Geared 36

Thanks for the vote of confidence Hardcore! But I'm still experimenting
in this unknown environment, and I have no intent myself to produce
geared unis for sale. Having posted all this in the public forum, I
will leave production to others who are more set up for that. But I'd
be happy to talk to anyone interested in making the parts, I'm sure we
can do it economically as a kit with instructions or something like that
(to keep the costs down).

There's still alot of sorting out to do, but the 1.5 overdrive is
clearly insufficient for fast riding on the flats. I've had no problems
with maneuverability; it feels just like a bigger wheel in speed, but
still acts like a 36 in steering. I can't turn on a dime, but maybe you
could!

The only non-normal factor from a regular uni is that John Childs
demonstrated the theoretical lever effect on the frame. But I have had
no problems whatsoever riding up short hills. Climbing dynamics feel
pretty much the same. But I will do more hill testing when I get the
chance.

My next step is to bump the ratio on this model up to 1.67, and I have a
v.2 still in the planning stage using belt drives and a 1.85 ratio. So
until I start finding the limits of rideability, I'm not gonna have
anything other than prototype parts in my garage. Anyone interested in
making and selling jackshafts?? I could probably write instructions &
specs on how to assemble all the after-market parts.

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I'm confused about shifting. How do you get this in 1.5 mode. Are the
parts off the shelf items that need some modification or are they custom
made? Maybe someone like Tom Miller at the Unicycle Factory would be
interested in producing these if the capital investment is minimal.

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TonyMelton said:

*One question for HAndyAndy: if you're using a wide hub in your Coker
wouldn't the upper chainring have to sit a long way out from the frame
(possibly hitting your leg with every pedal stroke)? *

yes, it's one of many problems. and the drawing i worked up is scaled to
a 24" wheel so it would sit a little lower but still an issue. it's not
likely to ever happen and it it did it would be mostly a novelty.

sorry about the late reply, i was in Orlando for a week and this last
week i have been busy getting my car running

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There is no reason that a wheel designed only for speed shouldn't be
dished a certain amount, should Q become a major issue in pedaling
efficiency.

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'Strongest Coker Wheel in the World'
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Do you think it would be possible to make this design shiftable? I am
thinking that you could have some way to lock the hub to the spindle and
disengage the cogs if you wanted 1:1. Is this possible, and would it be
worth doing?

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I can't think of a way to make it shift, short of a bad-ass miniature
shiftable jackshaft (but then why have the jackshaft...). This is
fixed-gear only. No matter to me, as it's still very rideable.
Greg Harper (Mr. Blueshift) lives nearby and has seen this, but we
haven't yet discussed the design possibilities of combining the
different approaches.

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So today a few of my friends took their first spin on Purple Phaze.
Then, it was Mr. HARPER's turn. True to his reputation, he spun the
locktighted and lock-ringed jackshaft cogs on his very first mount
attempt, a running-leap-on type. PP is back in the shop for a
re-design...🙁
Oh well, if a uni ain't Harper-proof, then it's NO DAM GOOD!!

For those interested, here are the "exploded" parts of the jackshaft
assembly:

+----------------------------------------------------------------+
| Attachment filename: 36geared.v2.jackshaft.jpg |
|Download attachment: http://www.unicyclist.com/attachment/253326|
+----------------------------------------------------------------+

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unisk8r said:

*he spun the locktighted and lock-ringed jackshaft cogs*

I'm not sure if I understand this. (In fact I'm sure I don't understand
this.) The lockrings are the bottom parts in your exploded view, right?
The picture is almost too small, but the lockrings seem to have three
little indents on the outside which I assume match (lock on) three
notches on something else. On what? And what exactly spun with respect
to what?

Klaas Bil

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Klaas Bil said:

*I'm not sure if I understand this. (In fact I'm sure I don't
understand this.) The lockrings are the bottom parts in your exploded
view, right? The picture is almost too small, but the lockrings seem
to have three little indents on the outside which I assume match
(lock on) three notches on something else. On what? And what exactly
spun with respect to what?

Klaas Bil *

The indentations in the lockrings are there so you can fit a lockring
spanner on to tighten or remove the lockring.

Here's a picture of a Park Tool bottom bracket lockring spanner
(wrench). A lockring spanner for a rear cog (as used on track bikes) is
typically different and usually only has one tooth. But this picture is
good enough to give you an idea how a lockring spanner fits on a
lockring. 'Park Tool bottom bracket lockring spanner'
(http://www.parktool.com/tools/HCW_5BIG.shtml)

Here's a picture of a different style of lockring pliers
(wrench/spanner). 'Tools for track racers'
(http://www.businesscycles.com/trtool.htm)

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unisk8r said:

*So today a few of my friends took their first spin on Purple Phaze.
Then, it was Mr. HARPER's turn. True to his reputation, he spun the
locktighted and lock-ringed jackshaft cogs on his very first mount
attempt, a running-leap-on type. PP is back in the shop for a
re-design...🙁
Oh well, if a uni ain't Harper-proof, then it's NO DAM GOOD!! *

This Harper incident is most unfortunate. It was going to be *my* turn
to ride the Purple Phaze next. 😠

Bad Harper! <said in the tone used when scolding a dog>

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Klaas Bil said:

*I'm not sure if I understand this. (In fact I'm sure I don't
understand this.) The lockrings are the bottom parts in your exploded
view, right? The picture is almost too small, but the lockrings seem
to have three little indents on the outside which I assume match
(lock on) three notches on something else. On what? And what exactly
spun with respect to what?
Klaas Bil *

John is correct as always. There are 2 kinds of lockrings, a track type
with as few indents as possible for strength, and the 6-notched, as I
have, which are meant to be removed & re-installed more often.
Klaas, Harper reverse-spun the big cog on the central cog body, a common
problem with any other track cog setup (and a problem on most giraffes -
that's why we weld the cog to the hub). His response was "Get some
24-hour epoxy, that'll take care of it!" True, but it will also take
care of any hope of ever changing the gear ratio on the jackshaft by
using a different size cog!

