What's your Rohloff combo (chainring, cog)?

[martinf]

Found this link to a short Chainglider test:

http://www.bicycles.net.au/2012/07/squeak-free-clean-bike-chain-hebie-chainglider/

Also read that you shouldn't use a master link with the Chainglider - my 1/8" chain on the test bike has one of the old style 3-piece master links, so probably exceeds the 9 mm maximum at this point.

I don't suppose a modern 3/32" quick link (SRAM Powerlink or similar) would pose problems, but I gave up using those after having some come apart when riding.

[berchman]

I have just resumed cycling after a thirty year layoff. I sold my two DF bikes and bought a recumbent trike (Catrike 700) with a Rohloff hub. I have a 36/16 with a 700c x35 tire. I find the gear information on the Sheldon Brown site somewhat confusing, so would appreciate it if someone were to tell me what my gear range is in inches. I calculated 19-99, but I don't know if that's correct. Being an old guy and a weak rider, I find I need gear 1 on some of the hills around here. I have not yet determined the percent grade they represent, but I have acquired a GPS and plan to do so. They are definitely not the steepest hills in my area. On the flat I usually use 8. I have been thinking that to tackle a real killer hill I would definitely need a considerably lower gear. Does anyone know what a Schlumpf drive would give me with the 36/16 combination?

[Danneaux]

Hi Berchman!

Welcome to the Forum! Though a diamond frame hasn't worked out well for you, hopefully the recumbent/Rohloff combo will do the trick. "Old guy"?!? How 'bout "experienced"?   So long as you're back on the bike, the type that allows it isn't so important -- it is the doing that counts!

I find the gear information on the Sheldon Brown site somewhat confusing, so would appreciate it if someone were to tell me what my gear range is in inches.

Here is an alternative that offers a graphic representation; I really like this Rohloff gear calculator:
http://www.gear-calculator.com/#
Once at the link, go to the section on the left labeled "Gearing" and pull down the option for "Rohloff Speedhub". Everything else is a matter of just selecting your chainring/cog combo. Hint: the 'rings and cogs can be dragged across the grid to quickly see the results of a change. A very nice little tool for comparing alternative drive schemes, including Rohloff/Rohloff or Rohloff/Derailleur.

An alternative gear calculator that can be made to work for a Rohloff/Schlumpf combo with a little finagling is available here:
http://rbr.info/support/guides/151-gear-inch-calculator.html To make it "go", first use the calculator I referenced at the earlier link. That way, you can see what your Rohloff gearing is and back-engineer it to see what 'rings and cogs would be required to match it in a der setup. Note the "naughty" combos and lay them aside. Then, take that 'ring/cogset combo and enter it in the Schlumpf calculator immediately above. This will do the pencil-work for you. For example, if your Rohloff setup is the equivalent of a 22/32/44 chainset with an 11-12-14-16-18-21-24-28-32 cassette, enter that, then select the "Internal Hub - Schlumpf Mountain Drive Bottom Bracket" option and off you go. You'll get two charts, each showing a full range of 27-speeds available for 1.0 (same as stock) and 0.4 (reduction) depending on which "gear" you select in the Schlumpf.

For quick reference, using a nominal 27" wheel for the calculations, the 1.0, 22x32 combo yields a low gear of 18.6 gear-inches. With the 0.4 Schlumpf reduction Mountain Drive engages, that same 22x32 combo yields a low gear of 7.4 gear-inches, a gear so low balance becomes a real problem, though you could easily pull stumps with it. With a trike, balance wouldn't be a problem!   Rohloff longevity will definitely be the limiting factor. These low gear-inch numbers point out the care needed to avoid over-torquing the Rohloff hub, and also the need to carefully figure your low gearing to best take advantage of that the Schlumpf low can really offer. Obviously, it won't be practically useful to have a lot of gears down in the single-digits in terms of gear-inches.

Back in the days when I was a do-it-yourself derailleur gearhead, I found I could still comfortably pedal a 12 gear-inch low gear at about 2.5mph and my usual 100RPM+ cadence, but that was about as low as I could practically go; my Dad never did adapt to it. A 15 gear-inch low was both comfortable and practical and Dad did just manage that (the difference between us was our cadence, with mine being very fast and smooth; at slower cadences, balance becomes a real problem in such low gears). Slope is a factor as well. The steeper the slope, the lower the gear one can balance, at least in my experience. I did just manage a 10 gear-inch low on a 24% grade, but forward progress was truly slower than walking and a person gets as worn out from the cadence/effort as if they were pushing a much higher (i.e. 16.5-gear-inch) gear.

I have been thinking that to tackle a real killer hill I would definitely need a considerably lower gear. Does anyone know what a Schlumpf drive would give me with the 36/16 combination?

