Rohloff hubs

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Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Rohloff hubs

Postby Brucey » 29 Apr 2016, 8:17am

BTP wrote:Forgot to mention that I have had some issue with spoke breakages at the nipple end. The large flange married to a 26" rim creates an acute spoke angle at the rim. Rohloff recommend 2 cross lacing which I followed. However I suspect that, unless the rim has been drilled to suit the Rohloff, one is better lacing 1 cross.

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I have a theory that the method of setting the spokes and stress-relieving the wheel may make a big difference here. Brandt's method is to squeeze the spokes in the plane of the wheel; I think this may (whether you squeeze in either direction with 'kinked nipples') leave the spoke set in the nipple such that it can flex slightly within/near the nipple and thus promote fatigue failure in service.

It turns out that (quite by accident, to start with....) I have built many, many wheels in which I have stress-relieved the spokes by squeezing them at 90 degrees to the plane of the wheel. This may well leave the spoke set rather better at the nipple in wheels with 'kinked nipples'; certainly spoke failures in such wheels appear to be 'very uncommon indeed'.

Has anyone observed any variation in such spoke breakage, varying with stress relief technique?

cheers
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BTP
Posts: 56
Joined: 1 Sep 2009, 1:30am
Location: Perth, Western Australia

Re: Rohloff hubs

Postby BTP » 29 Apr 2016, 8:59am

Brucey wrote:
BTP wrote:Forgot to mention that I have had some issue with spoke breakages at the nipple end. The large flange married to a 26" rim creates an acute spoke angle at the rim. Rohloff recommend 2 cross lacing which I followed. However I suspect that, unless the rim has been drilled to suit the Rohloff, one is better lacing 1 cross.

I'm a trendy consumer. Just look at my SM-N910G using Tapatalk


I have a theory that the method of setting the spokes and stress-relieving the wheel may make a big difference here. Brandt's method is to squeeze the spokes in the plane of the wheel; I think this may (whether you squeeze in either direction with 'kinked nipples') leave the spoke set in the nipple such that it can flex slightly within/near the nipple and thus promote fatigue failure in service.

It turns out that (quite by accident, to start with....) I have built many, many wheels in which I have stress-relieved the spokes by squeezing them at 90 degrees to the plane of the wheel. This may well leave the spoke set rather better at the nipple in wheels with 'kinked nipples'; certainly spoke failures in such wheels appear to be 'very uncommon indeed'.

Has anyone observed any variation in such spoke breakage, varying with stress relief technique?

cheers

Interesting. My way around my problem was to unlace the wheel and use a suitable sized drill shank to carefully bend the eyelet into a line more inline with the angle of the spoke.

I based my bodgery on the assumption that the eyelets were fairly ductile! My hypothesis seemed to work. For the life of that rim (Alex DM18) I had no more spoke breakages at all.

Which presumably means that most spokes are regularly cyclically stressed to somewhere near their endurance limit?

Anyway you sound alot more knowledgeable on the subject than me!

Tony

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pq
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Location: St Antonin Noble Val, France
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Re: Rohloff hubs

Postby pq » 29 Apr 2016, 5:24pm

I haven't read all this thread, so apologies if it's already been covered...

My understanding of this problem is that Rohloff machine their hub flanges from aluminium billet, which creates a hub more prone to flange cracking than a forged one. The problem with forging, that while it's technically superior, it has huge set-up costs, so unless you're producing in high volumes, it's uneconomic. That's why Shimano hubs are forged and designer hubs are machined.

Given this inherent weakness, I'm surprised Rohloff don't offer the hub with more spoke holes to spread the load more. With such massive flanges, there's plenty of room.

Rohloff take customer service very seriously and really look after people who have hubs fail when they're in the back of beyond, but I'd rather not have the failure in the first place.
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reohn2
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Joined: 26 Jun 2009, 8:21pm

Re: Rohloff hubs

Postby reohn2 » 29 Apr 2016, 7:20pm

pq wrote:......Given this inherent weakness, I'm surprised Rohloff don't offer the hub with more spoke holes to spread the load more. With such massive flanges, there's plenty of room.....


Rohloff now make there hubs in 32 and 36 hole,but because wheel's built with a Rohloff have no dish the spoke tension is more even,drive side and non drive side so if the wheel is built well the 36hole should be bombproof.

I believe the odd problem they have with flange breakage is flaws in the Alu billet used make the hub from,the flaw can't be detected until it breaks.That's my layman's understanding of it,perhaps Brucey may be able to elaborate more on the subject.
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Des49
Posts: 609
Joined: 2 Dec 2014, 11:45am

Re: Rohloff hubs

Postby Des49 » 29 Apr 2016, 10:50pm

I have just obtained the flange support rings and intend rebuilding my hub with them. My hub is pretty old, a 4 digital serial no. hub bought 2nd hand a long time ago.

Can't really see how they can do any harm, but they may extend the life of the flanges or prevent any failure in the first place, or just hold things together if there is a problem.

Wish I had got them early this year as I had to rebuild the wheel in January due to a pranged rim. That would have been the perfect time to fit the rings.