motorizing a foldable bike (HELP)

[kevinky1994]

Hey all, this is my first time posting to any sort of forum, so I hope I am doing this correctly.

I'm a college student looking for a more convenient method of transportation, so I'm hoping to motorize (gas) my foldable citizen gotham 7 bicycle.

Here's a link to the bike:
http://www.citizenbike.com/catalog.asp?product_category_id=1&product_id=24

My bike has a rack mounted on the rear tire, and I was thinking that it could be possible to mount a motor there, and perhaps a gas tank under the seat on the stem? I'm not trying to show off to everyone and make this thing look like an actual motorcycle, like a lot of the bikes I've seen on the internet. I'd like it to look as "modest" as possible.

Anyways, is motorizing this bike with a gas engine even possible? Will mounting the engine to the rear rack work? If not, are there any other options? Thank you for your time; any advice will be greatly appreciated!

 

[2door]

Welcome to the forum. You'll get lots of advice about your proposed project so I'll start off. Yes, your bike could be motorized but it will take some metal fabrication skills and the right tools and equipment. It will not be a bolt-on installation.

The easiest route would be to explore a friction drive system whereby an engine driven roller engages the rear tire to propel the bike. A chain drive is possible but mounting a rear sprocket is going to be a challenge.

Is there a reason you're looking at a foldable bike? We should warn you that a motorized bicycle will weigh at least 25 to 30 pounds more than a non-motored version of the same bike. That will impact the portability if not the foldability of the bike you linked to.

Here is a quick search result on the subject > http://www.google.com/cse?cx=partne...b=0&gsc.q=motorizing foldable bike&gsc.page=1

Good luck with your project and I'm sure others will offer some opinions and suggestions.

Tom

 

[crassius]

I, also, was thinking friction drive, but a front wheel drive with self-contained fuel tank - not great for hilly areas tho.

 

[kevinky1994]

Thank you for replying, Tom.

I'm looking at a foldable bicycle because that's what I have right now. Also, the size is convenient, and I guess I just think it'd look cooler than any standard bike. I'm kinda going for the scooter/ moped look rather than a mini motorcycle.

Are the metal fabrication skills only needed for the friction drive engine? I was looking at some friction drive kits, and it seems like metal work is only needed to create a mount for the engine. I unfortunately, have very basic tools and no experience with metal working.

Considering this, would it be more feasible to use a chain drive engine, and mounting it to the rear rack? I could reinforce the rack/ buy a sturdier one. I've never changed a sprocket before, why is this considered a challenge?

 

[kevinky1994]

thank you for responding. Is there a reason why you would recommend a friction drive over a chain drive? I am planning on using this bike to climb fairly large hills.

 

[2door]

Hilly areas require a lower gear ratio (bigger rear sprocket). Without actually seeing the rear wheel of your proposed bike I can't offer any suggestions on mounting a sprocket to it. Nevertheless, you'll need to consider spoke count/spacing and how to attach a sprocket to the rear hub for a chain drive system. That is where I see some mechaincal skills as well as fabricating a secure engine mount to the existing frame/rack.

Keep in mind that most small 2 and 4 stroke engines rely on a gravity feed fuel system so the fuel tank will need to be higher than the carburetor. That should certainly be a consideration during your design stage.

Tom

 

[crassius]

the force required on the chain to pull you & the bike up a hill is enough to crush most carrier racks - you'll need a very solid mount

 

[maniac57]

I think either a chain drive or a friction drive would be possible on the bike you linked.
Looks to me like a standard rag joint sprocket mount would fit your rear rim which allows a rack mount engine setup like you describe.
A friction drive will also fit but personally, I prefer chain drive since it is dependable in all weather conditions. Friction also wears tires much faster.
I'd look at Dax or Staton for kits to fit your needs, as a standard china girl 2 stroke will not work in a rack mount without some custom fabrication beyond most beginners.
Both companies offer rear mount kits and you can get some idea of what is available.

 

[Avalanche]

I think you should seriously look into getting an electric hub motor. might be a little more expensive but there will be zero maintenance, your bike will look almost exactly the same, the sound is almost as silent, and the install will be considerably less/easier. check out the endless-sphere forum, many people have done electric folding bicycle conversions.


here is a gas engine solution.

http://www.staton-inc.com/store/pro...0_hp_Four_Cycle_Outside_Drive_kit-397-15.html

 

[kevinky1994]

Thank you all for replying, you're all great. It's amazing how helpful everyone on here is. I've read through all of your posts, and I'll be considering my options for a little while. I'm too busy with school right now to build this thing. I'll post a picture of the finished product when I get a chance. Again, thank you all for the advice!

 

[5-7HEAVEN]

A 20" Dahon folding bike was one of my first motorized bikes.

First, I used a Robin 35cc 4-stroke engine with friction drive ans 1.125" roller.
It was an excellent first bike. It handled well, cruising @ 20mph. Top speed was 27mph on a slight decline.
Bike ran fine, handled well. Big disadvantage was that the bike never folded.

Next I installed a rear chain drive with 2.2hp Mitsubishi engine onto the tiny bike.
Bike became very quick, but also very squirrelly in handling.
To keep from killing myself, I removed the engine and gave the bike away.

After that, I motorized 26" cruiser bikes, comfort bikes and mountain bikes. They handle MUCH better with speeds above 25mph.

 

[Joe Hill]

A 20" Dahon folding bike was one of my first motorized bikes.

First, I used a Robin 35cc 4-stroke engine with friction drive ans 1.125" roller.
It was an excellent first bike. It handled well, cruising @ 20mph. Top speed was 27mph on a slight decline.
Bike ran fine, handled well. Big disadvantage was that the bike never folded.

Next I installed a rear chain drive with 2.2hp Mitsubishi engine onto the tiny bike.
Bike became very quick, but also very squirrelly in handling.
To keep from killing myself, I removed the engine and gave the bike away.

After that, I motorized 26" cruiser bikes, comfort bikes and mountain bikes. They handle MUCH better with speeds above 25mph.

Did bike become hard to handle because of hi top speed? what gear did you use?
what was top speed with both??
thank you