The Brompton Tongxin/or alternative hunt continues

[jerrysimon]

Well after loads of emails and searching I now three DIY possibilities for converting my Brompton when it arrives this month

1. Use a Cyrstalite 209 75mm front hub motor ready built on a 16" wheel see here

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Advantage pops straight into existing forks, disavantgae its heavey (4.5kg in the wheel )

2. I have a chance of a one off Tongxin 80mm 260RPM but its only 24 volt. This is ready built in a Brompton 16" wheel.

Advantage light, almost what I am looking for and can run off two light 12V 4.3 Ah NiMh power packs (1.2kg). Disavantage only 24v ?

3. A Tongxin 36volt 260RPM 100mm motor (not built in a wheel). It looks like I have found a source for 100mm Tongxin motors. I will confirm later.

Avantage very close to what I am looking for. Disavantage I need to get it built in a wheel and what am I going to do about expanding those 75mm forks

None of the very few kit providers want to sell me a set of ready made Brompton 100mm forks.

Failing all the above its either a kit from freedom-e or EWC sigh.......

Regards

Jerry

 

[AndyOfTheSouth]

Jerry - sympathies. What about the Bafang used by Dan. Well, not that actual motor, but you know what I mean...

 

[jerrysimon]

Whats the view on a 24v motor for a Brompton given I live in Cambridge and its pretty flat ?

The light battery option is also VERY attractive.

Regards

Jerry

 

[jerrysimon]

Jerry - sympathies. What about the Bafang used by Dan. Well, not that actual motor, but you know what I mean...

Andy I think if I did get the Bafang I would probably get the 24v one. I really am not happy about spreading the forks to 100mm though.

I am told that the 24v Bafang is more than enough power in a Brompton.

I should also add that I continually hear that the Tongxin is prone to roller wear and is unlikely to last more than 18 months with everyday use. I am still convinced though that this is when it is used aggressively e.g on standing starts especially hilly ones.

Regards

Jerry

 

[AndyOfTheSouth]

Since you live in Cambridge, why not simply leave the Brompton as it is?

If you really want to add a motor, surely it has to be a Tongxin or clone in order to make use of the Brompton's portability. The indications seem to be that the Tongxin would work in the Brompton without being subject to too much load.

But then, I haven't yet got a Tongxin so I am speaking from ignorance, alas.

 

[jerrysimon]

Since you live in Cambridge, why not simply leave the Brompton as it is?

If you really want to add a motor, surely it has to be a Tongxin or clone in order to make use of the Brompton's portability. The indications seem to be that the Tongxin would work in the Brompton without being subject to too much load.

But then, I haven't yet got a Tongxin so I am speaking from ignorance, alas.

Andy re your first point your right but I am a lazy ass and like assistance

The Tongxin IS the answer but a 36v 260RPM 80mm one ready built in a wheel which really means the Freedom-e or EWC kit. I am just being a tight git

Regards

Jerry

 

[flecc]

Whats the view on a 24v motor for a Brompton given I live in Cambridge and its pretty flat ?

In a fairly flat area I think it's preferable on a folder where weight is so important, as it helps enable a smaller battery. Wisper have chosen this route with their new 806fe, 24 volts and probably Suzhou Bafang motor:

 

[jerrysimon]

Yes Flecc I think your right. And if all the above options fail then I think the Electric Transport Shop in Cambridge would provide that with their kit which includes a Bafang 24 volt and widened forks. I would still prefer to use my own lighter battery though.

Being local I would also have them on my doorstep for any comeback.

Regards

Jerry

 

[daniel.weck]

I am told that the 24v Bafang is more than enough power in a Brompton.

Well, the Tongxin rates at 180W continuous power, whereas the Bafang rates at 250W...now, that doesn't exactly reflect the reality, as it is more a "political" value than a practical one. In the real world, the power curve (and the peak power in particular) matters more, as that is a better indication of how much assistance will actually help you moving forward.

A a rule of thumb, a motor with a smaller Voltage will require more Amps to achieve a given Wattage. That translates into current draw from the battery, so the battery needs to be sized accordingly: a higher capacity does not just ensure a better range, but also more capacity to deliver "power" at one given time (e.g. when climbing a steep hill or facing strong winds) ... baring in mind this depends on the chemistry, discharge rate, etc.

I chose to go ahead with 36V kits (Bafang and Tongxin) because I realized that a 10Ah battery in LifePo4 chemistry offered a good compromise of size/weight/range/instant power. I ended up with a 180W 190rpm 80mm Tongxin because it was the only choice in 36V, and it was cheap enough for experimenting The other option at the time was 24V 100mm 180W 260rpm (more expensive, for some reason).

