crank size for a trials muni

Unicycles and Equipment
1

Hi everyone,

I’m working on building a fully custom trials muni with the back wheel from a
mod Monty trials bike. The wheel with tire is about 21 inches, and I’m trying to
figure out what the absolutely longest cranks I could fit on would be without
them constantly hitting the ground. Hopping is much more important the rolling
in trials, but we still need to keep all factors in consideration.

So, if anyone has ever tried really long cranks (like 152s or even 160s on a 20
inch), I would REALLY appreciate any feedback you might have.

Thanks,

David Poznanter

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2

RE: crank size for a trials muni, + more

> trying to figure out what the absolutely longest cranks I could fit on would
> be without them constantly hitting the ground. Hopping is much more important
> the rolling in trials, but we still need to keep all factors in consideration.

The old Schwinn 20" came with 5.5" cranks (140mm). Even those hit the ground too
much for me, for freestyle at least. Another thing to be concerned about is your
heels and toes touching the ground due to very long cranks. You wouldn’t want to
get points for that.

I think the final choice will be a matter of how much clearance you need. Since
you don’t really tilt the cycle over much (like in a spin), that’s not a worry.
Instead you have to think about the rugged ground you’ll be on, and how much
room under the pedals will you need to get through your courses.

Personally, I would start with a pair of 6" (150mm). Or, if you have some longer
ones laying around, try them and see how they work. I guess you’ll want to be
pretty sure before you go and have super-strong ones custom made…

Or you can use the bicycle solution for ground clearance, which is a chain and
separate crank assembly, higher than the wheel axle. This would accomplish three
major things:

  1. You can use standard bike parts. Less custom work!
  2. Crank length won’t be as much of a factor.
  3. With the proper frame geometry, you should be able to jump like the
    bike guys!

Huh? What does he mean about geometry? Not doing it in a straight line, of
course. By levering your feet somewhere in front of the wheel, you’ll be able to
spring up like the bikes. This means a totally new shape for the unicycle, and
new choices for where to put the “handlebar”. I would start with the basic
recumbent design built by Eric Kolb and go from there:
http://www.unicycling.com/unifoss/garage/recumben.htm

I thought of it first!

Stay on top, John Foss, the Uni-Cyclone (reply to jfoss@unicycling.com)
http://www.unicycling.com

“Oh my goodness!” - speed champion Yuichiro Kato, headed down the mountain at
high speed in his first true MUni race, at NUC 99