Hub gear ideas

For discussions about bikes and equipment.
MartinC
Posts: 1857
Joined: 10 May 2007, 6:31pm
Location: Bredon

Re: Hub gear ideas

Postby MartinC » 20 Oct 2013, 11:34am

If you want to put a hub gear into vertical drop outs then chain tension is an issue with a variety of solutions. Chain tensioners, magic gears, half links or excentriker bb shells (spelling may not be right!). The other issue is non turn washers. Shimano ones are normally ok - they have a substantial 'lump' on one side, close to the axle hole. SA washers can't be used because they have tabs either side of the axle. SRAM washers aren't good - they have a bent tab some way from the axle hole and their strength and how they engage with the drop out, especially the non drive side, is suspect. Modifying Shimano washers to fit SA or Shimano hubs means reprofiling the axle hole - not easy.

Brucey
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Re: Hub gear ideas

Postby Brucey » 20 Oct 2013, 1:04pm

SA now do external single tab NTWs which are similar in pattern to Shimano ones, but don't look quite as well made.

IIRC the shimano single pulley tensioner has a built-in NTW; obviously this only fits shimano hubs unless modified

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

fatboy
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Joined: 5 Jan 2007, 1:32pm
Location: North Hertfordshire

Re: Hub gear ideas

Postby fatboy » 20 Oct 2013, 2:16pm

Thanks for all the input. I think I am convinced that the donor vehicle is wrong. Might look at a trekking bike from Fahrrad Manufaktur using Bike2work next summer. When I get the chance I'm going to pop to Cambridge and take a look at some in Chris' Bikes.
"Marriage is a wonderful invention; but then again so is the bicycle puncture repair kit." - Billy Connolly

PH
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Location: Derby
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Re: Hub gear ideas

Postby PH » 20 Oct 2013, 3:11pm

fatboy wrote:The desire for a bigger range is for when I take the tourer touring.

When I'm touring, it's not a bigger range I need than when commuting it's a lower one. If I didn't have a Rohloff I'd have an Alfine 8 and swap the chainring before a tour. I'd be happy to tour with a 75" top gear which would give me a bottom gear somewhere in the low 20s.

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db8000
Posts: 22
Joined: 9 Sep 2013, 7:20pm
Location: Bristol

Re: Hub gear ideas

Postby db8000 » 20 Oct 2013, 3:13pm

Fatboy, for what it is worth (and i know this is each to their own preference) i bought a ridgeback tourer with alfine 8 at the beginning of the year and the lowest gear is easily low enough for all Bristol can throw at us. It is considerably lower than my compact standard shimano 105 chainset.
Can you try one out first?
The range, if anyhing, is missing at the top end. 35kph on the flat is about it. More than enough for any commute of mine.
The big plus is the almost zero maintenance over the last 10 months!

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Hub gear ideas

Postby Brucey » 20 Oct 2013, 3:18pm

a lot of people criticise bikes with IGHs for being 'slow' and assume that it is the IGH that is responsible. Fact is that they tend to be fitted in certain types of bike, so you can end up buying a different type of bike as well as a different hub.

A trekking bike is a case in point. How would you compare that with your tourer?

Might be worth going somewhere where they have essentially the same bike both with and without an IGH fitted. Not too many places where that is on the cards though...

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

townbikemark
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Re: Hub gear ideas

Postby townbikemark » 20 Oct 2013, 3:24pm

Thorn? Looks like they're built from the ground up for touring (even if they're a bit ugly...)
stereotype nonconformance...unpigeonholable...

http://townbikemark.blogspot.co.uk/

fatboy
Posts: 3417
Joined: 5 Jan 2007, 1:32pm
Location: North Hertfordshire

Re: Hub gear ideas

Postby fatboy » 20 Oct 2013, 6:00pm

PH wrote:
fatboy wrote:The desire for a bigger range is for when I take the tourer touring.

When I'm touring, it's not a bigger range I need than when commuting it's a lower one. If I didn't have a Rohloff I'd have an Alfine 8 and swap the chainring before a tour. I'd be happy to tour with a 75" top gear which would give me a bottom gear somewhere in the low 20s.


