Holy crap. I broke my KH/Schlumpf Hub.

Unicycles and Equipment
1

This is not some kind of sick, post-April-fools joke. I broke my KH/Schlumpf hub while riding my amazing new, two-week-old KH36. I’ve been getting more and more confident riding in high gear, and this confidence has included acceleration and deceleration. Before tonight, I was able to lean pretty far forward to get great acceleration, and lean pretty far back to get great brakeless stopping even in high gear.

As I was riding about 9 miles per hour alongside my friend Todd (onelesscar), I told him, “maybe I can stop in one revolution in high gear… let’s see.” So I leaned back and decelerated hard, only to be thrown off my unicycle at the end of the stop due to gears in the hub simply letting go under my torque. I didn’t even feel like I stopped THAT hard; I’ve definitely stopped harder in the past. After a gut-wrenching grinding/crunching sound, the hub just started freewheeling and, moments later, I’d UPD’d.

Afterwards, Todd and I carefully tried shifting the hub up and down, rotating the cranks (by hand) around to see what exactly was wrong with the hub. In some cases, it wouldn’t shift at all; in others, it would go into the freewheeling mode as if it were getting ready to lock into the new gear ratio, but it’d freewheel for about 120 degrees of crank rotation before locking, making. Now, in first gear or high gear alike (I can’t even tell which is which anymore), the hub locks the wheel at one position and prevents it from turning relative to the frame.

I could go on a huge diatribe about it, but I’m sure it will suffice to say that…
I am not happy. It’ll probably be three to six weeks before I can get my hands on another hub (whether it’s this one fixed, or a replacement, I don’t care), and I was planning on spending the next eleven weeks to get confident on it for RTL.

I’m emailing Kris and Florian about this, too. I guess this makes me the first on the planet to break a KH/Schlumpf hub, and it wasn’t even from a drop. I guess I just pedaled too hard. At 9 MPH. In one pedal rev.

I can’t afford spending another $1300 on a new hub, and I really don’t think I did anything abnormal on it. Yeah, I stopped fast, but I’m sure no one ever envisioned that a fast stop could’ve completely destroyed the internal gearing. I hope I’ll get taken care of. And, whether or not I end up with a geared hub in the end, you can bet I’m going to watch how hard I actually pedal it in order to keep from breaking one again.

I donno, maybe there was ongoing wear happening the whole time, and the stop just happened to be the large-ish straw that broke the camel’s back. Who knows? I’m sure Florian will be able to dissect it and see if anything was wrong beforehand or if I’m just too dumb and torquey for my own good.

2

Ouch. That sucks. Maybe something has happened to the shifting pins that lock the two halves of the gearing together. It doesn’t sound like you were caning it too bad or anything, I know I’ve emergency stopped on my normal Schlumpf with no problems.

Do you have a normal 36 to ride while you wait for the hub to be fixed (or a spare hub to build into the wheel)?

Joe

3

i’m really sorry to hear about your bad luck with the hub- or awesome backpedaling power. Hopefully the problem was specific to your hub and not the whole bunch of them. I don’t think kris will leave you high and dry after you made a substantial investment in a hub that sells as being suitable for pretty serious muni.
mark

4

Eeeek! That’s about all I can say at the moment. Just Eeek!

Hope it gets sorted out soon for you.

STM

5

Hey, yeah, I still have my old Nimbus 36 parts all ready to go. I suppose I’ll build my stealth/niterider combo onto my superwide hub between now and when I get a new hub (somehow). It’ll be my fourth 36" wheelbuild in two weeks, and my fifth total, so I suppose I’ll be getting my practice. It’ll give me a chance to rock up my 102s and see what I can do in 1:1. Thanks for your concern, though.

6

…did you already talk to florian about that? i guess he will help you…

7

I’m really sorry to hear this. I hope you get a replacement soon and it is just the case of one defective hub. I would be equally unhappy. Keep us posted as to how it gets resolved.

8

Sorry to hear that Chuck - I haven’t ridden mine too much, yet. I’m sure that it will get repaired, but it is concerning that it happened. That thing is supposed to be very durable. I hope it was just a fluke! Never having seen the inner workings of the hub, I can’t even speculate what happened, other than teeth breaking off the gears. I’m hoping that you are just mutantly strong, or there was an unseen defect in your hub, and nobody else will experience this issue. Good luck getting back up to speed!

