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If you don't have a stepdown then you need stronger gear components which is difficult to do without a significant weight penalty - probably close to 100% at a guess.
I've been thinking about this, and I don't think it holds water - if you only have one front and rear sprocket, it's not much of a weight penalty to have them both quite large, and the torque situation is no different to singlespeeding - apart from the possibility of pedalling up much steeper stuff than normal singlespeeders...
The Rohloff gear hubs have a 2:1 limit.
Pinion: [url] http://www.pinion.eu/en/faq.html [/url]
[i]"In its present form, the P-1, including chainwheel, without cranks weights approx. 2.7 kg."[/i]
That's about 1kg heavier than the Rohly. But the CoG is in a better place.
Yes, not too bad. Any word about how much backlash there is in it?
The Rohloff gear hubs have a 2:1 limit.
how is this relevant ? They're not designed for BB mounting anyway
I'm just doing a project at work (engineering consultancy) reviewing different gearbox / drive systems for bikes. We have come to the conclusion that there is a reason that chains have been used for so long and will continue to be. They are cheap have good efficiency and allow for a lot of misalignment. Geared systems need comparativly high levels of accuracy in their machining and mounting. Plus you get issues with most of the load being taken by one tooth. This is why planetary gears are used, so the load is shared by more teeth. Yes you could make the gears from stronger material (and case harden it), but then it needs refinishing due to distortion. The cost of gears goes up and up, compared to bits of stamped out steel.
Systems like the Pinion may be very good for a few bespoke manufacturers, but until the big boys (i.e Giant) start making thousands of bikes that use systems like it, the humble BB and chain/deraileur system will continue to be used.
The Alfine system will start to be used more and more I think, and having it linked to a belt drive does make sense to me.
simonfbarnes - Member
'The Rohloff gear hubs have a 2:1 limit.'
how is this relevant ? They're not designed for BB mounting anyway
The relevance is that a heavy gear system would have to be even heavier to be used in that situation. I believe someone has prototyped a Rohloff in that position.
That was how the first G-Boxx's were designed, a frame-mounted Rohloff.
If a frame-mounted Alfine could be sorted out, especially one that could be retro-fitted, it could be a good thing. But would probably by ugly as sin.
Bear - get onto it then!
we've looked into using belts for some time and it's only just getting commercial now. we did also work on a gearbox hardtail idea that used the mount points for the gearbox as a way to have a Fisher CR-7 style mix of ti and aluminuim in the frame. but all in all, i couldn't imagine it being a better ride than an equivalently priced hardtail with xtr... it's good to work on these things to drive the industry forward, but if nicolai can't make a gearbox system that appeals to the masses i don't know who can. mechs and hub gears are the options that are here to stay for a long time yet.
actually having written that, i think of the Honda RN-01. it was made somewhere we have good links with. a great bike.. and they considered all kinds of transmissions, and what did they do? move the rear mech and cassette into the centre of the frame and enclose it in a box. it may have been a side-proect or engineer training but it was a brilliant conclusion imo.
simple and the best way forward i think. and, relatively easy to make and bodge into a frame. add a belt to transmit power from the box to the hub maybe, but call me old-fashioned, as much as i like belts i still would go for a simple chain on my own bike. i can't think of a good reason not to. they just work and are easy to work with.
I'm surprised that nobody has come up with a good CVT system using a belt yet.
CVTs are horribly difficult to get working correctly with any amount of torque, and torque is something cyclists have by the shed full.
if nicolai can't make a gearbox system that appeals to the masses i don't know who can.
Shimano?
er yes, maybe ) or probably, but although Shimano engineers are famous for giving nothing away, i get the impression that they don't see it as viable or worthwhile yet. tbh SRAM are more likely to do it first. Nicolai have a willingness to do something different and make it work as well as they can yet it's been a side-line idea for a long time now.
what i'm getting at is that nicolai have all the engineering intelligence to make systems like this work, yet their best efforts so far don't match an SLX drivetrain imo for general use. to make it more popular as a concept needs a lot less wight and more direct feeling, better efficiency etc.
maybe a shimano 2x10 'mech-in-a-box' is the best way then?
Ellsworth do a CVT. I forget what its called.
