SA 3 speed bikes?

[Victor]

'Where can planet pinions with clearance for needle rollers be sourced and what if any other mods are needed?'

Are you really sure you want to go there ?

[rogerzilla]

The planet pinion bearings were indeed used for a short while in earlier 3-speeds but made next to no difference, and when the unique - some might say flawed - AW design appeared in the 1930s, it loaded one end of the pins in high gear, so a plain bearing is better for that than a single-row ball race would be. Rohloff use ball races for the planets but they have multiple stages, so losses add up, and they were trying to create the ne plus ultra of hubs, not a mass-market product, so threw everything at it.

A run-in and oiled (not greased or gummed up with old 3-in-1) AW gets very close to the theoretical efficiency of the epicyclic gear due to its simplicity. The sun and planet sizes are about as optimal as you can get in the overall packaged size and most of what inefficiency there is comes from the poor gear teeth shaping. Later AWs aren't exactly precision-made, either; the tooling was wearing out and tolerances were slack.

[Geoff_F]

Something that occurred to me while out on a ride this evening - where I live is relatively flat in the town but quite hilly in the surrounding countryside. In town I use only 2nd and top but some routes out of town I must be in 1st and especially second gear for (time wise) longer than in top and when in top, a lot is freewheeling. So on these routes I am in the most efficient gear for those moderate climbs (I have top as normal at 66 inches) and overall probably more efficient than having second gear as normal- as then I would be in first most of the time. Also, psychologically, it helps to know and feel? that you are using most of your effort to get up the hill!

[Victor]

If riding a fixed gear (not racing), most people choose a gear of around 60"-70" as a compromise. Much lower and the cadence becomes silly on descents, whilst any higher makes climbing too hard. On a reasonably lightweight bike, aound 65" works quite well. Climbing is not normally the problem, descending is. Possibly, you'd choose a slightly lower gear with a single freewheel, maybe ~55". Most traditional 3 speed bikes are similarly geared with a middle, efficient gear in the mid 50"s-60"s. I think this makes sense from the POV of efficiency and not over-torqueing the gearbox. Climbing is expected to be an out of saddle effort, but at least you can sit back and relax on descents.

Whenever I've tried a 3speed, I found myself wanting to stay in gear 2 as long as possible, 1 and 3 felt noticeably less efficient. I do not have this issue with derailleurs.

If forced to ride a 3 speed, is there any reason not to base the 2nd gear choice on what you would chose for a single speed freewheel? Gears 1 and 3 will fall where they may.

In practice, if you do this, you will end up with a bottom gear comparable to an old road bike (but less efficient) and a top gear that's like a sporty fixed gear bike! Which I think explains their limited popularity, fantastic as they might have been in 1902.

[rogerzilla]

I have AMs on two bikes - geared for 60" in direct drive, you get about 52" and 69" in the other gears. That's much more useful. I found, when commuting on an SRC3 (same ratios as an AW) that I never used low gear, as the only hill was short and stompable in middle gear. Low gear was just too low and I'd have been roadkill.

[pjclinch]

If forced to ride a 3 speed, is there any reason not to base the 2nd gear choice on what you would chose for a single speed freewheel? Gears 1 and 3 will fall where they may.

That seems like a good general approach for most people most of the time, but in areas of more pronounced topography one might want to base 1st on what one wants to regularly get up, and let 2 & 3 fall where they may.

That's how my 3 speed Brom is set up (Dundee is not short on reasonably steep hills, and I live on the side of one), and in fact also my 11 and 14 too. I had to change the back wheel on the Brom a while ago, picked up a second wheel with 3 speed hub and plumbed it straight back in, forgot to count the sprocket teeth. Went from a 15 to a 13 and it actually made the difference between riding the bike and not because it made getting to and from my actual door significantly more like hard work. Once I switched the sprockets it was fine again.

Pete.

[fatmac]

When I was riding 3sp, I used to have a top of a comfortable cruising speed, & the other 2 for climbing, as I lived in a hilly area...

[rogerzilla]

The 2 speed hubs like the Sachs Duomatic give you a dilemma: a low gear for climbing/starting, or a high gear for downhill? The latter approach makes best use of direct drive but may not be what you want if you live sonewhere hilly, since you can always freewheel downhill. A 3 speed makes things much easier

[rjb]

My 3 speeds are all small wheel shoppers. I've set the gearing on them all to 40-54-71" approx. Despite riding mainly on the Somerset levels with a few hills thrown in I now finding the low gear hard work when climbing as I approach my 4th quartile. Time to fit a bigger sprocket to adjust the gearing down methinks, or employ the 24" gear.

