Geared hub unicycle

This past weekend I was graced with a visitor from the Pacific Northwest
- none other than Mr. Harper, the inventor of the uni.5 and Blue Shift
geared hubs. My house was his first stop on a cross country journey to
NAUCC - driving a car completely loaded with unicycles of all kinds.

We've colaborated a little bit on the design of a geared unicycle that,
hopefully, will be available in the near future at a reasonable cost.
My part of the project is the frame and Harper's part is, naturally, the
hub.

Last week Harper received some sample frame parts from the overseas
manufacturer so he sent them to me along with a prototype hub, also
manufacturered overseas, so I could check them out and make sure the
frame was what I had in mind and that the hub fits the frame.

I wanted to try and assemble the parts into a ridable geared hub
unicycle before Harper arrived Friday night. I was able to get a 29"
wheel laced to the hub and hub guts installed by Friday. Saturday
afternoon (after a morning MUni ride where Haper showed my how MUni is
REALLY done) we finished putting the frame together, installed the tube
and tire, cranks, seat, etc. and took it for a spin around my
neighborhood.

I put 170mm cranks on it mainly because that's all I had available to
use but I also had the idea it would make the thing easier to ride in
43.5" mode. Harper took the first ride and said that it was "10,000
times easier to ride than Blue Shift" with the long cranks. I thought
that was an exaggeration though ... it only seemed several hundred times
easier than what I recall about riding Blue Shift with 150mm cranks.

Harper rode the new geared hub uni and I rode my non-geared 29'er along
a paved bike path. I was pedaling like a demon while Harper was just
loafing along. The plan was for Harper to ride the geared uni "out" and
I'd ride the geared uni "back". Unfortunately it broke ... a weld
failed on the frame ... so we both got to walk "back". Oh well - that's
what prototypes are for and I'll have it fixed and ridable again this
week.

The attached picture is Mr. Harper with the new geared hub uni on his
right and my 29'er on his left.

Steve Howard


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That looks Awesome!


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So, any secrets as to how it works? Is there a chance of getting a nice
portable 20" geared to 36"? When you say 'reasonable cost,' is there a
ballpark figure of what that means?
That sounds like a great idea. I hope it works, 'cause the world needs
a good geared uni!


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Steve:
Your frames look really nice. It's a shame you didn't get to ride back
but at least it was the frame and not the reproduction hub that broke.

Greg (on the road):
Had you ridden on the 'overseas' prototype hub before Steve laced it to
a rim or was this your first go at it? Also, does this mean that you're
close to relasing a production epicyclic hub equiped uni? Steve, maybe
you can answer this since Greg's out on the open road?

Paco:
Harper's Epicyclic Hub (link):
http://tinyurl.com/hmsa


Cheers,
Jason


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To change gear, I guess you have to stop riding and get off? Does it
require tools to change the gears? How (basically) do you change the
gears?

-Hugh


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universacycle wrote:
*To change gear, I guess you have to stop riding and get off? Does it
require tools to change the gears? How (basically) do you change the
gears?

-Hugh *

You do need to dismount and fiddle with a bolt to change the gear.

There is a short lever arm that is part of the hub. When the end of
that lever arm is connected to the frame the hub is geared to 1:1.5.
When the lever arm is disconnected from the frame (and bolted in place
to the hub itself) the hub is in a 1:1 gear. Changed the gear is a
matter of removing a bolt, positioning the lever arm in its new
position, and putting the bolt back in. It takes a minute or so to
change the gear. With practice you can get faster at the gear change
process.


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Oh, and there are pictures of Greg's original version of the Uni.5 hub
in the gallery.
http://gallery.unicyclist.com/albun23
You can see the lever arm on the hub and how it bolts to the frame to
put the hub in to the high gear.

The hub that is being made overseas is slightly different in design but
basically the same.


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The geared hub uni is Harper's thing so I don't know anything about cost
or when they'll be available. I think the hub is very close but the
frame has some problems that still need to be worked out.

Greg made two epicyclic hubs - one was built into a 24/36" uni dubbed
"uni.5". His other hub is what Blue Shift is built around. The hub and
frame I have are the first overseas version that have been assembled
into a ridable unicycle. The big difference between Greg's first two
hubs and the new one I have is that the new one can be disassembled
without having to remove the spokes. That's a good thing! Other than
that it's just the same as the original version.

As John explained, the hub is shifted by changing the position of a
screw. The question that has been asked before is "can a hub be made
that will shift on the fly?" Anything is possible but shifting a
unicycle hub on the fly is a very difficult problem. One of two things
*must* happen when changing gears. Either the hub must be completely
stopped while BOTH ratios are momentarily engaged (thus locking the hub)
or the hub must free-wheel BETWEEN the two ratios. Either one would be
a problem on a unicycle. I'm sure someone somewhere could learn to
shift a unicycle while it freewheels but ...

Another problem with a shift on-the-fly unicycle would be shifting gears
in the rider's brain. The difference between 29" and 43.5" modes is
dramatic. I find it takes some time to get used to the difference after
shifting the hub. Again, someone, somewhere could learn to deal with
the instant change in ratio but I'm not sure I ever could.

Naturally, shift on-the-fly would make the hub more complicated and
expensive to make too.

Steve Howard


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This thing is already on the 4 first places on my wishlist.

Tell me more! Tell me more!:

As far as I remember there was once a problem with a bent axle on uni.5.
Will the new hub be stronger or do you just have to be carefull with
it?

Is it possible to use the hub with other frames?

Will other framesizes be available?

Does "hopefully, will be available in the near future" mean that it
might become available or that it will definately become available at
some point?


Morten


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Borges wrote:
*As far as I remember there was once a problem with a bent axle on
uni.5. Will the new hub be stronger or do you just have to be carefull
with it?*
I'm sure Harper will run the prototypes through the gauntlet to be sure
they hold up.
Borges wrote:
*Is it possible to use the hub with other frames?

Will other framesizes be available?*
The 29er frame has a hole machined for the fixing bolt. The original
uni.5's Torker frame was just drilled in the right place. I have no idea
what the plans are for frame sizes but unless you plan on gearing up a
Coker the 29er frame should accomodate all the other wheel sizes.

Check out Greg's lame web page too:
http://staff.washington.edu/gharper//


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