Mixing hub gears and triple chain ring

[Night Train]

Showing my age and ignorance here.

In my youth it wasn't possible to have a front deraileur and a Sturmey Archer hub gear as the chains were not compatible.

How is it done now?

I am looking to use an old Sturmey Archer 3 speed hub geared wheel on my longtail bike build but I want to retain the triple from the original crankset.

What parts would I need to consider for compatibility? I think the existing setup is all Shimano.

Simple terms and descriptions please.

Thank you.

 

[Arch]

My first thought wasn't that the chain was incompatible, but that you need to keep the tension on the hub sprocket, so you need a rear derailleur arm or similar bolted to the chainstay to keep the chain taut, no matter which chain ring it's on. I have a mech on my hub geared winter bike, because it's a vertical dropout, so fine hub adjustment isn't possible.

I guess a singlespeed/hub gear chain might be less flexible than one designed for shifting, so you're probably better to see if you can get away a derailleur chain. I don't think the pitch is different, just the width. Although when shifting on the larger scale of chainrings (as opposed to sprockets), even a singlespeed chain might cope.

I think modern hub/derailleur set ups use the Sram 3x7 or 3x9 dual drive set, where the derailleur and hub are both on the rear, so there's a rear mech anyway, so it takes up the tension for the front chainrings. I assume they use the 7 or 9 spd chain.

 

[Night Train]

From memory (and given it is over 30 years of memory) the hub gear sprocket was thicker, too thick for a deraileur chain to fit, and so used a wider chain which didn't work on the front deraileur.

Would it just be a case of fitting a thinner (if they make them) sprocket on the hub gear?

I would be using the existing rear deraileur to keep tension on the chain.

This is really just so I will be able to use an old cheap rear wheel that will change gear while stationary.

A 5 or 8 speed with drum brake would be nice as would a dual drive but that involves spending proper money.

 

[Arch]

Right, at great personal risk to my bare feet, I've just extracted a wheel with a 3spd hub from under my kitchen worktop and leant it against a chair, and my Galaxy from behind my winter bike (both leaning against my sideboard), and dangled the Galaxy over the wheel so that the sprocket engaged on the underside of the chain...

It seems to fit ok. Of course it wasn't under any tension, but moving the Galaxy back and forth seemed to turn the sprocket. I reckon you could give it a go anyway, if you have an old derailleur chain hanging about.

In my experience, things are rarely absolutely incompatible. They may just need persuading.

 

[Night Train]

Ahhh, maybe things have moved on a bit over the last 30 years.

I remember the chain on my brother's 5 speed racer being way too narrow to fit on my hub gear sprocket.

There are a lot of choices now so something will fit I guess.

 

[TheDoctor]

OK, let's get technical on its ass.
[/Pulp Fiction]

Back when dinosaurs walked the earth and and Sturmey Archer three-speeds ruled supreme, they used a 1/8 inch chain and sprockets. That had been pretty much standard until these new-fangled deraileur things came along, which needed a bendier chain, so 3/32 inch chain came to be.
Now.
A 3/32 inch chain and sprockets will work perfectly well for fixies, singlespeeders, hub gears and everything - Rolhoff use them for their insanely expensive 14 speed hubs. You can get 3/32 inch sprockets for other hub gears, in fact Cyclo used to make a dual sprocket that gave you 6 gears from a 3-speed hub, like the 6 speed Brommies do now. You can also grind 6 of the splines off a Shimano Hyperglide sprocket and it'll drop straight on.
Give it a bash!!!

 

[TheDoctor]

My first thought wasn't that the chain was incompatible, but that you need to keep the tension on the hub sprocket, so you need a rear derailleur arm or similar bolted to the chainstay to keep the chain taut, no matter which chain ring it's on. I have a mech on my hub geared winter bike, because it's a vertical dropout, so fine hub adjustment isn't possible.

I guess a singlespeed/hub gear chain might be less flexible than one designed for shifting, so you're probably better to see if you can get away a derailleur chain. I don't think the pitch is different, just the width. Although when shifting on the larger scale of chainrings (as opposed to sprockets), even a singlespeed chain might cope.

I think modern hub/derailleur set ups use the Sram 3x7 or 3x9 dual drive set, where the derailleur and hub are both on the rear, so there's a rear mech anyway, so it takes up the tension for the front chainrings. I assume they use the 7 or 9 spd chain.

They do, and you can get a triple chainset going on too. I've seen 'bents with 81 speed gears, involving a front and rear mech, a 3-speed hub, three gear levers and a set of log tables for working out all the duplicates.

