A-Bike Gear Cog

[greenbiker]

My A-Bike just had a critical breakdown after 10 days of use?

The gear cog for the chain simply broke into pieces. I was riding on a flat road (Toronto is flat for miles) going through the University of Toronto and the cog simply fell apart. The cog ha about 10 teeth on it (I only retrieved half of it)

The question is why? and what will it cost to repair? I know bikes and ran the repair shop for a bikeshop for years while going through university. The part is worth about $5 but the shipping the whole bike back to the UK and then returned will be over $100.

Any one else out there have this type of major mechanical implosion. I know I have never had this type of breakdown after 40 years of bike riding and racing.

John

[newcross]

Hi, I'm so sorry to hear that.

What I suggest is this...

1. take some photo of the broken part and where it was positioned in gear box.

2. send the photo via e-mail to the distributor (Mayhem?) you bought A-bike from, and ask for their advice.

It seems to me, since shipping A-bike costs alot, getting them to send a replacement part would be the most efficient way. I know some did order replacement gears, so it should be okay, but you have to fix the cog back to A-bike by yourself though...

If the broken cog was a part of complicated assembly, and you are not technical enough to handle it, ordering the whole assembly would be a good idea.

[Binch Shin]

Hi John

Your broken sprocket seems to be attached the rear-wheel.
In my knowledge, this critical failure can occur on a situation that an user has a harmful habit. For example, striking the padels 'tuck~ tuck~' as riding. This action is very harmful to our A-bikes because they have a big Gear Ratio.

If I were you, I would ask Mayhem to exchange the broken entire rear-wheel for another new one.
- You send the broken rear-wheel to Mayhem by Cash On Delivery.
- Mayhem will send you the new wheel by Cash Before Delivery.

The disjointing/jointing of the rear-wheel is easy.

Cheer Up

[Binch Shin]

Haa Haa

When I sought some English words, newcross already uploaded his post.
I agree with you, newcross.

[newcross]

Haa Haa

When I sought some English words, newcross already uploaded his post.
I agree with you, newcross.

Oh, Binch shin, I was admiring your post just now. It was so insightful and resourceful. Thank you for the info, I learned a lot from it.

(P.S. I'm a big fan of your Korean A-bike site!!)

[greenbiker]

I have taken a photo of the cog. I am also going to remove the rear wheel and find out if there was any scarring on the threads to have the new cog replaced.

I certainly can do repairs. I was a bike mechanic for years and did the tech support for a bike racing team.

As for any rough riding, that wasn't the case. My assessment is that the original chains were too tight and the tension took it out on the rear wheels cog. The metal does look hardened on the outside but its mor like less durable white metal inside.

My concern is how easy this fracture occured. I do have all my documentations, so hope that an email with the photo and copy of my recent mail order will expedidite a cog replacement this week.

Every item I ordered from Mayhem takes only 2-3 days from UK to my Toronto home.

So will keep you in the loop as I get the part and attempt the repair.

I did let Mayhem know that a local bike shop Urbane Cyclist is THE folding bike, commuter bike shop in the city and its about 10 houses from my place. I would love to get them as a local distributor and repair shop.

Who knows. I could do repairs myself. The mechanics are pretty straight forward and without complicated gears should be challenging but doable on a small scale. Afterall, unlike my tandem, an A-Bike only takes up a good size briefcase in terms of storage space.

John

[Guest]

I'm glad to know you, John as an engineer like myself.

I have no experience of a bike mechanic but I can assure you that the A-bike has less troubled parts than general bicycles from the viewpoint of its old user.

Deeply hope your pony will recover soon and you can enjoy A-bike life again.

P.S. To newcross, Thank you ^(^

[Binch Shin]

urg......
Sorry, the last was me......

[thatsme]

the more i read about technical stuff on here the more ignorant i feel.
i will buy the abike in may when i move back to london.

so by reading this forum i learn more and more.

what is Gear Cog?
can that problem happen often?

that's it
thanks for your help in advance.

[Binch Shin]

Hi thatsme

The Cog is a small gear wheel in my English dictionary.
So I think the Cog is a combination of an inner wheel-hub and an outer sprocket around it and the size is small.

About the fracture, I don't know how often it happen..
But I can say a fact that our member greenbiker's A-bike is the first case and fortunately he is an engineer.

[Guest]

the drive mechanism is weak and can break quite easily. this is "early adopter" problems and you should return your a-bike for a replacement.

[greenbiker]

I also see that the chain to the rear wheel had also snapped.

I let Mayhem know also about the chain. Now that the chain and cog are toast, I am going to take the housing off and look at the mechanism inside. I imagine there is a lot ot torque on the chain and cogs to get the momentum of a much larger wheel.

Does anyone know the equivalent "inches" to a standard bike with 700CC wheels?

Thanks

John
greenbiker
Toronto

[Guest]

When I found an specification of the rear chain(Long length & Small link size), a man let me know that the chain is #25 chain for Go-Kart and has 1/4" pitch X 1/8" overall width.

But he didn't know where we can buy it near home.

[greenbiker]

Well I took the housing off and found that my first assessment was not quite right. The gear cog that snapped was one of the central cogs on the gear assembly between the chainring attached to the pedals and the rear wheel.

So I will need to replace the whole middle section. The chains themselves are OK.

Anyhow, Mayhem have been very thoughtful but I have to communicate that they are sending the correct part.

[Guest]

Does anyone know the equivalent "inches" to a standard bike with 700CC wheels?

Thanks

John
greenbiker
Toronto

It's about 41".