Geared Uni Questions

hans said:

I built a 36" uni 2 years ago, it was too fragile for the LUT. So I
ordered a 29" Schlumpf in spring 2005. Florian did not deliver it till
Dec. 2005 because there were problems with the first generation hub. I
was concerned, that I would not have a uni for the LUT so I ordered
another hub from Florian in Oct. 2006. I upgraded my 36" with this
geared hub. I used 140 mm cranks and the uni was very hard to ride for
me in 1:1.55 mode. As the 29" guni came I was happy to use it for the
LUT.

I changed the cranks on the 36" after the LUT to 170 mm and I am very
happy with them. I rode more than 500 km since Feb. 2006 and I love the
geared 36". The hub on the 36" ( the only Coker parts are the tube and
the spokes) is in between the 1st and the 2nd generation. It still has
6 pins but the pins are conic like in the new hubs, so the gears cannot
slip.

A little comparison between the 29" and the 36" geared unis:
The 29" is
* easier to mount
* easier to shift (because of the newer hub)
* very easy to ride and idle in 1:1 mode
* fast enough for me in 1:1.55 mode
* easier to pack and transport in plains and trains

The 36" is
* more fun (I love the "Coker feeling"😉
* more stable because of the flywheel effect
* It rides over bumps more steadily
* easy to ride in 1:1 mode
* a manageable challenge in 1:1.55 mode

So I think, the difference is not too big, but the 29" is more easy and
reasonable and the 36" is more fun. I ride the 36" more than the 29". I
use it mostly in the flat and in 1:1.55 mode most of the time. I shift
down for up- and downhill, strong headwind, crowds and dogs, traffic
and bumpy roads. I thought about selling one of my gunies, but I cannot
decide which.

Hans

Thanks for that post Hans. It is great to get some input from someone
who has both a geared 29" and a geared 36".

So you are able to shift on the fly with your geared 36"?

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shapr said:

How fast can you go with the Coker set to 1:1.55 ?
What sort of average speed do you get on long flat rides?
That sounds like the ultimate high speed long distance unicycle.

I tried out der Uber coker up in NYC and it was very fast. I dont have
any calculated speeds for it though. It does indeed sound like the
ultimate high speed long distance unicycle, but with one flaw. Cokers
are pretty heavy, and when you add a geared hub it becomes heavier.
Going up steep hills would be a challenge if you had to do it a lot.
If you lived in a mountainous region, the geared 29er would probably be
the best bet. Actually, even going up very slight hills seemed kind of
annoying with the geared coker. I would think that the geared 29er
could handle better at a lot of things, but the geared 36" would just
be a beast and cruise on flats. I guess that if you hit any slight
hills you can switch the gear, but I dont know how easy it will be or
how hard it will be to quickly adjust your cadence comfortably.

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I've been riding my Geared 36" for a couple of weeks now, as has Roger,
and we're both extremely happy with them. Roger's scared by his, but I
wear my 661's and feel fine, I've not had a serious incident as of
yet.

In 1:1 it's a long (165mm) cranked coker, so it powers uphill, and I
can comfortably (with my low cadence) maintain 10mph.

In 1:1.55 it flies, your feet spin in lazy circles and you zoom along.
My current registered max is 16.0mph on my GPS, that was racing some
bikers through the common, on a slight downhill (I won, they never
caught me :p). The cranks are long enough to mantain decent control,
and I don't feel unsafe as long as I have space to stop and a clear
route ahead.

Shifting on the fly is very easy with the 2nd Gen hubs, I've shifted up
(but not down cos my right foot is not as dextrous as my left) and it
slotted straight in, no slip. I can freemount in 1:1.55 one in five
times (approx), with a slightly higher success rate on a downhill. I
currently have very low mileage (15 miles, max) as I've not had the
chance to get out for more than an hour or two to test it. It's also
not technically finished yet, it's got a CF seatbase and GB4 handle to
attach before I'll let it really get out of the stable.

I've done very little distance riding on a large wheel, so I know I'm
not getting the most out of either mode on mine yet, It'll take some
time.

Pictures (and a forum thread) will appear when it's all done and
complete.

Loose.

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Loosemoose said:

In 1:1.55 it flies, your feet spin in lazy circles and you zoom along.
My current registered max is 16.0mph on my GPS, that was racing some
bikers through the common, on a slight downhill (I won, they never
caught me :p). The cranks are long enough to mantain decent control,
and I don't feel unsafe as long as I have space to stop and a clear
route ahead.

I was wondering about this, once you're going fast, does air resistance
really start to kick in? I know on a bike, it starts getting noticeable
at about 20mph, and you're in a much more aerodynamic position.

