to ends of the prongs when applying a very low external input ratio when the hub itself is in high gear. One time in particular I remember the driver breaking when my indicator attachment had failed forcing me to pedal hard uphill with the hub in high gear.

However I persevered with this setup and even completed a 7,000 mile double transcontinental fully loaded camping tour with it in 1987.

I think one is more likely to get away with this sort of thing if you have smooth pedaling and shifting techniques. And also I believe some of the older SA parts are stronger than the newer ones due to changes in their manufacturing processes.

rhm

That is really cool! What did you do when the hub failed under load? I mean, you didn't you carry hub parts with you, did you? I guess back in those days it wasn't that hard to find a mechanic who could overhaul an AW.

bikamper

After cleaning out the cobwebs of my memory, I do run an AM with a triple cog. The big one is a 24 and I run a 46t chainring up front. The hub is 60 years old and just keeps going.

I'm also a believer in that short crankarms, high cadence, and lower gearing contribute to longer life of the components.

noglider 

Well, now we've heard from people who've broken planet gears from excessive torque, so it does happen.

John S Allen told me that SA used to use cyanide hardening, whatever that is, but they stopped. I'm sure the reason is obvious. So that explains the decline in durability of the parts.

cyqlist

I don't think I ever had a failure that totally immobilized me. If planet gears broke then I could still keep going in direct drive. On some occasions I was able to keep going by opening up the hub and removing the broken parts. I did carry some spare hub parts on my transcontinental trip, a driver, planet pinions, springs, pawls and an axle, but never needed any of them on that trip. I always did all my own mechanical repairs.

jonwvara 

Man! That is a seriously low gear! And it's good to know that things DO break when you go that low. I'm curious, however, about your solution to the problem of things breaking. You mention that you had a few failures early on but persevered. Does that mean, as it seems to, that as you persevered you began to have fewer or less frequent failures? If so, why? What did you do differently to prevent failures? Did you change your riding style, start using a different AW hub, or what?

cyqlist

I think it was just that some parts, probably older ones, were stronger and more durable than others, and once I got the stronger parts installed the failures stopped. Maybe also being more careful about pedaling smoothly and gently in low gears (e.g. never standing up to pedal).

rhm

If I were planning to do something like what cyqlist did, the first thing I'd do is replace my original 1950 trigger and indicators; they get a lot of wear and would be the first to fail. The internal hub parts don't actually get much abuse when the hub is in use, so would seem less likely to fail. More precisely, the early failure of my trigger and indicator is predictable and therefore preventable; failure of anything on the inside is not predictable and therefore not preventable.

tatfiend 

At some point during AW production SA shifted their production process from machined to sintered powdered metal technology for making most of their IGH parts. This was an economy move as a lot of parts machining was eliminated by the change.

This may have contributed to more brittle parts as I know Colt had durability problems with some of their revolvers after a similar change.

jonwvara 

It sure would be nice to know the year of that changeover. Anyone know? Do we have any former SA employees reading this?

tcs

...and then in 2000 the entire production shifted half-way 'round the world under the management of SunRace Sturmey-Archer:

"In any case, the quality of Taiwanese production from SunRace/Sturmey-Archer so far has been excellent, generally better than the quality of later English production. They have also made design improvements, including eliminating the chronic forward-freewheeling issue that used to arise wthen the shift cable was misadjusted.
"Some folks don't believe that the Taiwanese can make stuff as well as the British did, but there's no factual basis for that belief, and in many cases this attitude may be traced to racism." - Sheldon Brown

tcs

jonwvara 

Okay, here's what we know so far:

Sturmey-Archer recommends a minimum input gearing of 2: 1 for internally geared hubs. That seems to be safe, but one apparently can strip the internals at a 1.6: 1, as rhenning did with his mountain bike with 36-22 gearing. My guess is that hard usage was a factor there, since it was apparently used for fairly aggressive off-road riding ("You could climb almost anything with it").

In any case, 1:1 input gearing would definitely seem to be too low, given that cyqulist experienced repeated failures of multiple components with his 20-20 gearing.

If either of you are still following this thread, it would be very interesting to know the ages of the hubs in question, since older hubs are vaguely reported to be more robust than newer ones.

To add some new information, I stopped by the Harris Cyclery a couple of days ago to buy a 6 1/4" SA axle, and talked briefly with one of the guys there (I didn't get his name, unfortunately.) I asked whether he knew when SA went from machined internal parts to sintered ones, and he said it happened a long time ago--sometime before 1970, he thought. (He had been following this thread, apparently.)
I also talked on the phone with Aaron at Aarron's Bicycle Repair in the Seattle area, who advertises in Bicycle Quarterly and specializes in old and new internally geared hubs. He reports that he sees no real difference in reliability between old and new AW hubs, and that he has often geared them as low as 36-24 (or 1.5: 1) without any problems.

So there seems to be no definite conclusion. Based on our tiny data set, I now feel reasonably confident that I can make the 40-28 gearing I have in mind (1.4: 1 gearing work out), especially since it will be built around a 1966 hub. Worth a try, anyway.

This is pure speculation, but I can't help coming back to the fact that the safety factor in the hubs that do break is absurdly small. I mean, if an engineering department officially approves the hub for use at 2: 1 and knows that it's going start breaking at 1: 1 and maybe even at 1.5: 1, well, that's pretty lame. Admittedly, we're not talking about a suspension bridge or an airplane wing here. But gosh, that kind of safety factor would seem low for something like a plastic shower-curtain ring, let alone a machine with a lot of moving parts. I wonder if the older hubs might have been robust enough that they didn't break at that level, but that breakage increased as SA cheapened their process. If so, they may have left their gearing recommendation unchanged because raising it would have been an admission that the hubs were not as strong as they had been. By that time, most hard or serious riders were presumably using derailleur gearing, leaving the SA hubs to sidewalk cruisers, who presumably would be unlikely to bust them.

That theory might explain why cyqlist's hub stopped breaking after a while. Possibly the parts bins where he got his repair items contained a mix of old and new stock (this is often the case, I think) and eventually, through something like the process of natural selection, he ended up with older, stronger parts in the critical areas and the problem went away.

I guess this is as far as this can go without some firm information from someone at Sturmey-Archer. I've found it pretty interesting, though.