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Old 09-14-05, 09:56 PM   #1
grolby
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Multiple chainrings with internal gear hubs?

Hi there. I just happened to notice on the internal gear calculator on Sheldon Brown's webpage, and the fact that you can enter up to three different chainring values! That seemed a little crazy, but I entered some values, and holy cow! Combining a 46/36/26 crankset with an 18 tooth cog on the Shimano Nexus 8-speed hub would give a range of 22.8 to 101 gear inches on a bike with 26-inch wheels. Thats 443%! That's roughly comparable to using the same crankset with a Megarange freewheel or cassette, and has obvious benefits in a touring application.

Now, unless you're getting really high-zoot derailers and cogs, it's probably more cost effective to go with the derailer gearing option. The use of integrated brake/shift levers could easily push the cost the other way, however, and besides I'm curious: is this even doable? It would certainly require some tinkering - at the very least a chain tensioner to take up slack in the chain, and perhaps some fiddling to get the chainline straight in the middle chainring, but... man, what a unique bicycle that would be!

Does anyone think this would work? Have you done this? Do you know someone who has? Could you use a chain tensioner in that way? Am I crazy?

Anyway, let me know what y'all think. Cheers!
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Old 09-14-05, 10:56 PM   #2
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Keep going on Sheldon Brown's site... one of his bikes is rigged as a _63_ speed:

http://sheldonbrown.org/bicycle.html#otb
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Old 09-15-05, 03:17 AM   #3
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Sram used to make a 7 speed hub with 3 cogs.
Schlumpf make an internal gear for the front part of transmission that is used with hub gears. You dont need a chain tensioner with this one.
http://www.schlumpf.ch/md_engl.htm
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Old 09-15-05, 07:12 AM   #4
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Well, I appreciate the responses, but I am aware of both Sheldon's tinkering and of those particular innovations. They are pretty cool (and ways that one might accomplish something similar), but not really what I was asking.

For what it's worth, by the way, SRAM still makes a hybrid gearing transmission, but with a three-speed hub and 7, 8 or 9 speed cluster.
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Old 09-15-05, 07:23 AM   #5
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For what it's worth, by the way, SRAM still makes a hybrid gearing transmission, but with a three-speed hub and 7, 8 or 9 speed cluster.
I believe these are used with a single chainring crank and the 3-speed hub serves the same purpose as a triple crank and front derailleur.

I don't know SRAM's or Shimano's recommendations but Rohloff has a minimum chainring/maximum cog size limitation for its internal geared hubs to limit the maximum torque applied by the rider. I'm pretty sure a 26x18 combination would exceed this limit by quite a lot.

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Old 09-15-05, 07:32 AM   #6
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I built a tandem with 52/42 on the crank and 2 gears on the 3 speed hub, cant remember for sure the tooth count. That gives me 12 speeds with 3 shifters. I'm going to change it to a 5 speed rear hub and a 3 ring crank. That should give me 30 speeds with 4 shifters. It works well. Is it practical? No. Is it fun? Yes. Why did I do it? To see if I could. If I understood your question, you were pondering using multiple derailers/gears to get the same gearing range. I haven't tried it yet, but I think you could do it but it would have to be on a long bike like a recumbent or tandem.
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Old 09-15-05, 10:04 AM   #7
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Oh, for sure, HillRider. Despite SRAM's intentions, I don't see why a tinkerer couldn't use a double or triple crankset with the SRAM dualdrive, though. Using the same 46/36/26 crankset and a 12-34 cassette, this set up could achieve a gear range of 931% with 63 gears. That's pretty awesome, but it's of limited practicality for most uses. For normal riders it is simply overkill, and extra weight for more money. Granted, it's not a whole lot of extra money, but most people don't need gears from 13 to 127 inches (!). Unfortunately, it's not much good for most loaded tourers either, due to the complexity of the system. The SRAM dualdrive system uses exclusive shifters, derailers and cassettes, so if something failed, you'd be in a world of trouble. But it sure is cool! And for what it's worth, I see little point in contemplating multiple chainrings with a Rohloff anyway - it already has a range in the vicinity of 540%, so there's no need to enhance it with different chainrings anyway.

lrrice, that sounds pretty darn cool! as for my question, I was pondering a multi-speed hub (specifically the 8-speed Nexus) with one cog, but multiple chainrings. Hey, maybe sometime when I have some free cash lying around, I'll cobble up either something like that, or the 63-speed dualdrive bike. Conquer any hill - and outrun the cars on the way down!
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Old 09-15-05, 09:55 PM   #8
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I was also hoping for an answer to the specific question as I'm considering the same thing (or similar). I'm still thinking about front derailing between 46 and 32 while using a nexus 7 speed rear hub. The tourer I had built with nexus-7 needed a little more range. I have n't started experimenting with how to take up the slack yet. Locked rear derailer could work, but maybe one of those singleator devices would be sufficient. I haven't played with one yet. Anybody know if that might work.
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Old 09-16-05, 12:58 AM   #9
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You could build some amazing bikes.

