gganio

I have searched for A-Bike on taobao.com.
For what I have understood those companies in the Zhejiang province are now selling 8” and 6” wheeled A-Bikes.
Interestingly I have noticed that they are now offering also PU wheels. By my experience PU wheels, even though less comfortable, offer reduced rolling friction. I am sure that this addition will be appreciated by people living in towns with smooth surface. If the PU is good, then the bike might actually turn out to be pretty fast.

It is a while that I am working on a portable bicycle that uses also inline skate wheels (Mini125RD).
Actually I am designing it right now. I was willing to post my two cents about mini small wheels (below 8”), but I am too busy designing and building all of this stuff….
By the way, for what I have seen, Chinese bicycle prices have stabilized again. Corrected 11th 5 year plan or not those A-Bike are going to cost in China ex-works 10 times less the my ex-works cost here in Italy. I guess I have to wait for the 12th 5 year plan.

Maybe this link works:
https://search1.taobao.com/browse/0/n...at_topsearch=1

The category is折叠式/迷你自行车

Pocko

^ Bottom pic... the o'l Drum Brake... oh so simple, so light, and so effective (as long as you're not going backwards)

edwong3

I think that an A-bike with 8" wheels is a good thing. I've never viewed 6" wheels as being very practical, but that's just me.

I've been wanting a micro folding bike that I can take aboard a bus for example, and this looks like a good alternative. I've seen these A-Bike "knock offs" on eBay, but wonder how good they really are.

Regards,
Edward

Simple Simon

Fakers - wobbling on the shoulders of giants .

Amuro Lee

Those so called A-bikes selling on taobao.com are really low quality fakes.

The genuine A-bikes are selling here:
https://www.a-bike.net

PU wheels are dangerous for A-bike as they provide less grip force on the road surface than the pneumatic tyres.

Furthermore , the chief design engineer of A-bike advised us that they have done testing with solid tyres and they will seriously damage the A-Bike.
https://www.abikecentral.com/forum/vi...&sd=a&start=10

savethekudzu

PU wheels? PU? Plutonium?

Pocko

^ Polyurethane (solid soft-plastic wheels) like those used in 2-wheel scooters.

gganio

Indeed, I have translated some taobao posts with babelfish.yahoo and it seemed to say that the product was not of best quality. But I am not sure, it was a babelfish translation.

My experience is that solid rubber is not too fast. Somewhat similar to pneumatic tires at 90 psi.
You want to use Polyurethane with 75% rebound or better and 83A or less hardness.
If you use PU of 50% or less rebound then you are in a situation similar to solid rubber.

Maybe one day a new small wheel will come out that will join together the advantages of PU tires with the advantages of the pneumatic ones.

makeinu

Although I must defer to gganio to all matters related to small wheels (he's built, what, 10 different experimental small wheel bikes), I can't help but to open my big mouth. IMO:
1. A small wheeled bike must be of the utmost quality. You have less wheel, less, frame, less everything. So what you do have better work really well. The A-bike has too many hinges on its flexible plastic frame and the double reduction chain drive is inefficient. I feel that the stiff frame and top-of-the-line quality of the Carryme is an even bigger advantage than its 8" wheels.
2. PU wheels are not a good compromise. Although they may perform better, if there were ever a case to sacrifice a little performance for some extra comfort then this is it. Also, I don't feel that ultra small wheels are noticeably less efficient than their larger brethren (and I don't see anyone suggesting 140 psi tires for your 16" or 20" wheel folders). Besides, nobody is ever going to race ultra small wheel bikes anyway because the gearing is insufficient and they will never be approved by UCI standards.
3. As small and light as the A-bike is it's still not small or light enough. The convenience of a rolling stick design like the Carryme is better than shaving a little bit of weight or a few inches.

Dahon.Steve

This is interesting!

I've always said the super small 6' inch wheel of the A-Bike make it useless. You really had to work hard to get that bike faster than walking speed. I'm glad the 'Fakers' are improving the product because they clearly are thinking in the right direction. The new A-Bike did not impress me at all and the changes are structural and not performance related.

I hope the next upgrade of the A-Bike is the move to 8' or 10' inch wheels.

Dahon.Steve

I hate to defend the A-Bike but you can roll it easier than a Strida. Yup, I just tried it and it works easily. Here's a U-Tube of a couple of people rolling a Brompton and A-Bike. The A-Bike is way ahead.




https://www.youtube.com/watch?v=hUfSJ...eature=related

Amuro Lee

I think you have exaggerated the situation.

Although the gear ratio of A-bike (40.8 gear inches) is relatively low comparing with other tiny wheeled folders, I think it's appropriate for its intended designing purpose.

With the travelling distance of 3.2 meters per crank rotation, I don't think I have to work hard to get the A-bike just faster than walking speed (except when the tyres are not inflated to the correct tyre pressure, i.e. 90psi). Actually, it's quite hard to get balance on the bike at normal walking speed.


Here is the gear ratio information of A-bike, Strida and other tiny wheeled folding bikes/trikes.

