Rohloff with a Double ?

[Thomas777]

I work part time  in a bike shop a d since I have a Rohloff  on my wife's touring bike I am considered the "expert"!
So a Rohloff equipped bike came in with a double  chainring and a chain tensioner.
Anyone  familiar with this setup?  My wife  is interested because  she spins out on downhill.

[PH]

It isn't uncommon on a recumbent trike, where balance isn't an issue with really low gears, I haven't seen it on a convectional bike, but there's no reason it wouldn't work. I've used a double on an Alfine 8 speed, without problem, not really very different to using a cassette. The Rohloff tensioner has a capacity for 10 chain links, which roughly translates to a 20T chaining difference*, you don't have to use the Rohloff one, though most others don't offer an acceptable chainline without modification.  You'd have to play around with a gear calculator to decide where to put the extra gears, I think realistically it's going to provide an extra three. On the Alfine I set the extra gears at the bottom, it was a mistake, shifting at the top where you can afford to lose some momentum would have been better. Chainline isn't going to be critical, setting it for either of the chainrings or between them isn't going to make much difference. You still have the advantage of the chain only running to one sprocket, lots of ways to shift, I'd choose 8spd, friction shifting and a jump Stop.  You might also consider the Rohloff's maximum ratios, it's up to you whether you treat them as a rule or a guide and that might depend on whether the hub is still in warranty.
I occasionally spin out on a Rholoff, but not often enough to consider doing anything about it, the bottom gear is a low as I can go without falling off and the top gear is high enough that even with more gears it would be a lot of extra effort for marginal gain.  Nor saying someone else might not get the benefit, but the numbers need a proper look at first.

* EDIT - No need to do the sums, there's a choice of chain length calculators, like this one:
https://www.alpinetrek.co.uk/chain-length-calculator/

[martinf]

It worked for me on a Brompton, where for several years I used a double chainring with a 5-speed Sturmey hub to extend the gear range.

No real difference if using a Rohloff, or an Alfine 8 as PH has done.

I have the Rohloff on my Raven Sport Tour geared quite low - 42 x19, which gives a range of 15" to 80" with my tyres. I don't (yet) really need the lowest gear on this bike, 15" gives about 4.4 km/h at a "lazy" cadence of 60 rpm, so about walking speed.

And I could do without the highest gear, which gives 35 km/h at my usual cadence of 90 rpm, not a speed I can maintain on the flat for long. Though I have pedalled that bike up to 50 km/h on a gentle downhill just to see if I could do it (130 rpm, again not sustainable for long periods)

On my heavy tourer, I gear even lower at 13" to 67". My reasoning is that I sometimes use the very low gear when really tired at the end of a long day, and I wont need to (or be able to) go very fast with a full touring load. 67" is about 29 km/h at 90 rpm. 

I don't usually "spin out" on downhills, I just stop pedalling and save my energy for the next uphill.

But if someone does need more range than the Rohloff's 526%, a double chainring should work quite well.

[Andyb1]

If your wife ‘spins out on downhill’ she either likes to ride very fast or the crank / rear wheel sprocket ratio is too low.
Does she ever use first gear on climbs?   If not then maybe it is worth trying one tooth smaller on the rear cog?  As PH says, Rohloff give guidance on acceptable ratios.

I have read someone advising that Rohloff bikes should be set up so that gear 11 is used as the ‘normal’ cruising gear (as it is the most efficient gear) - but this would seem a bit too lowly geared.  On flat roads, no wind, I am usually in gear 9 so have 5 gears left!

[Danneaux]

... a Rohloff equipped bike came in with a double  chainring and a chain tensioner.
Anyone  familiar with this setup?  My wife  is interested because  she spins out on downhill.

Not yet realized but surely in my queue for my tandem update and for reasons similar to what Andyb1 described. So long as the ratio remains within what Rohloff recommends, I don't see a problem. I've got mine planned to deliver essentially duplicate gears throughout most of the range with an extended top range on one chainring and an extended bottom on the other.

My situation us a bit more complicated as I will need to machine and break out my torch to braze in spacers to narrow the dropout OLN spacing from 140mm to 135 and I'll convert my hub with internal shifting from the OEM torque-reaction arm to the longer external version so it can key into the PacMan fitting for my present Arai drum drag brake. The present derailleur will serve to tension the chain as the bike has vertical dropouts and the only eccentric is for the timing chain.

Fun stuff!