A friend at work (yes, honest) asked me why hub gear systems such as Alfines didn't come with double chainsets. I couldn't give him a conclusive answer - my guess is that the gear ratios are only calculated to work with a single chainring - but given that I don't know or understand the internals of an Alfine or Rohloff, is there an actual, true reason it's not done?
You would need a tension system to guide the chain slack, if you changed from a larger to a smaller gear.
Perhaps the simplicity of no 'visible' gears is the main attraction?
They will work, but you can't go too low or you'll over-torque the gears and strip the teeth. No reason not to go higher for ultimate speed if you've thighs of steel
I'm sure I've seen a custom Nicolai with a triple and a Rohly.
Saw a recumbent with 3 x9 and a rohloff
not reason not to alfine chainsets come in two sizes so you could have a double with those sizes
and also lots of hub gears are also combined with rear cassette clusters..
from 2 speeds cluster on a bromton 3 speed hub to upto 10speed cassette on 3 speed sram hubs etc..
Chain tension is the main issue. you would need to use ma rear mech to get a tensioner that would take up enough slack and then it all becomes rather pointless
Chain tension is the main issue. you would need to use ma rear mech to get a tensioner that would take up enough slack and then it all becomes rather pointless
or a mk1 alfine tensioner
rootes - thats only 10 tooth equvalent I thought
Of course sheldon brown has done it
http://sheldonbrown.com/otb.html
Isn't a tensioner just an admission that the chain tension isn't correct?
If you fit one you might as well have a rear mech.
I am sure there will be exceptions but surely the main point of hub gears is robustness and clean, simple, non damaging lines.
Having said that how about a 14 speed Rolhof plus 11 speed cassette plus a triple ring?
OK, I'm accepting 'pointless' as a reasonable answer. Means adding a front derailleur, extra ring etc so more weight. Thanks all.
By by reckoning, with a Rohloff, a 10spd cassette, a triple chainset and a Hammerschmidt you'd get yourself 840 gears.
And more than half of them unusable exceeding torque limits or leg limits 😉
Pah, details...
By by reckoning, with a Rohloff, a 10spd cassette, a triple chainset and a Hammerschmidt you'd get yourself 840 gears.
And duplicates of gear inches. So probably only 20 - 30 different "gears".
[i]Isn't a tensioner just an admission that the chain tension isn't correct?[/i]
or just the fact that the frame doesn't have a 'built in' method for adjusting the distance between hub and BB?
I use a Rohloff tensioner on my Giant NRS as I run it singlespeed and need something to work with the chain length changes as the suspension compresses.
no reason why alfine 8 and a double chainset wont work. Corratec built a 29er trekking bike a few years ago with just such a drivetrain.
going off on a tangent...
as far as i am aware, you do not lose substantial amounts of weight at the chainset part of the gearing by removing chainrings (50g at a time?) and unless you shell out £££ and go for, say an e-thirteen ss crankset then you may as well stick with that double or triple at the front.
theres a surprisingly large chunk of weight in the cassette, especially with the deore models.
maybe theres a logic to running a triple chainset combined with a hope trials hub at the rear with half of a shimano 10 speed xt cassette (i could easily live with a 5 speed cassette).
back to the topic, i would rather shimano released a close-ratio 8 speed hub for those of us wishing to use a double up front.
Surely it would be more reliable than a cassette, at least you are making far fewer gear changes and shifting the chain a much smaller distance.
A compromise until I work out how to get a frame mounted gearbox light enough and strong enough to make my millions. 😀
A compromise until I work out how to get a frame mounted gearbox light enough and strong enough to make my millions
[url= http://www.pinkbike.com/news/Pinion-gearbox-first-ride-2011.html ]like this?[/url]
What! they've copied my idea! Talk about nothing new under the sun.
I'll still have a go at a little experimentation.
Of course the answer to this in an Alfine with Hammerschmidt cranks.
Dead easy to do,
rohloff, pauls and shimano all make chain tensioners to run double/triple with a geared/singlespeed hub
Yup, got to say the more I look into it the more interesting it becomes.
My problem is that my Trek probably won't take a hub gear, due to the ABP pivots needing an axle that will go through the bearings.
I'm reluctant to buy an Alfine and then just drill it out and cut it down, only to find it still won't work.
However, I am going to look for a secondhand one and have a play.
I was going to use an 8sp Alfine in a stumpy FSR, with the Mk1 alfine tensioner and double up front until I found that
1) the drop outs wouldn't take the alfine locator tabs so the axle and hub wouldn't sit securely.
2) the chain run was so far out it was stupid.
Be interested to see how you get on tim.
The Rohloff has a plenty wide enough range for me.
I,ve read various posts about an alfine 8 and a double chainset, so this is what I,ve done and why.There is a massive jump between 5th and 6th gears on this hub, to "split" this gear I,ve used 46/42 rings(the best compromise to split other gears as well)with 27" wheel and 19t sprocket the 16 gears are nicely spaced 31.5-105.6 inches.I have used a twin jockey chain tensioner(easy to clean) to give good chain wrap around on the sprocket.L&R alfine rapidfire shifters on a 22mm bar I made and mounted next to the hoods give a lovely change.Careful sourcing from ebay(nearly new wheel and hub was £69 inc. del.) and selling all my 10s stuff, the work has cost about £20.This bike is used all winter so high chain/cassette costs are gone just a low cost chain now and again and much easier cleaning.I know I could have used alfine 11 but the cost would have been too high and anyway I have 16 gears.