Schlumpf crank (hub?) problem

Help! I’ve never been very good at fixing my guni. Even tightening and loosening the buttons has eluded me (I can always do it with the right-side button, but never with the left. I have it set up so that I push in the left side in order to gear it up). Background: This is one of the earliest-made hubs, #00080.

Anyway, I experienced that familiar sensation of a loose crank arm yesterday; I tried to fix it myself (luckily it was the right side), but when I rode the unicycle again, the arm came loose in just a few revs.

I took the uni to my local bike shop; the mechanic had never worked on the hub, but he has done a wheel-builld for another Schlumpf (I’m not sure whose), and he was very professional. He took off the loose crank and diagnosed the problem: It has worn away a bit on the very inner part of the crank – the part closest to the hub, if that makes sense. The result is that there is no way to tighten the crank sufficiently to keep it on. We gave it a try, but the crank loosened within a few hundred feet of riding.

So at best, I need a new crank arm.

But the other problem was that he and I could not figure out how to remove the left-side button. I still have the tools that came with the uni: That forked piece that holds the button in place (or turns it) and the tiny wrench-head that can fit inside the hole.

If I can’t get the left crank off, I’m a bit screwed.

So… thoughts? Should I just save up and get the new hub? I’m actually planning to do so. But is there any saving this hub?

Thanks, Uni Community!

The hub can be saved but it might be a bit of a process in removing the left button. I guess I’m confused how you can’t get the left off but could get the right one. You seem to be explaining it as you do not understand how to get it off rather than an issue like stripped set screw (the little screw inside the button). The left button should come off just like the right one. Please clarify.

Thanks. It might be a bit of both.

The thread isn’t stripped. But I’ve only ever taken the left button off once or twice. Maybe it’s stuck. The mechanic and I had no idea how to remove it. The issue was that there was no way to hold the shifting rod in place in order to loosen the button from it.

Of course, I maybe doing it wrong. (That’s what she said.)

Is it possible to put the other side shift button back on and tighten the set screw to hold the shifting shaft in place to prevent the shaft from spinning when loosening the other side?

If you have the set screw broken free on left side and tightened on the right side button, the act of loosening the left shaft should be the same act that tightens the right button against the set screw. It could give some leverage when loosening the stuck left side.

Maybe a bit of PB blaster on the stuck side may help loosen the set screw if it’s stuck. It needs to be as free as possible before attempting to loosen the left button.

The mechanic and I tried again. It looks like the pushrod on the left side is definitely stuck. We put in some oil, but it didn’t help. I’ll try later.

I think “pushrod” = “set screw”

Is the left crank loose? If not, why do you need to remove the crank (or the button)? Unless you want to change crank length, just get a new crank for the right and leave the left one alone.

Though if you are trying to remove the button, are you sure you’re doing the right thing? I’ve seen a lot of reports of people doing it wrong, and your suggestion about holding the shifting rod in place does suggest that to me, as there should be no need to hold the shifting rod to undo the grub screw. You first need to hold the button still with the forked tool and undo the grub screw inside using the tiny hex-wrench. Only when you’ve undone the grub screw should you try unscrewing the button.

FWIW I have an even earlier hub, #00031

set screw = grub screw but not the push rod. The push rod is the rod you can see on the right side with the crank and button removed. The set screw is the tiny screw that you should be able to turn inside the right button. It could be that this screw is stripped or stuck on the left side.