You will likely exceed the torque capacity of your Rohloff hub if you pair it with a Schlumpf *reduction* ("Mountain") drive. Rohloff have a lot to say on the matter here: http://www.rohloff.de/en/service/faq/faq_detail/archive/2005/11/july/article/Schlumpf_Speed_Drive_High_Speed_Drive_Mountain_D/index.html

When fitting a Schlumpf transmission, please bear in mind that it is still important not to undercut the smallest permitted sprocket ratios (see 'sprocket ratios').

The Schlumpf Mountain Drive is not permitted for use in conjunction with the Rohloff SPEEDHUB 500/14.

The Schlumpf High Speed Drive (1:2.5) is not permitted for use with the Rohloff SPEEDHUB 500/14 due to its standard 27 tooth integreated chainring. A number of alternative chainring sizes are however available from schlumpf so as to not undercut our smallest permitted sprocket ratios.

The Schlumpf Mountain (reduction) drive offers a 2.5 reduction ratio over whatever you're already running. The people who can best advise you as to the risk are CycleMonkey, who sell both. See: http://www.cyclemonkey.com/schlumpf-innovations.shtml Schlumpf have something to say about this combination as well, in their FAQ (Section 3.2) here: http://www.schlumpf.ch/hp/schlumpf/faq.getriebe.engl.htm#C

Some specific help for your question from people who have been there is available here:
http://www.bentrideronline.com/messageboard/showthread.php?t=38628
http://www.ihpva.org/projects/tstrike/building/rohloff.htm

As for quickly judging the grade of your hills, I can heartily recommend the SkyMounti inclinometer, which calculates rise-to-run as a direct-reading percentage to match road grades. Just match the leading or trailing edge of the bubble with the grid on the scale. For more on this fun and entertaining little gadget, see this post: http://www.thorncycles.co.uk/forums/index.php?topic=3896.msg20102#msg20102

I hope this helps.

Best,

Dan.

[berchman]

Thanks Danneaux, very helpful.

[Andre Jute]

The actual range of a Rohloff Speedhub on a 622x35 wheel/tyre combo with a 36x16 tooth gear combo would be 17.1 gear inches up to  89 gear inches. I don't know if you're a spinner or a masher but at 60rpm that's from 5.6kph to 29.5kph. On a trike you won't have balance problems, and you say you aren't a strong pedalist, so I wonder if yours isn't a really good case for ignoring Herr Rohloff's ultra-conservative rating on his gearbox and going even higher that the 2.250 ratio you have chosen (that's a lower number than 36/16).

I don't know about the Schlumpf. I looked into it but it would duplicate so many gears, one's head spins dizzily, and you gain only a gear or two, at most three, which you can anyway cover by coasting down the hills rather than pedalling madly, trying for undignified speed, sacrifing a gear or two at the top to add them on at the bottom. (I'd kill myself if I tried to keep up nearly 30kph on the flat!) The Schlumpf is actually good for something entirely different (for giving young, fit guys more top end breathing room without losing all their bottom end), but for adding low gears to the Rohloff it is expensive overkill. Just my opinion. If you are really keen on the Schlumpf, I can work the numbers again to allow for the Schlumpf.

Hope this helps.

Andre Jute
Are you the Keymaster? -- Ghostbusters, the movie

[berchman]

I am neither a spinner nor a masher. Until I get a cadence sensor installed, I'm guessing that I comfortably pedal about 70 RPM. I have no interest in pedaling downhill; the trike goes fast enough coasting downhill to put some fear into me. I think you have just saved me the expense of the Schlumpf; I rarely find myself pedaling in gear 14.

[Andre Jute]

What a couple of us on this conference have done to extend the range, in both the senses of the steepness of hills we can stilll attack and the distance we can still ride in any period -- in short to keep us cycling, is to fit an electric motor to fill in the gaps. This seamless solution has met with considerable acclaim from everyone who tried it. I'm not necessarily suggesting it to you if your Rohloff's range, as now revealed in the gear inch spread, will get you by on your roads, but it is a superbly practical, workable solution to keep you cycling through health problems, encroaching age, and so on.

My installation is fully described at http://coolmainpress.com/BICYCLING.html and there is considerable discussion on this board which you can find with the search function.

Andre Jute

[Tigerbiten]

I've a Rohloff and Schlumpf HSD on my recumbent ICE trike.
The gear range with this combo is fantastic as it gives you another 7 gears above the normal range.
I run in touring mode 30/16 on 50-406 tyres which gives me the range 10"-130" in 21 steps, ~1.7 mph min to ~40 mph max.
This is well below Rohloff's minimum spec of 14", so if anything breaks it will be my own fault.