James, how about an Alfine-base G-Boxx? Let me have a sample (or two) and I'll sort it out for you 🙂
gearbox on the RN-01 is specific because it is not a classic gearbox like the Rohloff Speedhub for instance. It is commonly thought that inside the gearbox there is a classic derailleur, a cassette and a chainring. This is actually not the case. This explanation is a coverup for the actual design of gearbox, the design of which is for the most part, unknown. The freewheel is not placed on the rear wheel but in the bottom bracket so the chain is constantly moving when the back wheel is spinning.
Wikkipedia. Must be true.
[img] 
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That doesn't look heavy at all. Oh no.
Just found this too:
[img] 
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james-o - Member
...i think of the Honda RN-01. it was made somewhere we have good links with. a great bike.. and they considered all kinds of transmissions, and what did they do? move the rear mech and cassette into the centre of the frame and enclose it in a box...
That makes a lot of sense. It's hard to make a gear system lighter than a derailleur setup, and there's nothing wrong with chains so long as they are well lubricated. Back in the days of oil bath chaincases it was not unheard of to get 20,000 miles or more out of a chain.
With a carbon fibre monocoque frame designed to contain such a setup, there should be no weight penalty. There would still be the extra drive train, but it could be compact and contained in an oil bath chaincase like the Katz.
Until that happens though, I'm going to continue aiming for belt drive solutions.
[url= http://www.srsuntour-cycling.com/dstore/products/V-BOXX/2954/GB10-VB-FR9-BAZ/GB10-VB-FR9-BAZ.html ]gearbox[/url]
Back in the days of oil bath chaincases it was not unheard of to get 20,000 miles or more out of a chain.
but the oil will add to the weight of the product
Having run a hub gear with a chain for over 4 years the only real advantage of the belt seems to be saving a bit of weight and a very small amount of maintenance. My last chain lasted 3 years and the current one has done over a year of off road commuting and general use and I've never done more than wipe it over with a rag and spray it with GT85. I still like the idea of one though.
R.lepecha - Member
gearbox
That gearbox weighs 4.52kgs!
avdave2 - Member
...My last chain lasted 3 years and the current one has done over a year of off road commuting and general use
Hubgear and SS don't have the chain dangling down next to the road grit and also a straight chainline is much more tolerant of wear, so that's a fair point. But it's even better if you have a belt for the same job, lighter, quieter, and cleaner.
I agree with you epicyclo I just think that most of the advantage comes from the hub gear itself and the belt only offers a relatively small improvement on top. However once these things are working properly in frames designed rather than adapted for the purpose and the teething problems are ironed out then I'd get the Rohloff converted. The best thing about the belt in my opinion though is that the reduction in weight may encourage more people to try hub gears. And the more people do that then the more time and money the manufacturers will spend in trying to improve them.
I'm not sure the belt offers any efficiency gains but it certainly doesn't appear to have any negatives there in my experience.
I'm currently using a chain on my Alfine hub and a belt on a single speed and also a 3 speed S-A. I would use a belt for all purposes if it was feasible, but most of all I would prefer a sealed oilbath chaincase - unfortunately with current componentry that is not feasible.
however once these things are working properly in frames designed rather than adapted for the purpose and the teething problems are ironed out
avdave - that's what I'm doing. 🙂
epicyclo - I hadn't seen the Katz before you mentioned it, but I believe Mike Burrows has made a few along those lines. Nice
alfine gearbox? if yu have the time and the tools.. ! be nice to move the weight off the rear axle but planetery gears always feel a bit 'soft' to me for some uses, great for some applications but i expect the reason the honda used a mech-in-a-box was the direct feel and efficiency. i think a home-made mech in a box would be more achievable.
but i'll not be bothering ) if it's too filthy for gears, it's SS time.
I'd like to think having the Alfine gubbins mounted on the frame might make it feel a bit more direct. Just think, you could run a fixie rear wheel if the freewheel is on the frame, keep all the moving parts out of the gunk. Its got potential...
I'd love to get hold of a Pinion though. Combined with a Katz and a belt-drive...
