Just spotted this light weight Bafang:

 

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Anyone tried it?

This has been discussed on the German Pedelec forum, with confirmation from the seller (ebike-solutions.de): basically, the downside of the SWXU motor being lighter is that is dissipates more heat than its bigger brother SWXK (i.e. it is less efficient). So in situations where there are a lot of steep hills to climb, or when carrying heavy weights, then the larger model is recommended instead. Apparently it is noisier as well.

 

Large close-ups:

 

http://daniel.weck.free.fr/Bafang/Bafang_SWXU_1.jpg

 

http://daniel.weck.free.fr/Bafang/Bafang_SWXU_2.jpg

 

More photos:

 

Bafang SWXU - nur 1,9kg - Pedelec-Forum

 

http://grafsport.eu/media/images/popup/pedelec_swxu_motor.jpg

 

http://www.elektrofahrrad-einfach.de/images/product_images/popup_images/46_1.jpg

 

http://www.elektrofahrrad-einfach.de/images/product_images/popup_images/18_1.jpg

Edited September 27, 201015 yr by daniel.weck

Depending on price, I might consider getting the motor only. It weights about the same as the Tongxin, but has loads more "oomph".

 

EDIT: actually the controller wiring is very neat ! (scroll below)

 

http://www.pedelecs.co.uk/forum/electric-bicycles/4682-diy-stage-1-received-bafang-tongxin-kits-photos.html#post59187

Edited September 10, 201015 yr by daniel.weck

Mind you, the whole kit provides a very neat loom indeed:

 

http://www.elektrofahrrad-einfach.de/images/product_images/popup_images/32_4.jpg

 

http://www.elektrofahrrad-einfach.de/images/product_images/popup_images/32_3.jpg

 

http://www.elektrofahrrad-einfach.de/images/product_images/popup_images/32_2.jpg

 

http://www.elektrofahrrad-einfach.de/images/product_images/popup_images/32_0.jpg

The kit without battery and motor costs 100 Euros in Germany (it would be neat on a Brompton):

 

http://www.elektrofahrrad-einfach.de/images/product_images/popup_images/49_0.jpg

 

http://images.qxlricardo.com/ImgUsers/2/6/607/60754/6075409/607540986_2_Big.jpg

 

http://www.szbaf.com/images/product/type/20091119145989841.jpg

Edited September 10, 201015 yr by daniel.weck

The 8-Fun european website is still under construction...

 

8Fun Bicycle Motors

 

Dan still 100mm width though

 

Obviously no big shakes but needs quite a bit of stretching. It would be interesting to try on a Brompton though I agree.

 

Regards

 

Jerry

I check my fork regularly for stress where the steel was bent due to the widening, and so far it has coped well with the stretch from 74mm to 100mm

I use spacers at the moment (big fat washers) so that the 80mm Tongxin fits tight within the dropouts. It's nice to know that I can swap for the 100mm 8-Fun at any time with minimal work

FYI, the motor alone costs 200 Euros + 20 Euros postage to UK:

 

Bafang SWXU Vorderrad-Umbausatz - ebike-solutions.de

 

Heavier items cost 40 Euros postage.

You can contact Ebike-Solutions.de via their website, they speak English well.

 

Otherwise this German website sells them too:

 

Bafang Vorderradmotor 250W - SWXU - DER Leichte

 

Cheers, Dan

Edited September 27, 201015 yr by daniel.weck

Seems there are a few of these e-bike website suppliers in Germany that can supply parts. Shame there's nobody equivalent in the UK.

 

One of the links lead to a site selling SB motors bare, but with different gearing for different rim sizes. The rationale seems to be being able to hit the EU speed limit of 25Kmph. For those of us who don't care about this, there's an obvious trade off between hill climbing ability and top speed. So how stupid and/or clever is say taking a 20" specific motor and lacing it to a 26" rim?

 

ps. I have got that the right way round, yes? A 20" rim spins faster for the same 25kmph. So using that gearing with the same motor rpm but a 26" rim will lead to a higher top speed and less hill climbing torque. Providing the motor can produce enough watts to overcome the higher aero and other drag.

Edited September 27, 201015 yr by jbond

One of the links lead to a site selling SB motors bare, but with different gearing for different rim sizes. The rationale seems to be being able to hit the EU speed limit of 25Kmph. For those of us who don't care about this, there's an obvious trade off between hill climbing ability and top speed. So how stupid and/or clever is say taking a 20" specific motor and lacing it to a 26" rim?

 

ps. I have got that the right way round, yes? A 20" rim spins faster for the same 25kmph. So using that gearing with the same motor rpm but a 26" rim will lead to a higher top speed and less hill climbing torque. Providing the motor can produce enough watts to overcome the higher aero and other drag.

 

You are correct.

 

Well, one thing to consider is that the reduction gear might be different from one motor to another (depending on the rated max RPM), but I read somewhere (Endless-Sphere I think) that the windings are sometimes different too. I'm not sure though...

on Bafang-motor is always the windings different, in this way they motor is made for 25Km/h in a 20" rim or in 25km/h in a 28" rim.

