RE: Bent rims/slipping sprocket: questions
Good advice from John Childs. I’m adding some more:
> Your average unicycle wheel (especially one made in “T”) cannot take a lot of
> abuse especially from an adult.
Not only are machine-built wheels less strong then hand-built ones, all but
specialty unicycles are manufactured with “light use” intended. They know
only a small percentage of the unicycles they make will ever be ridden more
than a few feet.
And this applies to almost all unicycle brands, not just ones from “T”. Most
“average” unicycles are built with low end components, including not only the
rim, but the spokes, tubing, pedals, cranks, and axle as well.
If you get really into hopping, the axle will eventually be the issue. A cheap
wheel can be tensioned as John described to take quite a bit of punishment. But
unicycle axles will eventually metal fatigue under that kind of load, and break.
But that’s a lot of hopping, or at least a decent amount of very hard hops and
drops. For a strong axle go to Semcycle, Miyata, or even higher end brands. DM
currently has the strongest unicycle axle, on the ATU and the Vortex, but these
are splined, requiring a whole new crankset and financial outlook.
If your rim has already failed once, best bet is to toss it and replace it with
a stronger one. If it’s a 20" you have lots of choices of great quality rims
from the BMX world, at reasonable prices. There are less choices in 24", but
still plenty to be found. Most rims you can buy at a bike shop are much better
than the original ones that came on your unicycle. Naturally, any time you
rebuild a wheel, replace the spokes and nipples as well.
I’m about to do this with my carbon MUni. The poor thing’s been neglected since
I got my DM ATU with Gazzaloddi tire. This is because the carbon has this skinny
rim on it, and the tire is all over the place now when I ride it like I ride my
DM. I’ll get a much wider rim, replace all the spokes, and have the bike shop
start with a fresh new Miyata axle (the only kind that fits my frame until Roger
Davies comes up with something new…). The original axle is fine, but it has
hundreds of miles on it so now’s a smart time to replace the $15 axle.
> Welding the sprocket on a giraffe is one way to keep it from ever slipping.
Yes. In your case, problem solved. Other problems created of course, like
rebuilding the giraffe wheel if you can’t get behind the sprocket. Try not to
hop on the giraffe too much… Worst case scenario you have to replace the wheel
as a unit and start fresh.
> A less drastic way is to use strong RED Loctite. This is the permanent
> loctite. And then tighten the sprocket on like heck along with a lock ring.
That’s right. I once had a bike shop do this with a batch of six Schwinn
Giraffes my friend and I had found at a school in Ohio. They were all the
older kind, with the screwed-on sprocket. But the bike shop second-guessed me
on the red loctite. “That’s permanent” they thought, so they used green. I
tested one of the cycles in the parking lot and nearly fell on my butt. I
marched back inside and told the guy at the counter that I wanted the other
mechanic, the one that wasn’t colorblind, to put on the red loctite. Tell
the bike shop we mean red.
That was in a big, reputable bike shop, with lots of mechanics (Brands, in
Wantagh, NY). Problem is, with something like a unicycle, they always seem to
assign the doofiest entry-level mechanic because how complicated can a unicycle
be? The parts should be thoroughly cleaned of grease and dirt before assembly,
then tightened, as John said “like heck” or better. Sprocket tightness is a
major safety issue on giraffes.
The lock ring style of screwed-on sprocket is basically defective manufacture.
Like an old Chevy Corvair, it’s engineering that should never have been allowed
on the road because it’s simply dangerous. Later models of the Schwinn Giraffe
had the bottom sprockets attached with three bolts.
Stay on top, John Foss, the Uni-Cyclone http://www.unicycling.com
“It’s never too early to be Friday” - John Foss