Hub gear ideas

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TwoWheelsGood
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Re: Hub gear ideas

Postby TwoWheelsGood » 21 Oct 2013, 6:58pm

MartinC wrote: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.

I've tried a bike with the Alfine 8 hub and was distinctly underwhelmed despite being a fan of hub gears. The gap between gears 4 and 5 was more noticeable than I thought it would be, the hub was slow to change between certain gears and it didn't feel that efficient at times either, though at least Shimano have now changed the push-button shifter so that it shifts the same way as their derailleur set-ups (the old shifter was distinctly annoying for that reason alone). The Alfine 11's supposedly faster to shift and feels more efficient but of course is more expensive (initial purchase price as well as an expensive and mandatory oil change early on) and less tolerant of abuse.

The SRAM G8 could be good but its relatively narrow overall gear range does make me question its actual worth; all that additional complexity, weight and potential for efficiency loss over a 5 speed hub for something that doesn't exactly give that much back in return aside from narrower gear steps, though I suspect that the G8's target market relates to heavy, continental-style utility bikes that could be towing trailers. If the hub was lighter, the bike would be lighter and there would arguably be less need for narrow(er) gear steps as a consequence.

And then there's the new SA 5 speed hub, which is arguably the most interesting of the lot for many purposes, having a wider gear range than the original SA 5 speed hub but narrower than the 256% of its successor (which is possibly too wide a range for only 5 gears) but still wide enough to offer benefits over a tradtional 3 speed hub. There's also an extremely rare Shimano Nexus 5 speed hub (overall range 206%, gears roughly equivalent to 2,4,5,6,7 of a Nexus 7) which may be officially launched next year (my guess) if Shimano decides to make it more widely available, but it doesn't offer a significantly greater range compared to a 3 speed hub.

cycle tramp
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Re: Hub gear ideas

Postby cycle tramp » 22 Oct 2013, 6:25pm

fatboy wrote:
eddiewalkling wrote:I see your thinking but arent you only loseing a cassette that way?

With double chain rings you might only be able to use a narrow chain which would be just as likley to wear. If thats true you have just added weight but not made it any tougher.


Hmmmm I see this needs more thought!


( The link to Chris Bell's very capable touring bike built around the same idea http://www.highpath.co.uk/highpath/tour ... index.html )

Indeed if you went down that route its true that you would still have to keep the changer reasonably clean in order for it to move the chain from one chain ring to the next, but the rear wheel should be stronger (as there is less wheel dish) and when you'd come to replace the sprocket, it should be cheaper than the cassette....
....another hub that hasn't caught on yet in the Nu-Vinci N360... which i'm currently using... a slightly better range than the alfine 8, and because of its unique transmission comes with an infinite number of gears within the range... however, the down sides are that it weighs at least double that of any other hub gear, and no efficiency figures have been quoted. However, if you get a chance to ride a bike with such a gearing, i would take up that offer. As one person described the hub ~ it feels more like sailing, than cycling!

Brucey
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Re: Hub gear ideas

Postby Brucey » 22 Oct 2013, 7:40pm

I have recently been using a chain which is a bushingless 1/8" chain. This means it is as flexible as a derailleur chain, but is going to wear the sprocket at a much lower rate. However, I'm not convinced that it will enlongate very much more slowly, because the bushing area is similar to a 6s/7s chain; however there is a handy space there in the middle of each bushing to act as a lubricant reserve, so who knows....

Anyway this chain is just about the right width that it will even run on some 6s blocks, I reckon. It will certainly go onto a typical double chainset/IGH setup I think, because some of the chainring spacing is there to accomodate the angled chain on small-small running, which of course you don't get in the same way with an IGH setup. I think most 1/8"chains will be OK for similar reasons.

I still think that a single pulley tensioner should be OK for this kind of setup, if it is the right one. Unfortunately the Alfine single pulley tensioner is not spring loaded IIRC.

cheers
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SA_SA_SA
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Re: Hub gear ideas

Postby SA_SA_SA » 23 Jun 2020, 2:10pm

Brucey wrote:... Unfortunately the Alfine single pulley tensioner is not spring loaded IIRC.....

