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Old 02-10-09, 04:12 PM   #1
gganio
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Dude build Mini125 Modoki

I just got this news from Japan.
A guy has built and tuned his own prototype of the Mini125.
(Mini125 : the portable bike that I am developing)
Take a look at this link and pics.
Well, that guy improved the full thing making it a full suspended bike.
Subarashi Modoki!
As you might understand, depending where you live and ride, you might appreciate a certain bike layout over another one as well as wheel diameter.
The Mini125 got conceived while living in Tokyo and needless to say it is rather well adapted to be used in that town.
I like this news because I am dreaming to make the Mini125RD bike as a CC (Creative Commons) object http://creativecommons.org/ .

BTW, for what I have understood, all these bikes are from one guy that build several bike projects and sometimes re-build existing bicycle concepts, such as the Strida or the Mini125. I read the blog with http://babelfish.yahoo.com .

http://blogs.yahoo.co.jp/bonbon200/2150339.html

Gallery:
http://blogs.yahoo.co.jp/bonbon200/G...html?fid=0&p=6



























An interesting party of sub 8” wheeled bike







http://cycle.blogmura.com/cycle_customize/
http://www.blogmura.com/

http://cycle.blogmura.com/smallwheel/
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Old 02-10-09, 08:58 PM   #2
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I suspect that such questions must have been asked hundreds of times but then these are that naturally come to mind: What is the benefit compared to rollerblades? How hard is it to keep balance on such bikes? I suspect that cranks provide more angular momentum than wheels.
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Old 02-10-09, 10:42 PM   #3
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I suspect that such questions must have been asked hundreds of times but then these are that naturally come to mind: What is the benefit compared to rollerblades? How hard is it to keep balance on such bikes? I suspect that cranks provide more angular momentum than wheels.
While I haven't ridden the Mini125 in particular, as a big fan of another ultrasmall wheeler I'd have to answer your questions with:
1. Gearing. While roller blades do have a sort of variable gearing, the mechanical leverage is still quite limited compared to a bicycle. Plus sitting requires less effort than standing.
2. Balance is easier (especially at low speeds) because the entire weight of the bike is as low to the ground as possible. Experimental bikes with reverse flywheels have shown that the gyroscopic effect is almost undetectable in normal riding anyway.

Last edited by makeinu; 02-10-09 at 11:09 PM.
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Old 02-11-09, 03:34 AM   #4
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Cool! In it's own unique way...
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Old 02-11-09, 05:53 AM   #5
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I suspect that the streets of tokyo are far smoother than those of my neighborhood...
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Old 02-11-09, 08:43 AM   #6
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Thanks for posting this guiseppe.

I am intrigued by small suspended wheels (I guess I should buy Dr Moulton's book). Just as people talk about the pedal, seat, and handbar positions emulating a larger bike, it almost seems that if you can move the contact patch around enough (ie with a suspension) then a small wheel should be able to also emulate a larger one.
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Old 02-11-09, 11:35 AM   #7
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with rollerblade..u have at least 8 wheels to support u while this bike have 2 wheels...i wonder how much weight can this bike hold...probably not more than 150 lbs.
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Old 02-11-09, 03:48 PM   #8
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2_i,
BTW, the Mini125 got invented when in Tokyo, but the serious design work and maiden trip got done when in Michigan. I co-designed it with my brother that was in Italy and I was in Detroit. Maiden trip in Plymouth. First failure in Ann Arbor, somewhere in the campus.

For the balance, it turned out that even with 4" wheels, there is no feeling of lacking in gyroscopic effect.
All the super small wheel riders (a-bike, carry-me, ...) can confirm you this. Therefore, probably bicycle balance is done 98 % with direction correction and 2% out of gyro effect.

Rollerblades have no brakes (easy brakes). It takes 100 seconds, maybe more, to deploy rollerblades and skate. It takes 1 second to jump on the bike and ride. Basically they are similar but different scooting tools. I can not skate. I see some people showing up at he critical mass with inline skates, here in Turin. They seem having a lot of fun skating. As soon as I am done with this project , I got to learn skating and check it out.


