Did my Rohloff break my TI frame?

[pakcyclist]

I had a custom TI frame built 11 years ago, with sliding dropouts to accommodate the Speedhub.  Recently, the bottom-left seatstay completely cracked in two while riding, for no apparent reason.  (Luckily, I was going slowly uphill at the time, so it didn't causes a crash.)  It has over 100,000 km on it.  The repair guy said he needed to "reinforce" the frame after the initial repairs to accommodate the Rohloff.  (Not sure exactly how its "reinforced," I still haven't gotten it back.)  I know there is the torque arm available, but from what I understood from the manual, this is only needed on standard frames (without sliding dropouts).   Was I supposed to have the torque arm on my bike, despite it having sliding dropouts?  Was that the reason my frame broke?  (BTW, if I ever get another frame, it will definitely be steel . . . at least when it breaks, its a lot cheaper to repair/replace, and it can be recycled!)

[GamblerGORD649]

It would sure help if we had a photo.
   Anyway, get that long arm put on. You can bend it to match the flow. It will vastly strengthen the bike. I really don't see how that little nub plate takes all that torque. It will easily pry the slot apart. I really don't get the BS guys say about how ugly it looks. These are the same guys that ride with PATHETIC defaileur hangers. LOL. My steel custom has a track dropout as well. I also use it with a SA XL-RD5w.
   There is no downside to having more stability and just one more #6 bolt to take off. The goofy QR connector for this arm IS dumb, IMO. You might have to DIY a strap, like I did. My long arm actually maybe saved my chain stay, when a motorcycle hit it there, in Vietnam. Paint it any damn color you want.

[leftpoole]

1)Titanium
2)Heavy hub
3) No torque arm
4) New frame required not a 'repair'
5) Obviously a steel frame is required to accommodate that heavy lump at the rear!

[buffet]

I've seen numerous non-Rohloff frames with cracked dropouts (incl sliding dropout style) both with my own eyes and on the Internet. It is one of the weak spots of a bicycle frame in general, it has not much to do with your frame being equipped with a Rohloff hub.

For sliding dropouts, one of the main reasons for such cracks is pushing the sliders all the way outward and going on heavy duty offroad rides. I've seen Kona and Soma frames cracked this way, all of them steel.

I don't think that a Rohloff hub can output such torque that it can crack the dropout. (equpping your bike with a 180-203mm rear disk rotor with powerful hydraulic brakes can put much more stress, for example). Singlespeed MTB bikes produce much more torque at the rear wheel than a Rohloff, yet the issues with frame cracks due to such torque forces are not common.

11 years and 100k km is a nice lifetime for a frame, IMO

[pakcyclist]

I did try to post a photo, but it was over 512k.  (Is there a was to "downsize" it here?)  How exactly does a Rohloff increase torque anyway?  Is it just because the hub weighs a lot more?  Or, is it related to the lack of dish in the wheel?

[Danneaux]

I did try to post a photo, but it was over 512k.  (Is there a was to "downsize" it here?)

No, there are no tools here to downsize a photo; that is something you will have to do on your own. One method is to email the photo to yourself, as mail clients sometimes offer a downsizing option. For more on posting photos to the Forum, see:
http://thorncyclesforum.co.uk/index.php?topic=4313.0

How exactly does a Rohloff increase torque anyway?

The Rohloff's torque reaction arm or tab serves to counter the forward torque applied to the hub under drive. The internal gearing of the hub also multiplies torque on the tab, so there is additional stress applied to the portion of the frame where the torque arm or tab is attached/contained. Rohloff provide a good explanation here:
https://www.rohloff.de/en/service/handbook/speedhub/assembly/torque-anchoring#c26000

Best,

Dan.

[Andre Jute]

There's an elephant sleeping in the room and everyone is tiptoeing around it. Time for some blunt speaking:

I would have thought that after 11 years and 100,000km you've had full value out of a titanium frame and should well before this have started thinking about replacing it. I certainly wouldn't ride on a ti frame "repaired" in such a critical place. Is this man you've entrusted with the work welding titanium (special tools and skills required to do it right) or bonding it (not as easy as it sounds)?

As for the torque of the Rohloff breaking the frame, it seems to me very unlikely unless the ti frame ends (that near-horizontal slot is technically not a "dropout") were under-specced to start with, in which case they would have broken with derailleurs or even a lesser HGB than the Rohloff, say the Shimano Nexus, before now. Herr Rohloff has a long history, well known to us and several times the subject of discussions here, of covering his backside with ultra-conservative specs, especially in the permitted torque (controlled via the maximum chainring/sprocket tooth counts ratio permitted) and the service schedule.

My bet is on a fatigue fracture that was due in titanium at a quarter or a half of the actual mileage you've achieved, regardless of which components were fitted. If you can somehow get the bike and the broken-off piece X-rayed, you will see a stress pattern of a figure eight with the crossover centred on the break. There could also be crystalline structure on the break faces, visible under a magnifying glass.

Seems to me you've been pretty lucky to escape the fate of most ti bikes for so long.

[JohnR]

I did try to post a photo, but it was over 512k.  (Is there a was to "downsize" it here?)

This is what I use https://www.bricelam.net/ImageResizer/ .

[PH]

Did the crack start at a weld?  This is the usual failure mode for ti frames, it's down to poor control in the manufacturing process. 
I had a custom ti frame built by XCAD in China when they weres a cheap option.  Not that dissimilar from the Mercury though it pre-dated it by a couple of years or I wouldn't have bothered.  Cracked at the headtube after 9 years, I sent it off for repair where they discovered a couple of other cracks forming, game over. 