But I have a question. Assuming that you could get these enormous numbers of combinations, and the amazing ratios, for climbing 40% slopes, for example , how slowly would you have to be moving uphill before you would fall over through lack of balance?

Last edited by gmason; 09-16-05 at 02:04 AM.
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Old 09-16-05, 01:44 AM   #10
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Go read up on recumbent trikes. They've tried all the crazy combinations, and use the super low gears for hill climbs. 3 wheels seems to really help with stability.
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Old 09-16-05, 04:09 AM   #11
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Quote:
Originally Posted by grolby
Hi there. I just happened to notice on the internal gear calculator on Sheldon Brown's webpage, and the fact that you can enter up to three different chainring values! That seemed a little crazy, but I entered some values, and holy cow! Combining a 46/36/26 crankset with an 18 tooth cog on the Shimano Nexus 8-speed hub would give a range of 22.8 to 101 gear inches on a bike with 26-inch wheels. Thats 443%! That's roughly comparable to using the same crankset with a Megarange freewheel or cassette, and has obvious benefits in a touring application.

Now, unless you're getting really high-zoot derailers and cogs, it's probably more cost effective to go with the derailer gearing option. The use of integrated brake/shift levers could easily push the cost the other way, however, and besides I'm curious: is this even doable? It would certainly require some tinkering - at the very least a chain tensioner to take up slack in the chain, and perhaps some fiddling to get the chainline straight in the middle chainring, but... man, what a unique bicycle that would be!

Does anyone think this would work? Have you done this? Do you know someone who has? Could you use a chain tensioner in that way? Am I crazy?

Anyway, let me know what y'all think. Cheers!
I have a recumbent with 7 sprockets, 3 speed internal gear hub, and double. The internal gear hub is excellent for commuting/touring, since it gives you a chance to downshift on the stop.

Neither a chain tensioner nor a singulator would adjust enough to adequately tension the chain, at least per their marketted condition. You might be able to modify one or make one of your own that does the job. A rder would be the easy solution, but you might save .5-1W vs. a rder if you go the singulator modified for the purpose.
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Old 09-16-05, 07:38 AM   #12
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And I've already done the experimentation to adapt a brake-shifter to the nexus-7. I used a travel-agent attached to the downtube boss and it seemed to work OK. I haven't posted details and pictures because I've only briefly tested it on the stand -- not on the road (and the shifters are now dedicated to another project). So I'm still thinking about modifying my nexus-7 based tour bike to add brake-shifters. The right side would be adapted to the nexus, left side shifting between two chainrings. (Yea. might be ready by next year's Wisc trip)
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Old 09-16-05, 09:22 AM   #13
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Quote:
Originally Posted by grolby
Hi there. I just happened to notice on the internal gear calculator on Sheldon Brown's webpage, and the fact that you can enter up to three different chainring values! That seemed a little crazy, but I entered some values, and holy cow! Combining a 46/36/26 crankset with an 18 tooth cog on the Shimano Nexus 8-speed hub would give a range of 22.8 to 101 gear inches on a bike with 26-inch wheels. Thats 443%! That's roughly comparable to using the same crankset with a Megarange freewheel or cassette, and has obvious benefits in a touring application.

Now, unless you're getting really high-zoot derailers and cogs, it's probably more cost effective to go with the derailer gearing option. The use of integrated brake/shift levers could easily push the cost the other way...
There would be no reason to use such fancy shifters. With a system like this, you would do most of the shifting with the Nexus shifter, and only use the derailer to select high-medium-low range. This could be handled with a simple $12 thumb shifter or down tube shifter.

I've been seriously toying with doing something like this myself, probably using a 52-42 double and an 18 or 19 tooth sprocket, giving me a 2.5-9.3 Gain Ratio (33-125 inch) or 2.3-8.8 (32-118 inch) range.