9

I hope this link works;
http://www.unicyclist.com/index.php?page=gallery&g2_itemId=117458
but due to restrictions on my work network, I can’t see it to be sure. But, anyway, this should be the video that shows how the inner workings mesh together, and give some clue as to what is bent/broken/snapped.

STM

10

Holy crap, that totally sucks!! It sounds like the muni hub isn’t quite up to snuff. Let me know what Florian and Kris say.

corbin

11

Have you checked that the bearing holder on the lever arm is tight enough? Ashley’s hub had somewhat similar behavior due to the bearing holder not being clamped down.

12

Not good news given the dough I just spent getting one (24) laced up. Hope it was a defective hub and not endemic to the whole batch.

JL

13

=p

i think ill just stick to a standard kh36 wen they come out, the hub sound so much more comlicated to use than i first antisapated :thinking:

14

I had that exact same problem (I didn’t set it up properly) and the grinding/crunching sound seems familar, particularly in high gear. You want the usual tightness on the plain bearing, and very tight on the knurled bearing. As the setup is new and starting to get bedded in, unicycles are always worth a few extra-careful check-ups and re-tightening of components at more regular intervals in the first few weeks, like a car’s or motorbike’s first early service.
The rest sounds nastier, fingers crossed.

15

Welcome to the world of early adopters. :slight_smile: If you’re lucky, it might be as simple as what Tom and Mike described above. If not, your hub may be under warranty, and Florian and Kris are anxious to see what happened inside your hub. Could have been a defect in the build, or you may have found a weak spot. My guess is that you might even get a new one in exchange.

These are complicated mechanisms and I know Florian and surely Kris as well have worked very hard to make a solid, strong and safe product for all of us. With the amount of miles I’ll be putting on my borrowed Schlumpf Nimbus 36, it’s imperative to know the hub will be reliable, and that it’s extremely unlikely that it will spontaneously freewheel while I’m going 15 mph or faster. Please keep us posted!

16

Same here.

Make sure you tighten the Knurled side really tight. When I first assembled it I had the same grinding problem where it would just randomly freewheel, and I just had to tighten those bolts really tight.

I actually put some loctite on the bolts so that they wouldn’t come loose to prevent that from happening to me while I was riding!

I hope it is just something as simple as that!

17

Just stand up and ride it like a giant BC Wheel :slight_smile:

18

Hey all,
I just got email back from Kris, and he gave me the address to ship it to Florian, and he says it’ll get replaced or repaired, so they’re taking care of me. I’m sorry if it sounds up above like I made a huge stink about it… I did, but __it happens, y’know? :slight_smile:

This’ll give me a chance to throw those old 102s back on and see what I can do, I suppose.

Oh, and re: the question of the tightness around the knurled bearing, yes, that side I had tightened way, way down, and the other side as normal. I did checkups and tightenings pretty much every few nights just making sure things were tight, etc. Maybe, to prevent this much torque from going on my next hub, I’ll avoid REALLY clamping down the knurled bearing side, and only tighten it enough so that it will slip just before the gears in the hub would otherwise collapse. (If this is a design problem instead of a yucky fluke.)

Those of you with geared hubs, though, I wouldn’t be afraid of them! Didn’t intend to make anyone leery of your hubs! I’m totally sure that, riding at any speed, the hub has absolutely no danger of “letting go” as it did with me, because, for mine to let go, I had to do an emergency-stop type stop and heard the crunching. Till we know more about what happened in my hub, I’d just recommend not applying your full and complete “single-burst back-pedaling power.” (I did about 80% of mine.)

19

Do any of you think that there’s a mathematical way to figure out the amount of torque with which to tighten the knurled-bearing-holder bolts given the amount of pedal torque required to break the hub? We’d need the coefficient of static friction of the knurled surface with the frame material, plus knowledge of the amount of compressive force in the bearing holder as a function of screw-tighten-torque. Methinks that with those three tidbits we could make a setup that would never break a hub, and would only cause the bearing to slip.

20

Congratulations on your fantastic backpedaling power :slight_smile: No really that’s a serious bummer especially when you’re training for something as big as RTL. Good to hear that Florian and Kris are taking care of the issue though. Frankly, I would have been surprised if they wouldn’t…

If it wasn’t tight enough, would that lock the wheel to the frame (in that it can’t rotate)? Can’t see how that would work.

BTW, were these knurled bearings designed to take such a big clamping force? A regular bearing would deform and then ‘grind’ if you tighten the bearing holders even half-hard. So these must be extra-sturdy then.