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Old 2009-10-13, 01:38 AM   #1
unicyclo
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An Unsuccessful Geared Unicycle (A-Uni)

Tried to convert an A-bike into a geared unicycle without sawing, drilling or welding (only a weld to fix the freewheel). However, due to the too high gear ratio (41 inch effectively) and the too high internal friction of the dual chain gearbox, it is impossible to pedal when I am on it.

The gear ratio is 14:8 and 35:12. Since the two chains are different in size and the gearbox is too small, I can't skip the middle gear to make a 14:12 gear either.

The seatpost's connection to the "mast" is weak too although the unicycle can fold with this design. Alternatively, the original plan is to put the seat on the top of the "mast". Since the seat, pedals and the wheel are not aligned, it is impossible to sit on it and keep in the idling position.

Finally, I think it will become an A-bike again (the only fixed gear A-bike in the world maybe). Therefore, I post some photos here as a record.
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Old 2009-10-13, 02:14 AM   #2
oddsends
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That is marvelous. Its too bad it doesn't work.
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Old 2009-10-13, 02:27 AM   #3
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Yes, very cool. Except for the drivetrain issues of course. To fix that would probably involve rebuilding the whole chain system, defeating what appears to have been the purpose of your experiment. If it had worked, then you probably would have realized the tiny wheel would be your next problem...
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Old 2009-10-13, 02:48 AM   #4
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lol i bet that wheel screams when/if you pedal it by hand even...
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Old 2009-10-13, 04:39 AM   #5
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Not really a failure at all,you thought outside the square and came up with a design for a guni and then built it,that in itself is a great accomplishment.You now know the limitations in that design.Well done.

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Old 2009-10-13, 08:49 PM   #6
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Wow, I just had a look at the website for the A-Bike. Looks like the next illogical step from the Strida. Similar shape and concept, but even smaller wheels.

What's the A-Bike like to ride on rough tarmac/asphalt? I guess the answer is "awful" otherwise you wouldn't be chopping it about to make something else with it.

(I have already formed a provisional opinion about what it's like to ride on deep mud, scree slopes and rock gardens, so there's no need to expand on that!)
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Old 2009-10-13, 09:06 PM   #7
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Quote:
Originally Posted by Mikefule View Post
Wow, I just had a look at the website for the A-Bike. Looks like the next illogical step from the Strida. Similar shape and concept, but even smaller wheels.

What's the A-Bike like to ride on rough tarmac/asphalt? I guess the answer is "awful" otherwise you wouldn't be chopping it about to make something else with it.

(I have already formed a provisional opinion about what it's like to ride on deep mud, scree slopes and rock gardens, so there's no need to expand on that!)
This video explains a lot.

basically, it's half the size of a strada, and much more portable, but not enough to make it worth it. The A bike just has a reeeeally rough ride.

I think if it had a less rough ride, you could easily ride a 41 gear inch uni, but when your wheels trip up on a pebble. . . . meh

I still wonder why nobody has made a 20 inch uni with a Low-as-possible giraffe design, so that you could have as large a gear as you reasonably would want with a small wheel. it may not be much taller than a 36 inch either.
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Old 2009-10-13, 10:47 PM   #8
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A-bike has the shortest distance between the wheel and the center of the pedals. Thus, lower center of gravity. Also the center of the pedals is only a bit not aligned with the wheel & the top of the "mast" (which I originally planned to put the seat on it). Of course, I finally find that the little mis-alignment already makes it impossible to ride.

I would like to build a 20-inch shortest giraffe too if possible. But it involves a lot of welding, sawing which I need to find the suitable place, equipment and skill.

Therefore, I buy this A-bike (an inexpensive chinese copycat with larger 8-inch wheels) to do the experiment as its design lets me to do the conversion without major welding or sawing. I only need to bring the freewheel to someone for a small welding and cut the brake wire of the rear brake. Now, I can convert it back to a fixed-gear A-bike just without the rear brake in half an hour. Of course, I don't think I will ride a lot on this bike with such small wheels eventually. I tried it on the bike lane before I chopped it. I think I can only ride for 1 km max. Even as a bike, it can be for fun only.

In my unicycle experiment, my goal is 100m on a flat surface. Of course, it didn't work.

On the other hand, I also gain more experience. I didn't ride a giraffe before. I find that mounting on a giraffe is difficult. As pedals are not in the center of the wheel, the pedals and my weight need to shift from the back of the wheel to the top of the wheel (I need to raise my CG).

I had another plan to convert a folding 20" bike into an unicycle before (see my previous post http://www.unicyclist.com/forums/showthread.php?t=78345). But its pedals are far away from the wheel and its CG is too high for a 48-inch geared unicycle. I didn't realise it and worked on the A-bike instead.
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Old 2009-10-14, 12:10 AM   #9
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Quote:
Originally Posted by juggleaddict View Post
I still wonder why nobody has made a 20 inch uni with a Low-as-possible giraffe design, so that you could have as large a gear as you reasonably would want with a small wheel. it may not be much taller than a 36 inch either.
They are often referred to as penguins but I guess that is just a brand name. Here is a response about penguins from another thread.

Quote:
Originally Posted by johnfoss View Post
Penguin was a unicycle brand, from the 70s. A couple of riders in RTUC had Penguin giraffes and I've seen a Penguin standard uni. They're long gone as a brand, but that's where the name comes from. I have a 5' custom-made giraffe, but it's not very low-rise, just not very tall.

Tom Miller (The Unicycle Factory) also made some low-rise giraffes, often with gear ratios, in the 80s. He called them Travelers.
Thanks for the video Juggle, I didn't even know that folding bikes existed. I think I would rather just ride a normal bike especially since our busses have bike racks on the front.
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Old 2009-10-14, 05:04 PM   #10
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Quote:
Originally Posted by juggleaddict View Post
This video explains a lot.
Thanks. Approximately what I expected.

From time to time I look at the Strida as a possible fun purchase, but when I saw one close up the other day in Nottingham, it looked a bit unconvincing.
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Old 2009-10-14, 06:05 PM   #11
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I want to mountain bike ride the A-bike.

Great innovations. The future is looking bright. Making a geared folding unicycle is way cool! Some day soon you or someone will make it work(with welding). It would fit in my grandma's purse.
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