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Could you do what we did on the new Nimbus Giraffes? We use a hub body
designed for disc brakes, but use the bolt holes to bolt on the sprocket
(with some thread lock). It has been 100% reliable so far and we
implemented the design last April.

Roger

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Thanks for that suggestion, Roger. Problem is, how to set up the hub
section and drill the cogs so that they are perfectly concentric. How
do you accomplish that?

Then there still must be room for sealed bearings inside the "hub".

My other idea for a jackshaft was to weld the 2 track cogs to a steel
tube (1.375" OD), and somehow insert the sealed bearings and axle. Same
issue though, how do you set up these parts so the sprockets will be
concentric? Weld them on a lathe (he asks, not being a machinist...)?

Harper suggested using 2 freewheel sprockets and a freehub body, but
every sprocket I've seen fits pretty loose and would be hard to weld
concentric.

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unisk8r said:

*So today a few of my friends took their first spin on Purple Phaze.
Then, it was Mr. HARPER's turn. True to his reputation, he spun the
locktighted and lock-ringed jackshaft cogs on his very first mount
attempt, a running-leap-on type. *

I am very pleased that I was able to break something other than my own
leg. I had to beg Ryan Atkins to break Steve Howard's splined axle
because I couldn't do it myself. I feel like I'm back in business.
Especially pleasing is the knowledge that JC was denied a ride because
of my excessive abuse.

Another notable: Irene Genelin is the first to have ridden both versions
of geared Cokers (jackshaft and internal) and is the only living human
who can make a comparison.

--
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-Greg Harper

B L U E S H I F T

"You go through life and you choose." - Greg Harper

"Find weak people and take stuff from them" - Greg Harper
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unisk8r said:

*Thanks for that suggestion, Roger. Problem is, how to set up the hub
section and drill the cogs so that they are perfectly concentric. How
do you accomplish that? Then there still must be room for insertion
of sealed bearings on each side of the "hub".*

The holes are batch produced so my guess is that there is no flash
tooling. But it works! My guess is the number of holes help.

When I was designing it I was thinking it needed a machined inner ring
that fits on a machined section on the hub. Although this was not
possible due to way the hub was built. In then end it was not needed.

On the matter of fitting a bearing, I would have thought it was better
because these hubs are front hubs. Some are fitted with sealed bearings
and have a 20mm shaft through the centre. It may be that these could be
used with less adaption than using rear ones.

Roger

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I visited Tom Miller this weekend and I believe he would willing to
build one of these for someone. I gave him a paper copy of this thread
because he has no internet access, but he already knew about it because
he provided the spokes for this project.

Contact info:

Tommy Miller
765-452-2692

--
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Kokomo Juggler
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Just thought I'd post an update on this project. The first gear ratio
tried was 1.5, using 22t drive cogs and 18t cogs on the small sides.
Then I went to 17t cogs, which was a 1.67 ratio. Now I'm using a 16t
cogs, which is a 1.89 gear ratio. It's getting easier to ride the more
time I get on it, but still takes some getting used to. Freemounts are
indeed possible! My speeds have increased with each increase in the
gear ratio, but not quite in proportion to the gear.
Another issue is crank lengths. With the 1.5 ratio I used 150mm cranks.
With the 1.67 I went to 170mm, and noticed a lot more control. Now
with the 1.89 I currently have a set of 172.5, but will soon be
installing a set of 175s.
I also cut & re-welded the jackshaft cage to make it narrower.
Here's the current frontal view:

+----------------------------------------------------------------+
| Attachment filename: 36geared.v3.sidesm.jpg |
|Download attachment: http://www.unicyclist.com/attachment/272784|
+----------------------------------------------------------------+

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Purple Phase is a real beauty. Thanks for sharing the project
developement. Nice piece of work.

--
Chrashing - Just Lucky

Regards,
Chrashing
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Wow Pete! What sort of speeds are you doing on that? I'm also curious
to know the speed progression with the different gearing ratios. I
imagine that by now it's the wind resistance that is starting to hold
you back more?

Nice cranks too...she looks like a very expensive project :p

Ken

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o-kO
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Thanks Chrashing!

GizmoDuck said:

*Wow Pete! What sort of speeds are you doing on that? I'm also
curious to know the speed progression with the different gearing
ratios. I imagine that by now it's the wind resistance that is
starting to hold you back more?
Nice cranks too...she looks like a very expensive project :p *

The carbon cranks are used and from eBay. Not much more than high-end
cranks on uni.com.
Yes, wind resistance IS a factor at 15+ mph, esp. at 20+. I'm not
saying that I can go riding & average near 20 (truth is it's more like
15 for me), but top speeds are as fast as your mind can tolerate.
(20mph = 100 cadence with this gear!) It's more that we just don't yet
have the experience of riding 20+, nor the desire to take a hard fall at
well-above-runout speeds. I wear pads all the time, but getting in the
time at 20 is mentally tough.

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