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I suspect that such questions must have been asked hundreds of times but then these are that naturally come to mind: What is the benefit compared to rollerblades? How hard is it to keep balance on such bikes? I suspect that cranks provide more angular momentum than wheels.
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Old 02-11-09, 05:01 PM   #9
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Another blog in Japanese which shows a lot of pictures of small wheeled folding bicycles:
http://leonarhodo.exblog.jp

An excellent Japanese translation website:
http://www.excite.jp/world/english/web/
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Old 02-11-09, 05:21 PM   #10
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gganio,

so another issue, continuing a bit the line opened up vincentny, the pressure on the wheels must be humongous. How long can those wheels last in this application? Of course, you could always turn to steel, but you might be damaging the surface you'd be moving on. Myself, I have no direct familiarity with either a-bike or carry-me and there is a chance that they satisfy impulse buying needs and not those of long-term use. Otherwise, clearly, congratulations on the design! Even if it works partially, it is a serious accomplishment. This balance is an interesting issue. Skaters don't e.g. continue on one skate only for too long, but then they need also to balance the forward-backward direction.

I see that a-bike was designed by the same guy who introduced the first portable computer, or what counted for a computer at the time. Creativity boiling in some people deserves admiration.
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Old 02-11-09, 05:25 PM   #11
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It takes 100 seconds, maybe more, to deploy rollerblades and skate.
That's actually why I stopped skating (way before I even discovered folding bikes). However, now that I have a lot of experience with both I think the biggest difference is in mechanical leverage (ie skating is comparatively overgeared) and being able to sit.

A common rule of thumb says that for a given effort skating is twice as fast/efficient as running and cycling twice as fast/efficient as skating and IMO the gearing and ability to sit accounts for most of the difference so that a small wheeled bike is much more comparable to a standard bike than skates.
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Old 02-11-09, 05:34 PM   #12
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so another issue, continuing a bit the line opened up vincentny, the pressure on the wheels must be humongous. How long can those wheels last in this application? Of course, you could always turn to steel, but you might be damaging the surface you'd be moving on. Myself, I have no direct familiarity with either a-bike or carry-me and there is a chance that they satisfy impulse buying needs and not those of long-term use. Otherwise, clearly, congratulations on the design! Even if it works partially, it is a serious accomplishment. This balance is an interesting issue. Skaters don't e.g. continue on one skate only for too long, but then they need also to balance the forward-backward direction.
Why would it be any worse than what a regular bicycle wheel is subjected to? Except these aren't made out of thin branches (ie spokes) asymmetrically stretched (dished) several feet across.

Not to be rude, but I find it very strange how people's intuitions about things like small wheels, recumbents, etc are often so irrational. What could possibly make you think the smaller wheel would be weaker? Reality check: larger wheels are the ones that have to turn to steel because they are weaker, but since small wheels are so strong they can get by just fine with polyurethane.

Last edited by makeinu; 02-11-09 at 05:50 PM.
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Old 02-11-09, 05:50 PM   #13
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Why would it be any worse than what a regular bicycle wheel is subjected to? Except these aren't made out of thin branches (ie spokes) asymmetrically stretched (dished) several feet across.

Not to be rude, but I find it very strange how people's intuitions about things like small wheels, recumbents, etc are often so irrational. What could possibly make you think the smaller wheel would be weaker? I can't think of a single reason.
Not intuition, but knowledge. A small diameter, relatively hard wheel, has a small contact area with the surface one rides on. The large resulting pressure will act to deform the wheel and underlying surface enhancing the likelihood of destruction for both. E.g. I think that bad things might happen when trying to ride a micro bike over a tiled floor. Every material has critical tensions that it can withstand and the issue is how close you operate to those.

Otherwise, I am puzzled by the reality-check remark and am put off by ease with which the discussions here gravitate towards flame wars.