On a stock coker, it's only noticeable when you're cranking it hard at
about 16mph or so, but I guess that speed wouldn't be too hard to keep
up on a geared coker on the flat. I do find the coker much more hassle
in a headwind than a 29er though, it's really annoying on days you have
a strong wind how high up you are. The day last year when I did 50
miles in 30mph+ winds was really bad for that.

I can get up to 19mph on my coker with a very slight downhill. I've
fallen off at slightly slower than that and broken ribs, also done
other crashes at similar speeds which involved much pain. I'd be really
worried that a crash at 20mph+ would hurt lots.

Joe

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Loosemoose said:

My current registered max is 16.0mph on my GPS, that was racing some
bikers through the common, on a slight downhill (I won, they never
caught me :p).

Sorry to go a bit off-topic, but...
where do you people find these bikers who can't do 16mph downhill?
🙄
Or were you racing little children with 16" wheels and stabilisers? :p

Good luck with the Schlumpf anyway - sounds dangerous.

Rob

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rob.northcott said:

Sorry to go a bit off-topic, but...
where do you people find these bikers who can't do 16mph downhill?
🙄
Or were you racing little children with 16" wheels and stabilisers? :p

Good luck with the Schlumpf anyway - sounds dangerous.

Rob

Cheers Rob, the common has a volountary cycling speed limit of 10mph,
some people strictly adhere to it and some who have just aquired £1000
worth of geared coker like to bend the rules slightly to see what they
can get out of themselves and it. I'm by no means the fastest person on
the common, and its pretty empty when I push it hard.

The bikers basically mocked/admired me in equal measure ('thats rather
a large wheel for someone with one missing' and the like, very good
natured banter) and then watched me mount in 1:1.55 and then said 'well
cool, good luck and we'll try and keep up!' partially sarcastically,
since they thought i'd be pretty slow. They never caught me up, but I
think they kept pace, just behind at a safe distance.

Loose.

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Loosemoose said:

Shifting on the fly is very easy with the 2nd Gen hubs, I've shifted up
(but not down cos my right foot is not as dextrous as my left) and it
slotted straight in, no slip. I can freemount in 1:1.55 one in five
times (approx), with a slightly higher success rate on a downhill.

My trick for hitting the button into low gear (from hi) is to use my
ankle rather than the back of my foot. It's not a Q of dexterity. It
has more to do with the difficulty of shifting from hi to low -- it's
harder than shifting the other way, at least for me, due to several
factors. Anyhoo, it made a huge diff when I learned to use my ankle.

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SPEED[/B]
TO SUM IT UP, THE GEARED 36\" HAS SPEED POTENTIAL, THAT I DO NOT
USE. I AM A CAUTIOUS RIDER, WHEN IT COMES TO HIGH SPEED. I DO NOT FEEL
COMFORTABLE, WHEN I RIDE OVER 20 KM/H. SO MY CYCLE COMPUTER SHOWS AN
AVERAGE
OF 18 KM/H ON MOST LONGER RIDES, WHEN THERE ARE NO LONGER STRETCHES,
WHERE I
USE THE LOW GEAR (UPHILL, CROWDS, DOGS, CARS, DIRT ROAD). THE MAX IS
NORMALLY
AROUND 23 KM/H.
I KNOW, THAT IS NOT FAST. ON THE LUT THE FASTER RIDERS WHERE RIDING
SIMILAR
AVERAGE AND HIGHER MAX SPEEDS FOR LONG DAYS OF 60 TO 80 KM ON UNGEARED
COKERS
WITH SHORTER CRANKS. I WAS NOT MUCH SLOWER THAN THIS WITH MY UNGEARED
COKER
WITH 125 MM CRANKS. I FRIEND TRIED THE GEARED 36\" AND REACHED 30
KM/H ON THE FIRST TRY. SO IT IS OBVIOUS, THAT YOU CAN RIDE REALLY FAST
WITH A
GEARED COKER, IF YOU DARE.
THE BIG DIFFERENCE TO THE UNGEARED COKER IS COMFORT. THE LOWER CADENCE
MAKES
IT EASY TO KEEP THAT SPEED GOING. THE CHAFING IS MUCH REDUCED WITH THE
LOWER
CADENCE TOO. LAST MONDAY I WAS RIDING ABOUT 70 KM IN AN AFTERNOON AND
IT WAS A
RELAXED AND SUNNY RIDE ALLONG THE DANUBE.

[B]WIND RESISTANCE
Wind is definitely an issue. With 20 km/h there is always the feeling
of
headwind. As there is almost no hills where my traffic free routes are,
I get
my buzz from the wind that blows constantly along the Danube. With
some
training it is possible to work against a steady headwind in the big
gear. The
way back with a good tailwind is where the geared 36" beats everything.
It is
like sitting on the sofa and someone is pulling by the landscape really
fast.

