Problem with my new Schlumpf guni hub?

[David_Stone]

In a nutshell, one of the crank arms is loose on my (new) Schlumpf guni
hub. This is the same problem I had six months ago with my first
generation hub.

The loose arm is on the downshift-button side. That is the same thing
that happened to me last time, if I'm not mistaken. Luckily for me, a
fellow member of the NYUC also has a guni from Florian, so he may be
able to fix this when I see him tomorrow. If not, I'll have to
disassemble the wheel again (that's a lot easier than building it!) and
send the newer hub back to Switzerland.

I should note that I have not gone down any big curbs (nothing more
than a few inches, and only a few times). I think the only strain I put
on the guni was while riding up a fairly short hill today in high
gear.

Blah blah blah:
Back in October, my geared unicycle began having problems. On several
occasions it slipped out of geared (once causing a scary fall), but
worse still was the related fact that one of the crank arms was falling
off. I emailed Florian and spoke with him a few times in Switzerland,
and I tried repairing things on my own and with the help of fellow NYUC
club member (and fellow guni owner) Dave Bagley, but finally we
realized that there was no way to fix this unicycle's hub.

Florian had been working on an improved hub at this time, so rather
than trying to fix my hub or sending me a replacement, he generously
decided to give updated hubs to all owners of 1st generation hubs.
These newer models have 12 internal pins rather than 6, and this means
that the hub can switch into gear more smoothly. It took nearly six
months for the updated hub to arrive, and it finally showed up last
week [Florian had broken his arm and had gone to Laos on a unicycle
tour, adding to the delay.]

Once the hub arrived, I tried to rebuild the wheel (putting all of the
spokes back on the rim), but my two attempts failed. Rebuilding a wheel
is a Zen art, and I'm not even a Zen grasshopper when it comes to
truing a wheel, let alone building one from scratch. So I paid a bike
mechanic $35 for the job, and, as of Wednesday afternoon, was on my
way. Sure enough, the shifting was nearly seamless. I was able to make
transitions from low to high gear and back with little difficulty. I
rode it to Brooklyn and back to my mom's apartment on the Upper West
Side (a trip of about 8.5 miles each way) twice, logging a total of
about 36 miles on it until just an hour ago when I realized that one of
the crank arms is loose.

The loose arm is on the downshift-button side. That is the same thing
that happened to me last time, if I'm not mistaken. Luckily for me, a
fellow member of the NYUC also has a guni from Florian, so he may be
able to fix this when I see him tomorrow. If not, I'll have to
disassemble the wheel again (that's a lot easier than building it!) and
send the newer hub back to Switzerland. Ugh.


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[Gilby]

Hmmm... my left crank came loose during the Laos tour. We just assumed
it was the result of not being put on tight enough by the bike shop
that I had build the new wheel for me. After that day's ride, I
tightened it up and had no problem since. Though it'd probably be a
good thing now to to go over it with a proper torque wrench and make
sure it's tight.


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[David_Stone]

Wow. That's a relief. So maybe I can take it to the bike shop down the
block and see. Thanks for the note, Gilby. I'll write back when I know
more.

David


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[David_Stone]

Well, I took it to the bike store, but here is the snag: The loose crank
is the one off of the silver button, which is the one that does NOT
come off with the special tool. Now, I have never taken apart one of
these hubs, and I don't have Florian with me, so I wasn't sure what to
do. We got the other crank arm off easily (the first time I'd seen what
is behind a crank), but from there we had no idea what to do next. The
other crank and the other button were just taunting me.


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[pdc]

Are these cranks regular square taper? If so anti-seize the taper and
the bolt or nut thread liberally tap firmly but not too hard with a
rubber mallet and tighten the bolt/nut. Anti-seize is the key!


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[john_childs]

Schlumpf has manuals in PDF format for their bicycle geared bottom
brackets. The manuals explain how to adjust the shifting buttons for
depth in the cranks and other things. You can download the 'Mountain
Drive manual here' (http://www.schlumpf.ch/md_engl.htm) (scroll down to
the bottom of the page). Print that out and the bike shop should be
able to get the shifting buttons adjusted for you.


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[David_Stone]

Thanks, John. I checked out the site and eventually found the right
technical manual pages. Luckily I can take them to the bike mechanic
tom'w (whether he's available is another issue). I can also buy a
torque wrench and try the work myself or with a club member.

I really hope I can get this taken care of HERE rather than in
SWITZERLAND!

David


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[U-Turn]

What length and brand of cranks are they, David?


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[vicuniclub]

i know this is completely off topic but with the splinded geared hub
comming out in the summer. i was wondering if you can replace the axel
or do you have to replace the whole hub?


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[David_Stone]

U-Turn wrote:
> What length and brand of cranks are they, David?