UPDATE!:
[url= http://farm6.static.flickr.com/5213/5489727613_29693306f2.jp g" target="_blank">
[url= http://www.flickr.com/photos/ir_bandito/5489727613/ ]DSC_0405[/url] by [url= http://www.flickr.com/people/ir_bandito/ ]ir_bandito[/url], on Flickr
will get the rest of the bike back together over the next few days and report back...
looks industrial but good. I want one for my trance but they (belt drives) don't take well to tensioners
It'll not work on a Trance - you can't change the belt length.
This is on a Kona A which has a concentric pivot around the BB.
I know, hence the comment about the tensioner.
thepodge - Member
looks industrial but good. I want one for my trance but they (belt drives) don't take well to tensioners
My understanding is that there is not a lot of chain "growth" on the Trance or Anthem, so it would be interesting if someone measured that, because it may be possible to belt drive one if it is just a few mm.
Has anyone tried putting a tensioner on a belt drive?
I realise a singlespeed-style tensioner at the rear won't work but what about a tensioner at the crank end or halfway along the suspension arm? Surely you'd be able to get enough length change? (This is total armchair engineering, I don't even know how much chain stretch is require for a short travel full susser!)
I've always quite fancied trying a belt drive on my bike. I haven't been able to find out where to get Rohloff suitable parts though; not that I've been trying particularly hard...
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V8 - tensioners won't work as the belt can't be bent backwards.
I guess you could use a reverse sprung one though, as long as you still get adequate belt-wrap on the sprocket.
timangus, fitting the belt to a Rohly is a bit of a faff. Rohloff wil only change the fitting kit themselves (its not just a case of whipping the cog off), and only if you're putting it onto a certified frame design. They claim its to do with frmae stiffness, which I believe to be as much an issue with a singlespeed as a Rohly. I suspect its more the Rohloff can't handle the potential torque "bursts" caused by the belt ratcheting, which is why you have to fit a snubber. Also the Rohly can't handle the recomended tension, hence having to run it slacker which increases the chances of ratcheting. Vicious circle! Especially since the Gates snubber design is pants and can't handle the stresses caused by the belt climbing off the teeth as I've demonstrated. However, I have seen it done:
[url= http://farm6.static.flickr.com/5127/5279764790_365f7f38f6.jp g" target="_blank">
[url= http://www.flickr.com/photos/trafficbikes/5279764790/ ]Dropout Right[/url] by [url= http://www.flickr.com/people/trafficbikes/ ]trafficbikes[/url], on Flickr
I was thinking something mounted to the chainstay similar to the old DCD but sprung. might work for four bar systems but in the trance the chain goes through the frame and there are no joints / splits / pivots to thread the belt through
Heh, probably not worth the effort for now then.
out of interest, when using belt drive, why don't the valleys between the teeth on the chainring\sprocket just fill up with mud? Are they hollow underneath or sommit?
5lab - yeah, they have holes in. Only ridden in mud once (before I bent my previous snubber) and it seemed fine. Time will tell.
timabgus - yeah it is. I've thought about doing it to my Rohloff, but figured its easier not to. So this is being built singlespeed, and I intend to put a belt on an ALfine-11 in the future.
V8 - tensioners won't work as the belt can't be bent backwards.
I figured they would be similar to car cam belts? no problem bending them.
It says here:
[url= http://www.carbondrivesystems.com/images/uploads/installation_1239728288.pdf ]caution must be used before and during installation to avoid damaging the carbon tensile cords that make up the backbone of the belt’s strength. Excessive bending and twisting creates crimps which can lead to belt breakage under high load.[/url]
hmmm, i see what you mean, they make it sound as if it is particularly fragile!
Not to worry, it would be a while till I could afford an Alfine 11 for my superlight anyway, i'm just geeking 🙂
geek out, I say!
Its not that fragile, just doesn't like being bent backwards.
Watch this space for info on my A...
A tensioner could be rigged up below the front sprocket and push down. It would have to be for a setup with very little chain/belt growth though.
None of my conversions use no more tension than I would use with a chain.
I don't see any point in having the lighter belt drive if I have to have heavier duty components elsewhere.
Fundamental to getting off with low tension are no lateral flex/movement and precise chainline.
I'm more interested in the lack of maintenance than the weight. so I'd be happy if it weighed a bit more.
ir_bandito - where did you get the Gates parts from?