My Tongxin kit bike

[chantelauze]

TongXin cental axle is made of 2 separate axles



I am amending my past saying : out the 2 TongXin motors I bought 3 years ago , 1 went out of order due to improper use of a 48v battery pack on a motor supposed to accommodate 24 volt ( it’s entirely my fault and responsibility , as i already wrote )

But the other one was returned to me by a young friend of my daughter mentioning that the axle had suddenly broke apart ! ( but it was not flooded as I erroneously said previously … got confused with a hub motor from Taiwan with inbuilt controller ….very cleaver but very poor waterproof quality )

I can’t describe the conditions of that accident since I wasn’t driving it , and the driver was very young and athletic and probably ready for extreme conditions , I have always supposed . So how did he treat the front wheel hub motor , to such limits that finally the axle was broken ?

I have never known , but it may be interesting to know if other TongXin user had to suffer from a similar weakness from the axle …???

Also i discovered after the accident that the central axle is made of 2 separate axles that don’t go all the way in and out on each side , I suppose it could have explained for that weakness

As to other problems I don’t recall of any , except it’s the most pleasant motor I have ever tried in the last 3 years ( and I remember a good hill climbing , silence , and easy acceleration capacities )

To DIANA LIN at TONGXIN : any recommendation perhaps as to the maximum force or weight that the central axle can withstand ? any other report of similar accident ? can a cyclist of 80 kgs safely drive of it ? what about 120 Kgs ?

the cyclist that broke the axle was a youngster of 65 kgs and very athletic ; and I suspect he might have jumped from the side-walk onto the road a few times , but should that be enough to make one axle to brake down ?

3 years later , is the motor still made of two different axles or is there now one unique central axle …can you justify by photos of inside views ( 2 axles or 1 axle ? )

 

[john]

Yes, they are still 2 axles, welded to flanges which then bolt on to the body. This one I got about 6 months ago and took apart. Don't have any pictures I'm afraid.

I have not had any problem with the axles but I have had a ring gear break on one and on a second a magnet fell off. I also noticed water ingress on the first model but they seem to have better seals now.

My current motor has done about 1500 miles and seems to be holding up fine. Part of my journey is down a rough farm track and I have dropped the bike over a few fences. I also carry my 14 year old son on a crossbar seat sometimes so there can be a fair amount of weight on the front wheel. I do however have front suspension which should provide some axle shock protection.

My view is that this motor is built for maximum performance for minimum weight and cost. It seems to achieve that very well. However, the consequence of this seems to be that reliability may suffer.

Having repaired one of the motors, I now have a spare and am happy to risk another failure on that basis because it is such a joy to use.

 

[frank9755]

Interesting, John. Good to know you are getting decent mileage from it despite some demanding usage. Also well done on opening the motor up. I had understood they were pretty hard to open and hence were unrepairable, but clearly that is wrong.

I agree with your comment about performance, cost and reliability. I have a similar view. Given they are not too expensive I was happy to take a bit of a risk on reliability but treat it gently and enjoy the great performance!

Chantelauze, your comments are interesting also. I hadn't realised the axle was in two parts.
I have to say I am not optimistic that Tongxin will be able to give you the data. I've not seen any manufacturer provide that data - but I could be wrong!



Regards

Frank

 

[flecc]

I'd previously seen one US internet mention of spindle failures and the two part construction, but there was no substantiation or detail, so I've no idea of the veracity or whether misuse was involved.
.

 

[Kenny]

Hi Frank

I'm very impressed with your bike - It seems an excellent way of puting together an electric bike without the normal very expensive outlay. With such a small purchase price it "wouldn't be the end of the world" should the motor fail.

Could you please give a bit more detail of how you ordered the kit as I can't find any ordering info on the net
ie. Did you contact Diana directly at Tongxin?

Regards Ken

 

[frank9755]

Thanks Kenny

Yes, that's exactly what I did. I think I contacted her through this site which shows the kit they do. They've actually got a menu of components you can order from, depending on whether you need brake cut-outs, the type of throttle, etc.

It's Chinese new year this week so things may be a little quiet, but if you don't get anywhere let me know and I'll dig out the contact details I have.

Regards,

Frank

 

[Cyclezee]

Hi Frank

I'm very impressed with your bike - It seems an excellent way of puting together an electric bike without the normal very expensive outlay. With such a small purchase price it "wouldn't be the end of the world" should the motor fail.

