Author Topic: Rohloff with a triple crank?  (Read 438 times)

Thomas777

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Rohloff with a triple crank?
« on: April 30, 2018, 11:34:05 PM »
Today while out on a group ridecone fellow told me he has a recumbent with a Rohloff coupled with a triple crankset. I imagine there must be some type of chain tensioner.
Has anyone heard of a setup like this?

mickeg

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Re: Rohloff with a triple crank?
« Reply #1 on: May 01, 2018, 12:19:23 AM »
Nope.

When I was thinking about getting a Nomad I was a bit bummed that the step size between each gear was larger than I was used to on my derailleur touring bikes.  And I considered getting a double crank and front derailleur so that I could get twice as many gears and smaller step sizes between gears.  Then I realized that the Nomad lacked a derailleur hanger.  I bought the Nomad anyway and I eventually got used to the large step size between gears on the Rohloff and now I would think that adding a double would be more trouble than it is worth.

Maybe the Recumbant owner wanted a much larger range than the 526 percent.  But I would think that a double would more than suffice.

I saw a recumbant trike with a Rohloff.  Took a photo of it.  I just checked the photo, he had a single chainring on it.




Danneaux

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Re: Rohloff with a triple crank?
« Reply #2 on: May 01, 2018, 12:20:04 AM »
Quote
Has anyone heard of a setup like this?
<nods> Yes, it is not unknown in the recumbent world, where the Rohloff is also sometimes used in conjunction with a mid-drive that may be derailleur shifted as well. A Dutch friend of mine dropped dropped about €7,450 on his carbon Quest velomobile and is planning to convert to a Rohloff drive from derailleurs.
Quote
I imagine there must be some type of chain tensioner.
Yes, there is, sometimes a derailleur mounted at the mid-drive, other times at the rear dropout in the usual position as a tensioner. A mid- or long-cage rear derailleur might be needed depending on the gap between front chainrings.

Among many discussions of similar setups is this one: http://www.bentrideronline.com/messageboard/archive/index.php?t-127318.html

I know of at least three setups where the Rohloff was paired with a Schlumpf, Hammerschmidt or similar 2-sp internally geared bottom bracket setup. The owners had to take care not to exceed Rohloff's effective ratios, so they geared their bikes' low ranges for direct drive within those limits and used the crankset for overdrive. A discussion of some of the merits and cautions can be found here: https://www.bentrideronline.com/messageboard/showthread.php?t=133973

The topic was briefly discussed here on this Forum by a Nomad owner who also had a recumbent trike: http://thorncyclesforum.co.uk/index.php?topic=12517.msg92807#msg92807

As a longtime fan of half-step derailleur gearing, I have sometimes pondered a half-step Rohloff (a two chainring, 28-sp setup) as a conversion for one of my randonneur bikes, but after using my Nomad's conventional Rohloff setup, I think simpler is better. Chain efficiency losses quickly mount where the chain wraps around tiny 10t derailleur tension and jockey pulley, and a person also runs into issues of chain deflection. Maintenance increases as the pulleys usually use sleeved bushings, though sealed (cartridge) bearings would help (or even old Huret ball-and-cone pulleys) and the pulleys hang further down into the splash done where dirt and water are more likely to be kicked up.

If you use a chain tensioner with a single-speed or IGH setup, my tests show the most efficient kind use a single pulley pushing up from below, which maximizes chain wrap while minimizing friction.

Best,

Dan.

martinf

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Re: Rohloff with a triple crank?
« Reply #3 on: May 01, 2018, 07:25:18 AM »
If you use a chain tensioner with a single-speed or IGH setup, my tests show the most efficient kind use a single pulley pushing up from below, which maximizes chain wrap while minimizing friction.

I have this type of chain tensioner on my large visitor bike, which has vertical dropouts. I use a Surly chain tensioner with a single pulley.

With this setup, only some ring/sprocket combinations work - if there is too much chain slack you would have to use another type of tensioner or maybe have the Surly pushing downwards (greater risk  of the chain coming off the sprocket).

Danneaux

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Re: Rohloff with a triple crank?
« Reply #4 on: May 01, 2018, 08:37:07 AM »
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I have this type of chain tensioner on my large visitor bike, which has vertical dropouts. I use a Surly chain tensioner with a single pulley.
I once briefly used an "idler", "phantom", or "ghostring" on an IGH hub, but gave up on it because it didn't give the chainwrap I desired at the sprocket. It sure looked cool, though. For a photo and story detailing one person's experience with ghostrings, see:
http://rollinginboston.bostonbiker.org/2012/04/08/installing-a-ghostring-on-a-single-speed-or-internally-geared-bicycle/

Chainline should be close to spot-on, it can be difficult to find just the right size ghostring (it will vary with chain wear), and it is critical to insert it in the right place between the upper and lower chain runs else it can grind away on the chainstay which is Not Good. The result requires four emojis to describe: :o ??? :P ::)

Especially Not Recommended for Fixies but a notsobad solution for tandem timing chains and preferred by me over a mid-run tension pulley if the tandem has no eccentric.

All the best,

Dan.

mickeg

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Re: Rohloff with a triple crank?
« Reply #5 on: May 01, 2018, 03:16:31 PM »
Interesting solution, it would never have occured to me to fit a spare chainring (or sprocket) in the chain the ghostring way that was shown.

A friend of mine had a recumbent for a while, he had a very long chain and had a small support hanging below the frame to act as a chain guide.  I could see hanging something like that from a chainstay, that would slightly increase the chain wrap instead of reduce it.  But you would have to set it at the proper location on the chainstay to achieve proper chainline and then it would have to be adjustable for chain tension.  And that becomes complicated enough that the dérailleur hanger tensioner starts to look like a better option.  I think many decades ago when people were still trying to figure out the best way to install a derailleur that some were installed at the aft portion of the chainstay which I am sure complicated wheel removal.

Tigerbiten

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Re: Rohloff with a triple crank?
« Reply #6 on: May 05, 2018, 06:11:23 PM »
On my recumbent trike I wanted to extend the standard range of 15"-100" from a derailleur setup.
A triple and dual drive would have been to complex with only one hand.
Next idea was a triple and Rohloff.
But a Rohloff is really a 7 speed with a x2.45 set down so I combined it with the x2.5 step up from a Schlumpf HSD for a true 21 gear setup.
I further refined it with a 38/54 (95/135) double for better shifting between ranges.

I was a bit tempted to do a half-step and granny setup.
But the half-step is not needed in normal mode and there to much extra drag in overdrive mode to make it worth it the extra hassle.