SHIFTING
Shifting the new hub is relatively easy. I succeed shifting the 29"
with the
new hub in about 95%. I think that shifting a 36" should not be much
harder. But the difference between 6 pins and 12 pins is noticeable.
The
coasting experience lasts 30 deg or 60 deg. With 30 deg one knows, the
new gear
is always just a jiggle away. 60 deg is almost the way from horizontal
to
vertical crank position. Sometimes I pedal with the wheel and it takes
me a
full crank revolution till the gears engage again. Often I am in the
new gear
immediately. With the old hub you never know.
I always mount in low gear, which is easy with the long cranks. I ride
very
slowly (about 5-10 km/h) for shifting up and down. So it's no matter,
if
shifting does not work out. I wear shoes, that cover the ankle and I
rub over
the button rather than kick it.
Better riders (Beau Hoover et al.) can shift the old hub consistently.

Hans


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Hi Kris and everybody,

I wonder if there will be hubs with 3 or more gears in the future...a
lower than 1:1 ratio will be nice to have too :-p

is the play between the wheel and the cranks also noticable in the 1:1
ratio?

Thanks,
Flaviu

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UAC said:

is the play between the wheel and the cranks also noticable in the 1:1
ratio?

Yep.

If you're riding riding smoothly it's not very noticeable. It does make
you notice when you stop riding smoothly, or idle though.

Joe

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joemarshall said:

Yep. If you're riding riding smoothly it's not very noticeable. It does
make you notice when you stop riding smoothly, or idle though.

I disagree - -tho this could be a difference in hubs rather than
anything else -- my hub seems to have no 'play' (or 'slop'😉 in low
gear.

Unforch, my guni seems to have a lot of slop in high gear. This is
mainly noticeable on flats or uphills -- almost never in downhills. The
high-gear setup seems to make clanking sounds that make me fear it's
going to disengage. Does your guni have a 'loose' high gear?

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David_Stone said:

Unforch, my guni seems to have a lot of slop in high gear. This is
mainly noticeable on flats or uphills -- almost never in downhills. The
high-gear setup seems to make clanking sounds that make me fear it's
going to disengage. Does your guni have a 'loose' high gear?

I think mine has more slop in high gear than low gear, but there's a
definate little bit of movement if you go from forward to backwards in
low gear too.

Joe

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UAC said:

I wonder if there will be hubs with 3 or more gears in the future...a
lower than 1:1 ratio will be nice to have too :-p

I thought about this some last night and came up with a simple and
elegant solution. You could use magnetic gears where only the magnetic
flux 'connects' the drive and the load.

A quick google search today turned up prior research on this topic:

ATALLAH, K. HOWE, D.
A novel high-performance magnetic gear
IEEE Transactions on Magnetics
Vol. 37, No. 4, 2001, pp. 2844-2846

You can see pretty pictures of these particular magnetic gears here:
http://www.infolytica.com/en/coolstuff/ex0106/

For a unicycle hub, I'd add a layer of magnetic and stationary pole
pieces so that the pedals turn in the same direction as the wheel, and
different gearings would move the layer among inner and outer rings
with different numbers of magnets.
The idea is simple enough, but can probably can be simplified
dramatically by someone rich enough to purchase a downloadable copy of
the research papers.
For extra credit, a creative arrangement of Halbach arrays might let
you shift by changing the effective number of teeth in a layer,
probably doubling or halving the number.

Maybe some of the smart people out there already know how to improve on
these ideas?

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shapr said:

I thought about this some last night and came up with a simple and
elegant solution. You could use magnetic gears where only the magnetic
flux 'connects' the drive and the load.

A quick google search today turned up prior research on this topic:

ATALLAH, K. HOWE, D.
A novel high-performance magnetic gear
IEEE Transactions on Magnetics
Vol. 37, No. 4, 2001, pp. 2844-2846

You can see pretty pictures of these particular magnetic gears here:
http://www.infolytica.com/en/coolstuff/ex0106/

For a unicycle hub, I'd add a layer of magnetic and stationary pole
pieces so that the pedals turn in the same direction as the wheel, and
different gearings would move the layer among inner and outer rings
with different numbers of magnets.
The idea is simple enough, but can probably can be simplified
dramatically by someone rich enough to purchase a downloadable copy of
the research papers.
For extra credit, a creative arrangement of Halbach arrays might let
you shift by changing the effective number of teeth in a layer,
probably doubling or halving the number.

Maybe some of the smart people out there already know how to improve on
these ideas?

