Newcommer. Questions on fast unicycles
 

[image: http://img208.imageshack.us/img208/6...itled1ev1.gif]

Hi everybody. I'm a disegner of fast bikes (for speed records) and this
is one of my recent ideas (modyfied centaur (it had two wheels
before)). It has drive from hands and legs. Very beta drawing, just
idea.

I wold love to hear from unicycle experts :
1. would it be ridable?
2. are there hubs with integrated planetary gear for unicycles?
3. would it be possible to turn?

I like this bike bacause it's simple and has good aerodynamics = high
speed.


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mozg
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Newcommer. Questions on fast unicycles
 

Nice idea!

How does the hand pedalling work?

T.


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FORGIVE TOM, HE'S A NUTTER. OH, AND HE'S SCOTTISH, AND HAS A BEARD, ALL
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you'd need very strong arms...


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nickvb123

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Newcommer. Questions on fast unicycles
 

This is centaur (combi drive)

[image: http://img139.imageshack.us/img139/4336/kentavr7xf.jpg]

centaur in action:

[image: http://img47.imageshack.us/img47/1306/img47381bo.jpg]

In unicycle case hands drive do the same, but connected diractly (via)
chain to legs drive.


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hmmmm.


--
DarkTom

'*_My_Gallery_*' (http://tinyurl.com/9bnux)

FORGIVE TOM, HE'S A NUTTER. OH, AND HE'S SCOTTISH, AND HAS A BEARD, ALL
OF WHICH IS PRETTY FORGIVABLE TAKEN ALONE, BUT TOGETHER ADDLES THE
BRAIN. - LOOSEMOOSE
DON'T TAKE ANY NOTICE OF THE DARK ONE,HE'S A PLANK!!! - PEBBLES
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Newcommer. Questions on fast unicycles
 

oh now i get it. before i thought that you were pedalling with only your
hands :cool: That would be very fun to ride if you could make it


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i think it would be more efficient to just to use your legs only or your
hands only. you will would have to have your legs spinning at the same
rpm as your hands.


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stuckinwheeliemode
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Hi everybody. I'm a disegner of fast bikes (for speed records) and
this is one of my recent ideas (modyfied centaur (it had two
wheels before)). It has drive from hands and legs. Very beta
drawing, just idea.

Sounds cool - very cool.

I wold love to hear from unicycle experts :

I'm nowhere near an expert, but I'm going to stick my oar in anyway :-)

1. would it be ridable?

One thing I've learnt on these forums is that almost anything is
ridable :-) No matter how crazy an invention, there's always going to
be someone who can handle it.

I bet many people would be able to ride it sitting upright and not
using the hand cranks. Transferring to hand cranking too would be
interesting - you'd have to be going slow enough that you could grab
hold of the cranks.

Riding this would require decent balance - you wouldn't be able to
flail your arms around ;-) I don't know how much hand cranking would
disrupt one's balance...

What wheelsize were you thinking of? 36" wheels seem to be popular for
speed / distance riding, although geared 29ers have some merits too.

Oh, and a little safety point: it'd be really nice if you could fall
off the front of this without getting your feet tangled in any
machinery ;-) Although given you're unlikely to be able to run out of
a speed record attempt maybe that's not so important!

2. are there hubs with integrated planetary gear for unicycles?

Yes, see http://schlumpfdrive.com and search the forum history for
Harper's Blueshift and uni.5.

The Schlumpf hub is shiftable on the fly, Harper's hubs offer a choice
of two ratios you can change with a toolkit (by adjusting the torque
arm if I remember correctly - which I may not do).

Also, look for PurplePhaze which achieves much higher ratios using a
jackshaft system. Again adjustable using a toolkit, but a bit more
work. It also featured a "tuck" handlebar arrangement, vaguely like
your proposal (without the hand drive). OuttaPhaze is a proposed
production variant of this design.

3. would it be possible to turn?

If it could be ridden, then it could be turned.

I like this bike bacause it's simple and has good aerodynamics =
high speed.


--
mark williamson

Dave: Just a question. What use is a unicyle with no seat? And no
pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!
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The deisgn illustrated would have no advantages for speed at all.

On a bicycle, if you can increase the power input, you can ride a
higher gear at a given cadence, and therefore go faster.

Power is not the issue on a unicycle. Turning a 20 - 36 inch wheel is
not difficult and does not require a lot of torque at all. The problem
is simply one of coordination. How fast can you spin the wheel whilst
maintaining control? You can improve this by selecting an appropriate
length of cranks (short cranks = potentially faster, but at the expense
of some control) and by practising!

As I understand your diagram, the hands and feet are each contributing
driving force to the wheel, and are connected by a chain. I assume a
1:1 ratio between hands and feet. Anything other than that would be
very difficult to co-ordinate, allthough I guess 2:1 would not be
impossible.

So you are increasing the torque available, but not the rpm. In fact,
because of the additional co-ordination problem of having hands as well
as feet pumping away, you are probably losing rpm.

So you need to gear up the hub. Lots of people have experimented with
geared hubs. It is possible to gear up the rotation of the wheel to
about 1.6 or 1.7 (approx.) times the rotation of the cranks. Even that
is the equivalent of a very low gear on a bicycle.

At best you have a very pretty picture of something that would be more
difficult to ride, and much harder to steer than a conventiojnal
unicycle; which would if anything be slower on the flat, and a fair bit
more dangerous. The only advantage I can see - and that a theoretical
one only - is that it might be good for hillclimbing, on smooth
straight steep hills.


--
Mikefule

"The world is Hell, and men are on the one hand the tormented souls, and
on the other the devils in it."
Arthur "Cheery" Schopenhauer
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Thanks for link and replys
At least 1:3 gear needed.
Ok. I see. This is cool but probably not for speed record.


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