Rob_E

I'm planning on converting my rear wheel to an IGH. The bike has vertical dropouts, so I'll need a chain tensioner, so I'm thinking, if I have a chain tensioner anyway, why not leave the front derailleur on and give myself that much more gear range?

The only reason I can see not to would be if the chain tensioner didn't take up enough slack to allow me to shift between the front rings. Do tensioners specify how much slack they can take up, or are some known to be good or not good for that application?

I'm thinking of a 34/52 or a 34/54 compact double up front. I'd love to hear from anyone who has any experience trying a similar set up. Thanks.

tcs

You mean, like the Jamis Commuter 4?

tcs

Rob_E

That's exactly the kind of thing I'm looking for. But I can't find anything on the chainline for the Alfine tensioner, but given that the hub has a 42 mm chainline, I'm assuming the tensioner is right in that range as well, adjustable up to an additional 5 mm, which still doesn't put me where I want to be (51 mm). But other than that, that's just the type of thing I'm looking for. And so far it's the first I've seen that actually says how much slack it can take in (16 teeth), which is not quite as much as I'd hoped, but that's the type of info I need when picking out my chainrings. I could limit myself to a 16 tooth chainring difference, but I don't know if that's standard or just the Alfine tensioner that can do it, and the Alfine seems to lack the chainline adjustments that I need.

tatfiend 

The Rohloff chain tensioner has a capacity of 10 links per their web site and an adjustable chainline, via spacers. Not sure if 10 links is 10 or 20 teeth capacity. A rear derailleur, locked into the correct position, can also be used as a chain tensioner.

BTW keep in mind that many gear hubs list a minimum input ratio, chain ring teeth to hub input sprocket teeth. This is to limit the torque the hub is subjected to. Excessive input torque can damage a gear hub. Hubs from Rohloff, Sram and NuVinci all have clearly listed minimum input ratios.

Sixty Fiver

I once built up a bike with an SA rear hub and dual chain rings that used a standard short cage derailer to regulate the tension and the system worked flawlessly.

127.0.0.1

chain tensioners barely work on single speeds they are supposed to help

it will not work very well at all with varying chain lengths

the chain must approach the rear cog greater than 1/2 circumference, or
it will skip all over the place. derailleurs do this, chain tensioners will not
do this reliably

best to get a derailleur and lock it in position

Sixty Fiver

I am not enthused about many chain tensioners as a decent rear derailer can do a much better job (that is what they are designed for) and quite often costs far far less.

Rob_E

I knew Rohloff had one, but I seem to remember when researching it that it had the same problem as the Alfine, just in opposite direction: chainline is set too far out, rather than too close in, which is, of course, something I can't adjust with spacers.

I'm looking at the Paul Melvin Chain Tensioner, which can handle up to 20 teeth worth of slack, which would be perfect, but I can't find any chain line information on it. Still, it may be my best bet at this point. Short of a derailleur.

The hub I'm planning on using is the Nuvinci, and I've heard it can be little fiddly to get their vertical dropout kit installed in conjunction with a tensioner, so I'm concerned that trying to fit an full derailleur on there may not work, but I'm keeping it as an option.

And I do know about the torque limits of the Nuvinci. They require back to front ratio of 1:2, so I'm planning on going 17 in the back and 34 in the front. Then, because there's no upper limit for the front chainring, I'm planning on getting the biggest front chainring the tensioner will allow to give me the widest possible range.

Sixty Fiver

I have also set up a number of IGH bikes with a dual drive in the rear... an SA hub will accommodate two 3/32 cogs (instead of a 1/8 cog and spacers) and setting up a rear derailer and shifting system is fairly straight forward.

