September 3, 201015 yr http://daniel.weck.free.fr/BromptonBafangTongxin/IMG_3943.jpg Up to now, my DIY e-Brompton was equipped with the Suzhou Bafang motor (newer "8-Fun" SWXK unit), and my DIY e-Merc (Brompton copy) was equipped with the little Tongxin / Nano (albeit for experimental purposes only). Both e-bikes are front wheel drive 36V machines, designed so that parts can be easily interchanged. See my old build log for more information: http://www.pedelecs.co.uk/forum/electric-bicycles/4682-diy-stage-1-received-bafang-tongxin-kits-photos.html#post59183 One crucial difference is that the settings of the controller firmware are quite conservative in the case of the Tongxin kit, so that the motor runs "safely" below its recommended max power. The Bafang motor is rated at 250W whereas the Tongxin is officially a 180W unit. Obviously, these figures are nominal and do not represent the actual output. For example, I currently enjoy the relatively high torque and power offered by the 8-Fun motor: 400W peak, and happy to cruise at 380W continuous (all measured in real time by the Cycle Analyst). The Bafang motor would actually happily take more volts (i.e. from a 48V battery+controller) or more Amps (by pushing the 36V 15A controller to the max, or by using a bigger 20A controller), either way this would effectively result in delivering more power (i.e. beyond 400W peak). The Bafang is well-known to handle higher loads than its factory default, due to its robust construction (nylon-geared brushless no-Hall-sensors 250W unit, 255rpm for 16" wheel, 20km/h max). By replacing a single nylon gear (out of 3 in total) with a steel one, the motor would be noisier but it would be more reliable under load. I decided to make an experiment by using the Tongxin motor with the controller currently configured for the Bafang motor. I would essentially "overclock" the little Tongxin by feeding it more Amps than recommended. Thanks to the 3-power-level switch, I would be able to give the little motor a break by using level 2 (70%) instead of level 1 (full power). I could re-configure the Tongxin's 6-MOSFET 15A-max controller from e-Crazyman (Shenzhen Sucteam, Infineon EB806-XC-C-3 board), using USB and the ParameterDesigner.exe software. However I decided to simply swap the front wheel on the Brompton, as all the hardware is compatible. "Simples" ! The Tongxin is a smaller, more fragile motor based on friction rollers rather than permanently interconnected planetary gears. There is the benign risk of slipping under excessive load, but there is also the more damaging risk of stressing one of the inner parts, such as the rather weak axle wall. Never mind, I decided to go ahead as the motor itself didn't cost much, and it was sitting unused in a shed up to now ! I originally widened my Brompton forks to accommodate the bulky 8-Fun motor (100mm), so I used large steel washers to keep the narrower Tongxin in place (80mm). I then simply connected the 3 phase wires directly to the controller...easy peasy. RESULT: I rode 11km with at least 5km of steep hills, and I intentionally pedaled lazily to let the motor take the strain. The little Tongxin happily took 360W continuous (380W peak), without noticeable overheating on the motor's shell. The outside temperature was about 25 Celsius, the temperature inside the controller bag was 40 degrees max...all normal ! The 10Ah LiFePO4 battery from Li Ping behaved normally, as expected. Even with 400W peak and 380W continuous I am way below the recommended discharge rate. So what's next ? Well, I love how silent and light the Tongxin motor is. I will continue testing this configuration (hopefully not to destruction). I actually enjoy having to pedal harder: the power delivery of the Tongxin is much more "discrete" than the Bafang, which encourages putting-in extra human effort ! Note: the particular Tongxin model I own is a 190rpm motor designed for larger wheels (26"), so I effectively get less top-end speed with my tiny 16" wheels...maybe this explains why the motor tolerates higher levels of torque under load. Anyhow, be aware of the risks incurred when "overclocking" a motor !