But can the hubs take the torque to do a 20" gear? If so then this idea might have some legs.

Completely different track, do chain guards fitted to a dodangler bike help in any meaningful way? I tried a mud flap before but that seemed not to keep the chain any cleaner at all.
"Marriage is a wonderful invention; but then again so is the bicycle puncture repair kit." - Billy Connolly

Brucey
Posts: 39522
Joined: 4 Jan 2012, 6:25pm

Re: Hub gear ideas

Postby Brucey » 20 Oct 2013, 6:49pm

shimano have recommended input ratios but these appear not to be warranty-invalidating restrictions per se. Plenty of MTBers run lower gearing that 20" it seems.

Chains get dirty mainly from the front wheel and a little from stuff coming from above (off the rear wheel) too. A front mudflap needs to be pretty well dragging along the ground before it stops most of the crud from flying up onto the chain; most simply are not long enough. A chainguard can stop the crud from above but won't stop the rest of it unless it pretty well covers everything; I've yet to see a completely effective and practical dedangler chaincase. I guess something is better than nothing though.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

MartinC
Posts: 1857
Joined: 10 May 2007, 6:31pm
Location: Bredon

Re: Hub gear ideas

Postby MartinC » 21 Oct 2013, 9:08am

Brucey wrote:SA now do external single tab NTWs which are similar in pattern to Shimano ones, but don't look quite as well made.

IIRC the shimano single pulley tensioner has a built-in NTW; obviously this only fits shimano hubs unless modified

cheers


Thanks, haven't played with a new SA hub for ages. Looks like SA have changed to facilitate vertical drop outs, encouraging, wonder if they''ll produce a tensioner too? Shame SRAM don't catch up - there seems to be precious little information available about the G8 but I'm think I've seen it with their original NTW's. Knowing what the gear ratios are would help too!

Brucey
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Re: Hub gear ideas

Postby Brucey » 21 Oct 2013, 12:15pm

the Sram G8 hub has an overall range of 259.7% and (it is claimed) evenly spaced ratios. Evenly spaced ratios would mean intervals of +14.7% on every shift. They also claim that all shifts can be made under load using a 'new system'. A test bike has been spotted with a 38/20 input ratio which would suggest that the hub gears down and gears up (as all sensible hubs should do... :roll: ).

So great for urban cycling but not enough gears or a wide enough spread of ratios for touring or MTBing.

In the meantime (just when I was beginning to despair of SA's IGH range) we have a new five speed hub;

Image

http://www.bikerumor.com/2013/10/01/ib13-sturmey-archer-introduces-new-5-speed-hubs-for-2014-adds-new-2-speed-disc-hubs-in-135mm-and-120mm-spacings/

with rotary shifting, and 242% range (+24.7% average shift interval, exact ratios unknown) the C50 model will be available in coaster, hub brake, disc brake and brakeless forms. It looks to me that the internals are shorter and fatter than previous 5s internals, and that the hubshell is wider-mouthed to accomodate the new design. So no swapsies with other SA internals, then (with the possible exception of the 8s hub perhaps...?)

I wonder how much the C50 owes to the older 7s design? I know it wasn't universally well received, but I had a soft spot for it, if for no other reason than it was internally very simple, for a 7s hub. Far simpler than a Nexus 7, for example.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

MartinC
Posts: 1857
Joined: 10 May 2007, 6:31pm
Location: Bredon

Re: Hub gear ideas

Postby MartinC » 21 Oct 2013, 12:55pm

Brucey wrote:the Sram G8 hub has an overall range of 259.7% and (it is claimed) evenly spaced ratios. Evenly spaced ratios would mean intervals of +14.7% on every shift. They also claim that all shifts can be made under load using a 'new system'. A test bike has been spotted with a 38/20 input ratio which would suggest that the hub gears down and gears up (as all sensible hubs should do... :roll: ).


