New Bafang Crank-Drives

[speedmd]

Looks like they have been keeping posted on the 8fun reviews. More case to bb housing clearance and no recesses / smooth walled primary case. Also looks to have a bit more clearance for swing arm and chainstays in the case. Wondering if the bb mounting shaft is long enough for wider bb shells. It would be a game changer if they included some significant motor cooling.

 

[Warren]

"Wondering if the bb mounting shaft is long enough for wider bb shells."

The drawing at the link shows the crank axle, and chainring to center distance to be the same as the Bafang.

 

[Rollodo]

Looks to me that so far these SZXF motors have a larger footprint than the Bafang ones.

 

[rodgah]

what kind of wh/km are people getting out of the 750watt ones commuting with light hill climbing?

 

[nioko]

100% agree. My experience when using this drive for commuting duties is that you will get it up to 31mpg with the throttle but don't expect to leave it there and have the drive live a long fruitful life.

I am finding that 20mph to 26mph is the max continuous speed you can expect out of this drive and is what you get when using PAS only on the highest speed setting. Still not too shabby for a small quite compact drive IMO.

Hi Kepler and Everyone else

I'm currently using a BionX 250HT with the 40.7v Trek/Villiger/Diamant battery. Topspeed using PAS and serious pedaling is around 20mph, maybe 22 on a really fresh charge. I do a 8 miles commute with an altitude of 300 feet twice a day.

I wanted to buy a BBS-02 750w, to achieve better top speed, my target is 28mph using PAS (on the flat), but now that I've read your post, this does not seem to be realistic.

Could you explain a little further, why you think 26mph is the max continuous? What would you do?

Cheers from Switzerland
Nioko

 

[rodgah]

Could you explain a little further, why you think 26mph is the max continuous? What would you do?

It may take 1200w or so to travel at 30mph. The motor is probably only rated at around 8-900watts (750w being a safe conservative number) continuous, so all the time you operate this motor over its rated power is creating heat that the motor cannot shred fast enough....getting warmer and warmer till it overheats. Some motors like the GNG v1 are severely underrated...why is anyones guess, but this drive is rated very closely as Kepler has found out. With some method of fan or cooling would probably allow a bit more power to be run but it ruins the drives robustness.

 

[speedmd]

The drawing at the link shows the crank axle, and chainring to center distance to be the same as the Bafang.

Axle length looks the same, but what about the hosing it is in. No dimension listed. It may have a bit more length and fit a wider range of shell widths. With the recessed bearing and internal threads added in the end of the axle housing you could extend the housing to fit shells as wide as the crank arm would allow with a custom made tee nut.

 

[nioko]

Could you explain a little further, why you think 26mph is the max continuous? What would you do?

It may take 1200w or so to travel at 30mph. The motor is probably only rated at around 8-900watts (750w being a safe conservative number) continuous, so all the time you operate this motor over its rated power is creating heat that the motor cannot shred fast enough....getting warmer and warmer till it overheats. Some motors like the GNG v1 are severely underrated...why is anyones guess, but this drive is rated very closely as Kepler has found out. With some method of fan or cooling would probably allow a bit more power to be run but it ruins the drives robustness.

According to this:
http://www.kreuzotter.de/english/espeed.htm
750 Watts should get you up to 30mph (and that would be throttle only)...


Of course I don't know which calculation is more realistic, I hope mine of couse

 

[tomtom]

Hi Kepler,

I want to ask you. Can you please describe difference between you current bafang mid drive FS vs your modified Stealth Fighter. From trail riding perspective, if you can.
I think there will be no more than 5 kg difference between so pretty comparable. How big is unsprung weight in real wheel a problem - very steep uphill - etc etc - efficiency - fun factor. etc.

I think there are many people interested on such comparison and you have deep knowledge of both

Many many thanks

Tomas /Slovakia, Europe/

 

[ErikDK]

I've just received a BBS-01 and I'm quite astonished about the drag in the crank shaft without power.
I can hear at leat one pair of gears turning as I turn the crankshaft.
I'm used to Panasonic and old Yamaha mid-motors with neglible drag.

It's a girl's bike, but my son has trouble swinging his leg over typical boy's bike top tubes.