September 4, 201015 yr I am a little confused Dan (nothing new). So your not overvolting it, just drawing more current by using the Bafang controller ? The silent running of the Tongxin weighs heavy in their favor as far as I am concerned. My Tongxins are too precious and too hard to replace, to risk overvolting. Regards Jerry Edited September 4, 201015 yr by jerrysimon
September 4, 201015 yr Author So your not overvolting it, just drawing more current by using the Bafang controller ? Correct, I am over-amping it
September 4, 201015 yr I ran a 190 rpm Tongxin in a 700c wheel with the ezee torq controller in a torq. I am assuming that the controller would have been rated at 20 amps. I rode like this for year or about 3000 miles and the motor never missed a beat (in fact I still have the motor). It couldn't take full throttle off the line but would cruise up to 17 mph and pull surprisingly well up most hills. It was for me the perfect motor being so descrete and silent and did give me confidence in the tongxin. The only thing letting this combo down was the wiring and being tied to the dreadful ezee batteries and in the end I bought the Cytronex (via an agattu). This had a lower rated controller and the motor was less stressed being 175 rpm in a 700c wheel. However 18 months later and having broken 3 motors and two controllers I gave up on the Cytronex. I am not sure why the first motor was so strong and lasted so long, perhaps it was that the torq was throttle controlled rather than by switches as with the Cytronex. Edited September 4, 201015 yr by HarryB
September 4, 201015 yr Intersting Harry. My EBrompton is also throttle controlled. I am up to eight months now and approaching 1000 miles. That said, I did have to take it apart at about four months after it started quealling. The little springs had moved and were scratching the clutch plate/freewheel. A good clean and grease and its been working well since. Before I found out how to take them apart and got a special tool made, I abused it quite a lot to get it open (used a vice ). However it still seems to be going strong. I am guessing its luck in terms of failures. I have two spare motors so hopefully they will last me a few years. Its such a shame that they are so hard to source Regards Jerry
September 4, 201015 yr Author puncture... Just did 20km early this morning, this time I used mostly the intermediary power level, which seems to limit the current at about 8A max. The full power seems to deliver 10A. This explains the observed 380W peak and 360W continuous (36V LiFePO4 battery delivers 41V unloaded, and 37V including the voltage sag under load). The Tongxin is a great little motor, it does the job of helping me up the hills very well even though the bike luggage system was loaded with heavy objects. As expected the speed is not great (190rpm on 16" wheels...you do the maths), but that's actually perfect for me because when the power cuts off there is no drag to slow me down and I just keep on pedaling harder (hail human power ! ). On this particular ride I carried my toolkit...I'm glad I did as I had a puncture ! http://daniel.weck.free.fr/BromptonBafangTongxin/IMG_0265.jpg http://daniel.weck.free.fr/BromptonBafangTongxin/IMG_0266.jpg
September 4, 201015 yr Hi guys How did you get to know all this stuff? I love reading about what can be done with various motors and controllers etc but I always feel a bit of a twit afterwards I've been searching thru the forum and picking up bits and pieces but is there anything specific I can do to improve my understanding? I'm reasonably good at DIY and have some understanding of electrical wiring. Or is this stuff really only for the engineering members of the forum? I don't mean to hijack the thread but it just feels like a good place to ask the question. John
September 4, 201015 yr John of course your not hijacking the thread. Basically I was introduced to ebikes this time last year when I purchased a kit and fitted it to my mountain bike. Before then I knew nothing about ebikes though I did have an unstanding of batteries from my aero modelling hobby. To be honest if you want to tinker and get invovled in the DIY side the best way is to dive right in and get a kit and fit it to a bike you may have lying about. Of course you don't need to be an engineer or keen at DIY to enjoy ebikes as there are some great ready to buy models available and some really good shops that provide good customer service and backup. PS looking at your sig you have already fitted a kit. Regards Jerry
September 4, 201015 yr Hi Jerry - thanks for the reply:) As you mentioned I have fitted a kit and its because I enjoy tinkering that I'd like to learn more. I'd love to get a little bit more out of the motor - my average speed on my 16 mile commute is 16 -17 mph but after the 32 mile round trip there is plenty left in the battery. I'd sacrifice a little more speed for less distance. I suppose over time bits and pieces of information will stick and I'll get a better idea of whats involved. Cheers John
September 4, 201015 yr Author I suppose over time bits and pieces of information will stick and I'll get a better idea of whats involved. Exactly ! Gleaning information from this forum and others (like Endless-Sphere) is important. Besides learning technical facts, you also get to know people who are worth listening to when an argumentation / discussion is taking place (on this forum: Flecc of course but many others too). I hope you get to do your own DIY jobbies too, it's great fun ! Cheers, Dan
September 4, 201015 yr Hi Daniel, Does that fancy looking tyre lever thing resolve the problem Jerry mentions in the other thread with getting tyres on and off the Sun rim? Just did 20km early this morning, this time I used mostly the intermediary power level, which seems to limit the current at about 8A max. The full power seems to deliver 10A. This explains the observed 380W peak and 360W continuous (36V LiFePO4 battery delivers 41V unloaded, and 37V including the voltage sag under load). The Tongxin is a great little motor, it does the job of helping me up the hills very well even though the bike luggage system was loaded with heavy objects. As expected the speed is not great (190rpm on 16" wheels...you do the maths), but that's actually perfect for me because when the power cuts off there is no drag to slow me down and I just keep on pedaling harder (hail human power ! ). On this particular ride I carried my toolkit...I'm glad I did as I had a puncture ! http://daniel.weck.free.fr/BromptonBafangTongxin/IMG_0265.jpg http://daniel.weck.free.fr/BromptonBafangTongxin/IMG_0266.jpg
September 4, 201015 yr Pedalo, As I said its not impossible to get the tyres on and off but the first time you try to put a Marathon Plus on a 16" Sun CR18 rim, you will immediately realise what a struggle its going to be if you have to take it off again I can actually get the tyre on without levers just using the palms of my hands and my thumbs, but it takes about 30 mins and that is having done it several times now. The Sun rim has such a shallow well that the bead really has to be worked into it, to get the last bit over the rim edge (compare it to the Brompton one and you will see). Getting it off requires tyre levers and thats when you damage the bead covering. Other tyres are not so bad (but still get damaged when you take them off) but you really don't want punctures, so the Plus is the only real option. As Dan has confirmed the rubber round the bead will get damaged. This then means once refitted the exposed metal bead will rub on the tube and another puncture is likely to follow in a few months of riding. I am in the process of replacing my Sun rims with Brompton blank ones, drilled with 36 holes. Sorry to hijack the thread Dan, but I know Pedalo is about to build one of these and I want to save him a lot of hassle. When we built ours there was no alternative to the Sun rims, but now there is. Regards Jerry Edited September 4, 201015 yr by jerrysimon
September 5, 201015 yr Author Sorry to hijack the thread Dan, but I know Pedalo is about to build one of these and I want to save him a lot of hassle. When we built ours there was no alternative to the Sun rims, but now there is. All good, no worries.