Yebbut, they need to tell us what it gears up and down from 'cos just telling us it's got a 259.7% range isn't much use. I know where I am with ordinary 1 stage epicyclics with a direct drive and even numbers of gears either side! The other interesting thing is always how efficient each ratio is - it's not straightforward once you've got 1 or more set of gears involved in each.

I preferred the old Spectro 7 for commuting/utility (not enough range for touring or MTB though). Seven gears was enough and you could spend the most time in the efficient gears if you chose spocket and ring carefully. The one extra gear on the Alfine 8 isn't much of a benefit but going from most to least efficient between 4 and 5 is a pain. OK, you get efficient gears in 1 and 2 but if you ride somewhere hilly you'd want a better range anyway. I'd like to understand what the deal with the G8 is.

New SA 5' looks interesting. In my book 8 gears is too much, 3 a bit limited and 7 is only a bit better than 5 - so good and common (in the UK) 5 speeds are worth having. Rotary shifters are good too - I hope it's a SRAM style i-motion one rather than the fiddly Shimano cassette joint.

bobc
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Re: Hub gear ideas

Postby bobc » 21 Oct 2013, 1:34pm

Oooh - I like the look of that SA 5speed.
one of them with drum brakes & belt drive on an old roadie frame, sounds like my next commuting bike :)
Wonder when we'll find out about efficiency (probably never) and reliability.... I get the impression that SA have got a lot better on that front over the last few years.
That should be a proper zero maintenance bike.
On the belt drive front, 3 years ago there was info on t'web about an industrial 10mm wide carbon belt with 14mm tooth pitch - it was an alternative to gates at a third the cost: now I can't find it.... anybody seen anything like?

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Hub gear ideas

Postby Brucey » 21 Oct 2013, 4:03pm

MartinC wrote:
Brucey wrote:the Sram G8 hub has an overall range of 259.7% and (it is claimed) evenly spaced ratios. Evenly spaced ratios would mean intervals of +14.7% on every shift. They also claim that all shifts can be made under load using a 'new system'. A test bike has been spotted with a 38/20 input ratio which would suggest that the hub gears down and gears up (as all sensible hubs should do... :roll: ).


Yebbut, they need to tell us what it gears up and down from 'cos just telling us it's got a 259.7% range isn't much use.


They do say that the ratios are evenly spaced, and you know there has to be a two-stage gear in there somewhere, so there are bound to be one or two less efficient gears somewhere near the middle; there always are, that is how these hubs unavoidably work.... It is pretty much guaranteed to be a 2 x 4 system (or failing that a 3x3 with one missing perhaps) but there are going to be variations in efficiency for sure.

I'd like to know more about it too, of course, for similar reasons. But having said this I've found out far more about every IGH I've owned by owning it than I ever could find out from other sources; it is always a bit of a shot in the dark.

BTW I thought that the worst things about the i-motion 9 included the sealing, the spectacular lack of grease inside the hub, the complexity and the internal crush nut. But none of these things were even close to being as crummy as the shifter cable connection to the hub IMHO. In trying to make it 'easy to connect', they made 'it easy to break'. I anticipate that they will repeat the same ideas (mistakes..) with any new hub too. Not that the Shimano arrangement is especially good, but I'd sooner have that than the SRAM one, even if that was an improvement over those rotten click-boxes.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

xcalibur
Posts: 86
Joined: 20 Sep 2013, 2:19pm

Re: Hub gear ideas

Postby xcalibur » 21 Oct 2013, 4:43pm

I liked the i-motion 9 but I never got to use the bike more than 6 months. I remember I preferred the "finger type" shifter some nexus hub have to the twist grip type, but it was more of a getting used to the difference situation. I agree on the grease and water trouble some hubs have, nexus have had some worryingly open solution on some models. I had to replace the entire internals in a Nexus 7 at one point and with the replacement assembly came a new plastic side lid, which worked better than the original metal one, at least in the sense it closed more tightly. I haven't paid muched attention to numbers and shifting ratios, I care mostly about smooth easy shifting and enough gears to climb the local hills with ease.