DIY stage 1: received Bafang + Tongxin kits [photos]

[daniel.weck]

Table of Contents:

http://www.pedelecs.co.uk/forum/electric-bicycles/4682-diy-stage-1-received-bafang-tongxin-kits-photos.html#post59183

http://www.pedelecs.co.uk/forum/electric-bicycles/4734-diy-stage-2-received-li-ping-lifepo4-battery-photos.html#post59988

http://www.pedelecs.co.uk/forum/electric-bicycles/4737-diy-stage-3-motor-testing-fork-photos.html#post60039

http://www.pedelecs.co.uk/forum/electric-bicycles/4747-diy-stage-4-16-wheel-lacing-building-photos.html#post60153

http://www.pedelecs.co.uk/forum/electric-bicycles/4769-diy-stage-5-prepping-fitting-electricals-photos.html#post60345

http://www.pedelecs.co.uk/forum/electric-bicycles/4778-diy-stage-6-fork-hub-torque-protection-photos.html#post60504

http://www.pedelecs.co.uk/forum/electric-bicycles/4786-diy-stage-7-first-ride.html#post60641

http://www.pedelecs.co.uk/forum/electric-bicycles/4825-diy-stage-8-continuous-improvements.html#post60991

http://www.pedelecs.co.uk/forum/electric-bicycles/6956-diy-stage-9-a123-nano-battery-pack-photos.html#post88165

------------------------------------------

stage 2 already in place: 36V 10Ah LifePo4 Ping battery ordered (and prompt response from Li Ping to let me know about manufacturing times, etc.)

- Suzhou Bafang 8-Fun SWXK, 36V 250W 255RPM (model designed for 20" wheels)
- Tongxin 36V 180W 190RPM (model designed for 26" wheels)

The Bafang is a lot bigger and heavier than I imagined, but I'm getting used to it. The Tongxin is smaller, lighter. Both have 18 spoke holes per flange, so I now need to source 36-holes 16" rims (349mm). The motors have different diameters (Bafang: 125mm, Tongxin: 108mm - from spoke hole centers), so I need to source spokes of different lengths (I'm probably going to order from SJS Cycles, unless another tip comes up ?). I will probably opt for a 2-cross lacing design, and I will definitely use the spreadsheets from the Sheldon Brown website to calculate the required dimensions.

Each motor have a 10mm flat spindle, but the Tongxin has got a 12mm thread. The torque washers on both kits look decent enough, but there's clearly going to be some DIY challenges to make everything fit safely within the widened forks.

The controller is tiny, perhaps because I always imagined it bigger from the photos...Anyway, that's good news, as it'll look neat on my Brompton. It's custom-made by e-Crazyman (Keywin Ge, who uses Shenzhen Sucteam units, just like Infineon controllers it seems, marked as EB806 / XC-C-3).

I ordered a high-quality battery connector, which I think will be worth its money in the long term (Hirschmann STAS).

Product Browser Page

 

[daniel.weck]

Each kit comes with:

- brake switches (quite small)
- thumb throttle (which I prefer over bulky twist grips)
- 3-way switch (pre-defined speed/power selection)
- Pedal Assist Sensor
- specially-configured controller

The build quality looks good. Only long-term use will say, but so far so good.

 

[daniel.weck]

The "beast":

 

[daniel.weck]

The motors, side-by-side:

- Suzhou Bafang 8-Fun SWXK (100mm wide), 36V 250W 255RPM (model designed for 20" wheels)

2.905 Kg

- Tongxin (80mm wide) 36V 180W 190RPM (model designed for 26" wheels)

2.07 Kg

 

[AndyOfTheSouth]

Thanks. Looks very interesting. Please post as you work through the process - I for one would like to know! Is that an 80mm Tongxin from Frank?

 

[jerrysimon]

Yes Daniel please keep posting I am really interested to see how the builds go.

I am not sure if that is a later Bafang than mine, looks like it. Mine is black. I have heard that the newer Bafang's have a better free wheel and are much quieter.

I too want to experiment with a Tongxin and a much lighter NiMH battery on a very light fixed wheeled bike, so I will be watching your build closely.

I for one would like to know! Is that an 80mm Tongxin from Frank?

From what I remember in his other posts Andy I think it is. I think he purchased both from Frank.


Edit :Ah I should read the thread closer the Fun is for a 20" wheel. Mine is in a 26" wheel.

AND that Tongxin is the 108mm one. Where did you get it ? That's exactly what I want as Frank only has 82mm ones

Regards

Jerry

 

[daniel.weck]

Is that an 80mm Tongxin from Frank?