I noticed Taylor wheels sell shimano 3 speed IGH wheels with coaster brake, with 120mm OLN which I presume could be spaced to 135mm?....

I wondered if a coaster could be used in with vertical dropouts if the chain tensioner was simply adjusted to remove looseness then locked in place ie not sprung? Would any off the shelf tensioner be suitable.
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Brucey
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Re: Hub gear ideas

Postby Brucey » 23 Jun 2020, 6:41pm

SA_SA_SA wrote:I noticed Taylor wheels sell shimano 3 speed IGH wheels with coaster brake, with 120mm OLN which I presume could be spaced to 135mm?....


only if the axle is long enough. IIRC there is more than one axle length for such shimano hubs, and different length control rods etc to match.

I wondered if a coaster could be used in with vertical dropouts if the chain tensioner was simply adjusted to remove looseness then locked in place ie not sprung? Would any off the shelf tensioner be suitable.


to be safe the tensioner would have to be able to repeatedly withstand the chain tension loads that may occur during braking. AFAICT this effectively prohibits the use of a coaster brake with vertical dropouts/derailleurs. I think it has only be done commercially once; ISTR Sachs made a system of this sort, in which the derailleur locked solid (tension-wise) whenever the pulleys were turned backwards, using some mechanism that I do not know the details of. For whatever reason this product was not so successful that they sought to continue making it or revise it. My suspicion was that it was in effect a brake that 'wasn't reliable enough'.

I have not seen a tensioner that looks robust enough to withstand coaster braking loads, and furthermore it may be impractical in that the tensioner is bolted to a flimsy piece of aluminium on most modern frames which have vertical dropouts.

cheers
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SA_SA_SA
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Re: Hub gear ideas

Postby SA_SA_SA » 23 Jun 2020, 8:24pm

Brucey wrote:.... ISTR Sachs made a system of this sort, in which the derailleur locked solid (tension-wise) whenever the pulleys were turned backwards, using some mechanism that I do not know the details of. For whatever reason this product was not so successful that they sought to continue making it or revise it. My suspicion was that it was in effect a brake that 'wasn't reliable enough'.

I have not seen a tensioner that looks robust enough to withstand coaster braking loads, and furthermore ....

Thanks.

drat :)
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SA_SA_SA
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Re: Hub gear ideas

Postby SA_SA_SA » 26 Jun 2020, 5:49pm

The shimano 3 speed seems available in prebuilt 559 wheels with a 170mm long axle and a roller brake (although I am dubious about a roller brake for touring where one might use the rear brake a lot on down hills)....at least a large rear disc has no grease to boil....
it is also available in disc brake version although I can find no ready built 559 ones.
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Brucey
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Re: Hub gear ideas

Postby Brucey » 26 Jun 2020, 9:10pm

IMHO the shimano hub is hampered for heavy duty use by the steel hubshell. It does make it more difficult to build a decent wheel.

cheers
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simonineaston
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Re: Hub gear ideas

Postby simonineaston » 26 Jun 2020, 9:20pm

I totally think ihgs are the way to go for commuting - totally. Any way you want - go for it! When Y5 or 6 ticks round and you suddenly realise you haven't done anything more than just use the thing, you'll be so glad you went that route :-)
ttfn, Simon in Easton
(currently enjoying a Moulton TSR & a nano Brompton...)

mikeymo
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Re: Hub gear ideas

Postby mikeymo » 26 Jun 2020, 9:58pm

NUKe wrote:piggy backing on this anybody any clever options for elgantly fitting hub gears into frame withvrtical d drop outs. I 've been thinking of doing similar to my Dahon espresso. But want an elegant solution so I can use a chain guard (I dont need the double upfront)


This calculator reckons to give you the exact combination of chainring and sprocket, for a given chainstay length and chainlength, so as not to need any sort of tensioner or horizontal drop-outs. Though as the chain stretches presumably it goes slack.

http://eehouse.org/fixin/formfmu.php
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Brucey
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Re: Hub gear ideas

Postby Brucey » 26 Jun 2020, 10:29pm

mikeymo wrote:...This calculator reckons to give you the exact combination of chainring and sprocket, for a given chainstay length and chainlength, so as not to need any sort of tensioner or horizontal drop-outs. Though as the chain stretches presumably it goes slack.


