Bearing material?
Quick question: What flavor metal is the knurled bearing made from? Is it aluminum or something else? I have the not-newest generation without the bearing stop. My bearing is slipping in the bearing holder in high gear and I’m hoping my welding friend can just weld the bearing to the aluminum bearing cap. I don’t know diddly about welding, so feel free to tell me what a bad idea this is.
UtL
Likely a bad idea and not possible. The knurled bearing is steel and frame is likely aluminum and they can not be welded together. Here is a past thread with some ideas and what looks like a positive fix in the last post.
http://www.unicyclist.com/forums/showthread.php?t=93281&page=3
Thank you, sir. I suspected it wouldn’t be so easy. Perhaps I could steal a steel bearing cap from a nimbus frame? I think all the bolt holes and bearings would line up… I’ll have to stare at it for awhile.
Don’t do it. Have you tried less permanent and more reversible methods like:
Loctite bearing retainer
A very slim shim around the bearing. (I’d try tinfoil, as it’s just to get the clearances a bit tighter.)
Filing of a bit of the bearing holder where it clamps together.
If all that doesn’t work, find a friend with a mill, and have him do the same that flansberrium did: https://www.facebook.com/flansberrium/posts/2173381552895176
All these methods don’t destroy your hub, welding might.
Welding?, on a bearing, on only one side? no no no, don’t do it! Ever heared of welding deformation? You may destroy your schlumpf with this …
Agree with everyone. Dont weld on it. If you really want it to not slip, I’d be willing to machine a stop like I did on mine. It works just like the latest generations and it is impossible to slip. You can still replace bearings when needed and swap frames over.
Send me an email if you’re interested.
Here’s the exact modification.
I recently installed my Schlumpf hub into a 26" wheel. It was previously in a 19" trials wheel. I went on a 12 mile on/off road ride yesterday. Everything worked perfectly (I had one accidental downshift, but I am guessing my foot hit the button on that one). Which is good, because I had a lot of problems my first time around with the 19" Guni.
First of all, I was ill-informed about the use of a crank stop. My hub is an M800 series, and the specification allows spacers to press hard against the hub. I had some problems before figuring this out.
Second, I was performing small hops on the 19" Guni. Bad idea. I weight more than 200 lbs. This probably caused the interface to get loose. On my ride yesterday, I rolled everything and avoided any corrective hops during mounting.
Third, I wasn’t using LocTite, because I didn’t see the need for it. I thought that tightening the crap out of the crank bolts would be sufficient. But they still kept getting loose. So, duh, I learned my lesson there. On my 12 mile trip yesterday, everything remained tight.
Fourth, I was using the special 2nM driver from Schlumpf to lock in the shift buttons. The frequent use of that resulted in stripping out one of the tiny plugs (and me damaging the shifting rod trying to remove the shift button). I think I can get away with using less force, stopping the tightening of those tiny plugs before the tool “clicks”.
I think the internals of the Schlumpf hub are great, but the interface is still not bullet-proof. And I am concerned about the hardness of the crank bolts and the shift-button plugs. There’s a limit on how much I can tighten the crank bolts before they deform. I can use much more torque on the crank bolts on my conventional, ISIS unicycles, on the other hand.
I’ve never used loctite on my Schlumpf, had it like 2 years now and haven’t bothered to tighten it since the first couple of weeks of me buying it, and nothing seems to be slopping. Tightening the crap out of it CAN work, assuming you’ve got a 4ft long iron bar and a bit of patience 
Hopping on it shouldn’t affect it too much either, they’re built to really take a beating. What sort of torque are you putting on the cranks themselves when you tighten the bolt on?
Not as much as I want to. The bolts that came with the hub could only take so much torque before they started to deform on the inside. And I was not using a long wrench, either, just a small hex tool smaller than the size of my hand.
I spoke to Silva Cycles, the ones who built the wheel of my original Guni (when the hub was in a 19"). They also had recent problems with deformation of the bolts during tightening. I think this problem may be specific to the most recent 8XX series of hubs. Silva suggested that maybe the bolts were not hardened adequately.
I checked the tightness of the bolts a couple days after going on my most recent ride. The right bolt was completely tight, but the left bolt had significantly come loose. The crank was still pressed on the interface correctly, so the problem was not apparent until I removed the shift button.
My recollection, from the many times I’ve re-tightened the interface, is that one side tended to get loose more than the other, and maybe it was the left. I wonder if this is due to the the rotation of the left crank in the direction that would loosen the the left crank bolt. I never had a similar problem on my other, ISIS unicycles, however.
This has been a major concern and frustration. It makes me somewhat afraid to ride on the thing. Thanks for your help figuring out the problem, Piece Maker.
Schlumpf does now sell pre-tightening bolts that are a little bit more substantial then the bolts that are designed to have the shifter pass through them - it may be worth investing in one to get the cranks on and up to torque before just then nipping up the hollow ones for riding.
https://www.unicycle.uk.com/schlumpf-pre-tightening-bolt.html
I’ve also had issues with the standard ones deforming more than one might like when tightening up. A good set of allen keys helps but doesn’t completely remove the problem.