The theoretical torque limit of the example shown is 665Nm/m of gear
length. Does that mean the gear thickness? I don't know. There is no
indication what the gear thickness of the theoretical assembly is. If
the circumference of the gear assembly (hub) is 1m then its diameter is
32cm, about a foot, which is huge as well as massive if it is filled
with iron and magnets. The 665Nm of torque (450 ft-lbs) is -pretty-
high until you get the hub to some reasonable size. A 4" -average-
diameter, solid steel hub is already pretty beefy and the torque limit
has now dropped to 150 ft-lbs which is quit low. This maintains the
thickness of the theoretical example which is unknown but if it had an
aspect ratio of one (not unreasonable) then the hub would be a foot
thick. Reducing that to a 4" width would take the torque limit down to
50 ft-lbs which is far too low.

There is a slip that is introduced while applying torque and that
increases with rotational speed and torque. This means that the faster
or harder you spin, the sloppier or spongier the corrections are using
the pedals to maintain an upright position along the axis of travel.
The point at which you need maximum reverse torque is the point at
which when you get the least.

The extra layer of poles and iron to reverse the direction just adds
more air gaps and reduces coupling. The simpler thing is to anchor the
sun magnet and drive the "planet" iron pieces.

Sorry to have rained on your parade. Hopefully someone will soon come
along with an umbrella.

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shapr said:

I thought about this some last night and came up with a simple and
elegant solution. You could use magnetic gears where only the magnetic
flux 'connects' the drive and the load.

A quick google search today turned up prior research on this topic:

ATALLAH, K. HOWE, D.
A novel high-performance magnetic gear
IEEE Transactions on Magnetics
Vol. 37, No. 4, 2001, pp. 2844-2846

You can see pretty pictures of these particular magnetic gears here:
http://www.infolytica.com/en/coolstuff/ex0106/

For a unicycle hub, I'd add a layer of magnetic and stationary pole
pieces so that the pedals turn in the same direction as the wheel, and
different gearings would move the layer among inner and outer rings
with different numbers of magnets.
The idea is simple enough, but can probably can be simplified
dramatically by someone rich enough to purchase a downloadable copy of
the research papers.
For extra credit, a creative arrangement of Halbach arrays might let
you shift by changing the effective number of teeth in a layer,
probably doubling or halving the number.

Maybe some of the smart people out there already know how to improve on
these ideas?

That's pretty cool stuff! Some considerations in possibly putting this
on a unicycle include:

The potential sheer weight of the system. Magnets are heavy!

The cost of making the idea usable includes not only the cost of the
papers, but the costs of tools like Infolytica, which, without calling
for a quote, would be considerable.

The need to develop a transmission that would have enough strength to
avoid slipping, as seen in the torque/lag graph, may result in a
transmission that is quite bulky due to the size of the magnets.

At first glance one would slide additional magnets in from the side to
change gears. This further increases the size of the system.

There would be a varying lag based on pedal force and gearing, but it
would be quite smooth, so just about anyone who could ride a uni could
adapt to that.

Who knows... that idea may be at the core of the next or next-next
revolution in unicycling transmission!

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Thanks Greg for putting real numbers on it, though agreed that the
description is less than precise; it's not a technical paper.

harper said:

The extra layer of poles and iron to reverse the direction just adds
more air gaps and reduces coupling. The simpler thing is to anchor the
sun magnet and drive the "planet" iron pieces.

Would this actually unreverse the direction?

Perhaps a better solution would be to reverse the thrust mechanically
before (or after) it reaches the mag portion of the transmission.

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harper said:

Reducing that to a 4" width would take the torque limit down to 50
ft-lbs which is far too low.

Yes, for 660nM torque a 4" width hub would be too weak. I don't know if
that can be improved, reading the papers might help (but they cost
money to download). Maybe you can just increase the number of 'teeth'?

Quoted message said:

There is a slip that is introduced while applying torque and that
increases with rotational speed and torque. This means that the faster
or harder you spin, the sloppier or spongier the corrections are using
the pedals to maintain an upright position along the axis of travel.
The point at which you need maximum reverse torque is the point at
which when you get the least.

Are you referring to magnetic coupling specifically?
Another downside of magnetic coupling is that the better the coupling,
the harder it'll be to change gears. At least, I can't see a way around
that.

Quoted message said:

The extra layer of poles and iron to reverse the direction just adds
more air gaps and reduces coupling. The simpler thing is to anchor the
sun magnet and drive the "planet" iron pieces.

How do you disengage the other gears then?
If the sun gear is fixed, each middle planet gear would require its own
outer planet gear, each of which would have to move independently,
right?
Fewer air gaps increases coupling, but moving the middle layer was the
only way I could think of changing gears with one moving part.

Quoted message said:

Sorry to have rained on your parade. Hopefully someone will soon come
along with an umbrella.

Finding holes in an idea just gives opportunities to improve it.

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