Yes.
/Daniel

 

[daniel.weck]

I am not sure if that is a later Bafang than mine, looks like it. Mine is black. I have heard that the newer Bafang's have a better free wheel and are much quieter.

On the latest model, the cable entry is on the side, not into the spindle.

Cheers, Dan

 

[jerrysimon]

(Bafang: 125mm, Tongxin: 108mm - from spoke hole centers)

Sorry about the PM daniel I just read your reply. The above post says you have a 108mm Tongxin

Regards

Jerry

 

[daniel.weck]

Sorry about the PM daniel I just read your reply. The above post says you have a 108mm Tongxin

The entire quote is: "The motors have different diameters (Bafang: 125mm, Tongxin: 108mm - from spoke hole centers)"

As you can see, I am talking about the *diameter*, not the *width*

 

[jerrysimon]

Yes Daniel I just realised that sorry.

I see what measurement your talking about now. I just checked the spec on Franks site

Jerry

 

[jerrysimon]

How are you going to make up the gap from 82mm, to the width of your inside fork measurements ?

Regards

Jerry

 

[daniel.weck]

How are you going to make up the gap from 82mm, to the width of your inside fork measurements ?

Steel fork widening. That's how all the Brompton kit suppliers do it, based on an original Brompton fork (which has special features such as the folding stay).

Bicycle Frame Spacing

Cheers, Dan

 

[jerrysimon]

I really am confused now lol

So your putting this in a smaller wheel ?

I thought the 82mm was too narrow so the fork width would have to be reduced not widened ? I have read that you can use washer spacers or nuts.

My forks are 100mm wide which is why I am apprehensive about ordering one of these 82mm ones if I can find the wider 100mm Tongxin.

Regards

Jerry.

 

[cirrus18]

The Tongxin is smaller, lighter. Both have 18 spoke holes per flange, so I now need to source 36-holes 16" rims

Your posting sounds like you're going to put both motors on 16 inch wheels.

I have been reading on the forum that for 16 inch wheels, for a maximum speed of 20 Kph (12 mph), a motor rpm of 260 is required. For a better top speed, people seem to be using even higher rpm motors.

So, you're Bafang motor at 255 rpm is about right, but slow. The Tongxin would be painfully slow but a very good hill climber.

Perhaps I've got it all wrong but it would be interesting to know what you are exactly planning in regard to wheel sizes.
Did Frank supply the high-quality battery connector?

 

[flecc]

It's inevitable that this latest Bafang is appreciably heavier, the large diameter bearing surrounding the stationary centre side plate carrying the cable will contain far heavier components than the original small centre ballrace.
.

 

[jerrysimon]

Your posting sounds like you're going to put both motors on 16 inch wheels.

Yes re-reading his post again I think your right. I misred the first post which talked about the Tongxin being "designed" for a 26 wheel, though Flecc seems to imply in another post it has been more reliable in a smaller 20" wheel.

I really should get off this forum and get back to work

Regards

Jerry

 

[daniel.weck]

My bikes are a Brompton and a clone called Merc.
They are folding bikes, with 16" wheels and very narrow forks (< 80mm).
I will probably look into building a full-size folding bike as well, based on the Tongxin (if I end-up being disappointed by the low speed/RPM of the motor, which is designed for 26" wheels).
The 100mm-wide Tongxin is probably a better choice for a regular-size bicycle, ... but it's hard to source.

I really am confused now lol

So your putting this in a smaller wheel ?

I thought the 82mm was too narrow so the fork width would have to be reduced not widened ? I have read that you can use washer spacers or nuts.

My forks are 100mm wide which is why I am apprehensive about ordering one of these 82mm ones if I can find the wider 100mm Tongxin.

Regards

Jerry.

 

[daniel.weck]

So, you're Bafang motor at 255 rpm is about right, but slow. The Tongxin would be painfully slow but a very good hill climber.

That's correct

If the painfully-slow but powerful hill-climber Tongxin setup disappoint me, then I will build myself a 26" folding e-bike instead.

Did Frank supply the high-quality battery connector?

Yes, 14 Euros.

Cheers, Dan

 

[daniel.weck]

I misred the first post which talked about the Tongxin being "designed" for a 26 wheel, though Flecc seems to imply in another post it has been more reliable in a smaller 20" wheel.

I have re-written it as 'model designed for 20/26" wheels', which I think is less likely to confuse readers
These little motors come in different versions, with different RPM specifications under nominal power, to suit different wheel sizes.