The gear ratio of A-bike:
https://www.a-bike.co.uk/store/specification.php
Gear inches: 6" x 14 ÷ 8 × 35 ÷ 9 = 40.83"
Metres of development: 0.15m x π x 14 ÷ 8 × 35 ÷ 9 = 3.21m
Gain Ratio: 150mm ÷ 2 ÷ 140mm x 14 ÷ 8 × 35 ÷ 9 = 3.65

The gear ratio of Strida:
https://www.strida.com/en/products/?method=listing&sid=1
Gear inches: 16" x 100 ÷ 30 = 53.33"
Metres of development: 1.185m x 100 ÷ 30 = 3.95m
Gain ratio: 1185mm ÷ π ÷ 2 ÷ 170mm x 100 ÷ 30 = 3.70

The gear ratio of Handybike:
https://www.handybike.com/uk/technik.html
Gear inches: 6" x 52 ÷ 7 = 44.57"
Metres of development: 0.15m x π x 52 ÷ 7 = 3.50m
Gain ratio: Unable to calculate due to the unknown crank lenth

The gear ratio of Zerobike:
https://www.zerobike.com
Gear inches: 8" x (34 ÷ 14)² = 47.18"
Metres of development: 0.2m x π x (34 ÷ 14)² = 3.71m
Gain ratio: Unable to calculate due to the unknown crank lenth

The gear ratio of CarryMe SD or CarryMe DS in low gear:
https://www.pacific-cycles.com/produc...&cat2=7&pid=11
Gear inches: 8" x 84 ÷ 14 = 48"
Metres of development: 0.2m x π x 84 ÷ 14 = 3.77m
Gain ratio: 200mm ÷ 2 ÷ 160mm x 84 ÷ 14 = 3.75

The gear ratio of CarryMe DS in high gear:
https://www.pacific-cycles.com/produc...&cat2=7&pid=12
Gear inches: 8" x 84 x 1.65 ÷ 14 = 79.2"
Metres of development: 0.2m x π x 84 x 1.65 ÷ 14 = 6.22m
Gain ratio: 200mm ÷ 2 ÷ 160mm x 84 x 1.65 ÷ 14 = 6.19

The gear ratio of CarryAll:
https://www.pacific-cycles.com/produc...&cat2=7&pid=13
Gear inches: 8" x 64 ÷ 14 = 36.57"
Metres of development: 0.2m x π x 64 ÷ 14 = 2.87m
Gain ratio: 200mm ÷ 2 ÷ 160mm x 64 ÷ 14 = 2.86

References:
https://en.wikipedia.org/wiki/Bicycle...easuring_gears
https://en.wikipedia.org/wiki/Gear_inches
https://en.wikipedia.org/wiki/Gear_in...of_development
https://www.sheldonbrown.com/gain.html

gganio

I add here the gear inches of the Mini125s (the new name will be Mini125RD).
Normally these values should be corrected by the crank length. The Mini125 stock length is 165mm but we can provide you 158mm, 160mm, , 170mm, 172.5mm, 175mm if you really ask it. Let’s consider that 5mm shorter crank would make the ratio feel like 5 inches longer then what it is.

The gear ratio of Mini125RD stock:
https://www.geocities.com/gganio.geo/vepo/index
5*84/8 = 52.5 gear inches

The gear ratio of Mini125 pneumatic wheels:
https://www.geocities.com/gganio.geo/vepo/index
6*84/8 = 63 gear inches

The gear ratio of Mini125 stock with 7T sprocket:
https://www.geocities.com/gganio.geo/vepo/index
5*84/7 = 60 gear inches

The gear ratio of Mini125 110mm with 7T sprocket:
https://www.geocities.com/gganio.geo/vepo/index
4.33*84/7 = 51.96 gear inches

The gear ratio of Mini125 110mm with 8T sprocket:
https://www.geocities.com/gganio.geo/vepo/index
4.33*84/8 = 45.46 gear inches

I am building a Mini125RD bike to be used in the Milan to Venice randonnée. This is the gearing:
The gear ratio of Mini125 110mm with 7T sprocket:
5*122/7 = 87.14 gear inches

I am thinking about a Col du Galibier randonnée Mini125RD.
4*84/8= 42 gear inches

makeinu

Yeah, but then it's not so small anymore with 8" wheels so you might as well use something that unfolds to a better bike.

In any case, my point was not that rolling is the only important factor. On the contrary, there are many important factors in making a package convenient including size, weight, shape, rigidity, rolling ability, stability in various positions, etc, etc and my point was that I don't feel the A-bike is as well balanced in this regard as some other bikes (which is a big mistake for a bike that rides so poorly).

gganio,

What kind of chain and sprocket do you use for your Mini125? If it's ANSI #25 then maybe you can make some money selling us parts.

gganio

It uses the 25H chain. The favourite chain of PORTABLE BICYCLES!
The rear sprocket is a stock pocket bike one. Front chain ring is custom made laser-cut.

makeinu

^
^
^

See that Somna? Maybe Giuseppe here can get the chainring you want custom cut and mail it across the border.