 

[Night Train]

OK, let's get technical on its ass.
[/Pulp Fiction]

Back when dinosaurs walked the earth and and Sturmey Archer three-speeds ruled supreme, they used a 1/8 inch chain and sprockets. That had been pretty much standard until these new-fangled deraileur things came along, which needed a bendier chain, so 3/32 inch chain came to be.
Now.
A 3/32 inch chain and sprockets will work perfectly well for fixies, singlespeeders, hub gears and everything - Rolhoff use them for their insanely expensive 14 speed hubs. You can get 3/32 inch sprockets for other hub gears, in fact Cyclo used to make a dual sprocket that gave you 6 gears from a 3-speed hub, like the 6 speed Brommies do now. You can also grind 6 of the splines off a Shimano Hyperglide sprocket and it'll drop straight on.
Give it a bash!!!

OK, I'll give it a go.

It's amazing how things change after a generation or so.

 

[Arch]

They do, and you can get a triple chainset going on too. I've seen 'bents with 81 speed gears, involving a front and rear mech, a 3-speed hub, three gear levers and a set of log tables for working out all the duplicates.

Only 81? You need a Schlumpf BB Drive in there too. I wouldn't be seen on a bike with fewer than 162 gears...

 

[corshamjim]

I can't say I've ever tried it, because I hate front derailleurs with a vengeance, but I should think you will need a 3/32" sprocket rather than the usual 1/8" . Take a look at http://www.sjscycles.co.uk/sturmey-archer-shopsturmey_archer_pg1/#filterkey=cat&cat=68&page=2

 

[TheDoctor]

Only 81? You need a Schlumpf BB Drive in there too. I wouldn't be seen on a bike with fewer than 162 gears...

What, no great-granny ring? Pathetic.

 

[MacB]

you definitely can get a 3/32 SA sprocket as I have one on mine, it runs fine with a normal derailleur chain and will work no problem with a triple. You need an FD with shifter, an RD and the SA shifter of course. The only thing to consider would be input ratios and if you find a definitive answer I'd be interested. For example:-

Triple is 22/32/42
Sprocket is 16t

that gives you a 2:1 input ratio in the middle ring, the best I've been able to glean re SA hubs are some random claims that a 2:1 ratio is the lowest you can go, but that's not mentioned on the SA website and plenty of people poo poo it. However the inner ring will be a primary input ratio of 1.375:1 which is pretty low, SRAM have 1.73:1 as a lower limit, Rohloff is somewhat higher and there's an assumption on the Alfines of 1.65 as the Alfine range is limited to a 38t ring by the Alfine crankset and a 23t max cog, thus 1.65. However Shimano don't officially state a minimum and many people run the Alfines with a lower ratio using non Alfin cranksets.


That's a very long way of saying your middle ring and big ring should be fine but you may run a risk of breaking something in the inner ring. Personally I'd say it's worth a go as any internals you did break are easily, and cheaply, replaced, then you just don't run it that low again.

 

[tyred]

I have been pondering this one myself recently. Unless there is a huge difference in the number of teeth on the front chainwheels, you may get away with one of those spring loaded tensioners which clamp to the chainstay. The standard 1/8" SA sprocket can be ground or filed down, it's only 1/32" difference anyway.

 

[MacB]

I have been pondering this one myself recently. Unless there is a huge difference in the number of teeth on the front chainwheels, you may get away with one of those spring loaded tensioners which clamp to the chainstay. The standard 1/8" SA sprocket can be ground or filed down, it's only 1/32" difference anyway.

Oh man, I like a bit of DIY but grinding down a cog to save £4 on a new one is a step too far for me

By the way I'm intending to run my new Alfine 8 with a double chainring, I've bought an older style Alfine tensioner for the purpose, it looks like a derailleur but gets fixed in placed. The FD will be a road double, as the chainline is quite narrow, and a MTB thumb friction shifter to operate that(it's a flat bar setup).

But you could always skip the FD completely and just change manually when you want to, I believe an old spoke can be modded for this purpose.

If you were using, for example, 22/32/42 and a 16t this will give you 3 gear ranges, in gear inches, of approx:-

27 36 48
40 54 72
53 70 93

so you have 2 clear duplicates

 

[Mad at urage]

Nearly 20 years ago (! well more than 15 and less than 20) I set up an SRAM Super7 with a double front on a Spec. Rockhopper comp I had lying about in the back of the garage - needed chain tensioner of course and the SRAM sprocket had to be machined to fit the chain. Eventually it started slipping. Replaced the sprocket about a year ago, Sachs having taken them over the sprocket fits Sachs chain with no machining . Things have improved in some places