TongXin (a.k.a. Nano) motor project

[Jeremy]

I've just heard that my wheel will be ready to collect from my LBS tomorrow. It's a 406 rim ("20") so I'm hopeful that the slippage problem reported won't be a problem. From what I can gather the TongXin/Nano works quite well on small wheeled bikes, presumably because the torque demand is much lower.

I'm only looking for quiet, modest power assist, with low weight and free wheel drag. If I were after more power then I'd probably stick with the Crystalyte I already have, as that is way more powerful and heavy than I need, although it is fairly quiet.

Like Frank, I should have a report on performance before Christmas.

Jeremy

 

[Honk]

Thankyou for your answers.
I think I have to design and build the bicycle hub motor myself from scratch.
A couple of years ago I designed a brushless axial flux motor and I could use
my knowlegde from that experience to design the perfect electric hub motor.

It will have great torque but no internal gears. I might weigh some more
than the Tongxin motor, like 3.5kg, but there will be no gear problems.
I could ask my friend to laser cut the motor laminates for high precision.
If I use N50H ndfeb magnets I'll get great torque and heat withstand as well.
The windings will be made of copper bars for the lowest resistance possible.
Early calculations point towards 0.046R internal resistance.
This equals to an efficiency higher than 85% at maximum load.

But if I find another motor that have the same properties I might just buy that instead.

 

[flecc]

Where direct drive is concerned Honk, the BionX motor in it's 350 watt US/Canadian version is very good, so you might like to investigate that first.

The UK 250 watt version is quite a lot weaker, and the Sparta direct drive motor is also not very powerful. That's the only ones I know anything about, but there's the Chinese Goldenmotor as well, nothing known on that.
.

 

[Leonardo]

but there's the Chinese Goldenmotor as well, nothing known on that.
.

In Italy we had rather bad experiences with the Goldenmotor: Chinese poor quality in the most classical form. On the other hand we have quite good experiences with the Crystalyte and the Nine Continent kits, both Chinese direct drive hub motors if I'm not wrong. They are not the Bionx of course but they seem to be good value for money, especially the NineC.

By the way: the first Nano motor has landed in Italy, on the Brompton of a friend of mine and the first results are quite amazing, exactly the same as A to B.

 

[flecc]

Thanks Leonardo, I had heard from one source that the Goldenmotors were poor quality, but with no confirmation until now.

Good to hear the Brompton-Nano has lived up to expectations. I'm sure this is how this motor is best, with 24 volts in a small wheel, and in the Brompton's 16" wheel, it seems an ideal application. The torque then is unlikely to make the drive slip a problem.
.

 

[Leonardo]

If I'm not wrong the Nano Brompton is 36V though... Is there anything in the driving that one can bear in mind in order to reduce the drive slip risk?

 

[flecc]

Thanks Leonardo, I'd assumed 24 volts to keep the battery weight down on a folder, A to B not mentioning the voltage in their test, only the watt hours.

All you can do is to avoid snapping open the throttle at low speeds, since that's the most likely to provoke a slip in the drive. It's not going to be a big issue in a 16" wheel though, so if you just progressively open the throttle all the time, rather than treating it like an on/off switch, it's unlikely to give any trouble.
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[frank9755]

Tongxin actually makes two different controllers - one for 24v and one for 36v, but they deliver the same power with the 24v controller delivering proportionately more current, and the motors being geared to compensate. A good illustration of the rule that more volts does not automatically mean a more powerful motor!

You are correct, Leonardo, the Nano application uses the 36v version, to enable it to operate at lower currents. The battery sold with it is a small, I think 7Ah, Li

Frank

 

[flecc]

Interesting Frank, I would have expected the differently geared rollers on the 24 volt motor to be prone to more slippage, due to the lower rotational speed and higher relative torque, but users are reporting that 36 volts brings the problem on more. I wonder if they really are absolutely the same power, or just the 24 volt controller current raised towards that?

At 36 volts, the battery used in the A to B test would have been about 7.4 Ah.
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[Jeremy]

There seem to be at least three types of TongXin controller, as far as I've been able to find out. I have a 36V 15A controller, but the two most common types seem to be the 24V 15A and the 36V 10A.

It's a real detective job trying to pin down the exact specs of these Chinese products!