If I understand correctly, Schlumpf claims that the pre-tightening bolts are no longer necessary on his latest batch of hubs.
I just did mine with a regular ISIS bolt - pushed the shifting rod in first and the bolt itself didn’t touch it. I cranked it down as hard as humanly possible with a giant iron bar, then replaced it with the hollow crank bolt.
I’ll probably get the proper Schlumpf tightening bolt at some point though, I plan to re-do my wheel soon and want to do it right
It really sounds like elpuebloUNIdo needs to get the tightening bolt though!
Is that because the new generation hubs have standard bolts made out of a tougher steel?
I can’t see how anything could have changed otherwise.
I presume the issue is primarily that the bolts weren’t/aren’t tough enough and/or the hex isn’t really deep enough to spread the force from the allen key?
I don’t think all M12 axle bolts necessarily have a deep enough bore on the inside to recommend that as normal practice. You could very easily end up bending the shift rod if it’s just a mm or so too short.
A representative of Silva Cycles, the bike shop who’ve built many Schlumpf wheels, told me they were having deformation problems with the most recent bolts. Me, too. SO, it seems like the opposite is true…the new generation of bolts is made of less-tough steel.
The mechanics of tightening the interface are still somewhat confusing to me. I have to distinguish between two forms of tightening. The first form is what happens when the crank is being forced onto the tapered ISIS spindle. The second form happens after the crank has achieved a “stop” and the bolt is tightened further.
On my other unicycles, it seems I’m relying more on the second form of tightness to keep everything snug. In my collection of ISIS cranks are some that bottom-out without really squeezing on the spindle. I don’t need a crank puller to remove them. They just come right off. But I don’t have problems with them coming loose, because I use spacers and tighten the living crap out of the crank bolts. Again, that is the second for of tightness. To get to my point, I don’t see how pre-tightening bolts are going to help, because the second form of tightness, which I’m relying on, can only be done with the ultimate (final) bolt.
The other day, when I found the left crank bolt had come loose, the crank was still gripping the interface (first form of tightness). But that didn’t stop the bolt from unwinding itself. Even If I could tighten the Schlumpf bolts as much as the regular ISIS bolts, I don’t know if that would fix the problem of the bolt coming loose. The loctite I applied didn’t stop the problem.
I don’t have experience with past-generation hubs, but my understanding is I can use spacers with my M800 series hub (and I do use them). I don’t know how that changes the situation, regarding tightening.
Sorry for my layperson’s explanation of my problems. Thank for your input, mowcius and Piece Maker!
It’s a combo of all those: bolt is too thin for the force applied to it, steel is not the super hardened type. And also, it’s not exactly 7mm, and as most of the Allen wrenches out there are smaller than they should, there’s too much play. It took me a while to find a good wrench that has a very tight fit on the bolt. I’m also using the pre-tightening bolt, and since then I’ve been good.
ISIS cranks really should be tight on the spindle before they bottom out against a spacer. I believe UDC suggests a 2mm gap when you’ve put on the cranks by hand (and that’s generally what I aim for).
If your cranks can be removed by hand and are touching the spacer before you tighten them up, you should be using smaller spacers.
Your bolt coming undone is an odd one though. I’ve never had a bolt come loose without the crank also starting to come off with it, normally due to spacers that are too long so the loose crank is what helps to undo the bolt.
The newer hubs have a standard sized hex bolt hole, whereas the older ones have a slightly smaller one, so you have to use a smaller allen key to do it so it’s harder to yank that much torque through them without rounding it off. I think that’s pretty much all it comes down to, but I could be wrong!
Getting a disc to work with my old Schlumpf
After a lot of thinking, I’m considering whether I should go with the flow and try getting an external disc brake to work with my hub.
So, while I understand the need to take a file the outside of my frame to make this work, I’m just wondering how much I should be expecting to take off. Right now there’s about 3-5mm clearance without any modifications between the Spirit crank and the big weld blob on the outside of the frame, but it’ll probably be a bit smaller once I remove the cranks and bolt them back on again because it never quite fits together the same second time round!
It’s the older model Schlumpf (pre-spacers, with knurled bearing) so I’m not expecting it to ‘just work’ but I’m hoping to not end up with an unmaintainable mess that I have to re-tighten every 100 miles, as right now my cranks have held on very well without trouble and I’m hoping to keep it that way.
Cheers
I’d recommend just trying it and see. Just mount a disk on the crank and see how close you get with the heads of the bolts. I took nothing off the frame when I was doing it and it was pretty much fine on one side and an issue on the other (flipping the hub to try both sides).
There’s only a small amount you can take off the frame to move the disk in before you start having the disk crash into the IS-post mount adapter.
If you’ve not had any issues with cranks coming loose so far then I can’t imagine you’ll have an issue with a disk, but if you start using it hard, you do increase the risk of knurled bearing slippage (which was my biggest issue).