folding bike conversion?

[RVD]

update. i started this build this past weekend. all parts are here and arrived.

the dropouts on the dahon are 133mm. the dropouts on the bike are set for 135mm. it's a bit of a tight fit but i was able to get the wheel in there including the washers.

i am trying to use the lyen 9 fet controller and plan to use 10s lipo (maybe 12s if it's not too much). i am guessing that it will be too slow but i am also going to test 6s lipo to see if that's usable (to keep weight down and treat this more as a pedal assist type bike).

the build is a bit frustrating and it's not working right now. i created another thread for that though.

but i am happy to report that at least as of now, the bike still folds well and is light enough to carry here and there.

 

[RVD]

I will post pics.

But this was a success! I got everything installed today and it's pretty clean. It works!

A few points:

1) Getting the motor to fit was a PITA. The motor dropouts are 135mm, the Dahon Speed D7 dropouts are around 133mm. The bike has a chromoly frame. I think you can spread the dropouts but I was basically muscling the 2 mm to get it to fit. I got it in at the end though. I'm assuming this is ok but if not, please holla!

2) I bought a small pannier from REI that fits perfectly on the rear rack.

3) I am using 12s1p lipo right now to test. 44v. It's fast. I don't have a CycleAnalyst hooked up but I'll take some speed measurements with my Garmin. I have a watt meter to keep track of amp-hours, watt-hours, etc.

4) I am using a thumb throttle since the bike already has a twister for gears. I am also using the 3 speed switch.

I still need to install a kill switch (in case of runaway throttle problem, emergency, etc.).

The bike still folds up as usual and since I went with a 350 watt geared rear hub motor, it is still carry-able. It's not light by any means but I can lift it up with one arm. I wish the bike would glide better so you can just push it or pull it like a cart but it's a bit wobbly (and I believe common for Dahon bikes).

Stealth factor is also nice.

Again, I'll post pics. It's almost 1am and I just got done with the built about 30 minutes ago (went on my test ride around the block, etc.).

 

[cwah]

Hello there,

I'm also thinking about converting a Dahon. Maybe a speed or mu.

I'm thinking about using a Bafang 48V500W. Is it the most efficient system? Can I overvolt it without problem? I'm hoping to reach 30mph for 15 miles. Is it the best solution?

 

[RVD]

I think there are a few things to consider when converting a folding bike.

1) Folding bikes are a little twitchy until you get used to them. Everything is just a little bit smaller, etc. Dropouts, steel/alu, etc. For example, you may be able to get away with not using a torque arm on a regular bike but you probably won't get away with it here.

2) IMO, you should do whatever you have to do to keep the folding bike foldable and transportable. After all, that's the whole point right?

I'm not familiar with that motor but in general, when choosing a motor I would make sure that it's relatively light and works well in a 20" wheel (or 16", etc.).

Battery mount probably won't work in the frame since you have to fold it. Rear rack with a thin bag is probably the best way to go.

Things are going to be tight and working area will be cramped since you need to fold it and everything is pretty much made to fold up exactly.

30 mph is nice for 15 miles but that will generally require around a 15ah battery. For weight, I would go with lipo but if you aren't comfortable with lipo, lifepo4 is probably ok. i would just make sure that the width of the battery will fit ok to let the bike fold (or build your own with headways, etc.).

I actually think for weight, etc. 36v is probably enough which is why i went with a slightly underpowered motor (to also keep things lighter). But of course it's all up to you...

 

[cwah]

I think there are a few things to consider when converting a folding bike.

1) Folding bikes are a little twitchy until you get used to them. Everything is just a little bit smaller, etc. Dropouts, steel/alu, etc. For example, you may be able to get away with not using a torque arm on a regular bike but you probably won't get away with it here.

2) IMO, you should do whatever you have to do to keep the folding bike foldable and transportable. After all, that's the whole point right?

I'm not familiar with that motor but in general, when choosing a motor I would make sure that it's relatively light and works well in a 20" wheel (or 16", etc.).

Battery mount probably won't work in the frame since you have to fold it. Rear rack with a thin bag is probably the best way to go.

Things are going to be tight and working area will be cramped since you need to fold it and everything is pretty much made to fold up exactly.

30 mph is nice for 15 miles but that will generally require around a 15ah battery. For weight, I would go with lipo but if you aren't comfortable with lipo, lifepo4 is probably ok. i would just make sure that the width of the battery will fit ok to let the bike fold (or build your own with headways, etc.).

I actually think for weight, etc. 36v is probably enough which is why i went with a slightly underpowered motor (to also keep things lighter). But of course it's all up to you...

Yes, and that's exactly why I'm looking for the most efficient motor possible. To have lighter batteries and be able to carry it through stairs and the tube.

But I want it faaaaaaaaster!! Not fun when it's too slow! And I can already reach 15-20mph without motor. So what's the point about having an electric bike if I'm not significantly faster? :lol:

 

[cwah]

I'm now thinking to have a Bafang 500W48V at 201 rpm (high torque) with 3 Lipo winforce at 22.2V5.2AH because they are extremely cheap. So I'd have a total 66.6V, a speed around 40kph and autonomy around 15 km. Is it correct?

 

[RVD]

Ok details on my build are up. I posted them here: http://endless-sphere.com/forums/viewtopic.php?f=6&t=34958

Enjoy...