It is worth noting that I could run the Bafang with a 48V battery, and therefore get more pulling power out of it. However I would need to upgrade the controller as well. Let's not talk about "over-volting" the Tongxin

I should also add that I continually hear that the Tongxin is prone to roller wear and is unlikely to last more than 18 months with everyday use. I am still convinced though that this is when it is used aggressively e.g on standing starts especially hilly ones.

You mean roller slippage, not wear. There are other parts of the design that seem to be prone to failure or early fatigue (hollow two-part axle, casing, etc.)

The Tongxin on small wheels should be less exposed to stress though, thus why it is "perfect" for the Brompton.

 

[daniel.weck]

Well, you know my views on the Crystalite it's too big and heavy for a Brompton, it will kill your love for the bike and its magical folding design.

Widening steel forks is not hard, even with basic tooling. Doing it right is the hard part, in the sense that it highly depends on the motor's geometry (straightened dropouts, sufficient spacing, even on either side, etc.). The Bafang's bulk and torque washer design required fork adjustments that I had not foreseen (The Sparticle people at the Electric Transport Shop have their own technique...but they wouldn't share it with me). Getting sufficient clearance for the Tongxin was much easier, but this is only 80mm.

I wish I could give you some feedback on the Bafang vs Tongxin specifically in their application to the Brompton...but unfortunately I am not there yet I am expecting the Tongxin to offer much less assistance in the hills, but the silence, feather weight and discrete looks might win over me !

Cheers, Dan

Well after loads of emails and searching I now three DIY possibilities for converting my Brompton when it arrives this month

1. Use a Cyrstalite 209 75mm front hub motor ready built on a 16" wheel see here

Google Translate


Advantage pops straight into existing forks, disavantgae its heavey (4.5kg in the wheel )

2. I have a chance of a one off Tongxin 80mm 260RPM but its only 24 volt. This is ready built in a Brompton 16" wheel.

Advantage light, almost what I am looking for and can run off two light 12V 4.3 Ah NiMh power packs (1.2kg). Disavantage only 24v ?

3. A Tongxin 36volt 260RPM 100mm motor (not built in a wheel). It looks like I have found a source for 100mm Tongxin motors. I will confirm later.

Avantage very close to what I am looking for. Disavantage I need to get it built in a wheel and what am I going to do about expanding those 75mm forks

None of the very few kit providers want to sell me a set of ready made Brompton 100mm forks.

Failing all the above its either a kit from freedom-e or EWC sigh.......

Regards

Jerry

 

[AndyOfTheSouth]

Jerry - I wouldn't for one moment imagine that you are lazy.

To quote from the Lore of the Pedelecs:

'He who seeks the Way of the Tongxin cannot be lazy. Desperate, perhaps, but not lazy.'

 

[jerrysimon]

Jerry - I wouldn't for one moment imagine that you are lazy.

To quote from the Lore of the Pedelecs:

'He who seeks the Way of the Tongxin cannot be lazy. Desperate, perhaps, but not lazy.'

Andy its ok. And everyone else thanks for you input.

Regards

Jerry

 

[Andrew harvey]

I've got both a Tongxin and a Bafang, the SWXK version, both running at 36v.
The Tongxin is about 3 1/2 years old now, whilst the Bafang is 6 months old.
I'm running the SWXK with an Infineon controller with a 15 amp current limit set.
The Tongxin is about 2lb lighter but offers little loss in power in the real world. I can climb Zion Hill in Kidderminster, I do most days on the way home from work even though it's the long way home, with both motors and at the same sort of speed. 1 in 7 hill around 7mph, running a 52 tooth chain ring 20 tooth rear sprocket and 1st gear on a 7 speed Nexus, without the motor I couldn't get up the hill without changing down the front ring.
The noise on the Bafangs of old was just resonance, common with a lot of electric motors under load, with the lightened SWXK running as I do at 15A max current the noise is barely audible, it's about the same as a loaded Crystalyte. That's a huge improvement on the old motors but the low current helps.
All in all I'm really happy with the SW motor, it is I feel a great compromise for anyone worried about Tongxin reliability, ( which I personally have no fears over ). Both motors lack some of the brute force of the Ezee and Whisper motors but uses a lot less current, yet still manages to pack a lot of low down torque in.
The next job on the list is a 24v SWXK, run with the 15A controller at 36v it should make an interesting project.

 

[daniel.weck]

None of the very few kit providers want to sell me a set of ready made Brompton 100mm forks.

Have you tried Ben Cooper at Kinetics ?

Kinetics - UK Specialists in Folding Bikes, Recumbents, Electric Bikes, Cycling Esoterica...

Kinetics - the blog…

 

[jerrysimon]

Have you tried Ben Cooper at Kinetics ?

Yep he said no can do

Regards

Jerry