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Reality check: larger wheels are the ones that have to turn to steel because they are weaker, but since small wheels are so strong they can get by just fine with polyurethane.
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Old 02-11-09, 05:59 PM   #14
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Not intuition, but knowledge. A small diameter, relatively hard wheel, has a small contact area with the surface one rides on. The large resulting pressure will act to deform the wheel and underlying surface enhancing the likelihood of destruction for both. E.g. I think that bad things might happen when trying to ride a micro bike over a tiled floor. Every material has critical tensions that it can withstand and the issue is how close you operate to those.
Oh of course, that must be why the wheels on these things typically destroy the runway before being squashed into oblivion:



I'm sorry for being rude and I'm not trying to start a flame war, but I don't know how else to respond to statements which fly in the face of both physics and common sense. Experiment and theory confirm that contact patch area is relatively insensitive to wheel diameter (in fact, so much so that with standard bicycle wheels it's usually considered to be completely unrelated) and even if it wasn't experiment and theory also confirm that are smaller wheels are able to withstand much higher forces anyway.

Last edited by makeinu; 02-11-09 at 06:03 PM.
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Old 02-11-09, 08:39 PM   #15
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I'm sorry for being rude and I'm not trying to start a flame war
That is OK. Addressing

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physics and common sense
though,

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Experiment and theory confirm that contact patch area is relatively insensitive to wheel diameter (in fact, so much so that with standard bicycle wheels it's usually considered to be completely unrelated)
That, in fact, is pretty obvious. For a similar weight and pressure in tires, the patch size needs to be about the same. Smaller wheels need to deform more, though, for the same patch size, and they should be slower.

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experiment and theory also confirm that are smaller wheels are able to withstand much higher forces anyway.
As to experiment, this was the type of answer I was looking for. As to theory, obviously, in a micro bike the wheels must be subjected to 4 times or so larger tensions than in rollerblades. If they take it OK, they must be pretty overengineered. Otherwise, for 120 kg rider+bike and 5 bar pressure, the tire patch must be 12 cm^2. For a rollerblade wheel I cannot imagine the patch to be larger than 2 cm^2, but, admittedly, I do not have much experience with those wheels. Putting 60 kgf on each wheel yields stress of about 3MN/m^2 which is close to the tensile strength of some common materials, e.g. brick. I hope that I do not make a mistake here, but this implies that you might damage brick when riding on it with a micro bike.
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Old 02-11-09, 09:01 PM   #16
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Oh of course, that must be why the wheels on these things typically destroy the runway before being squashed into oblivion:



I'm sorry for being rude and I'm not trying to start a flame war, but I don't know how else to respond to statements which fly in the face of both physics and common sense. Experiment and theory confirm that contact patch area is relatively insensitive to wheel diameter (in fact, so much so that with standard bicycle wheels it's usually considered to be completely unrelated) and even if it wasn't experiment and theory also confirm that are smaller wheels are able to withstand much higher forces anyway.
i'm sorry..the tires u trying to prove ur point is totally different from the tires on this small bike. tires on the plane and other folders are made out of rubber with air in them. while the tires on this small bike seem like no air in them and are the same wheels that u see on rollerblade (or even worse..hard plastic instead of soft plastic). apples and oranges.

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Old 02-11-09, 10:09 PM   #17
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As to experiment, this was the type of answer I was looking for. As to theory, obviously, in a micro bike the wheels must be subjected to 4 times or so larger tensions than in rollerblades. If they take it OK, they must be pretty overengineered. Otherwise, for 120 kg rider+bike and 5 bar pressure, the tire patch must be 12 cm^2. For a rollerblade wheel I cannot imagine the patch to be larger than 2 cm^2, but, admittedly, I do not have much experience with those wheels. Putting 60 kgf on each wheel yields stress of about 3MN/m^2 which is close to the tensile strength of some common materials, e.g. brick. I hope that I do not make a mistake here, but this implies that you might damage brick when riding on it with a micro bike.
I think those are more likely scooter wheels than skate wheels and as small wheels are quite common among hand carts, fork lifts, and other devices designed to carry extremely heavy loads, I'd be very surprised if they could damage brick. I can, however, think of more than a few bicycle frames that would be damaged by a 120kg rider. I obviously haven't done the engineering myself, but if your calculations were even close then old men with canes would be wreaking carnage the world over.