I have a thread on this in the folding forum... doing this on a Twenty was a little more involved as I had to make a few more mods but the drive works beautifully.

https://www.bikeforums.net/folding-bikes/398693-another-damn-twenty-thread-twist.html

Rob_E

That's an interesting thought. Certainly if I was going to need to run a full rear derailleur anyway, that might be a way to go. No point in having a full front and a full rear derailleur if only one of them will actually be used in shifting. Although I still need a good look at the way the Nuvinci is seated in the vertical dropouts to see if I would have the clearance to install a full derailleur. And I'd have to see if two cogs would fit on the back. I'll have to keep that in mind if I can't get this tensioner thing figured out.

Pocko

There are spring-loaded single speed tensioners with adjustable chainlines, but they could be inadequate.

What about using a short-cage derailleur? The Ultegra would be pretty light and compact. You can install a short (2-3 inch) bare inner cable between the cable adjuster-screw and the parallelogram cable-clamp, so that you can get the "feeder" wheel lined-up roughly to the IGH sprocket. Then the derailleur cable adjuster-screw would then work to fine-tune the chainline alignment.

.

Rob_E

Yes, from the research I've been doing, it seems that single-cog derailleurs don't take up enough slack for shifting, or, at their most extended position, don't give you enough chain wrap on the rear cog. Although if someone has a different opinion on that, I'd love to hear it because a nice, single-speed tensioner would be easier.

The derailleur option may work, but it's all going to depend on whether or not I have the room to install one. And while I like the idea of having that built in adjustment, I would rather not put a full derailleur on there if it's not necessary. It seems like a bulky piece to use when you don't actually need it to shift. But then, if I was going to worry about the weight of the pieces, the Nuvinci would probably not be my choice of hub.

I do think I found one BF member who said they used a Melvin with a Nuvinci, so that may be my best option so far, although the derailleur may be the cheaper way to go.

a77impala

I found out the hard way that a chain tensioner will not work. I put a 52 by 44 crank on my single speed and went for a ride shifted it to the 44 tooth chain ring and worked fine until going up an incline I stood up to pedal. The chain climbed over the rear cogs fell off the gear and I went flying to the concrete. I hit on my butt and the back of my head, my helmet hit hard enough to split in two. Other than injured pride I was okay.
The lesson learned, the chain has to contact more cogs than it did. If I was to do that again I would use a derailleur on the back and that would work. I have given up on multiple chainrings for that reason, if I have to use a derailleur I might as well have a multiple speed bike.

Rob_E

Ouch. What kind of tensioner were you using? Some of my reading other places has mentioned that a single pulley tensioner with too much slack might not give you enough contact with the rear cog. That's why I'm now looking at double pulley systems. They seem to pull more chain and keep it farther up, giving you more chain wrap around the cog. The trick seems to be finding one that can be adjusted to match the chainline of my hub.

Pocko

^ I have been thinking about this too and appreciate the dilemma... on one hand a 2speed crank has merit to be paired with an IGH to double the gears... on the otherhand, an IGH paired with a derailleur (used as the only viable chain-tensioner) looks odd and just doesn't make any sense. The combination is a double weight penalty on the rear axle too.

There could be another solution but the technology is still at early stages. In downhill mountain-biking, Bionicon and SRAM have both been developing a 2speed planetary crank... or Internal Gear Crank (IGC).

The images you'll see of it are pretty "hefty" as the cranks are designed for extreme off-road use (jumping & trick riding). If (that'll be a big IF) these companies ever decide to make a lightweight road version, that might be the solution you're after for your IGH. With a slotted dropout, a chain tensioner won't be necessary.

Have a look:
https://www.bikerumor.com/2008/09/04/...rbox-crankset/

and a movie:
https://www.youtube.com/watch?v=tt6hJDvKFKo

SRAM also makes one called the Hammerschmidt:
https://www.spoke.ie/2008/09/23/sram-hammerschmidt/


.

Rob_E

Yes, that or the Schlumpf (sp?) drive would solve the problem. But at a hefty price. Plus the bike I'm building up does have vertical drops, and I'm unlikely to change frames just for the benefit of horizontal drops. As a result, some type of chain tensioner will be required, so I figure why not make it one that I can use with front derailleur.

