Broken Schlumpf Crank

I may feel like I have to post about every ride I do, but, honestly, I
only post when something interesting happens. This morning I got some
'good karma' (http://tinyurl.com/yoayad). So, to make up for it, and
to balance the world out, on the way home this evening, I got some bad
karma.

Heading down Clerkenwell Road, I was approaching some traffic lights
that were about to change, so I had to speed up a bit to get through.
Just as I got to the other side I noticed my right foot felt a bit
wobbly. If you've ever had a loose crank, bent pedal spindle or pedal
bearing loss then you'll know exactly the kind of feeling I mean.

So I stopped ASAP and took a look. I waggled the pedals but the felt
ok. Wiggled the crank and there was a bit of movement. Was that it?
Ah, no, it's a Schlumpf, so there's always a bit of play. Tried
wiggling the crank in relation to the opposite one and it was solid.
With the uni upside down I 'rode' it with my hands but couldn't feel
anything out of the ordinary. Maybe I'd just imagined it. I'll jump
on and carry on home.

Strait away I notice that something really wasn't right at all. So I
hopped off and took another look. This is what I saw;

25065

25066

25067

Now, I don't do trials. I don't hop, and, apart from the odd kerb I
drop down, the thing almost never leaves the floor. At 13 stone I'm
not exactly a real heavy weight. So, I long ago resigned myself to
never being able to tick the box on the unicycle quiz to say that I'd
broken a crank. But there it is.

I know that when I'm in high gear it does feel like I'm pushing very
hard on the cranks, and particularly when I change up it can be a push.
But I really didn't expect it to go like that.

So, all you non-splined Schlumpf owners out there, are there any
particular brands of crank that you recommend? I'd guess ones with
very low Q factor, but I'm just wondering what works well for you.

STM - gutted to be losing almost a week of RTL training


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I wonder if hard knocks from UPDs caused the initial crack rather than
just regular hard pedaling. Then once the crack was started regular
hard pedaling could have made it bigger till it became noticeable. The
anodized coating could have covered up the crack (or manufacturing
defect) during the initial stages so that it wouldn't have been
noticeable by casual visual inspection till it got to the point where
the crack expanded and became very obviously noticeable.

You ought to see if Florian wants you to send in the crank so he can
see if there was possibly some sort of manufacturing defect (a void in
the metal or something).


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semach.the.monkey wrote:


STM - gutted to be losing almost a week of RTL training



Don't worry...I am 100% confident in the Goonies finishing RTL as the
#1 team!

...even with a week less of training.


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john_childs wrote:
I wonder if hard knocks from UPDs caused the initial crack rather than
just regular hard pedaling. Then once the crack was started regular
hard pedaling could have made it bigger till it became noticeable. The
anodized coating could have covered up the crack (or manufacturing
defect) during the initial stages so that it wouldn't have been
noticeable by casual visual inspection till it got to the point where
the crack expanded and became very obviously noticeable.

You ought to see if Florian wants you to send in the crank so he can
see if there was possibly some sort of manufacturing defect (a void in
the metal or something).



It could have been there for a while I suppose. I'll admit that I've
never really inspected the cranks for things like that - but then
again, I've never felt the need to. Although I've had several UPDs, I
can't remember any that would have been particulaly harsh on the
pedals, although I'm normally paying more attention to how I land than
what the unicycle is doint!

I'll send Florian an email anyway as I expect he'll be interested to at
least see photos of it, and possibly post them if he wants.

Oh, and siafirede, don't worry. I'm not going to miss the week of RTL
training after all. I commuted in on my 24" Hookwormed Blizzard. It
didn't take as long as I expected, but it's a whole new experience
riding something that size for 5 miles in London. I think that has now
become my 2nd favorite commuting uni!

STM


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Mine did exactly the same when I was in NZ. I think it may be a warranty
thing, but you have to wait for the part to come.

http://tinyurl.com/2nladm

I have a pair of 150s at mine, but I guess you're in London at the mo.
They are prowheel cranks, and seem to work okay.