Could you please give a bit more detail of how you ordered the kit as I can't find any ordering info on the net
ie. Did you contact Diana directly at Tongxin?

Regards Ken

Hi Ken,
you can email Diana Lin, overseas trading manager for TongXin @ xinyue_china@hotmail.com and download theTongXin prices spreadsheet here http://www.tongxin.net.cn/ebike_components0610.xls
She contacted me this morning, so she around. I have found her very helpful.

John

 

[Kenny]

Thanks for the info Frank and John - I'll post how I get on if I decide to go for the kit.

Ken

 

[chantelauze]

Li-ion & Li-Polymer packs from TongXin

from above web link at TongXin http://www.tongxin.net.cn/ebike_components0610.xls , does any one know what are those batteries ? the Li-ion seems to come with a BMS , but not the Li-Polymer

are you here Diana ? anybody else knows about those battery packs , that i consider reasonably priced ( but what about cycle life expectations and much more important : safety issues )

what Li-ion chemistry are you selling Diana ? Cobalt, Manganese , Ferrous phosphate or ?
is it safe to provide some Li-Po without a BMS that can monitor the different cells in coordination

 

[chantelauze]

TongXin consumption patterns seem a waste of energy , why ?

Frank ( and other members of course ) : if Frank is using the 36v x 13 Ah of his Lithium battery pack and can only go up to 25 miles , it looks like this supposedly efficient motor is using a lot of energy

36v x 13 Ah = 468 Watt/hour of energy tank , but only lasting 25 miles ( or 40 kms ) !

so apparently has a consumption pattern of 15 watts per mile ( or 9.5 watt per Km )

seems to me a lot , why ? is it the controller that would cause some problem ?

do you think Frank ( & other TongXin owners ) overtime that you could report other measurements so that we really know if that motor spends litlle ( like its size ) or a lot of energy ( in reverse proportion of its mini size ! ) ....

one australian member of Enlesssphere forum reports also very large capacity peaks of 20 Amp on it's Watts Up device , see underneath photos
does anyone have a power analyser or similar device , to confirm or infirm ?

 

[Jeremy]

Power consumption is almost entirely a function of the bike, rolling resistance, rider weight, terrain, aerodynamic drag, wind, air temperature etc. The difference between the most efficient motor and controller and the least efficient is much less significant than these other factors.

15Wh per mile is not at all unreasonable for an upright bike. This figure may well vary by plus or minus a couple of Wh's between one day and the next anyway. Assuming an average speed of 15mph, then the flat, zero wind, power demand would be about an average of 170W. 170W at a typical 80% efficiency gives a power consumption of about 212W. 212W from a 36V battery is about 6A average. The theoretical power per mile for a power consumption of about 212W at 15mph is 14.1 Wh, pretty close to the figure that Frank seems to be getting, especially as this figure assumes no hills and no wind.

It's unlikely to be inefficiency in the controller, as this would appear as a lot of heat, so would be easily spotted. The same goes for the hub motor.

20A is a modest peak current, my Crystalyte 405 easily hits the 35A current limit on the controller for very short periods.

Jeremy

 

[Tiberius]

I'm getting fairly repeatable 13 Whr per mile at average 18 mph. That's with me pedalling, and if you factor in something for that extra power then its in line with those theoretical figures.

Nick

 

[chantelauze]

yes such factors as rolling resistance & aerodynamic drag are certainly important but I suppose they are in favour of Frank because the bike I drive is 38 kgs , standing straight upward on the large saddle , of good quality by Chinese standards ( but terrible to fair in my opinion ) , and the Bafang geared brushless motor it’s equipped with ( but no throttle since they are forbidden in France ) takes me for at least 45 miles ( 75 kms ) with an SLA 36v 12 ah battery pack , and I am over 80 kgs and I give little human effort since the Bafang motor will not enable any other type of pedalling

my Bafang motor is the very same that comes with the eZee or Wisper models you have in England

so why am I getting on such a long distance ( 2 years of observations ) ? , I really tend to think the difference comes from the controller ; I see no other explanation since the bearings of the Tongxin should play in favor of a better efficiency and longer range , as opposed to traditional planetary toothed gear systems like my Bafang motor

another reason should also be my average speed much lower than Frank or Tyberius ( 12 mph instead of 18 mph ) and if I recall correctly from school : the energy consumption should increase in relation with the square of the additional speed ( ?? ) and the magical 3,1416 figure ; is that so ?

also using my Watt’s up display I am very often averaging 100 watt/hour ( no hills & no wind ) …or 90 watt less in summer , but at only 12 mph avg.speed,
( which average speed is boring and can even be dangerous in city cycling conditions as velocity can be a main ingredient to safe riding downtown )

 

[coops]

Consumption will be much higher at the speeds Frank is doing, chantelauze, since his motor is geared for 20-25mph speeds - even at 20mph consumption is around twice what it is at 15mph, especially given the higher wastage from inefficiency losses at the higher power level.