Honestly, I don't remember. The thing is in the car, anyway. I'm so
annoyed about this. I think they were 140s or 150s, and I'm curious as
to why you wanted to know.

Florian wrote me today, asking whether I had tightened the crank arms
or whether he had. When I sent back my hub, I also sent back the
attached cranks because I had no way of taking them off (or if I did, I
didn't know it). But D4 sent his hub back without the cranks, so maybe
he will know what to do (when I see him tomw) or will have the tool for
tightening the crank.

I assumed that the assembly would come back to me in perfect shape and
that this issue would have gone away. It's hard to believe I waited 6
months for this. I do know that the cranks seemed fine when I got the
assembly back -- otherwise the mechanic and I would have noticed the
loose crank earlier. So I'm guessing that something went wrong within a
few miles of riding the new assembly, which seems odd, but it's my only
guess. Is it possible that Florian used some of the same components
when he gave me the new hub? Perhaps the cause of the loose crank was
never dealt with and I'm just riding the same faulty crank? I wish I
knew enough even to make a good guess (or at least to be able to
explain it to a bike mechanic).


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[David_Stone]

Gilby wrote:
> Hmmm... my left crank came loose during the Laos tour. We just assumed
> it was the result of not being put on tight enough by the bike shop
> that I had build the new wheel for me. After that day's ride, I
> tightened it up and had no problem since. Though it'd probably be a
> good thing now to to go over it with a proper torque wrench and make
> sure it's tight.


What I'd like to know is how you 'tightened it up' in the first place.
At the store yesterday, the mechanic and I failed to figure out what to
do in order to effect any tightening whatsoever. We managed to take off
the crank that was already tight, but it didn't allow us to get to the
loose crank or to do anything about it. The mechanic was understandably
nervous about doing anything that could make the situation worse --
he'd never seen this sort of assembly before.

Also, what tool did you use for tighening? You alluded to a torque
wrench, but Florian wrote to me about getting a torque screwdriver (the
thin one that goes into the hole of the button). I take it that this
tool is not commercially available other than thru Florian. So I'm not
sure what to do (or what to tell a mechanic to do).


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[Gilby]

You need the uber tiny alen wrench to remove the button from the crank,
then you just use a torque wrench to tighten the nut just like on a
regular unicycle. The torque screwdriver is used to put the button back
on and I used Florian's since he was on the LUT. Oh, and when removing
the button, don't do what I did and unscrew the hex screw all the way.
It's soo tiny and would suck to loose that. You just need to loosen it
and then spin the button off with your hand.

If you have the same cranks that you had on the old hub, it sounds like
since the crank came loose before and you rode on it, you may have
damaged the cranks, meaning that it'll never stay tight now because
they are deformed. That's typical with alloy cranks when they get
loose.


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[David_Stone]

I went to the bike shop, which was not helpful bc they don't carry
torque screwdrivers.

D3, the cranks only say 'Schlumpf Innovations' on the outside, so I am
guessing they are his own creations. I guess they are 127s, bc the
number 127 was etched into the cranks.


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[David_Stone]

Gilby wrote:
> You need the uber tiny alen wrench to remove the button from the crank,
> then you just use a torque wrench to tighten the nut just like on a
> regular unicycle.

we did all of that, and the nut we came across was good and tight.



> If you have the same cranks that you had on the old hub, it sounds like
> since the crank came loose before and you rode on it, you may have
> damaged the cranks, meaning that it'll never stay tight now because
> they are deformed. That's typical with alloy cranks when they get
> loose.


Yeah, so I either have to return the cranks or the whole crank/hub
assembly. The problem is that I can't remove the cranks, tho I believe
my fellow club member can help me with that tomw.


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[U-Turn]

David_Stone wrote:
> I think they were 140s or 150s, and I'm curious as to why you wanted to
> know.
>

Well, I was just guessing that the axle design and fabrication is very
fine, but that the cranks are added as a necessary afterthought. Since
unicycling puts more strain on cranks than bicycling, I reasoned, then
the cranks added are possibly not up to snuff. This is why I asked
about the brand.

From the technical manual it appears that replacing cranks is a simple
matter provided that one has a small set of Schlumpf-provided tools. I
don't know whether these come with a unicycle or must be a separate
purchase.

It might be reasonable to replace the factory-provided cranks with a
set that are more unicycle-tested. This is why I was asking about the
length.

From the manual it is evident that there are dimension restrictions on
cranks that may also affect one's choice of cranks that are suitable
for that hub.


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[David_Stone]

U-Turn wrote:
> From the technical manual it appears that replacing cranks is a simple
> matter provided that one has a small set of Schlumpf-provided tools. I
> don't know whether these come with a unicycle or must be a separate
> purchase.

There are just a few small tools that are provided with the uni. One is
a tiny allen screwdriver attacment that is necessary in order to remove
the button. Another is a two-toothed job that holds the other button in
place so that you can twist the first thing around without it going in
circles.

