New 2 speed hub gear ...

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rogerzilla
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Re: New 2 speed hub gear ...

Post by rogerzilla »

The Achilles heel of the TF is its need for 12-spline sprockets, which haven't been made since the 1940s. I asked Eggrings if they could make some and they said no. You can't 3D print them, either; they need to be hard steel.
pwa
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Re: New 2 speed hub gear ...

Post by pwa »

On a bike with normal size wheels you would really have to hate front mechs to prefer a hub gear as a substitute. Hub gears are inherently less efficient, wasting more of your energy, and they lack the flexibility you get by being able to tweak ratios through ring choice. As someone who has no problems with front mech and multiple chain rings I can't see why I might want to swap them for an energy sapping hub gear.
cyclop
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Re: New 2 speed hub gear ...

Post by cyclop »

pwa wrote: 9 May 2021, 5:17am On a bike with normal size wheels you would really have to hate front mechs to prefer a hub gear as a substitute. Hub gears are inherently less efficient, wasting more of your energy, and they lack the flexibility you get by being able to tweak ratios through ring choice. As someone who has no problems with front mech and multiple chain rings I can't see why I might want to swap them for an energy sapping hub gear.
Ditto.Some of my front mechs,triple xt,double 105,double ultegra,I don,t think I,ve touched in years.Some of the most reliable bits of kit on my bikes.
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Tigerbiten
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Re: New 2 speed hub gear ...

Post by Tigerbiten »

pwa wrote: 9 May 2021, 5:17am As someone who has no problems with front mech and multiple chain rings I can't see why I might want to swap them for an energy sapping hub gear.
You'd treat it as a 1x setup with a few extra gears.
So you'd be in the direct drive range with no extra energy loss most of the time.
It's only when you run out of gears up/down do you need to shift into overdrive/underdrive mode with the extra drag so you use the extra gears.

That's how I use my Schlumpf HSD with twin chainrings/Rohloff setup.
Gears 1-17 are used in direct drive mode on the flat, 2-20 mph, so no extra energy loss.
Gears 18-24 are used downhill in overdrive mode, 20-50 mph, so the extra energy loss is not really an issue unless I'm trying to max my speed out.
The other 32 gears in my setup are all duplicates of the above gears and are not counted.

Luck ............ :D
rogerzilla
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Re: New 2 speed hub gear ...

Post by rogerzilla »

The losses in a good single-stage epicyclic gear, with sensible tooth count, good tooth profile and suitable lubrication (oil is best) amount to 3% when gearing up or down, and practically zero in direct drive. Things get sticky when you cascade epicyclics or add other complications.
pwa
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Re: New 2 speed hub gear ...

Post by pwa »

rogerzilla wrote: 9 May 2021, 5:14pm The losses in a good single-stage epicyclic gear, with sensible tooth count, good tooth profile and suitable lubrication (oil is best) amount to 3% when gearing up or down, and practically zero in direct drive. Things get sticky when you cascade epicyclics or add other complications.
The system in the OP is for single chain ring 11 speed, which is already hampered by higher efficiency losses than, say, 2 x 9 speed. And then you add on further efficiency losses. Okay, there might be some sense in losing the front mech if the bike really does spend half its life in gritty conditions, but the rear mech is still there! If grit in the works is the issue the only alternative that really stacks up is the heavy but reliable lump of a Rohloff, which would cost a lot less.
jimlews
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Re: New 2 speed hub gear ...

Post by jimlews »

I must re-commission my 48 sp set-up based around an FW.

FW Four speed with four closely spaced sprockets on the end and a triple C/W up front

I didn't notice much 'inefficientcy' with that set up. The derailleur gears were used to fill the gaps between the Sturmey ratios and extend the low end.

Actually a very good arrangement for light touring.

Also works with an S5. = 60 ratios. But I prefer the FW, personally. One can have too much of a good thing.
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mjr
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Re: New 2 speed hub gear ...

Post by mjr »

pwa wrote: 9 May 2021, 5:17amHub gears are inherently less efficient, wasting more of your energy, and they lack the flexibility you get by being able to tweak ratios through ring choice. As someone who has no problems with front mech and multiple chain rings I can't see why I might want to swap them for an energy sapping hub gear.
As someone with no recent experience, you seem to be relying on lab reports and ignoring that derailleur efficiency stinks worse once a modern narrow bendy chain is plastered with road crud. Normally, you can tweak ratios through ring and sprocket choice but I am not sure about this hub.
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
All the above is CC-By-SA and no other implied copyright license to Cycle magazine.
zenitb
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Re: New 2 speed hub gear ...

Post by zenitb »

Mick F wrote: 8 May 2021, 7:37pm I cannot recommend the SA CS-RF3 highly enough.
https://www.sturmey-archer.com/en/produ ... rf3-silver
In a normal world - not hilly Cornwall - it would take the place of a triple.

or perhaps a double? ..................... you lose a bit of efficiency in 1st gear, but 3rd is great, so you could just use it as a double.
Have to say the SA CS-RF3 looks very well engineered Mick .. and I suspect much better value for us mere mortals. I really like the way the axle is well supported by seriously sized bearings.. no piddly little sealed bearings ...

SA Internals
SA Internals
http://www.sturmey-archerheritage.com/i ... il&id=1140

(PS: really missing Brucey's input on this thread :-( )
pwa
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Re: New 2 speed hub gear ...

Post by pwa »

mjr wrote: 10 May 2021, 9:15am
pwa wrote: 9 May 2021, 5:17amHub gears are inherently less efficient, wasting more of your energy, and they lack the flexibility you get by being able to tweak ratios through ring choice. As someone who has no problems with front mech and multiple chain rings I can't see why I might want to swap them for an energy sapping hub gear.
As someone with no recent experience, you seem to be relying on lab reports and ignoring that derailleur efficiency stinks worse once a modern narrow bendy chain is plastered with road crud. Normally, you can tweak ratios through ring and sprocket choice but I am not sure about this hub.
I did go on to say that 1x11 derailleur systems are also inefficient, which means that what is essentially 1x11 combined with a hub gear gives you the worst of both. Okay, when in direct drive you only have the inefficiency of a 1x11 to overcome, but is 2x11 so bad? 2x11 is potentially more efficient than 1x11. I can see the logic of going for a hub gear system and I can see the logic of going for 1x11, but I can't see the logic of using both together. 2x11 or simply a hub gear system seem to me to be the better choices.
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Mick F
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Re: New 2 speed hub gear ...

Post by Mick F »

zenitb wrote: 10 May 2021, 11:27pm Have to say the SA CS-RF3 looks very well engineered Mick .. and I suspect much better value for us mere mortals. I really like the way the axle is well supported by seriously sized bearings.. no piddly little sealed bearings ...

http://www.sturmey-archerheritage.com/i ... il&id=1140

(PS: really missing Brucey's input on this thread :-( )
Spot on on both here.
One, it's well engineered, and two, we miss Brucey's input.
Mick F. Cornwall
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Mick F
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Re: New 2 speed hub gear ...

Post by Mick F »

PS:
Zenitb's picture shows two locknuts on the LH side.
135mm with both on.
Remove one locknut, and it's 130mm like in this picture.
130mm SA.png
Mick F. Cornwall
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