I bunged an old pair of steel cranks on mine for a couple of days when
I broke mine, does the blizzard not have square taper?

Joe


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joemarshall wrote:
Mine did exactly the same when I was in NZ. I think it may be a warranty
thing, but you have to wait for the part to come.

http://tinyurl.com/2nladm




Yup, that does look like exactly the same thing!


joemarshall wrote:

I have a pair of 150s at mine, but I guess you're in London at the mo.
They are prowheel cranks, and seem to work okay.




Yeah, I'm in London, but also with a lack of tools. I've got a crank
extractor, the special metal sleve required, and even some random
cranks sitting back in Nottingham. But that's 150 miles away


joemarshall wrote:

I bunged an old pair of steel cranks on mine for a couple of days when
I broke mine, does the blizzard not have square taper?
Joe



The Blizzard has some 127 Qu-Ax cranks on, but they've got pretty high
Q factor. So, combined with the lack of tools, it's not really an
option. But the Blizzard was fun this morning, so I'll ride that for
the rest of the week. I'm sure there must be some kind of multiplier
that I'm allowed to use if training on a 24" wheel. Maybe I could
count it as muni?

STM


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I've had hairline cracks develop in cranks over a long time (most
recently a pair of prowheel 150s on my muni) but never actually had one
snap completely. Perhaps I'm just paranoid - I always inspect them and
change them if any cracks start appearing because I had one snap on a
bike once (mountain bike with cheap cranks that had been dropped a lot)
and it took a big chunk out of my calf.

Glad you didn't crash.

Rob


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rob.northcott wrote:
I've had hairline cracks develop in cranks over a long time (most
recently a pair of prowheel 150s on my muni)



Your timing is fantastic! On the strength of Joes 'Prowheel cranks
work fine' comment, I have just ordered a pair of 127 Prowheels! Being
a bit shorter, they should be a bit stronger.

Well, I'd been considering the benefits of shorter cranks anyway, even
though I liked the 150s I had. If I can get the broken ones swapped
under warranty then at least I'll have some 150s I can change back to,
and something else to put in the spare parts bag for RTL

STM


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semach.the.monkey wrote:
Your timing is fantastic! On the strength of Joes 'Prowheel cranks work
fine' comment, I have just ordered a pair of 127 Prowheels!


I don't think there's anything wrong with prowheels - in fact I think
they're some of the better square taper cranks on offer in useful
unicycle lengths. The ones that started to crack on my muni had been
on there for a couple of years, done a lot of miles of pretty rocky
riding and been dropped numerous times down rocky slopes. At £15 a
pair I think two years is a reasonable lifespan on a muni. I had no
worries about buying another pair to replace them.

The problem you might have on a road machine is they're quite angled so
you'll end up with a big Q, which I actually like on the muni.
Strength-wise I don't think there's a problem. They look quite nice as
well.

Rob


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Well, at the weekend I changed the cranks over. Of all the unicycle
related scary things I have ever done, I think that changing a Schlumpf
crank is the worst. Tightening the crank extractor in to the adapter
which then goes in to a finely crafted and delicate mechanism was bad
enough, but the pressure I had to put on it to actually get the right
crank off (the left wasn't so bad) will give me nightmares for months
to come!

Anyway after close inspection of the left hand crank, I noticed that
there's a crack appearing in that too in exactly the same place.
Florian has confirmed that there was a dodgy batch of 152mm Schlumpf
cranks about 2 years ago and is sending over some replacements. If you
are riding with a set of these, I'd suggest you give them a careful
inspection soon.

So, on went the 127 Pro-Wheels. They looked to have a bit more
Q-factor than I'd have liked, but the shifting was very successful
actually. Possibly more successful than with the old cranks on. Mind
you, at the same time as swapping cranks, I also swapped to MG1 pedals
and a new pair of trainers. It seems to be a combination that works.

On the flat, the shorter cranks certainly seem a bit faster as I can
spin that much quicker. There were lots of opportunities on Saturday
to test them out for hill climbing, and they were certainly harder to
climb with, although not quite as hard as I'd expected.

STM


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