[pakcyclist]

Well, I was under the impression that TI "lasted a lifetime."  The reason I spent so much freaking money for it was because I thought I wouldn't have to worry about something like this happening!  In the long run, I thought I'd save money, as opposed to buying carbon frames with their 5-year life expectancy.  (Never did trust carbon.  Bet it wouldn't last me a month!  But after what happened to the TI frame, I'd be scared spit-less to even ride carbon!)  If I knew this, for sure I'd nave gone with steel.  (And any frame I get from now on will be steel.)  And with what I paid for the repair -- and after waiting over 5 months (and counting) to get it back -- I'll use it until it does give out again.  (But I'll be darn sure to regularly check over the whole frame.)

I took photos of my photos here to "downsize."  The break appears to be at or just above the weld.  There was also another very small hole/crack beginning to form on the other seatastay.

[Aleman]

To me, that looks like a welding issue ... however, the choice of material has an impact on it. While steel and Ti have similar levels of compliance steel has more resilience. Cracks will develop at fatigue points (like welds) in both over time, but as a steel frame is more resilient it will take longer. Throw in a poor weld, or poorly designed mating surfaces, and failure is inevitable

[Captain Bubble]

Agree with the above comment. But where is the torque arm for the Rohloff? Simply securing the hub in horizontal drop outs is not sufficient to hold it in place. Having trouble taking the OP seriously as he can't even post good clear pictures in this day and age, having bought a Ti frame bike with a Rohloff hub you would have thought he would be able to at least do this from the start. Life time warranty of Ti frames is usually applicable to their anti-corrosion properties and not issues of metal fatigue or issues with welding failing. 11 years use and 100,000 km seems a pretty good lifespan for a frame.

[PH]

Agree with the above comment. But where is the torque arm for the Rohloff? Simply securing the hub in horizontal drop outs is not sufficient to hold it in place.

It isn't a horizontal dropout, it's a sliding dropout, quite common, though Thorn are dismissive of them as it puts the bolts in sheer.  However many manufacturers and frame builders use them, including some very high end. 

Life time warranty of Ti frames is usually applicable to their anti-corrosion properties and not issues of metal fatigue or issues with welding failing

Which lifetime warranties?  Those I've seen cover all faults and I know of people who've had frames replaced under them. 

[Andre Jute]

Agree with the above comment. But where is the torque arm for the Rohloff?

A Shimano Nexus hub and similar can be mounted with the axle directly in a (near) horizontal slot, usually open-ended at the back.

But a Rohloff isn't mounted with the axle directly into those two slots per side as in the photo of the broken rear end. Instead a machined aluminium axle hanger for each side is bolted into the two slots per side, and is further braced and guided by a stave in a channel on the inside of each frame end which will also spread the torque evenly to both sides of the frame and all the stays. The axle of the Rohloff hangs in a vertical dropout cut out of the axle hanger and the non-driveside hanger has an extra-long dropout in which a little nub on the Rohloff fits -- and this little nub is the torque arm; it doesn't have the length one would normally expect for a torque arm. (Rohloff also sells the usual ugly type of torque arm, but that is for conversions, not for Rohloff specific frames with sliding frame ends as on the particular ti frame we're discussing.)

In any event, the Rohloff torque arm fits on the non-drive side of the bike.

Scroll down in
http://coolmainpress.com/AndreJute'sUtopiaKranich.pdf
and you'll come to a collage of three photographs of the non-driveside Rohloff mounting on one of my bikes. If you look closely in the long slot of the bright ali axle hanger, at its bottom end you will see a black oval with two screws in it: that's the Rohloff torque reactor.

Forward in the frame, the punched half-moon connecting the stays together only on the non-drive side is actually a brace for a disc brake I didn't specify, but it also serves as additional bracing for the torque reactor. Notice that any torque is reacted directly in line with one of the three stay-tubes. This bike won't suffer any failures, and even if does, it will stay together, and not just because it is steel. It is a question of design as well. This bike's frame is stiffer than a big modern Rolls-Royce.

My personal opinion is that the breakage on the ti bike wasn't caused by incompetent welding but what John Leftpoole said, the choice of Ti for the frame and a 100,000km of repetitive stress. All metals cheap enough to make bicycle tubes from suffer from stress, some just taking longer to break. A short life is one of the prices one pays for choosing ti -- 100,000km makes that one a great-great-granddaddy of a ti bike.

[John Saxby]

That's nicely written, Andre, and a model of its kind -- complete, clear and accessible.

Reading it, I could only think that subtle ironies abound here, and occasionally, fortune favours the witless--in this case, me.

To wit: I have a ti-framed light tourer, which I bought early in 2003.  I've ridden it in South Africa, 'Straya, Europe and Canada, but with nowhere near the accumulated mileage of the OP here.  The simple reason was a built-in governor that appeared nowhere in the spec and invoice for the bike: years and years of derailleur headaches limited the annual mileage I put on the bike.  And, after a decade, those same headaches drove me cursin' and screamin' into the confirmation queue for the Church of Rohloff, where I was duly confirmed after buying my Raven-mit-Rohloff.

In retrospect, I think I had an extra bit of backup on my ti frame: My LBS in Québec from which I bought it, Pecco's, ordered their frames from Germany.

Cheers,  J.