The sprockets/gearbox is always the same

it would be to complicatet to change the planetary gears to receive different speed.

To change the winding is much more easy and cheaper for the producer.

 

If you use a 20" Motor in a 26" rim you can drive faster but lose some torque. You can do it this way in flat terrain but dont do it if you live in mountain area because you lose the advance of an e-bike at the hill ;-)

 

regards

frank

 

So how stupid and/or clever is say taking a 20" specific motor and lacing it to a 26" rim?

 

eZee did this in a big way to produce the Torq 1 back in 2006. They took the powerful SB motor that was geared for the 20" wheels in the Quando and laced it into 700c for the Torq.

 

The result was 22 mph assisted but very poor power only hill climbing, not even able to manage 7% gradient without pedal assistance. Fun with a strong enough rider though, since the optimum torque/power point for climbing was around 13/14 mph and moderate hills could be stormed at 15 to 18 mph, leaving lycra types passed at that speed staggered.

.

on Bafang-motor is always the windings different, in this way they motor is made for 25Km/h in a 20" rim or in 25km/h in a 28" rim.

The sprockets/gearbox is always the same

it would be to complicatet to change the planetary gears to receive different speed.

To change the winding is much more easy and cheaper for the producer.

 

If you use a 20" Motor in a 26" rim you can drive faster but lose some torque. You can do it this way in flat terrain but dont do it if you live in mountain area because you lose the advance of an e-bike at the hill ;-)

 

regards

frank

 

Excellent information. Thanks Frank !

eZee did this in a big way to produce the Torq 1 back in 2006. They took the powerful SB motor that was geared for the 20" wheels in the Quando and laced it into 700c for the Torq.

 

The result was 22 mph assisted but very poor power only hill climbing, not even able to manage 7% gradient without pedal assistance. Fun with a strong enough rider though, since the optimum torque/power point for climbing was around 13/14 mph and moderate hills could be stormed at 15 to 18 mph, leaving lycra types passed at that speed staggered.

 

Was this a 250W motor or more powerful than that? There seems to be a 622 and 700 option available, I wonder if lacing a 622 into a 700 rim would be a better compromise.

Was this a 250W motor or more powerful than that? There seems to be a 622 and 700 option available, I wonder if lacing a 622 into a 700 rim would be a better compromise.

 

Yes it's a 250 watt legal motor, but with the eZee controller about the most powerful possible, maximum of around 720 watts continuous peak power compared with say the powerful Wisper 905se at around 550 watts.

 

The 622 and 700c are the same thing, both 28", just different ways of expressing size, one the rim and one the overall size with a nominal tyre. This chart extract from the Schwalbe site shows the comparisons

 

 

26" 35-559 26 x 1.35

26" 40-559 26 x 1.50

26" 47-559 26 x 1.75

26" 37-590 26 x 1.5

26" 42-590 26 x 1.7

28" 25-622 700 x 25C

28" 28-622 700 x 28C

28" 32-622 700 x 32C

28" 37-622 700 x 35C

28" 40-622 700 x 38C

28" 47-622 28 x 1.75

28" 40-635 28 x 1.95

.

Edited September 27, 201015 yr by flecc

I've used a variety of SB motors over the years.

Some are more powerfull than others. They used to make the hill king motors, 115mm wide as powerfull as those in the Torq but wound differently for lower speed, mine was always a 2 miles an hour slower than a Torq but I never had any problem on hills, at the time I was using it I hada Uplus2 I used to tow two children on. Maximum gradient regularly rode was 1 in 10.

Now I've succumed to temptation and dropped a SWXH into my trike, a customer asked if it could be done. !7+ mph on a fresh battery and able to climb any hill around here.

I have always tended to drop 20" geared motors into 26/28" rims for myself, I like the extra speed. At 50 years old and 12 stone I have no problem with this, but it will depend on the individual, how fit you are what you weigh and what you expect the motor to do for you.

The other alternative I've used is to fit 24V motors to 36v controllers.

Last summer I was running a US geared motor, .ie. 20mph 26", at 36V. An interesting combination with a 20A controller it was cruising at 25mph without pedalling on the flat, 28mph with a little rider effort and cresting the hill on the way home at 20mph (a fair bit of rider effort here). However it did destroy my battery pack, ( a 2 year old 8Ah Lipol ) fairly rapidly. On full power it was drawing 20+A upto 22mph. I still managed one 50 mile ride out, being very sparing with the throttle, using power only as hill assist and climbing hills at a rather sedate but relaxed 7/8mph.

 

A common mistake with electric motors is to multiply the controller current by the battery voltage and assume this equals the power output of the motor, it does not. The power output of electric motors is the motor current multiplied by the back EMF of the motor.

The max power output for the Ezee motors is more like 500w.

...

 

A common mistake with electric motors is to multiply the controller current by the battery voltage and assume this equals the power output of the motor, it does not. The power output of electric motors is the motor current multiplied by the back EMF of the motor.

The max power output for the Ezee motors is more like 500w.

 

That's a very good point but I think you mean efficiency? assuming 85% the Ezee with 20amp controller would produce 37v x 20amp x .85 = 629w for nominal battery voltage and 714w on a fresh battery....

