36" Oracle hub failure

Anyone else had this happen? The other day I was making a turn while standing on the pedals and felt/heard the snap and assumed a spoke had broke (which would’ve only been the second spoke to break in 3k miles or about 2 years) but upon inspection turned out to be way worse. Now I’m going to order the all steel nimbus wide disc compatible hub. Because of this I think alum is too weak and not worth the weight savings for the hub, especially when what really matters is the rotational weight of the tire/tube/rim strip and rim.

Anyway…highly disappointing. My 36" nimbus nightrider I ordered early 2010 is still functioning (the hub at least) and has a lot more miles on it…

Haven’t seen this one happen, but breaking flanges seems to be a bit of a theme with 36", a few Schlumpf hubs did suffer from that also… I’m a bit puzzled on why we’ve seen so many hubs failing at the flanges in the unicycle world. Yes, it’s twice the weight per wheel compared to a bike, but cargo bikes and mountainbikes should see similar stresses, and I haven’t heard of failures like that there.

Personally I never understood why so many brands develop full aluminium hubs, the weight savings are there, but it’s really not a point where you notice it much. (Although I recognise that this failure could have also happened on a steel hub with pressed on aluminum flanges, which I think are in theory a good design). Can someone please focus on building seats that don’t weigh a ton instead?

It happened to ed pratt. And Cary gray too I think.
I was in the process ordering a wheel built with a steel hub for this exact reason, but then I found a good deal on a new 36". I hope this won’t happen to me anytime soon.

This is the first new Nimbus aluminium hub that I’ve seen broken, but honestly aluminium flanged (or entirely aluminium) hubs should probably be considered long term consumables on unicycles, especially when they’re used and abused and not checked for true and even tightness every so often. Almost everyone I know rides their unicycles until something brakes.

It’s not an unknown issue with bike hubs either, but it definitely seems less common.

KH and Nimbus hubs used to be like this, but creaking problems between the flanges and axle plagued them so they’ve both moved to one piece hubs again (either steel or aluminium).

I’ve personally rebuilt a wheel with a broken flange, and seen many (less often ridden unicycles) with corrosion and apparent stress fractures that will no doubt be a hub replacement eventually.

@DSchmitt, when you take things apart, I’d be interested to see if there’s any noticeable wear on the ISIS interface on that hub too.

Aluminum flanges are only good for about half way around the world. From Ed Pratt video.

No even half. Only Kazakhstan. But this reminds me, Pratts hub isn’t the standard alu hub we get now.

No, his was the clicky multi-part generation with a steel axle.

I think the aluminium alloy used has changed now too.

I believe it was the one below. It has an aluminum flange and aluminum axle.

Were the 125s all alloy axle or did they make steel ones too that looked very similar?

The 100mm width version that I owned definitely had a steel axle.

I’ve got the axle still from a broken 125 version somewhere, but sadly it’s at another house or I’d double check what it’s made of.

I think there was (is?) a CrMo 125mm hub with disk but it look a lot more like a KH Moment hub than this picture.

There was both aluminum and CroMo spindles for this style of hub in 125mm. The weight difference was quite striking when I held one of each. If I remember right the visual cue differentiating them was the colour of the flanges.

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I was fooling around with the Wayback machine and found that they sold a 125mm hub for the Oregon with steel axle and green flanges. So you remember right!

Apparently they thought that aluminum was strong enough for road use; that’s what came on the 36" Oracle.

I think it may have debuted on the Impulse. Its selling point was being light and having a disc brake. It had a drilled rim too from memory.

Hi Dschmitt, Where are you? I happen to have one of those Nimbus ISIS drive LT, Green anodized flanges, beautiful, great looking. Did I mention Brand New in the cardboard tube? 36 hole 125 width? I was trying to sell it but if the cost of shipping isn’t too much it’s yours ($40 us. all others interested)

ps. Just like the one JimT picture above in green.

pps. OK, after reading all the posts again, maybe steel (green flange)

With Disc mount flange!

Wow, no bites! Still FREE to DSchmitt. $30. and shipping any others.

i sent a message to @DSchmitt asking for his old broken hub but he hasn’t responded to that or to anything else on this thread.

What do you need an old broken hub for? I’ve got a brand new one, cheep.

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i would like a broken one to wrap in foam or something and put cranks on it and make a trampoline une. so I would have the hub and cranks in my street/flatland frame and be able to do tricks on the trampoline. so the best thing for me would be a hub that is still in decent condition, just with the flanges broken, like @DSchmitt’s broken hub

The problem with subjecting aluminium to cyclic stress is fatigue. The hub flanges go through changes in load every time the wheel rotates.

Steel (and Titanium) have fatigue limits where stress below a certain level does not cause fatigue. Any amount of stress to aluminium will cause fatigue. The number of cycles before it cracks depends on the level of that stress.

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