Here is my trouble: I can remove only one of the crank arms. The other
one appears fixed, like it's attached to the hub diff'ly. Can someone
else please corroborate this for me?


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[U-Turn]

http://www.schlumpf.ch/handbuecher/WHB.md.engl.pdf

Page 17 tells how to remove crank arms. This is for the mountain bike
model. I do not know how this relates to the unicycle hub.


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[David_Stone]

Thanks, D3. I have already printed out that page (and a few others), but
as you noted, there is no photo about the removal of the cranks for the
uni. Luckily for me, D4 has already removed the cranks from his uni, so
I can work with him tom'w at the club to get that job done.

Florian was specific with me about two things: 1) He doesn't have extra
hubs -- they're all spoken for, which is great (I'm glad his work is
getting so popular), and 2) He never replaced the original cranks which
are causing the problem now (due to friction wearing them down the
first time), so he wants me to put other cranks on, and I can do that
tom'w, too, since D4 has an extra set.

So by tom'w evening, I may have this under control.


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[Gilby]

I would assume each side is the same as far as removing cranks go. There
is a special "small tube" that goes over the shifting shaft that allows
you to use a regular crank extrator to remove the crank. You didn't
mention that as a schlumpf tool you had, but it did come with the uni
(or with the replacement hub when I got mine).


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[David_Stone]

My only hope was answered today at the regular convening of my uni club.
Dave Bagley, who among other things is the webmaster for Tommi Miller,
had pulled a groin muscle while riding his sideways-riding uni, Crabby,
which Tommi built for him recently.

Since Dave was unable to ride and since he is such a great guy, and
since he is the only other owner of a Schlumpf geared uni on the East
Coast, he volunteered to help with my guni this afternoon.

It turns out that the only difficulty I'd had was removing the button
on the loose crank side. It turns out that both cranks are attached
identically, but tho that makes sense, I wasn't sure owing to the fact
that this is a geared uni.

Dave was able to get this button off, but he said it was tricky. Once
done, he could have either tightened my loose crank or replaced it with
an extra one he had. And being Dave Bagley, naturally he replaced it
for me gratis.

Now I have my geared uni back in anction, and I can fix it myself if a
crank ever loosens again.

Thanks, Dave! And thanks, too, to Gilby, Stockton, and Childs for
trying to assist, too.


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[Klaas Bil]

On Sun, 2 Apr 2006 20:16:30 -0500, David_Stone wrote:

>Thanks, Dave! And thanks, too, to Gilby, Stockton, and Childs for
>trying to assist, too.

And thank you for putting the whole issue on here. If my crank ever
gets loose, or if I want to swap them (I have 170's on, and 150's
spare), I'll hopefully remember what to do...

[David_Stone]

Klaas, 170s are really long!

1. What is the length of the cranks on your Coker?
2. What's your top speed on both?
3. Why did you opt for such long cranks on the guni?
--- terrain?
--- fear of riding-difficulty?
--- you're accustomed to long cranks on the Coker?

I almost went with 140s but decided on the 127s. I think that's like
what I have on my Coker. I think I might get a pair of 140s when I move
to a more rural area soon -- the road conditions might require it. But
I like the speed of the 127s and can't imagine riding with 170s. That's
like using flippers, no?

Oops, that's another question:

4. Are 170s on the guni like wearing flippers?


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[Klaas Bil]

On Mon, 3 Apr 2006 12:32:45 -0500, David_Stone wrote:

>1. What is the length of the cranks on your Coker?
I don't even have a Coker. I've ridden a Coker once, with 125's, and
liked it. I've tried 110, 125 and 150's on my 29'er and liked 125 the
best.

>2. What's your top speed on both?
* Coker with 125's, not measured. Cruising at 18 km/h (I never checked
until now, but I saved the GPS track record). I could have gone faster
easily but I held back since a friend was on my non-geared 29'er.
* Ungeared 29'er with 125's, 22 km/h but I find it scary.
* 29'er Schlumpf with 170's, 20 km/h but potential for more, I've only
done a couple of rides due to many reasons.

>3. Why did you opt for such long cranks on the guni?
>--- terrain?
no, I plan to do road rides only on the Schlumpf, and roads are soooo
flat down here
>--- fear of riding-difficulty?
yes, including mounting difficulty
>--- you're accustomed to long cranks on the Coker?
no, but I have 170's on my MUni and that is what I do most. I have
180's on my bike, which I ride more often than all of my unis
together. So indeed I'm used to long cranks, but not exclusively.

>4. Are 170s on the guni like wearing flippers?
No I don't see any similarity. The comparison made me smile.

Thanks for the interest.

[skianduniaddict]

im sponsered by them because my dad is friends with florien the owner
but im no techie ill ask him


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