DavidL

why don't you just make it a geared bike if you're going to go through so much trouble. and for what? so you can use the internal hub instead of a freewheel and a rear derailleur? I've never actually used and igh before, and maybe there's something i'm missing, just my 2 cents

Rob_E

Because I don't want to. That's the short answer.

I have two bikes. One is an old 3 speed. One has a front and rear derailleurs. What I like about the 3 speed is that I can shift any time and the drive train stays pretty maintenance-free. I suspect that the cog and chainring that were on the bike when I got it are the ones that were on there originally 30 years ago. The drive train seems impervious to any riding weather, and if/when I do wear the drive train down, one cog, one chainring, and one chain will be easy and fairly inexpensive to replace. What I don't like is the gear range and the gear options. What I like about the other bike is the many gears I have to choose from and the difference between the high and low end. What I don't like is the fact that after two years I'm about to need a 3rd rear gear cluster and probably new chainrings in front as well. I ride in all weather, and I can see the result of that in the speed at which my cogs wear out and the way that rear cluster collects grime. I don't like having gears I can't use because of chainline and chain stretch issues. In fact when you look at the unique, usable gears compared to the actual gears, there's really not a huge amount of gear options, although still considerably more than my 3 speed.

With an IGH in the back and a compact double up front, I have a better gear range, minimal chainline issues, and, with the nuvinci hub, a nearly infite number of gears to choose from within that range and the option to choose between most of them whether I'm in motion or stopped.

At least that's the theory. If I can get it to work, I expect to have most of the benefits of both of my current set ups with most of the downsides gone or at least lessened. It may end up being more trouble than it's worth, but it seems like it also may end up being as easy, or even easier, than a more traditional set up. The chain tensioner of some sort is necessary whether I go with a gear cluster or an IGH. The only trouble I'm going through that I can see is getting the right chain tensioner from the get go. Once I have all the pieces, I expect that they will go together without much more trouble than a normal derailleur set up, and once they are set up, I hope for less maintence and adjustment than what I see in my current derailleur bike

And also, the Nuvinci looks like a fun thing to play with. And that's probably the best reason. I'm in this to have fun.

Sixty Fiver

An IGH with a dual drive is very efficient as it maintains a very good chain line and the internal gears are still very well protected from the elements... with my 3 speed dual drives I have also gotten some very nice 6 speed gear ranges with no overlap.

I set up my Twenty so that it had good top end for general riding and a low range that got used for towing a trailer and climbing some extreme hills.

In very cold conditions the IGH also continues to run very well due to the fact it can be oil lubricated and synthetics can be used.

That... and it is a very inexpensive way to upgrade an IGH to give it a wider range.

tatfiend 

By the time you combine a gear hub and a two speed IG crankset such as the Schlumpf you are approaching the cost of the Rohloff gear hub which comes with the wide range wanted and can be set up for lower gears than any other gear hub if you stay within manufacturers input ratio guidelines. The Rohloff is also a lot lighter than the solutions being discussed.

The NuVinci, again staying within input ratio guidelines, can have a low of between 25" and 27" depending on wheels and tire sizes selected. No way to get lower while staying within recommended input ratios. The iMotion9 has similar limitations. Either one will give a high in the 85" to 95" range with this gearing, again depending on wheel and tire sizes used. Do you actually need a higher gear than this for most riding? It might be a lot cheaper to improve your cadence.

The solutions being discussed all add complexity, weight and expense. The purpose of an IGH IMO is to simplify the chainline. The discussed solutions, other than the 2 speed IG cranksets, do not do so. Might as well stick with a wide range derailleur setup.