That's a very good point but I think you mean efficiency? assuming 85% the Ezee with 20amp controller would produce 37v x 20amp x .85 = 629w for nominal battery voltage and 714w on a fresh battery....

 

The amount of power put into a PM motor is equal to the battery voltage times the current. The amount that is converted into mechanical power is equal to the back-emf voltage times the current. The conversion efficiency from electrical to mechanical energy is therefor simply the ratio of the back-emf voltage to the applied voltage.

 

Information about Hub Motors

 

A common mistake with electric motors is to multiply the controller current by the battery voltage and assume this equals the power output of the motor, it does not. The power output of electric motors is the motor current multiplied by the back EMF of the motor.

The max power output for the Ezee motors is more like 500w.

 

A lot more than that 500 watts net power on the Quando/Torq 1 SB motor. Current/voltage measured at almost touching 1000 watts peak by Tiberius and others with a good battery.

 

The Quando would be unable to climb as it does on motor-only with just 500 watts net power.

.

No.

The maximum power is not produced at maximum efficiency, typically this would occur towards the top of the speed range for the motor, whilst the maximum power is produced further down the speed range.

 

If the controller was able to supply more current than motor could draw then maximum power would be produced around half the no low speed.

At the no load speed the back emf of the motor is just below the supply voltage, within a couple of volts, the motor drawing only sufficient power to over come it's clogging torque. so at half this speed the back EMF would be half the supply voltage.

With the motor and controller sets we use the current is limited by the controller so we do not get maximum power at half speed.

For an SB motor with a 60A controller I've measured 44A at 36V supply at 12mph, the no load speed of the motor was 24mph. this gives a power output of (44 X 18)w, 792w.

With a 20 controller I was getting 44A on hill starts droping to 20/25A after the first inrush, the current fell to 20A as the bike accelerated until about 15mph, when the current started to fall of more linearly.

Given that the Back EMF is a linear function, a reasonable approximation for the output would be

15/24 x 36 x 20 = 450w

The 15/24 function is the reduction factor for the back emf compared to the supply voltage at 15 mph.

Please remember that these are backyard experiments so they can only be considered as approximations.

 

Back to efficiency, have you ever felt that you can get more out of your battery on days when your feeling energetic and going for it than on a normal day when your plodding to work, (my opinion ), you are not just adding more power but also running the motor in it's more efficient zone and hence getting more out .

The amount of power put into a PM motor is equal to the battery voltage times the current. The amount that is converted into mechanical power is equal to the back-emf voltage times the current. The conversion efficiency from electrical to mechanical energy is therefor simply the ratio of the back-emf voltage to the applied voltage.

 

Information about Hub Motors

 

Ah! Thanks Dan, that's cleared it up.

The 622 and 700c are the same thing, both 28"

 

Doh! my bad. Of course I meant 26" and 700c.

I've been trawling the endless threads on Endless Sphere(!) and whilst I've not sorted this out in my head yet it appears there's more to this than meets the eye....certainly with regard to the intelligent controllers like the Infineon based ones.

 

The current use Andrew observed on his bike could be accounted for by a setting for these controllers that multiplies the phase current at the expense of voltage so at half speed the motor could well be drawing more than the supply current. There's also a Blanking factor that can be set for x number of seconds to allow for high current draw during startup...effectively increasing torque for a brief period to aid acceleration from standstill. I need to go over threads again, there's a lot of noise and no single place where all this stuff is written.

 

I also found a couple of posts about calculating power output at the motor and if I've read them correctly the 1Kw electrical input I see on my Peugeot translates into 855W output at the motor.

 

On another tack I looked at the effect of voltage on wheel speed given the 3 speed settings I have on the bike. These seem to be programmed to 100%, 75% and 50%

 

I checked with three different battery voltages and the ratios remained the same so I was able to work out the motor Kv as 25.95 or 6.035 after the 4.3:1 gear reduction. Just over 2v for every 1mph @ 100% so on low speed setting (50%) a voltage increase raised the speed at half the 2v = 1mph ratio or 2v = 0.5mph

 

I use the low speed setting a lot and get around 7.5Wh from it compared 11~12Wh when on medium. Of course my average speed is lower at around 12~13mph vs 16~17mph but its curious to see that over the same route the peak input amps to the controller is very similar at 20 or so...more reading needed I think to understand what's going on.....

Edited October 1, 201015 yr by NRG

This is all on the Peugeot? Is the motor sensored or sensorless?

 

On a sensorless motor, I can't work out what frequency the controller is feeding the three wires. Is it timed to match the current motor RPM, presumably using the other two phases to work out where the magnets are?

 

My perception is that the BPM motor and SB controller produce just as much torque at low revs in all three modes. On a steep enough hill so that speed is below 11mph, the hill climbing ability seems to be the same. As if the motor is receiving 36v at max amps. And I kind of think that acceleration up to the max speed in each is the same. So 0-11, all three modes are the same, and 11-16 is the same between medium and high. So the modes are really just a max speed limit. But that doesn't match up with your voltage results.