Unisk8r Geared 36"

Then it would run backwards, like a 2 wheeler. So yes, you are missing
something. Before you build a design it helps to try and think through
it completely, or at least to the point where you know which direction
the wheel will spin.

It must either be 2 chains or 2 gears. Also, why use a gear? They are
more expensive, harder to make, harder to tension, and not any more
dependable than a chain.

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oxfordrider said:

Am I missing something? Wouldn't it be easier to just have one gear and
one chain.

Yes you are missing something, and I think Gerble is missing something
too unless I am more confused than I know. The two chains in unisk8r's
design operate together to make ONE gear only. One chain drives an
auxiliary axle, the second chain drives the hub.

Klaas Bil - Newsgroup Addict
--
"Deflating pi does not reduce calories, it just concentrates them. - billham"

You are thinking of gear in a different manner than I. By one gear I am
thinking a chain on the outside and a gear on the inside. If by "one
gear" it is meant that there is only 1 possible gear ration useable,
then you are right, the jackshift setup is only 1 gear.

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enough that the people know there was an election. The people who cast
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I was thinking of a set up similar to a giraffe. Why wouldn't that
work?

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Has anyone ever thought about using a drive belt and pulleys? Either a
standard V belt or a cogged belt.

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It could work, except that it would BE a giraffe. You see, the cranks
would need to have to be a distance above the axle in order to run a
chain, and once you have them high enough to clear the wheel, well, then
you have a 36" giraffe. Not that there's anything wrong with that. I
suppose there would be a sense of adventure to having your head 9' above
the ground while riding on one wheel at 17+mph.

oxfordrider said:

*I was thinking of a set up similar to a giraffe. Why wouldn't that
work? *

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"I suppose there would be a sense of adventure to having your head 9'
above the ground while riding on one wheel at 17+mph."

Having ridden my 5-foot giraffe - which is geared to make it equivalent
to a 37.5" wheel - at a pretty good speed, I would say there is
definitely a sense of adventure... I'd love to take a 9' high giraffe
with a Coker wheel out for a spin... the adventure factor would
definitely be greater... and my geared giraffe practice shopuld help
out!

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I was thinking more of a reversed girafe, ie cranks in normal position
and sprocket up higher.

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There is only one "fixed gear", in the ratio determined by the cog
sizes. The jackshaft assembly simply ties the 2 upper cogs together, to
transmit drive energy across and down to the hub.

One on one said:

*Has anyone ever thought about using a drive belt and pulleys? Either
a standard V belt or a cogged belt. *

See my previous posts...I already threw the idea out there of cogged
belts, and that's gonna be the drive system for my next model.

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One on one said:

*Has anyone ever thought about using a drive belt and pulleys? Either
a standard V belt or a cogged belt. *

I'm slowly working out some ideas that would use a belt drive in a CV
transmission. I'm basing my ideas on waveform gearing concepts.

I believe that if I can get it to work it would be the first shiftable
(continuously variable no less) unicycle.

Since it's all been in my head so far I don't have any drawings or
anything. If I ever get serious about it I'll post what I create for
feedback.

-mg

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mgrant said:

Since it's all been in my head so far I don't have any drawings or
anything.

There are drawings and a description of the principle on
<http://cvt.com.sapo.pt/waveform/waveformgearing.htm>. Interesting
concept. I don't understand how the belt stays 'dented' where there's
no idler wheel. And if it doesn't, whether it still gears as much.

Klaas Bil - Newsgroup Addict
--
"Deflating pi does not reduce calories, it just concentrates them. - billham"

Klaas Bil said:

*There are drawings and a description of the principle on
<http://cvt.com.sapo.pt/waveform/waveformgearing.htm>. Interesting
concept. I don't understand how the belt stays 'dented' where there's
no idler wheel. And if it doesn't, whether it still gears as much.
*

Is this for real?

If you reduce a chain drive to levers (which is what it really is for
ratio numbers), the distance the chain is from the pivot points (the
fulcrum) when it makes first contact with the teeth is the -only- place
that is important for setting the ratio. The length of chain used is
irrelevant. The contact point on this system essentially stays the same
at all times; hence the ratio would remain the same. This system looks
like it would change the distance between the drive and driven
sprockets, not the ratio. The depth that a chain is on a sprocket only
affects the amount of power that can be transmitted without damaging the
sprocket.

And I agree with you - what keeps the belt dented where there's no
idler.
😕

--
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Brian C. Slater
AKA: Snoopy

Ok, I am now officially in my normal state of -advanced- confusion.
Don't try to confuse me, it won't make any difference.

