Re: Geared hub unicycle

vivalargo said:

*

I second that motion, though a 50% speed increase while Cokering is a
frightning, but exciting, proposition. Imagine a cruising speed of
22MPH?! Might have to start riding in full leathers . . .

JL *

All going well, I'll be riding one of these pretty soon! Can't
wait!!!!

Kris Holm.

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okay, about that adjustable crank idea, i sait it was showard but i was
wrong it was onewheeldave in 'this thread' (http://tinyurl.com/2plgy)
that i was thinking of, the CAD drawings are showard's tho.

Quoted message said:

Does this mean that it is possible to have future unicycles shift gear
while riding and freewheel? imagine that- it'd be just like a bike,
only with mandatory balancing abilities.

have a look at 'this thread' (http://tinyurl.com/2b2yh), it covers that
very topic at some point (this was one i was thinking of earlier but
could not find then)

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i ~will~ put one of these on my coker, and i want to know about when
they will be available, and about how much they would cost. thank you.

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Just a thought - I'm sure somebody has already considered this, but
still...

Make the hub with the epicyclic gears permanently engaged (with the arm
permanently attached to the frame), then have two clutches (actually
would be more like two drum brakes) that would lock the axle to the hub
body in one position (1:1) and the outside of the epicyclic mechanism to
the hub in the other position (1:1.5 or whatever). Obviously the
brakes/clutches would have to be set up so that there was a moment
during the shift where neither gear is engaged (i.e. freewheel) to avoid
locking up, but this would be a very short time if shifted quickly.
Using clutches like this would avoid the problem of having to engage
teeth and ought to be shiftable on the fly using a cable and bike-type
gear lever under the saddle.

So, what's the catch? Too complicated/expensive? Too big/heavy? Too
weak? What I see in my mind is inspired by a combination of car
overdrive and bike drum brake...

Rob

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mmm, can't wait for the techies to get here...

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Quoted message said:

Make the hub with the epicyclic gears permanently engaged (with the arm
permanently attached to the frame), then have two clutches (actually
would be more like two drum brakes) that would lock the axle to the hub
body in one position (1:1) and the outside of the epicyclic mechanism to
the hub in the other position (1:1.5 or whatever). Obviously the
brakes/clutches would have to be set up so that there was a moment
during the shift where neither gear is engaged (i.e. freewheel) to avoid
locking up, but this would be a very short time if shifted quickly.
Using clutches like this would avoid the problem of having to engage
teeth and ought to be shiftable on the fly using a cable and bike-type
gear lever under the saddle.

Now, I have never actually unicycled before (I've been reading this
newsgroup in order to learn about them before I buy one), but it seems
like there would be a big advantage to being able to disconnect the
wheel from the pedals, in order to coast, and have wondered if there are
unicycles with clutches. If it were possible to coast and stay upright
and on the unicycle, this method would be a really good way to do it.

The problem with freewheeling on a unicycle is that normally the
forward/backward balancing is done by the pedaling action - without the
drive it's very hard to stay on. Some people have built unicycles with
freewheeling hubs and can ride them, but in normal circumstances it's
not a good thing.

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rob.northcott said:

The problem with freewheeling on a unicycle is that normally the
forward/backward balancing is done by the pedaling action - without the
drive it's very hard to stay on. Some people have built unicycles with
freewheeling hubs and can ride them, but in normal circumstances it's
not a good thing.

I suppose if you were able to adjust the friction on the freewheel very
accurately, it would be <i>possible</i>, but I bet it would take a
rather large amount of practice to get the hang of it.

Mike Roberts said:

rob.northcott said:

The problem with freewheeling on a unicycle is that normally the
forward/backward balancing is done by the pedaling action - without the
drive it's very hard to stay on. Some people have built unicycles with
freewheeling hubs and can ride them, but in normal circumstances it's
not a good thing.

I suppose if you were able to adjust the friction on the freewheel very
accurately, it would be <i>possible</i>, but I bet it would take a
rather large amount of practice to get the hang of it.

I rode a small one at the Uni-meet at Kidderminster here in the UK last
month. It does take some getting used to, but the hardest bit is getting
on I'd say.

Fantastic fun though.

Cheers,

Roger
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I'm still waiting for the unibike, the motorbike with one wheel only.
😎

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I never cease to be amazed at how a thread that started a year and a
half ago can be revived. Anyway, being a motorcycle enthusiast, I'm
with Ileberg on the unibike thing.

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rob.northcott said:

I'm sure somebody has already considered this

Haven't heard of it yet.

