1.9kg Bafang motor

[Pedalo]

Just spotted this light weight Bafang:

Google Translate

Anyone tried it?

 

[daniel.weck]

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

 

[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

 

[daniel.weck]

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

 

[daniel.weck]

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

 

[daniel.weck]

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

8Fun Bicycle Motors

 

[jerrysimon]

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

 

[daniel.weck]

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

 

[daniel.weck]

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

 

[jbond]

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.

 

[daniel.weck]

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...

 

[mechaniker]

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

 

[flecc]

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.
.

 

[daniel.weck]

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 !

 

[jbond]

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.

 

[flecc]

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
.

 

[Andrew harvey]

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.

 

[NRG]

...

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....

 

[daniel.weck]

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

 

[flecc]

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.
.