Author Topic: How the Rohloff hub gearbox works its gearing magic  (Read 487 times)

Andre Jute

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How the Rohloff hub gearbox works its gearing magic
« on: May 20, 2018, 11:30:36 PM »
Here is an excellent description with a cutaway Rohloff of how the gears and pawls and shaft do their their hitherto invisible thing.
https://www.youtube.com/watch?v=s4UpwoDmOb4
Actually, it is better than merely excellent, for the dyed in the wool Rohloffie it is exciting.

PH

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Re: How the Rohloff hub gearbox works its gearing magic
« Reply #1 on: May 21, 2018, 10:02:38 AM »
Thanks for that :D
it's complex isn't it!  Thank goodness I don't have to understand it!!! With all that going on it's a wonder it's so reliable and an explanation of why they aren't mass produced and those who've attempted to do so haven't managed the same reliability.

geocycle

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Re: How the Rohloff hub gearbox works its gearing magic
« Reply #2 on: May 21, 2018, 02:26:26 PM »
Thanks Andre, that is a really good resource.  i admire these folk who can put things back together and find it still works! I'd not have the nerve with my rohloff.
 

John Saxby

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Re: How the Rohloff hub gearbox works its gearing magic
« Reply #3 on: May 21, 2018, 07:53:24 PM »
Thanks, Andre, hugely interesting, tho' now I have a case of "brain fag", to borrow VS Naipaul's great phrase (or from Michael Palin, "I want to see a brain surgeon--my brain hurts.")

Trying to imagine the brainstorming that preceded the design, with the team wingnut saying, "Listen, guys, it'll only work if we have three planetary gears and four clutches," with the rest of them saying "Yeah, yeah, Manfred, we know, but it'll be way too complicated..."

Luckily for us, Manfred the wingnut prevailed.

Andre Jute

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Re: How the Rohloff hub gearbox works its gearing magic
« Reply #4 on: May 22, 2018, 03:34:57 AM »
I must say, if I knew about tiny white plastic bits being in charge of the final drive, I'd have tried again with Shimano boxes or waited for the Pinion.

It's worse than Manfred the wing nut, John. Much. I believe Dan has Barbara Rohloff's book, and has read it, so he can correct me. But the legend is that two mud pluggers got married and went off on their honeymoon with their bikes. Riding with wild abandon on a beach, the derailleurs of both bikes got sand in them and were wrecked beyond operation. So the bridegroom, a young engineer of no particular distinction to this point (except that from our perspective graduation from a German technical school is already a very high distinction), one Bernd Rohloff, spent his honeymoon designing a sandproof transmission, and while he was about it, being German, he also made it proof against cyclists and other holy fools. Presumably Frau Rohloff's book recounts her reaction to speeding from newly married to golf widow in a few days...

Actually, on second thoughts, don't correct me, Dan. I like my retelling of the legend much better than inevitably dull truth.

I'm interested in the intersections of technology with psychology and economics, so thanks, John, for setting this up (next time I'll your straight man): I think the Rohloff gearbox demonstrates the huge benefit of being designed by one obsessed engineer and not having a committee in charge. The first parameter a committee would have set would have been low mass, and right there disaster would have struck the project -- and by now the Rohloff would have been forgotten. Instead it grows from strengh to strength exactly because weight was not the first consideration. Knee-jerk reactions by people with their minds set on railroad tracks in their youth, almost always reinforced in committees, who in late middle age still don't merely ride or exercise, but "train", are responsible for probably 90% of what is wrong with bicycles today, and 100% of unsuitable components on bikes to which the components' design criteria have no earthly functional relevance. Rohloff was further lucky  -- and so are we -- in that the most upmarket of the German baukasten (they're a sort of semi-custom bike manufacturers, this one known as the Rolls-Royce of German bike manufacturers, a good description) immediately took up the Rohloff for their touring bikes, a steady, prestigious market Herr Rohloff had probably not considered. But again, Utopia are nutters for functional design, no matter how unconventional, and besides test every component to destruction before fitting it to their bikes so that their ten-year guarantee has real bite, and therefore wouldn't have touched the Rohloff if it were designed down to a "cycling mass" and thus a less than permanent installation.

John Saxby

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Re: How the Rohloff hub gearbox works its gearing magic
« Reply #5 on: May 22, 2018, 05:12:37 PM »
Quote
he also made it proof against cyclists and other holy fools

Mind you, just supplying a video in place of a user's manual would ensure that all but the incredibly wealthy and/or utterly witless would send any misbehavin' hub back to the factory for repair/re-education.

Quote
The first parameter a committee would have set would have been low mass, and right there disaster would have struck the project -- and by now the Rohloff would have been forgotten. Instead it grows from strengh to strength exactly because weight was not the first consideration.

Well, not just a committee, but some pretty good engineers, too. Before buying the Rohloff, my one misgiving or frisson of apprehension came from the fact that it seemed to violate comprehensively and unrepentantly (if hubs can be repentant or unrepentant, but bear with me) a basic approach to design which I'd heard attributed to Colin Chapman: "Simplify and add lightness."  The Rohloff does neither, obviously.

Sent the vid to a riding buddy here, and it wowed him.

Cheers,  John

Andre Jute

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Re: How the Rohloff hub gearbox works its gearing magic
« Reply #6 on: May 22, 2018, 11:25:58 PM »
....a basic approach to design which I'd heard attributed to Colin Chapman: "Simplify and add lightness."

I can understand why cyclists mention Colin Chapman with implicit approval, but that man did the small English sports car a great deal of permanent harm by turning it into a joke, not that it needed much help, as anyone who ever drove an MG TC (max speed of mine was 68mph -- after I unchoked the engine) will tell you.

On the other hand, that was a Lotus-engineered bike (Type 108)-- a decade after Chapman killed himself burning the candle at three ends -- under Chris Boardman at what is still my most treasured memory from bicycle sports, the Track Pursuit at the 1992 Barcelona Olympics:
https://www.youtube.com/watch?v=W3VVVHk5_xM
And here is the Lotus T108 gold-medal winning bike in the MIRA wind tunnel:
https://www.youtube.com/watch?v=RMpMP1nu5jc
« Last Edit: May 23, 2018, 01:53:22 AM by Andre Jute »

John Saxby

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Re: How the Rohloff hub gearbox works its gearing magic
« Reply #7 on: May 23, 2018, 01:05:01 AM »
Brilliant stuff, Andre. And to think that Boardman did it with his front wheel going backwards! Maybe it was the JPS black-and-gold that did the trick?

Then again, Jens Lehmann, the guy on the other bike, was a goalkeeper for Arsenal, if memory serves  ;)

Andre Jute

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Re: How the Rohloff hub gearbox works its gearing magic
« Reply #8 on: May 23, 2018, 01:58:13 AM »
Sorry about the bad wind tunnel link; the right one mustabin blown over. Correct link for gold medal winning T108 Lotus bike in MIRA wind tunnels substituted above or you can click it here:
https://www.youtube.com/watch?v=RMpMP1nu5jc