Quoted message said:

Make the hub with the epicyclic gears permanently engaged (with the arm
permanently attached to the frame), then have two clutches (actually
would be more like two drum brakes) that would lock the axle to the hub
body in one position (1:1) and the outside of the epicyclic mechanism to
the hub in the other position (1:1.5 or whatever).

It's a nice idea, and as Mike Roberts pointed out, the option to coast
is a nice extra. Another extra is that you have a brake, if the two
drum brakes can be operated independently. And if they are, you can
also determine yourself how much 'coasting time' there is while
switching gears. I don't know how technically feasable this whole
thing is though.

Klaas Bil - Newsgroup Addict
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lleberg said:

I'm still waiting for the unibike, the motorbike with one wheel only.

Look at the Bombardier Embrio, e.g. at
<http://www.gizmohighway.com/transport/bombardier-embrio.htm>. But
indeed you'll have to wait...

Klaas Bil - Newsgroup Addict
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Klaas Bil said:

* Another extra is that you have a brake, if the two
drum brakes can be operated independently. *

That's a good point - I hadn't thought of that... if the two
brakes/clutches are both partially engaged it would act like a brake. I
would imagine the control linkage would get a bit complicated though -
could have two cables, one for each brake, then the brake lever would
have to operate them both in the same direction while the gear shift
lever needs to operate them in opposite directions. Could possibly work
if the gear lever was mounted on the end of brake lever. Hmmm... Could
get horrendously complicated - both to build and to ride 🙂

Rob

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rob.northcott said:

*
That's a good point - I hadn't thought of that... if the two
brakes/clutches are both partially engaged it would act like a brake.*

I think it's easier than that. During normal riding one of the brakes is
already fully engaged (blocked) - which one depends on the chosen gear.
I imagine that the lever is somehow (for the time being) fixed in the
fully engaged position. Now when you want to brake, keep that one fully
engaged, and operate the other lever to the degree that you want to
brake.

Klaas Bil

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Ahh, so you see it as having two separate gear levers, one for each of
the brakes, so when one gear was engaged the other lever could be used
as a brake? Sounds good in theory... but would manipulating two levers
to change gear be too taxing (of course, at the same time having to cope
with the change of gearing without falling off!)?

I suppose you could have the two levers next to each other so that one
is engaged when back and the other is engaged while forward. Then to
change gear the rider would just grab both levers and move them
together, then braking would be done by fiddling one lever only (but it
would have to be the correct one depending on which gear is selected -
the other one would introduce slip rather than braking).

Sounds interesting, but unfortunately I don't have the equipment or
skills to build one and see what happens, so it'll probably stay as
theory (unless one of you engineer types wants to make me one 😉) Could
get expensive as a one-off I imagine.

Rob

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rob.northcott said:

*would manipulating two levers to change gear be too taxing (of
course, at the same time having to cope with the change of gearing
without falling off!)?*

Not more than (in a manual-shift car) operating the accelerator, clutch
and gearstick in a coordinated fashion (of course, at the same time
having to cope with traffic around you).

I think the idea has potential but I'm far too un-techie to give it a
go.

Klaas Bil

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I'll start and stop with the most obvious problem. Where do these cables
run? Do they come out the axle? They would have to in order to keep them
from tangling in the spokes or frame. Where do they go from there, do
you just hold them or do they loop around your legs and back onto the
frame? Remember, on a unicycle there's a pedal and a crank that has to
go around on both sides of the axle. On a bicycle that's not the case
because it's chain driven and the axle is stationary. Does the cable
rotate with the axle? There has to be some running surface inside the
hub and outside the axle so the cable doesn't twist constantly. Where do
you put all this stuff? Then you have these two cable loops, one on each
side, trying to snag anything they can find on either side of you.

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I've been thinking about this and realised that the problem is how to
connect the levers/cables - I knew there ought to be a catch 🙁

I see Harper has already beaten me to it by posting this fact - I'm glad
it was you who noticed this - I imagine you must have done plenty of
research into this type of thing before coming up with your design,
that's why I expected my ideas to be shot down straight away!

I think it COULD be done in theory by having some sort of sliding
collar/trunnion arrangement so the cable wouldn't have to come out in
the middle of the axle, but that would necessitate some sort of
ridiculously complicated concentric bearing-inside-bearing that would be
pretty much utterly impractical.

Harper - I hope you don't think I was trying to suggest I could do
better than your design... it's just that the discussion about it got
me thinking about things. The tone of my post was intended to be "why
is this a stupid idea?" rather than "this is how it should be done".
I'm always a pessimist - there's (nearly) always a catch, and Sod's Law
always prevails 🙂

Rob

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