making geared uni.

well, i bought an old bike on sale at a thrift store today…i’m going to chop that up for a frame, and i have a few ideas… i’m going to have multiple gears, and i’d like to keep that little swingarm thingee with a little gear on it, so i can have extra chain, and change the gears easily… i’m going to rid myself of the gear changers (MAYBE) and try to make this a penguin… i don’t know how tall i want it to be…
i’ll post pictures when i get them.

UniBiker. Do a search. Jeff Baker (UniBiker) had a multispeed converted bicycle with a variety of drag brakes. It was a cool machine.

Here is his gallery.

Here is a time trial thread.

ooh… it’s nice, but that’s not what i was aiming for…

i was hoping for a more erect frame, like an actual giraffe… not so much that kinda thing…

thanks though…

now i have another question.

IF i made this from a freewheeling gear, i hear it isn’t possible to shift gears on the go. If this is not possible, it is no problem, i just want to know whether i should keep the shifter attached or not.

i have a few designs which i will post when i can fix my drawing program.

You can’t keep the little swingarm thing. Problem with this is that the thing was made for one direction, not two. Also, unicycle physics and dynamics differ greatly from bicycle physics and dynamics.

oh. really?

taht sucks…

oh well, the b*ke i’m using is an old Nishiki Blazer. it’s red, and is going to be awexome when done.
and you’re sure i can’t keep the swingarm thing?

well, i can’t decide whether to cut off everything but the lower part of the back “forks” and the pedal hub, or to leave almost the entire back part of the bike intact for stability…

it’s almost 3/4" thick, and i don’t know whether it’ll hold up or not to human weight… i might beef it up a bit… but the inline frame soundsand looks best in the design stage…

ok. here’s a pic of the b*ke before i rip it apart.

now you can see the thickness of the lower rear part of the fork.
could i use this alone, or should i beef it up more?

At least only one tire is flat. I guess you won’t have a spare.

heh… i have a couple of more tires lying around my house. :smiley: thanks for the concern, though.

You’re going to have to do some thinking and experimentation if you want to make a chain drive unicycle that can be shifted to different gears.

The chain tensioner thing on the derailleur is a jockey pulley assembly. It’s the spring loaded arm that takes the slack in the chain. It can only take chain tension going in one direction. If you try to pedal backwards you’ll just end up pulling up all the slack in the chain instead of actually driving the wheel.

A fix is to use two sets of cogs and two derailleurs. One on each side of the wheel. Each facing the opposite direction. One will be in tension when you are pedaling forwards and the other will be in tension when you are pedaling backwards. You’ll be able to pedal forwards and backwards and be able to control the unicycle. It will be very tricky to do and require some MacGyver skills. It will require two chains (one on each side of the wheel). Each crank will need a chainwheel.

Somewhere on the web I saw a tricycle or some other custom contraption that used two derailleurs and two freewheel cogsets like that to make a fixed gear shiftable bike/trike/HPV. Wish I could dig up the picture. I can’t find it now. Oh well. Maybe that’ll be enough to get you thinking.

huh…

well. i’ll think on that, and yes, like many of you out there, MacGyver is my idol. seriously. So i’ll do my best for that… i might just end up shortening the chain though, and driving the wheel directly with no derailleur.
by the way, if i don’t use the derailleur, i want to know what gears i should use. i’m thinking the big one or middle one up front, and the biggest one or the second one in back.

I HAVE
!!! well, kind of… i have to do some reinforcement in places, and get a new chain, but it looks great for my first home made giraffe deal. also, i came out of this with not one, but TWO great contraptions.

Construction pics:

Before:

After:

General Layout plan:

Construction:

Semi Finished Product:

and, the other product that came out, because i refuse to throw away anything that could be a potential awesome contraption. I likes to call it

the S.M.D


it is so much harder than a BC wheel, i think… but someone who can ride one has to tell me when they get a chance to try this.

I think you need to do a little maths to decide which chain wheel to use, that wheel looks like a 26" and even using the smallest top gear and the largest bottom gear you’ll still be getting atleast 2:1 ratio by the look of it (count the teeth to confirm) So that’s an effective 52", which will be very hard to ride. Do you have nay pegs or drop brackets you could fit on the axle of the S.M.D to place your feet on? It would be interesting to see how that rides.

It’s impossible to ride. Mainly because in order for your centre of gravity to be over the center of the wheel, your seat would need to be close to the center of the wheel, making your steering wheel tip nearly onto the ground.

To the impossiblility to ride thing, i’ve already coasted 4 feet or so…

and yes, i do believe that the smallest gear on top would be quite adaquate. I wanted the 2:1 ratio, because i thought it’d be cool to pass a bicyclist on this thing. i think it’ll work well, but i’m not sure HOW well. And i think i’ll be able to learn.

I am also going to go back to town today and get me some things i can use as platforms. I was trying to get better last night when i fell and loosened the weld around the joint, so today i’m going to re-weld it, and get some pegs or platforms. i’ll post pic later.

oh, i forgot to mention, the SMD has a brake, so you can slow it down if the wheel gets too far ahead of you.

oh and yes. the center of gravity does force me to push the bars down WAY low when trying to stay on (i can’t say riding yet because i have yet to learn) the hard part is keeping myself in that position, and the wheel too…

I really like your optimistic attitude. Have lots of fun building and trying to ride those … things :slight_smile:

thanks!

i think i have that kind of attitude. It’s helpful.

well, the reinforcement has started. I ripped of the seatpost holder, and am in the process of putting scrap metal in the little triangle area, so the seat doesn’t snap off when i ride it. also, i am going over each and every one of my previous welds to make sure they don’t break.

this thing should be completely finished by week’s end.