 

[Jeremy]

The other big factor is the pedelec system that you have to use, Chantelauze. Pedalling will very significantly reduce the motor power demand, so will increase the range a great deal. When A to B magazine tested the Nano/TongXin motor equipped Brompton, they obtained a massive range from a modest battery. Most believe it was because the tester inadvertently pedalled a fair bit, as the bike was relatively easy to ride!

 

[chantelauze]

axle dimensions of Tongxin and standard fork dropout slot spacing ??

hub motor axles are generally flatened down to 10mm on 2 opposite edges ( see attached photo ) , because standard dropout slots are also 10 mm wide , so that the hub motor axle can easily slide into place .

unfornutanely the very few information that one can access from the Tongxin website ( in attached photo ) cannot precisely let anybody understand the shape and dimensions of the Tongxin axle, is it flatened ? is it 8 or 9 or 10 mm from one flat edge to the other one ? when it would have been so simple to add another photo as the one i have here attached ( but from another DIY Kit manufacturer )

it's a real detective's game to get this information from Tongxin , does anyone know if the aboves dimension constraints are easily met ? Frank perhaps , or other Tongxin owners ( but how many of them in Europe and Noth America ? 50 to 100 in the last 3 years ...probably less )

 

[chantelauze]

torque arm or special washer to avoid damages

whatever is the limited amount of nominal power of that small hub motor , it's probably capable of withstanding instantaneous power of 500 to 700 watt for a few seconts ...( the controller enables 36v x 15 Amp H )

under such circumstances a torque washer should be necessary in order to avoid damages to the fork ( one photo attached )

any Tongxin owner to tell me if Diana from Tongxin - now so silent - provides such locking washer ?

 

[Jeremy]

All hub motors need, or at least very much benefit from, a torque arm, in my view. These are fitted to quite a few electric bikes as standard and I suspect the motor manufacturers expect bike makers (or those of us using their parts to build a one-off) to make such an arrangement.

The TongXin is supplied with a pair of anti-rotation washers, but these aren't really that effective in my view. I made a simple torque arm for my Crystalyte motor that fits the TongXin just as well. As far as I can tell, hub motor shafts seem to be pretty standard. They all seem to be 10mm across the flats, as this is the standard drop out width on most bikes. The thread size seems to be 12mm x 1.25mm, and again seems to be pretty standard.

The potential problem with all hub motors, particularly high torque ones, is that they will all tend to want to twist and open out the ends of the drop out slot. Several Crystalyte hub motor owners have found this to their cost, with a result just like yours.

Fitting a torque arm prevents this, by transferring the motor reaction torque to another point. Mine is a simple piece of 3mm stainless steel sheet, with a slotted hole that is a tight fit over the axle. It is secured to the fork using one of the mudguard stay screws. I will try and take a photo later today.

Jeremy

 

[chantelauze]

tks Jeremy, but i'm afraid the new motor axle is in different dimensions than the typical hum motor axle ( in photo )

do you yourself own a Tongxin hub motor ( the new model without the 5 hall lead wires , a version probably appreared mid or end of 2007 )

because their new drawings does not let me think the kept the traditionnal axle dimensions

 

[Jeremy]

I do own a TongXin motor, one of the three wire ones with no Hall sensors. I fitted the torque plate that I made for my Crystalyte motor to it with no problem at all, so am sure that it's the same size. My TongXin certainly has 12mm threads and a 10mm wide section across the flats, like your second drawing. It was purchased just before Christmas from ebikes.ca in Canada so is probably a mid-2007 model.

I think that the top drawing in your message shows the size across the flats of the axle, as the 6mm x 8mm cut-out (shown to the right of the drawing) is on the underside of the axle; it's where the wires come out. This means that the drawing shows the view along the line of the drop out slot, which is why it gives the width as 10mm.

Here's a picture of the anti-torque plate fitted to my TongXin motor:

Jeremy