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

[daniel.weck]

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.
.

The kit available from The Electric Transport Shop (Sparticle) uses the 24V version of the Suzhou Bafang (8-Fun) SWXK...could it be a lighter model ? More importantly, could it have smaller dimensions ?

 

[cirrus18]

The kit available from The Electric Transport Shop (Sparticle) uses the 24V version of the Suzhou Bafang (8-Fun) SWXK...could it be a lighter model ? More importantly, could it have smaller dimensions ?

I see that on Frank's page, the specification for his motor gives it a weight of 2.78 KG, so it isn't that much heavier than the Tongxin.
If you have some kitchen scales, it would be interesting if you would please let us know the weight of each motor.

 

[daniel.weck]

If you have some kitchen scales, it would be interesting if you would please let us know the weight of each motor.

- 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

 

[monster]

you can get any size 14g spokes from ebay. just seach for them cheap and good service.

 

[daniel.weck]

you can get any size 14g spokes from ebay. just seach for them cheap and good service.

I've worked out the desired spoke length, using the "spoke-calc" spreadsheet (cross-2 lacing pattern): Bafang: 126mm, Tongxin: 130mm

SJS Cycles sell 14g short steel spokes, but at 30 GBP per wheel (including brass nipples, excluding delivery), I am willing to find a cheaper supplier I will check fleeBay (EDIT: yep, 27 GBP delivered...from Tawain).

British made 14g stainless steel plain gauge spoke

Candidate rims (36 holes 349mm 16") ... if my findings are correct, 330mm ERD (Effective Rim Diameter):

Sun CR18 16 x 1 3/8 / 349 Side Wall Rim 36 Hole

Sun CR18 16 x 1 3/8 / 349 ABT Side Wall Rim

From the Sun CR-18 webpage:

Welcome to the SUNringlé Web Site. Featuring Wheels, Hubs, Rims, for Mountain Bikes, BMX, and Road Bikes.

SIZE:
406mm, 451mm, 507mm, 541mm

E.R.D.:
389, 438, 494, 532

I therefore estimate the 349mm rim to have an ERD of 330mm (I will double-check when I receive the rim).

 

[jerrysimon]

Great pics and info Daniel.

I would love to have a go at building my own wheel but I am not sure I could

I see you can do short courses on how to do it. Don't you need special tools/equipment ?

My local bike shop said they would spoke up a hub motor for me, for £50.

Regards

Jerry

 

[daniel.weck]

I would love to have a go at building my own wheel but I am not sure I could

I see you can do short courses on how to do it. Don't you need special tools/equipment ?

My local bike shop said they would spoke up a hub motor for me, for £50.

You should check this:

Building Bicycle Wheels by Sheldon Brown

 

[jerrysimon]

Thanks interesting web pages and other articles.

I think if I was going to do it a short course would be my preference.

Regards

Jerry

 

[cirrus18]

- 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

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

2.905 Kg

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

2.07 Kg

Many thanks for the information. At 2.905 KG it's a little heavier than their specification but not worryingly so.
The Tongxin motor certainly is lighter but then they have had a lot of problems with them breaking up.
I had a word with Frank on the telephone and asked him which was the most reliable out of the two motors and he said that he would recommend the Bafang.
I think reliability is more important than the extra weight don't you?.

 

[daniel.weck]

Many thanks for the information. At 2.905 KG it's a little heavier than their specification but not worryingly so.
The Tongxin motor certainly is lighter but then they have had a lot of problems with them breaking up.
I had a word with Frank on the telephone and asked him which was the most reliable out of the two motors and he said that he would recommend the Bafang.
I think reliability is more important than the extra weight don't you?.

Yes, the Tongxin becomes unreliable when put under too much load. It is a small lightweight silent low-power motor. If you accept its limits, and setup the controller to protect the motor against unreasonable current loads, then it'll be fine. Yes, the "gears" will slip if too much torque is applied, but for gentle use on a e-bike that looks and sounds like a regular unassisted bike, the Tongxin is unbeatable.

...that's the theory anyway

I'm looking forward to receiving the battery so I can at least run the motors unloaded, on the forks (to check they work fine, measure the rotational speed, listen to the noise they make, etc.).

 

[Andrew harvey]

The Bafang motor is their latest SWXK, it's been about 4 years in developement and is the lightest Suzhou Bafang currently produce. They have reduced weight by lightening the internal chassis, They are currently my favorite hub motor.
The photos show the attention to detail the manufactorers have made on the outside, open them up they're as nice inside. The freewheel looks like all the others found on simaler motors but does indeed seem to offer minimal added resistance. I've done a few checks with my Cycle analyst in the past on several motors, typically you get under 50 watts worth of clogging torque driving a direct drive motor at no load speed (Crystalyte mainly used), and the freewheel here is far nicer to pedal at speed.
If you need more speed they will run at 48v, without getting warm.

