DustinSchaap said:Greg, why is the axle so wide? I don't really have any experience with
geared unicycles, I rode a 36" geared for a minute or two at Unicon and
it was quite disapointing... saying that the unicycle had 125mm or
140mm cranks on which didn't get me more speed than 80mm or 90mm, a 36"
with short cranks would probably ride better. Maybe Greg can answer
this question, why are all the gear ratio's so small? Myself I would be
going for a smaller wheel and a heavier gear ratio instead of a big
wheel with a 'small' ratio like 1.5 is it because above 1.5/1.6 is
mechanically impossible or is there a longer train of thoughts behind
it?
The first pass making the geared hub, I wanted enough taper on the axle
to make sure I could get any cranks on it. I was unfamiliar with making
the tapers. It increased the "Q" substantially and when I made the
first hardened axle upgrade I shortened it to match the CroMoly axle
profiles.
The limit of the simple planetary hub gear ratio in this mode (fixed
sun, driven planets, hub connected ring) is 2. The 2 is actually
unattainable because it requires infinitesmally small planet gears. The
ratio goes as
1+sun/ring
where sun is the number of teeth in the sun gear and ring is the number
of teeth in the ring gear. The sun/ring ratio is limited by
ring=sun+2*planet
where planet is the number of teeth in a planet gear. Higher gear
ratios require going to a compound gearing system. This adds quite a
bit of weight and complexity.
I personally think that the larger and heavier the wheel is the more
stable the ride is. I have ridden light 24" up through Coker wheels in
1.5 mode and found that stability increases with diameter and weight
or, better, stability increases with wheel inertia.
--
harper
-Greg Harper
*jc is the only main man. there can be no other.*
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