I think get away with it three reasons.
1:- I'm on a recumbent, so I cannot standup and honk up hills. So less maximum force through the pedals.
2:- Small wheel, so the Rohloff is spinning faster than if it was in a 700c wheel, so less strain on it.
3:- It's a trike, so no real minimum speed hill climbing. My normal minimum speed is only around 1.7 mph so I'm putting half the force through the hub as compared to having to keep a speed of around 3.5 mph just to balance. Only +20% hills get hard work.
So far I've had it around one year and covered around 6k miles on it.
Tend not to use the overdrive with the bottom half of the Rohloff as it duplicates the top half of the Rohloff in normal drive mode. You can fell the extra drag from all the hubs spinnings.
The main downside is I spinout in B14, the gear before I switch into overdrive, at only 15-16 mph. This really is one gear to low.
I'm thinks of fitting the 21t rear sprocket on the Rohloff and then getting the spider for the Schlumpf HSD so I can fit a 48-36 tooth double.
This would let me keep the silly low gears while also upping the top end a bit.

[Andre Jute]

Fascinating, Tigerbitten; I reread that several times and hauled out my gearing spreadsheet, which has a Schlumpf on it from when I considered it for myself. Thanks for that. More ways than one to skin a cat, for sure!

Andre Jute

[Slow Legs]

Just released on the Rohloff website..
They have reduced the lowest permissible ratio from 2.35 to 2.1 (for riders who weigh under 100kg)

So for a 17 tooth rear sprocket thats a reduction from 40 at the chainring to 36 (my calculation). Great news for large loads, steep hills, high altitudes and for when you've run out of jelly babies.

Link:
http://www.rohloff.de/en/news/news_rss/news_in_detail/archive/2012/11/december/article/SPEEDHUB_UEbersetzungsfaktor_von_mind_235_auf_ak/index.html

Regards
SL

[Andybg]

Definetly a move in the right direction and good news for us spinners

Andy

[Andre Jute]

I've long said that Herr Rohloff revels in a massive built-in margin of safety on his hubs. (And Andy Blance and others said it before me.) Now we know how much the superfluous margin was: at least 12%. "At least" because it is difficult to believe that the habits of a cautious German engineer have suddenly changed all the way. If that happened, Frank Sinatra would crawl out of the grave to come sing the theme tune...

That's a very interesting report, especially the admission that the maximum load on the Rohloff gearbox was set by reference to derailleurs. Let's see: a sturdy set of solid gears, totally enclosed, running in an oil bath, not permitted to be stressed more than a derailleur with thin lightweight bits, being abraded out in the open with one of the most efficient grinding pastes (ground rock and light oil mixture) known to man. Yup, that sounds fair...

Twenty years later, the goalposts have shifted for derailleurs, and the Rohloff goalposts are moved — to match derailleurs exactly!

I'll take bets that there will be no perceptible increase in Rohloff hubs being returned for service, or reported as broken or damaged because of the new permitted cog ratio.

In fact, I'll bet money that we'll eventually discover that the real capability of a perfectly reliable Rohloff hub is a cog ratio in the order of 1.7 or better, something totally undreamt of in derailleurs. Those are two fundamentally different types of gearboxes, so the claim that this is the last permission shift is as "reasonable" (heh-heh) as the way the ratio was set in the first instance.

Call me a cynic if you like...

Andre Jute

[martinf]

In fact, I'll bet money that we'll eventually discover that the real capability of a perfectly reliable Rohloff hub is a cog ratio in the order of 1.7 or better.

You're probably right.

And their 2.1 ratio is for 100 Kg riders, so those of us who weigh significantly less than this should have an additional margin of safety.

The Rohloff announce comes just a few weeks too late for me - I would have specified 38x17 (lowest ratio that fits a Chainglider) instead of the 38x16 I chose in order to remain within the approved range.

[berchman]

I have a 36/16 and will soon be substituting a 32/16 and, if necessary, a 32/17. At my age (75) and level of fitness I have no fear of damaging the Rohloff with excessive torque.

[Danneaux]

The Rohloff announce comes just a few weeks too late for me - I would have specified 38x17 (lowest ratio that fits a Chainglider) instead of the 38x16 I chose in order to remain within the approved range.

<nods> That's exactly the direction I'm heading, Martin, going from a 40x17 to a 38x17 just as soon as I can convince Surly to produce a 38T stainless 'ring in 104BCD for my HollowTech II crank. Currently, their 104BCD 'rings top out at 36T -- fine alone, but too small for a Chainglider at present. Now, if we could just talk Hebie into producing a 36T-compatible Chainglider....

As an aside, Andre, I think the spinners among us may have a bit more leeway in Rohloff's safety margin than the mashers will. Fast 'n' light keeps my knees happy, says Dan of the hummingbird cadence.

A very nice find well-shared, SL, many thanks and welcome to the Forum. You too, berchman. Nice to have you both aboard.

Best,

Dan. (...who is really looking forward to some stump-pulling low gears now they are "Rohloff-legal" and won't void the warranty)