September 5, 201015 yr Brompton undrilled rims Hi Jerry You mention you are getting an undrilled Brompton rim - could you let me know where from - is it SJS? We have a few 36 hole motors that we would love to use but couldn't get these a while back. Thanks!
October 20, 201015 yr Daniel.weck, What exact (bafang?) controller do you use in this experiment to drive your Tongxin hub-wheel? Have you got a link to a store or a picture of the controller? Thankyou Carsten J
October 20, 201015 yr Author Daniel.weck, What exact (bafang?) controller do you use in this experiment to drive your Tongxin hub-wheel? Have you got a link to a store or a picture of the controller? Thankyou Carsten J Hi, e-Crazyman sells them (small 10A programmable brushless sensorless controllers with 3-way "power" switch): eBay My World - e-crazyman Lots of photos in my build thread: http://www.pedelecs.co.uk/forum/electric-bicycles/4682-diy-stage-1-received-bafang-tongxin-kits-photos.html#post59185 Cheers, Dan
October 20, 201015 yr Ask him, I ordered a controller a few weeks ago and it was sent from a London postal address...
October 24, 201015 yr "small 10A programmable brushless sensorless controllers with 3-way "power" switch" I can´t find any such (36v) controller on his website. "Ask him" How do I ask him? I cant find an email adress to get in contact with E-crazyman Carsten J
October 24, 201015 yr Author "small 10A programmable brushless sensorless controllers with 3-way "power" switch" I can´t find any such (36v) controller on his website. "Ask him" How do I ask him? I cant find an email adress to get in contact with E-crazyman Carsten J Try this: ecrazyman@gmail.com ...or otherwise via the eBay messaging system.
April 25, 201412 yr Author It's been a while since I last used the 36V Bafang "8-Fun" SWXK 255rpm hub motor (rated 250W) which I have laced into my 16" Brompton wheel. Instead, I have been riding with the much quieter 36V Tongxin 190rpm (rated 180W). Both motors are brushless no-Hall-sensors with 3 phase wires (I use the same controller for both), but the Bafang is nylon-geared unlike the Tongxin which uses friction rollers rather than permanently-interconnected planetary gears (so in theory, the Tongxin is more likely to slip under heavy load). Recently, I configured my small 6-FET 15A controller (Infineon XC846 chip, EB806 board) to handle higher currents, and the Tongxin is happily driving the wheel at 12A continuous for a few minutes (max assistance in uphill rides). Of course, most of the time the e-assistance reaches 8-9A max, which is a safer peak power. However it is good to see that this perky little Tongxin can handle the torque without slipping. My guess is that the 190rpm model is really geared for larger wheels, so maybe the elliptical friction gear demultiplication is such that I am loosing top speed in favour of reliable low-end torque (which is fine by me, as I only need assistance at low speeds). I have configured my 3-speed switch so that the middle setting is safe for the Tongxin (9-10 amps max), the low setting is good for walking alongside the bike (e.g. when pushing it uphill), the high setting is 100% (basically, whatever phase/rate current I set in "KeyWin eBike Lab" ParameterDesigner.exe) I still use the same two batteries: 10Ah LiFePO4 Li-Ping "big" pack + 2.6Ah A213 "mini" pack. Both handle over 1C discharge rate without complaints. I am still trying to figure out what the stock settings are for my controller, any idea? (I've been searching on endless-sphere as well) Cheers, Daniel http://daniel.weck.free.fr/BromptonBafangTongxin/IMG_3943.jpg http://www.pedelecs.co.uk/forum/electric-bicycles/4682-diy-stage-1-received-bafang-tongxin-kits-photos.html#post59183
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