Note that you must have a rear derailer as well as a front, to take up the slack. A typical overpriced singlespeed chain tensioner won't have sufficient take-up capacity to handle even a 10 tooth jump, much less the 20 tooth you propose. On the other hand, since ther'll only be one rear sprocket, you don't need a wide range one. I've got an old Hurét Jubilee set aside for this project, the lightest rear derailer ever made (and, by all accounts a pretty poor shifting one as well, pretty as it is.)

Sheldon "Sometimes Uses Gears, But Rarely Uses Derailers" Brown

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|  One can never know what is enough  |
|  until one knows what is too much.  |
|                    --William Blake  |
+-------------------------------------+
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Old 09-16-05, 02:12 PM   #14
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Dude, I keep waiting for somebody to do the following:
-Start with a rohloff
-attache a cassette body to where the sprocket goes
-put on a 10-speed cluster
-use a triple chainring AND a schlumpf bottom bracket

You'd get an amazing 14x10x3x2=640 gears!!!
I couldn't even begin to calculate the range on that, but it'd be word. Very word.
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Old 09-16-05, 04:18 PM   #15
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Yeah, 640 gears, and probably 30 that don't repeat themselves.

Sheldon given us his 2 cents, and it comes down to this certainly being possible, but lacking the elegance a hub transmission provides.
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Old 09-16-05, 04:33 PM   #16
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Quote:
Originally Posted by lrrice
I built a tandem with 52/42 on the crank and 2 gears on the 3 speed hub, cant remember for sure the tooth count. That gives me 12 speeds with 3 shifters. I'm going to change it to a 5 speed rear hub and a 3 ring crank. That should give me 30 speeds with 4 shifters. It works well. Is it practical? No. Is it fun? Yes. Why did I do it? To see if I could. If I understood your question, you were pondering using multiple derailers/gears to get the same gearing range. I haven't tried it yet, but I think you could do it but it would have to be on a long bike like a recumbent or tandem.
Assuming you're speaking of Sturmey-Archer hubs...I would advise against this. The Sturmey-Archer 5-speed hubs are MUCH less durable and reliable than their 3-speeds. I too have use Sturmey-Archer 3-speeds on tandems, including a 54 speed (6 sprockets on the Sturmey-Archer, 3 chainrings) but no way would I trust a Sturmey-Archer 5-speed for tandem use.

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Old 09-16-05, 04:36 PM   #17
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Did I read somewhere that Rohloff has an 18 speed now?
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Old 09-16-05, 10:48 PM   #18
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Quote:
Originally Posted by Sheldon Brown
There would be no reason to use such fancy shifters. With a system like this, you would do most of the shifting with the Nexus shifter, and only use the derailer to select high-medium-low range. This could be handled with a simple $12 thumb shifter or down tube shifter.

I've been seriously toying with doing something like this myself, probably using a 52-42 double and an 18 or 19 tooth sprocket, giving me a 2.5-9.3 Gain Ratio (33-125 inch) or 2.3-8.8 (32-118 inch) range.

Note that you must have a rear derailer as well as a front, to take up the slack. A typical overpriced singlespeed chain tensioner won't have sufficient take-up capacity to handle even a 10 tooth jump, much less the 20 tooth you propose. On the other hand, since ther'll only be one rear sprocket, you don't need a wide range one. I've got an old Hurét Jubilee set aside for this project, the lightest rear derailer ever made (and, by all accounts a pretty poor shifting one as well, pretty as it is.)

Sheldon "Sometimes Uses Gears, But Rarely Uses Derailers" Brown

Code:
+-------------------------------------+
|  One can never know what is enough  |
|  until one knows what is too much.  |
|                    --William Blake  |
+-------------------------------------+
Oh, such shifters would unquestionably be over-the-top for that sort of application - I was actually referring to the cost of a derailer bike using brifters and nice derailers versus the Nexus-8 setup. A cheap cyclist like me who loves seven-speed freewheels and friction shifting could probably get a setup with better range for less money by using derailers and multiple cogs. But a lot of people need 9-speed and brifters, the cost of which actually could make the Nexus-8 setup more affordable.

Anyway, it's good to know that I would need a derailer. I was a bit concerned about the fragility of a chain tensioner. But what cyclist doesn't have a cheap old derailer lying about? Well... I have one, anyway. I don't know how likely I am to attempt something like this, but it could be fun, and it has the advantage of being pretty low-maintenance. Good luck with the project. Sounds like a great use for that Huret Jubilee!

Hey genericbikedude, check your math - that's 840 gears! Intense, yo. Might be fun to put together just because you could (although getting a freewheel onto a Rohloff would be pretty tricky).
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