One member of the Yahoo Geared Hub Bikes group, link below for those interested, is running a vertical dropout 650C road bike with the SRAM 7 speed gear hub and the Surly single idler pulley chain tensioner with totallly satisfactory results from his posts. The Surly has a wide range chainline adjustment and is about as simple a chain tensioner as it is possible to find. It actually increases chain wrap slightly as it runs below the lower run and tensions by pushing up on the chain lower run based on the photos of it installed I have seen.

https://groups.yahoo.com/group/Geared_hub_bikes/

Except for the Rohloff gear hubs still all have limited gear ranges and limits on low gear. Until someone comes out with a 400% to 450% range 11 to 12 speed, or CVT, hub at a reasonable price that allows a 20" low gear this will remain true. If a 300% to 350% overall range, and the current low gear restrictions, do not meet your needs then stick with derailleurs. Either way you will be better off than all of the folks riding single speed and fixed gear bikes a far as versatility goes.

Rob_E

No doubt it would be. But I've been riding pretty much the same way, with no consistent cadence to speak of, for 25 years, so my preference is to get a bike that works with my riding style, rather than adjusting my riding style to match my bike. I'm basing my desire for a slightly higher range on the fact that the Nuvinci hub alone has a slightly lower range than my current 3 X 8 set up, and I occasionally have a desire for a little more in the upper range. It's true that it's not most of the time, but it's often enough that I thought the boost in the upper range would be nice.

Maybe I'm thinking about this wrong then, but I was thinking that even with a double up front, my chain line would be much improved over a double derailleur set up. In each gear my chainline would be less than one chain's width of straight, which seems to be a much better scenario than my double derailleur set up.

I understand that using a front derailleur is more complex than not using one, but then using any gearing is more complex than no gearing, just not as useful to me. It just seems that it hinges on the selection of my chain tensioner. With the right one, the set up for the front derailleur will be no more complex or expensive than any other front derailleur. And as for weight, well every component pales in comparison to the Nuvinci hub's weight, so I don't expect weight of the front derailleur will be an issue.

Pocko

^ Let us know what you come up with by way of a chain tensioner.

I've got a SturneyArcher 3 speed and I'm thinking of using it for a project where a 2 chainring crank would be ideal. I'm interested in this format.

I'll be rummaging through the internet to see other tensioner offerings that can handle the slack of a 2-ring crank set-up.

Cheers.

.

Rob_E

So far I've seen one person on these forums mentioning using a Paul Melvin chain tensioner for this, so unless I can find another option or unless I hear that that will not work, I may have to give that a try. The Melvin also pulls the most chain of any other I've looked up for this: 20 teeth. But for your purpose, you might look at the Alfine tensioner. Lots cheaper, but as long as the Sturmey hub doesn't put the chainline out too far, it may do the trick, although it'll only pull in a 16 tooth difference, I believe.

DavidL

Touche

jtarver

Okay, I just got a few pieces towards an IGH Touring set up.
What I have:
Inter-7 Hub
Alfine Chain Tensioner
Problem Solver Travel Agent
Deore FD
Sugino XD600 26-36-46 74/110 7/8spd Cranks

My main goal was to build a bike suited for touring Mexico. A friend had told me that he often had to take buses and his RD suffered badly. I have a 1976 Raleigh SuperCouse MKII I was going to use, but after realizing the Alfine tensioner would require a RD claw to function. I'm trying to keep it simple so I opted to look for a true touring frame with RD hanger braze on. I have a tensioner that mounts similar to a RD Claw, but again, too bulky.

So, my point is,now I'm wondering if I'm going to like the set up I planned? It doesn't really solve the RD problem as the Alfine tensioner is just a simplified RD. It would seem to be vulnerable to bending. The hub is really heavy, I'm not used to IGH so it really suprised me. I also want to use barcons, which will require the Travel Agent. It really sounded great at first, but I think it was just the thrill of pulling off this hack that I got caught up in. I think maybe I'll just build a commuter with the Nexus and remove my RD and tape it to the chainstay or something when getting on a bus. Hope this helps some, I'm not discouraging the OP by any means, hell, I may still have a go at it myself, it's just where I'm at in the process. The Rohloff may be what I really want and just got sticker shock.