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Gear ratio information about different models of the A-bike

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Gear ratio information about different models of the A-bike

Postby Amuro Lee on Fri Aug 27, 2010 7:09 pm

A-bike / A-bike Plus / 6" wheeled A-bike Smart
Dual Chain ratios: 14:8 and 35:9
Tyre Size: 15cm/6" diameter x 3.2cm/1"
Crank length: 140mm

Gear inches: 6" x 14 ÷ 8 × 35 ÷ 9 = 40.83"

Metres of development: 0.15m x π x 14 ÷ 8 × 35 ÷ 9 = 3.21m
This means that the bike travels about 3.21 metres per crank rotation.

Gain Ratio: 150mm ÷ 2 ÷ 140mm x 14 ÷ 8 × 35 ÷ 9 = 3.65


A-bike City / 8" wheeled A-bike Smart
Dual Chain ratios: 14:8 and 33:11
Tyre Size: 20cm/8" diameter x 3.2cm/1"
Crank length: 140mm

Gear inches: 8" x 14 ÷ 8 × 33 ÷ 11 = 42"

Metres of development: 0.2m x π x 14 ÷ 8 × 33 ÷ 11 = 3.30m
This means that the bike travels about 3.3 metres per crank rotation.

Gain ratio: 200mm ÷ 2 ÷ 140mm x 14 ÷ 8 × 33 ÷ 11 = 3.75


What is "gear inches"?
http://en.wikipedia.org/wiki/Gear_inches

What is "metres of development"?
http://en.wikipedia.org/wiki/Gear_inches#Calculating_metres_of_development

What is "gain ratio"?
http://www.sheldonbrown.com/gain.html

Information about measuring gears:
http://en.wikipedia.org/wiki/Bicycle_gearing#Measuring_gears

Gear ratios comparison among tiny wheeled folding bikes:
http://www.abikecentral.com/forum/viewtopic.php?f=2&t=1369
http://en.wikipedia.org/wiki/Amuro_Ray

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Re: Gear ratio information about different models of A-bike

Postby Rob Friedman on Sun Aug 29, 2010 12:15 pm

has anyone tried or figured out if a internal gearedhub ie: a 3 speed or 6 speed a:could be used and b: would make a difference?
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Re: Gear ratio information about different models of A-bike

Postby Stevbike on Sun Aug 29, 2010 11:55 pm

Although I ride a copy version of the bike, the gear ratio is just right for the bike. It is not designed for high speed riding, just short trips. The extra gearing would add greatly to the cost of the bike as well. The basic design of the bike really well though out.

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Re: Gear ratio information about different models of A-bike

Postby Rob Friedman on Mon Aug 30, 2010 1:45 am

I too ride a copy that is very much like yours 8" solid tires.. but while this nis not for a long ride it just came to me that an internal gear hub might make a difference
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Re: Gear ratio information about different models of A-bike

Postby Stevbike on Mon Aug 30, 2010 2:10 am

It would be interesting see how a multi-speed hub could be placed in the tiny rear drive wheel. It would be interesting see it get at least 55 to 60 inches of gearing so the bike could reach at least a 18 to 20 kph average speed.

I get about a 12 to 14 kph average speed with the 42 gear inches. I do not know how you find the bike at speed but on slight down hill sections anything above 25 kph is a bit scary on a A-bike design. The wheel base is on the short side to handle any high speeds that could be asked to do with higher gear ratio's. If greater distances are needed, a bike more suitable these needs should be used, at least in my thinking.

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