I have completed my second design pass for the epicyclic hub. The gear ratio has been reduced to 1.5 to 1. The gears are commercially available and much beefier than before.
You can view the design at the bottom of my lame web page:
The ring gear is the pricey one at about $55. I think I can get the gears to make 2 units for $170 total or $85 per unit. The bearings, shafts, and retaining clips are all standard and commercially available but I haven’t priced them. The wide tab that you see if you look at the web site figure will be welded to the sun gear assembly and will attach to the fork. The technical problems I foresee are the torque applied to the frame by the sun gear assembly which must remain stationary around the axle. This will tend to push the seat in the direction pedaled making it essential for the rider to keep his or her weight on the seat. Since it is attached to only one side of the fork it will also apply a slight torque around the seatpost axis tending to make the seat rotate as the rider pedals. I don’t know how dramatic these effects will be but when I build it I will find out as will those who want to try it at NUC 2002 and UNICON XI. I plan to make the dimensioned detailed drawings soon and begin machining parts.
As usual, any comments are welcome. If you are interested in more detailed drawings, contact me by e-mail.
the idea sounds cool. do you know where NUC 2002 and UNICON XI will be held? me and my friend nick really want to go but im curious where it will be so i can prepaire in advance if needed. thanks in advance for any info you give. good luck with the custom hub and hope to see you there(hopefully)
harper wrote: > > I have completed my second design pass for the epicyclic hub. The gear > ratio has been reduced to 1.5 to 1. The gears are commercially available > and much beefier than before. > > You can view the design at the bottom of my lame web page: > > http://www.harper.unicyclist.com/
Hey there Greg,
You know… you don’t quite look like what I envisioned a nuclear
physicist to look like! But, you do look cool doin’ the karate kid pose
on the uni.
Christopher Grove
“Be Bold and mighty forces will come to your aid.” -Basil King (Anyone who
can give me more info on THIS Basil King please email
me.)
In article <9tpfhb$kle$1@laurel.tc.umn.edu>, harper
<forum.member@unicyclist.com> writes: > > As usual, any comments are welcome. If you are interested in more > detailed drawings, contact me by e-mail. >
I’d think that from-scratch constrcution would be pretty tedious. Why
couldn’t you just hack up old 2 or 3-speed bicycle hubs? I’d think they’d
have all the bits you need and only a little machining and welding would
be needed. I’ve read about geared hubs being done this way before - mostly
for giraffes maybe. Is this crazy?
============================================================
Gardner Buchanan <gbuchana@rogers.com> Ottawa, ON FreeBSD: Where you want
to go. Today.
I’ve heard lots about geared hubs being made that way. That’s primarily why I’m not doing it that way. I have read several threads about chain drives and kluge jobs and their associated problems. I decided to design a fixed gear hub specifically for a unicycle and develop it around commercially available, inexpensive drive components. Then I have to machine several parts and do a couple of welds. But the finished product will be reasonably close to the best attainable. Even an “ideal” geared hub is going to exhibit some quirkiness on a unicycle. I wanted to build one to make a 36" wheel equivalent (Coker) from a 24" wheel so many people (NUC 2002, UNICON XI) can ride it and make comparisons. If they like it they can have all of the drawings.
“Gardner Buchanan” <gardner@gromit.dhs.org> wrote in message news:RDCM7.188101$5h5.83135662@news3.rdc2.on.home.com… > In article <9tpfhb$kle$1@laurel.tc.umn.edu>, harper > <forum.member@unicyclist.com> writes: > > > > As usual, any comments are welcome. If you are interested in more > > detailed drawings, contact me by e-mail. > > > > I’d think that from-scratch constrcution would be pretty tedious. Why > couldn’t you just hack up old 2 or 3-speed bicycle hubs? I’d think > they’d have all the bits you need and only a little machining and > welding would be needed. I’ve read about geared hubs being done this way > before - mostly for giraffes maybe. Is this crazy?
2/3 speed bike hubs have lots of parts inside and are pretty
complicated. They also tend to be directional so not work well on
a unicycle.
On a giraffe they are okay, because you can put them in place of the wheel
hub, but as they are designed to run off a cog, you can’t just fit them
onto a direct drive unicycle. To bodge them onto a direct drive unicycle
you have to split the main axle, which is really going to screw up the
strength of the whole unicycle.
The idea of the single gear custom geared up hub is that it uses
comparitively very few parts, most of which are standard so could be
replaced if/when they break and doesn’t compromise the axle strength. The
machining needed is not too much, so assuming they work they could
probably be produced for not too much money, maybe even making a geared up
700c wheel cost the same as or less than a coker, but with all the
advantages of having a standard wheel size, or even a super coker 54 in
equivalent, imagine being able to ride at speeds of up to 30 mph on your
Coker. Some road bikers ride fixed with 60+ inch gears even over hills, so
it would definately be worth trying as a road machine.
A coker with a shift while stopped gear would be the best,
switching between
2.1:1 and 1:1, you could ride fast to some trails then blast away off road
with the 1:1 gear.
harper wrote: > > I’ve heard lots about geared hubs being made that way. That’s primarily > why I’m not doing it that way. I have read several threads about chain > drives and kluge jobs and their associated problems. I decided to design > a fixed gear hub specifically for a unicycle and develop it around > commercially available, inexpensive drive components.
I was totally unaware that there were “commercially available drive
components”. It sounds like you can just go down to “Joe’s Gear Warehouse”
and pick and choose from bins. I always thought gears were always made
custom for whatever they were used in.
Where is this Joe’s anyway?
BTW Greg, I don’t have any experience with CAD programs. What do you
use, and what might be a good program for a total beginner to get his
feet wet with?
Christopher Grove
“Be Bold and mighty forces will come to your aid.” -Basil King (Anyone who
can give me more info on THIS Basil King please email
me.)
“Joe’s” is QTC gears, KH gears, FAG in the UK I think, MRC bearings, Small Parts, Inc. (shafts, retaining rings), McMaster-Carr (shafts, retaining rings), Boston gear, SDC (stock drive components) and a host of other vendors. Just go to any search engine and type something like “gears, internal” or whatever you want. You can also try the Thomas Register online.