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i'm sorry..the tires u trying to prove ur point is totally different from the tires on this small bike. tires on the plane and other folders are made out of rubber with air in them. while the tires on this small bike seem like no air in them and are the same wheels that u see on rollerblade (or even worse..hard plastic instead of soft plastic). apples and oranges.
And? The fact of the matter is that polyurethane is perfectly suited to the very gentle demands of small wheel cycling and, while you're perfectly free to fuel your doubt with ignorance, there's no rational reason to think otherwise.

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Old 02-12-09, 11:28 AM   #18
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I think those are more likely scooter wheels than skate wheels and as small wheels are quite common among hand carts, fork lifts, and other devices designed to carry extremely heavy loads, I'd be very surprised if they could damage brick. I can, however, think of more than a few bicycle frames that would be damaged by a 120kg rider. I obviously haven't done the engineering myself, but if your calculations were even close then old men with canes would be wreaking carnage the world over.
Since you have invoked physics, I brought in introductory physics considerations. While I have no engineering background, I can't see flaws in my reasonings that would prevent them from being useful for estimates. From the material strengths that I can find, the micro-bike wheels might also harm some woods. I further suspect that they might dent warm US-quality asphalt. As to your cane remark, in my home there had been chairs with caster wheels left-over from carpet floors. These managed to ruin solid an area of hardwood floor before they got replaced with supports that had larger contact patches with the floor.

Looking at material strengths there seems to be no problem finding plastics that have significantly higher strength than the deduced 3 MN/m^2 = 3 MPa (= 30 bar). This would suggest that one might need to worry more about the surface that one rides on than the wheels. On the other hand, there might be an issue of compromise. To get a larger contact patch, one would want to use a softer material. On the other hand, softer materials tend to have lower strengths. I do not know myself where this compromise ends up for the rollerblade wheels. Let us take, though, the strength of their material to be at a representative 30 MPa. There should be no problem with a wear to that wheels in average use. However, I suspect that the problem might occur when riding over a sharp stone, when the contact area between the wheel and the underlying surface dramatically decreases. A sharp stone might dent the wheel and I suspect that it would be bad to ride them over gravel.

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And? The fact of the matter is that polyurethane is perfectly suited to the very gentle demands of small wheel cycling and, while you're perfectly free to fuel your doubt with ignorance, there's no rational reason to think otherwise.
Seemingly mistakenly, I hoped that we were done with the issue of flame wars, at least for this discussion. I am not sure what your plane was supposed to illustrate, but I hope that you have no intention of testing it over gravel .
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Old 02-12-09, 12:07 PM   #19
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I think those are more likely scooter wheels than skate wheels and as small wheels are quite common among hand carts, fork lifts, and other devices designed to carry extremely heavy loads, I'd be very surprised if they could damage brick. I can, however, think of more than a few bicycle frames that would be damaged by a 120kg rider. I obviously haven't done the engineering myself, but if your calculations were even close then old men with canes would be wreaking carnage the world over.



And? The fact of the matter is that polyurethane is perfectly suited to the very gentle demands of small wheel cycling and, while you're perfectly free to fuel your doubt with ignorance, there's no rational reason to think otherwise.
great! then u should have no problem getting this bike when it is first out in the market? let us know how the test ride goes.
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Old 02-16-09, 04:19 PM   #20
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About the wheel wear we have noticed that with the pneumatic tires it was inversely proportional to the wheel diameter. Basically, if the wheel is 5 times smaller then normal 28” wheels, then the tire will wear off 5 times faster. That gives you a good 200 to 300 miles per tire. Since these bikes are used mostly to scoot around for short distance trips, this tire mission interval is more then enough. Good polyurethane wheels last longer, more or less as the normal 28” race tires.
To show the reliability of the bike, once and for all, this year, I want to take part to the Milan to Venice randonée. Additionally, I want to climb the Col du Galibier, which is a classic Tour de France mountain pass, near by where I live.
One year ago a guy was supposed to take part to the Seattle to Portland bike race, but eventually he preferred to run away with those bikes.
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