It does indeed. But for running VDOs

a) tensioners are not that bad in the grand scheme of things; if you can have a sprung-loaded one with one large-ish pulley it is about the least aggro. I quite like the DIY one posted recently (using a v-brake arm); a variation on this design could be both sprung loaded and screw-adjustable so as to prevent excess movement in the other direction.

b) slack chains are 'not that bad after all' if they have curved inner side plates etc. They fall off surprisingly un-often and develop other running problems only when the vertical slack in the chain is about 3" or so, much slacker than you might imagine.

c) between half-links (equivalent to 1/4" axle movement), chainrings which differ by 1T (equivalent to 1/8" axle movement) and filing VDOs a little, you can run with a fully tensioned chain if you want to. You only need 1/16" axle movement in the dropouts, provided you are happy to run with a slightly slack chain sometimes.

d) you can get eccentric BBs that fit in BSC threaded BB shells; this is a bit pricey though.

cheers
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mikeymo
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Re: Hub gear ideas

Postby mikeymo » 26 Jun 2020, 10:32pm

Doh!

Vertical Drop Outs
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mikeymo
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Re: Hub gear ideas

Postby mikeymo » 26 Jun 2020, 10:42pm

Brucey wrote:
mikeymo wrote:...This calculator reckons to give you the exact combination of chainring and sprocket, for a given chainstay length and chainlength, so as not to need any sort of tensioner or horizontal drop-outs. Though as the chain stretches presumably it goes slack.


It does indeed. But for running VDOs

a) tensioners are not that bad in the grand scheme of things; if you can have a sprung-loaded one with one large-ish pulley it is about the least aggro. I quite like the DIY one posted recently (using a v-brake arm); a variation on this design could be both sprung loaded and screw-adjustable so as to prevent excess movement in the other direction.

b) slack chains are 'not that bad after all' if they have curved inner side plates etc. They fall off surprisingly un-often and develop other running problems only when the vertical slack in the chain is about 3" or so, much slacker than you might imagine.

c) between half-links (equivalent to 1/4" axle movement), chainrings which differ by 1T (equivalent to 1/8" axle movement) and filing VDOs a little, you can run with a fully tensioned chain if you want to. You only need 1/16" axle movement in the dropouts, provided you are happy to run with a slightly slack chain sometimes.

d) you can get eccentric BBs that fit in BSC threaded BB shells; this is a bit pricey though.

cheers


I thought about doing this when I was searching for a steel frame, with 135 OLN, but horizontal or "semi-horizontal" drop outs.

I wondered if there could be a system where you had 2 (or 3, or 4) chains that you swapped until they were all tiny bit worn. Then changed the sprocket/chainring combination to take out the slack, and run the same multiple chains, until they were a tiny bit more worn. Repeat until the chain is actually worn enough to damage sprocket or chainring. Start over again.

Then I thought - Bob Jackson charges £105 for new rear drop-outs.
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Jdsk
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Re: Hub gear ideas

Postby Jdsk » 26 Jun 2020, 10:46pm

Brucey wrote:d) you can get eccentric BBs that fit in BSC threaded BB shells; this is a bit pricey though.

There's an eccentric axle advertised on the same page as that calculator: any experiences anyone?

Jonathan

mikeymo
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Re: Hub gear ideas

Postby mikeymo » 26 Jun 2020, 11:10pm

Jdsk wrote:
Brucey wrote:d) you can get eccentric BBs that fit in BSC threaded BB shells; this is a bit pricey though.

There's an eccentric axle advertised on the same page as that calculator: any experiences anyone?

Jonathan


Does that not obviate what the OP is asking about though? A hub gear system?

To be honest even if I were building a fixed gear/single speed bike (which I assume is what that hub is intended for) I wouldn't build the whole bike around a particular component like that.

As I said, I looked into this, when I was hoping to build up the perfect steel frame hub geared bike. And I came to the conclusion that achieving chain tension through component jiggery-pokery was a lot harder than just doing it the old fashioned simple way - with horizontal dropouts.
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