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brian.slater said:

Is this for real?

Maybe not. There are only very few references found via Google and it
looks like it's an untested invention.

Klaas Bil - Newsgroup Addict
--
"Deflating pi does not reduce calories, it just concentrates them. - billham"

I haven't got a clue what keeps the belt dented, but i'm sure they've
come up with something... (probably!)

changing the length of the effective "lever" will change the size of the
moment which is transmitted, but the waveform idea can still change the
gear ratio.

Surely you would agree that, if we were just using a normal belt with
normal pulley wheels, if there was a bigger wheel on the primary drive,
the final drive would be spinning faster. This is because the wheel on
the primary drive has a larger circumference(sp) so it pulls more of the
belt across it each time it turns. The waveform idea effectively makes
the pulley bigger, by pushing the belt into the gaps between the teeth,
so when the pulley turns it pulls more of the belt through.

the problems i can see with it are:

1) when in low gear, the belt is only in contact with the tips of the
teeth, so i would think you would lose traction, especially if it's
wet.
2) The whole system is only as strong as the mechanism that holds the
idler wheel. The force of the belt trying to push that wheel away would
be enormous. ands there would be a lot of friction if the bearings the
idler wheel is on were not up to scratch.

--
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brian.slater said:

*Is this for real?*

Good question. There are very few places where Google finds this. From
reading those, it seems to be an as yet untested idea (with serious
intention though).

Klaas Bil

(Reposted directly to the forum because the original reply via Usenet
doesn't seem to have made it here.)

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Klaas Bil said:

*There are drawings and a description of the principle on
<http://cvt.com.sapo.pt/waveform/waveformgearing.htm>. Interesting
concept. I don't understand how the belt stays 'dented' where
there's
no idler wheel. And if it doesn't, whether it still gears as much.

Klaas Bil - Newsgroup Addict
--
"Deflating pi does not reduce calories, it just concentrates them. -
billham" *

The belt does not stay dented as is shown in the pictures on the website
referred to above. The waveform is only applied where the idler wheel
engages the drive pulley.

The more you can deform the belt the greater the changes in gearing. I
envision a system with two or more idler wheels that adjust in and out
to alter the gear ratio.

Since I have no access to the type of equipment needed to create such a
design I'm going to start crudely and build a wooden model that should
demonstrate the theory. If that goes well I'll engage the help of a
machinist to build parts that could be used for a unicycle.

-mg

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If I view that Waveform drawing correctly, the axles of the blue "input"
drive and the grey "final" drive remain centered in the sprockets which
are mounted to them. Thus the diameter of those sprockets always
remains the same, REGARDLESS of where the chain may actually contact
those sprockets (which contact point is varied by the idler gear). Now
I'm the one missing something, because I can't see how changing the
chain contact point on the sprocket can change the gear ratio between
the input and final sprockets.

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unisk8r said:

*If I view that Waveform drawing correctly, the axles of the blue
"input" drive and the grey "final" drive remain centered in the
sprockets which are mounted to them. Thus the diameter of those
sprockets always remains the same, REGARDLESS of where the chain may
actually contact those sprockets (which contact point is varied by the
idler gear). Now I'm the one missing something, because I can't see
how changing the chain contact point on the sprocket can change the
gear ratio between the input and final sprockets. *

I have not seen this design prior to this thread, so I am no way an
expert on the subject. And like you, I was unable to see how this
design would work. That was until I took a second look at it now. I
think the key is to imagine this design using a smooth belt and not a
chain. With a chain, the links must mesh with teeth of the sprockets.
With a belt, the belt can be in any position in relation to the
sprocket. (NOTE: I know I’m not making much sense, but I'm having a
load of trouble putting my thoughts into words)

The general principal is, the belt has to travel farther when the idler
sprocket is engaged because follows the teeth of the input drive
sprocket, and that effectively increases the diameter of the input
drive. When the idler is disengaged, the belt travels a smaller
distance and that results in a "smaller" input sprocket diameter.

I’m not certain I have the concept right. I haven’t had time to read
through the entire article, and I’m very tired, so it’s possible I only
think I know what I’m talking about.

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If you did this, the higher sprocket would be connected to the cranks
via a chain but disconnected from the wheel (remember, the cranks are
connected to the axle which passes through the center of the hub but
spin independently of it because of the bearings.

oxfordrider said:

*I was thinking more of a reversed girafe, ie cranks in normal
position and sprocket up higher. *

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