 

[daniel.weck]

The Bafang motor is their latest SWXK, it's been about 4 years in developement and is the lightest Suzhou Bafang currently produce. They have reduced weight by lightening the internal chassis, They are currently my favorite hub motor.
The photos show the attention to detail the manufactorers have made on the outside, open them up they're as nice inside. The freewheel looks like all the others found on simaler motors but does indeed seem to offer minimal added resistance. I've done a few checks with my Cycle analyst in the past on several motors, typically you get under 50 watts worth of clogging torque driving a direct drive motor at no load speed (Crystalyte mainly used), and the freewheel here is far nicer to pedal at speed.
If you need more speed they will run at 48v, without getting warm.

I have the same positive feeling about this motor, thus why I will prioritize the building of my main Brompton folding bike with the Bafang (probably the trickiest setup due to the extreme fork widening, but well worth the effort it seems).

I bought the Tongxin because it was cheap, and I wanted to try different configurations. I intend to learn a lot through DIY and experimentation. If it doesn't work for my second Brompton (well, a Merc copy actually), I can just reverse the operation and lace the motor into a 26" rim instead (as you know, the 190rpm version of the Tongxin is designed for this size of wheel). I fancy doing a lightweight folding full-size bike conversion, probably based on a Dahon (I'm watching the second-hand market for these)

 

[AndyOfTheSouth]

Hi Dan

You mention a lightweight Dahon - I've got an Espresso - 26" and good to ride. The Jack looks better and has more interesting tyres (Big Apple) and is slightly lighter, but is more expensive, has a smaller gear range and lacks the steel forks of the Espresso. I bought mine from Warlands Cycles of Oxford for under £300. The owner seems to know his stuff about bikes (including torque arms!).

I have just fitted an older style Bafang to it but will move it to another bike soon. I am going to get a Tongxin and fit it to either that bike or, more likely, a lightweight 20" or 24" bike to maximise hill-climbing ability. I'm not concerned about the top speed of motor assist.

So you can understant that I am following your projects with interest!

Andy

 

[flecc]

Daniel, when you get a chance can you let me know the spindle size on that latest Bafang? Is it the same 12 mm as the cable entry spindle or back to the standard 10 mm bike size?

If it's 10mm it holds out the prospect of rear motors able to have the cassette system instead of multi-sprocket freewheels.
.

 

[daniel.weck]

Hi Flecc, as per my first post:

"
Each motor have a 10mm flat spindle, but the Tongxin has got a 12mm thread.
"

Looks like good news then

Daniel, when you get a chance can you let me know the spindle size on that latest Bafang? Is it the same 12 mm as the cable entry spindle or back to the standard 10 mm bike size?

If it's 10mm it holds out the prospect of rear motors able to have the cassette system instead of multi-sprocket freewheels.
.

 

[daniel.weck]

If money was no object, this would be mine:

Folding Bicycles and Folding Bicycle Accessories by Dahon: Cadenza 8

Invisible folding mechanism, 8-speed Shimano Alfine gear hub, no front suspension, Schwalbe Big Apple, Ergon grips, .... I mean, it's just perfect out of the box !!

Yes, the fork is alloy, but a torque arm is not hard to make/source:

Folding Bicycles and Folding Bicycle Accessories by Dahon

Hi Dan

You mention a lightweight Dahon - I've got an Espresso - 26" and good to ride. The Jack looks better and has more interesting tyres (Big Apple) and is slightly lighter, but is more expensive, has a smaller gear range and lacks the steel forks of the Espresso. I bought mine from Warlands Cycles of Oxford for under £300. The owner seems to know his stuff about bikes (including torque arms!).

I have just fitted an older style Bafang to it but will move it to another bike soon. I am going to get a Tongxin and fit it to either that bike or, more likely, a lightweight 20" or 24" bike to maximise hill-climbing ability. I'm not concerned about the top speed of motor assist.

So you can understant that I am following your projects with interest!

Andy

 

[daniel.weck]

I am going to get a Tongxin and fit it to either that bike or, more likely, a lightweight 20" or 24" bike to maximise hill-climbing ability. I'm not concerned about the top speed of motor assist.

There seems to be quite a range of Tongxin models out there...let us know which ones you find. I really thought that the 260RPM models were only available in 24V, but it seems that both the Freedom and the Nano kits use 36V high-rpm versions ! (reminder: mine is 36V, 180W, 190RPM => low velocity) On top of that there is choice of 80mm and the 100mm...

My mind is boggling !

 

[AndyOfTheSouth]

I don't think you need worry too much about the Cadenza - you'd have to change the front brake straightaway (it's disc) and for all its sophistication, it is heavier than either the Espresso or the Jack!

 

[daniel.weck]

I don't think you need worry too much about the Cadenza - you'd have to change the front brake straightaway (it's disc) and for all its sophistication, it is heavier than either the Espresso or the Jack!

Oh that's right ! The Tongxin doesn't play nice with disc brakes !!!

Regarding the weight: yes I was very surprised to find that out ! The older models look so much bulkier compared to this slick new folding frame !

Anyway, the main selling point for me is the 8-speed gear hub (Shimano Alfine), which is a fantastic piece of kit.

 

[monster]

are you expecting any problems using the same controller on both motors?