[rogerzilla]

SA hubs are not supposed to go below a 2:1 chainring/sprocket ratio, although the actual torque on the hub internals depends on your strength and other factors. I know an AW is unlikely to.last long in tandem use

[Carlton green]

I had to change the back wheel on the Brom a while ago, picked up a second wheel with 3 speed hub and plumbed it straight back in, forgot to count the sprocket teeth. Went from a 15 to a 13 and it actually made the difference between riding the bike and not because it made getting to and from my actual door significantly more like hard work. Once I switched the sprockets it was fine again.

A Brompton is a bit outside of my budget, but one never knows what the future might bring and keeping informed is a good idea. I’d thought that a 14T was the most that could fit on a Brompton (without catching on something) but you seem to have gone bigger, am I mistaken in that maximum size or is some special technique(s) employed?

My 3 speeds are all small wheel shoppers. I've set the gearing on them all to 40-54-71" approx. Despite riding mainly on the Somerset levels with a few hills thrown in I now finding the low gear hard work when climbing as I approach my 4th quartile. Time to fit a bigger sprocket to adjust the gearing down methinks, or employ the 24" gear.

At the moment I use my ‘shopper’ pretty much every day, they can be quite liberating bikes. My top gear is circa 10” lower than yours and works well for me, though I’m not slim and haul my 11kg terrier along on his ‘pillion’ seat; I’d encourage you to drop approaching 10% and accept a slightly lower top speed.

SA hubs are not supposed to go below a 2:1 chainring/sprocket ratio, although the actual torque on the hub internals depends on your strength and other factors. I know an AW is unlikely to last long in tandem use

imho that SA (company) guidance is to be taken with a pinch of salt. A strong young man might possibly manage to over torque an SA hub but I’m neither (strong or young) and hence need lower gears. Fit what gearing ratio you need, and if the hub breaks then mend it. My 700C wheeled bike was geared 38 x24 and showed no distress (eventually that old Sram sprocket became too worn and the SA hub is now geared 38 x 23, the largest new sprocket I could find for 3/32” chain was 23T).

[pjclinch]

A Brompton is a bit outside of my budget, but one never knows what the future might bring and keeping informed is a good idea. I’d thought that a 14T was the most that could fit on a Brompton (without catching on something) but you seem to have gone bigger, am I mistaken in that maximum size or is some special technique(s) employed?

£3 from SJS, https://www.sjscycles.co.uk/sprockets/s ... at-hsl945/, on it goes with no special rituals required

Recent ones seem to be going for a 4 speed derailleur or that mixed with the 3 speed hub for more range but derailleurs, even compact ones. Meh. I will probably treat myself to the Kinetics 8 speed belt conversion when I retire, not too far away now.

Pete.

[rareposter]

A Brompton is a bit outside of my budget, but one never knows what the future might bring and keeping informed is a good idea. I’d thought that a 14T was the most that could fit on a Brompton (without catching on something) but you seem to have gone bigger, am I mistaken in that maximum size or is some special technique(s) employed?

The largest you can fit on the standard bikes is a 16T. Some can be pushed up to 18T without any modification. Beyond that, you're into significant customisation territory.

The new G-Line uses an 8sp Alfine hub gear and that can take up to a 22T sprocket.

Plenty of videos online covering standard and custom Brompton gearing set-up options, Brompton themselves are pretty open about usual possibilities (ie, the ones that don't involve voiding the warranty by filing away bits of frame!)

[jimlews]

How low can you go ?
My original trailer towing log hauling bike, a rod braked Norman, was furnished with a 22t chainwheel & a 22t sprocket. The chainwheel was a refugee from a kiddies bike. I drilled it with five holes using a TA cyclo-Tourist outer chainwheel as a guide and bolted that to a cottered crank from which I'd hack sawed and discarded the original chainwheel. It all worked just fine up and down Devon's lanes and the AW survived the abuse until the bike was eventually stolen.
The TA cyclo Tourist crank has a bolt circle diameter that can accept a smallest chainwheel of 17t. However, nobody makes one though, it is alleged that a freewheel sprocket can be used but I've never identified which freewheel provides a suitable donor.

I have posted about this set-up several times now on this site, so I apologise if it is becoming tedious.

[Victor]

Whilst it's an option for an older bike, how many of you either have or would buy a new bike with a 3 speed hub that was not a Brompton?

Why wouldn't you choose an Alfine 8 instead?