Hello net unicyclists one and all! I finally am motivated to make myself known,
after lurking for, well, too long.
About me briefly: I live in Oakland CA, where the weather is currently gorgeous.
I started riding a uni at age 38, 7 years ago. My wife, bless her heart, noticed
the longing in my gaze at the uni in the bike shop, and got it for me for
Christmas. I proceeded to teach myself by trial and much error, having no source
of instruction. I’ve ridden on and off since, getting better only slowly due to
lack of practice.
I recently jumped at the chance to buy a used giraffe from a fellow nearby. I
have been practicing much more lately, and have been making rapid progress. I
can now do a curb mount on the giraffe, soon it will be a freemount!
NOTE: Anyone live in my general vicinity? Gimme a holler - let’s ride!
Anyhow, lately I have been in the process of trying to figure out whether it
would be possible to adapt a Sturmey-Archer 3-speed hub to a giraffe. (Yeah, I
guess you could say I’ve really got it bad!)
I have done some analysis of the hub, and after scratching my head for quite a
while, I don’t see how it could easily be made to work. I have heard things
mentioned here about people using geared unis, and I would like to either find
out how someone has already solved this problem, or to engage other unicyclists’
ingenuity in arriving at a workable solution.
The problem is this: to enable the ratio of crank revolutions to wheel
revolutions to be changed on the fly, yet to prevent all free-wheeling while a
gear is engaged, that is, any time except when shifting between gears. It is in
preventing freewheeling while still permitting shifting that I need help.
Here’s what I have so far. I got a used Sturmey-Archer model AW (very standard)
hub from a bike shop. I found a Glenn maintenance manual in a used bookstore
with a pictorial procedure for overhauling my exact hub. (BTW, as a kid, I used
one of these for years, so I understand exactly how it works from the user
perspective, such as when it ticks, when the pedals spin free between gears, the
order of gears, etc.).
OK, so I began taking it apart little by little, peering into holes, pulling the
chain and moving things as I went, in order to begin to understand how the thing
works from the internal perspective. To make a long story short, I now
understand how it works as designed. (Aside: it’s no wonder these hubs are
still in use around the world. I don’t think I know of another mechanism that
packs such complex function into such a relatively simple package. It is
fiendishly clever!)
>From this point on, it’s kind of technical. I originally wrote
quite a bit more, but deleted it for brevity. If anyone wants more, I
still have it.
It comes down to two problems:
1 If we could find a way to lock the hub for one gear's power path, that
would be great, though no better than having no gears, I guess. The
problem is changing gears. We might find a way to lock one gear, but we
must be able to _unlock_ it to use _other_ gears.
2 There is quite a bit of slack movement of the driver when power
changes from pushing to coasting. This, I think, permits the clutch to
move easily among the three gears, and was not a problem for the
original designers because they _wanted_ it to freewheel, and there's no
difference from the user perspective between slack and freewheeling. But
it's a problem for us because, even IF we can figure a way to lock and
unlock gears to the hub, it still won't be acceptable unless we ALSO
find a way to do it with little or no slop.
BOTTOM LINE: Does anybody know how this is done?
Thanks ever so much for reading and head scratching. To misquote W. C. Fields,
“Everybody has to believe in something: I believe I’ll have lunch”.
>> Mark
Mark Schecter 3735 Maple Avenue Oakland, CA 94602 510-482-2094 home
510-645-3466 work