Jeremy

 

[frank9755]

I've got my Tongxin working. Needed to fiddle around with a few connections. Took it for a spin round the block and was very pleased!

I'll report back in a few days time when I've tried it out properly.

Frank

 

[frank9755]

While taking my bike for its second test run it unfortunately developed a fault.

I was going along with the throttle engaged (on a flat road so only moderate load) when the motor cut out. I checked the fuse I had fitted to the battery and it had blown. It was a 20A fuse. When I got home, I replaced the fuse and it blew instantly. This happened again with throttle and motor disconnected from the controller - when there shouldn't be any current being drawn.

I checked the connections and they were ok. Am I right in thinking this sounds like a short-circuit in the controller? Should I be using a different fuse? I thought 20A would be enough given the controller is only rated at 12A

It was a shame, particularly as it was performing so well!

Has anyone experienced this type of fault, or have any bright ideas?

Frank

 

[Jeremy]

Sorry to hear of this problem, Frank. It does sound very much as if the controller may have developed a fault. The real snag is that the controller isn't easily repairable, as, if it's like mine, then it'll be potted with resin.

It might be worth checking the motor wires for a short, although this will need a pretty good multimeter, as the normal resistance of the windings will be very low. If the resistance between any two wires is much lower than on the others, then this might indicate a motor, rather than controller, problem. I would guess that the motor might be easier to get at to fix, although without striupping one down I'm not at all sure just how easy!

I have heard reports of the TongXin sensorless controllers being a bit flimsy, but have yet to look into the possibility of a more robust replacement. If I find anything suitable I'll post it here.

With luck my wheel might be ready by the weekend, so I should get the opportunity to test my motor out.

Jeremy

 

[frank9755]

It's definitely not a motor problem as it blows fuses when the motor (and throttle) is not connected. I've checked all the connections and they seem fine (ie nothing visible which could be causing a short). I fear it is something in the innards of the controller which, as you say Jeremy, looks pretty impregnable!
I've sent an email to Tongxin - let's see what happens. Good luck with yours.

Frank

 

[flecc]

Sorry to hear this Frank. Tony Castles of Electrodrive may know something about this, as he's been working on the Nano with the Brompton for some while in different experimental ways. He is sometimes away for a while after Christmas though, but here's his mobile number to try if you wish:

tel 07974 723996
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[Jeremy]

Someone on Endless Sphere has posted a link to the TingXin price list as an Excel spreadsheet, (prices in RMB) direct from TongXin in China. Here's the link: http://www.tongxin.net.cn/ebike_components0610.xls

The hub motor is just under £30, and the controllers seem to be just under £12 each. No doubt shipping, handling charges, duty and VAT will bump the cost up a lot, but even so they still seem quite reasonably priced.

It's interesting that they also sell a pedal torque sensor, complete with cranks and chain wheel, for just under £14, which I assume is a spring bias one.

Jeremy

 

[frank9755]

That's their price list. If you email them, as I did, they'll send it out. My kit came to about £120 delivered. Had to pay for a bank transfer but it managed to get through without VAT or import duty.
As you say, Jeremy, they're not expensive but, given mine isn't working, not yet clear that they're good value!

Frank

 

[frank9755]

Tongxin have replied to my email, which is good. They've asked me to send the controller back so they can fix it - so, alas, my new bike will be off the road for a week or two. Can't wait to get it back though - it was great while it lasted!
Frank

 

[Jeremy]

I'd be interested to know how they'd go about fixing it, as it looks pretty impregnable to me!

My guess is that they might just ship you a new one and try to do some failure diagnosis with the one you send back.

I bet it costs more than £12 to send the controller back in postage.

Hope everything gets sorted quickly - with luck my wheel should be ready this weekend, so I can give mine a go.

Jeremy

 

[HarryB]

My only thought about this is that if you were to order a TongXin motor and controller, then buy the hall sensor version rather than the sensorless. At least that way if the controller turns out to be rubbish then you could use a controller from another manufacturer - with the sensorless version you are stuck. Schwinn have proved it is possible to ruin this motor with a rubbish controller. The sensorless version is very clever but I don't think it adds much to the reliability as the sensors are in themselves very reliable - it is the rest of the motor will fail first. Sorry is this is bolting the stable door for those who have already ordered the motors (unless you are clever enough to make your own sensorless controller).