 

[EVTodd]

Hi Kepler,

I want to ask you. Can you please describe difference between you current bafang mid drive FS vs your modified Stealth Fighter. From trail riding perspective, if you can.
I think there will be no more than 5 kg difference between so pretty comparable. How big is unsprung weight in real wheel a problem - very steep uphill - etc etc - efficiency - fun factor. etc.

I think there are many people interested on such comparison and you have deep knowledge of both

Many many thanks

Tomas /Slovakia, Europe/

I would think there would be a HUGE difference between the bafang setup and a modified bomber. That's like comparing a moped to a sport bike.

I would actually be more interested to see how he compares it to his friction drive setup on a normal street commute.

 

[spinningmagnets]

I'm quite astonished about the drag in the crank shaft without power

ErikDK, I'm sorry to hear about the noticeable drag. This surprises me, and I suspect there is something wrong that is fixable. Do you feel confident to partially dis-assemble the unit...if only to add some grease?

There are two internal freewheels in the BBS series, one if inside the large secondary gear, so that the pedals can turn without back-driving any part of the reduction...and there is a roller-clutch inside the white plastic primary driven gear.

 

[Kepler]

Could you explain a little further, why you think 26mph is the max continuous? What would you do?

It may take 1200w or so to travel at 30mph. The motor is probably only rated at around 8-900watts (750w being a safe conservative number) continuous, so all the time you operate this motor over its rated power is creating heat that the motor cannot shred fast enough....getting warmer and warmer till it overheats. Some motors like the GNG v1 are severely underrated...why is anyones guess, but this drive is rated very closely as Kepler has found out. With some method of fan or cooling would probably allow a bit more power to be run but it ruins the drives robustness.

According to this:
http://www.kreuzotter.de/english/espeed.htm
750 Watts should get you up to 30mph (and that would be throttle only)...


Of course I don't know which calculation is more realistic, I hope mine of couse

Keep in mind that calculator is based on actual power at the cranks.

The 750W unit on PAS only pulls about 550W. Subtract 100W to 150W for parasitic drag of the drive's internal gear system and motor efficiency losses. Put in a more realistic ebike weight like 45lb. Now see what you get. I think the figures will be more in line with what we are reporting the real world.

 

[ErikDK]

I'm quite astonished about the drag in the crank shaft without power

ErikDK, I'm sorry to hear about the noticeable drag. This surprises me, and I suspect there is something wrong that is fixable. Do you feel confident to partially dis-assemble the unit...if only to add some grease?

There are two internal freewheels in the BBS series, one if inside the large secondary gear, so that the pedals can turn without back-driving any part of the reduction...and there is a roller-clutch inside the white plastic primary driven gear.

Is there any chance it will free up once the motor is powered up and run for some time?

I'm willing to open up the drive to fix it, but I wanted to make certain that it's a bug on my specimen and not a general "feature" of this type of motor.

 

[rodgah]

Keep in mind that calculator is based on actual power at the cranks.

The 750W unit on PAS only pulls about 550W. Subtract 100W to 150W for parasitic drag of the drive's internal gear system and motor efficiency losses. Put in a more realistic ebike weight like 45lb. Now see what you get. I think the figures will be more in line with what we are reporting the real world.

even just a 10km/h headwind and mtb tyres at sea level will require 1200watts to go 30mph by that calculator.....its hard to have a rule of thumb, especially at that speed where the drag is beginning to get exponentially worse.

 

[Kepler]

I'm quite astonished about the drag in the crank shaft without power

ErikDK, I'm sorry to hear about the noticeable drag. This surprises me, and I suspect there is something wrong that is fixable. Do you feel confident to partially dis-assemble the unit...if only to add some grease?

There are two internal freewheels in the BBS series, one if inside the large secondary gear, so that the pedals can turn without back-driving any part of the reduction...and there is a roller-clutch inside the white plastic primary driven gear.

I agree, doesn't seem right. There is only very slight drag in the crank without power on mine. turning the crank without power will drive the intermediate gear but it doesn't drive any further than that. I suppose it depends on your definition of a lot of drag. On my drive, with chain off, a hard spin by hand will see the cranks turn about 10 to 15 times before stopping.

 

[ErikDK]

I agree, doesn't seem right. There is only very slight drag in the crank without power on mine. turning the crank without power will drive the intermediate gear but it doesn't drive any further than that. I suppose it depends on your definition of a lot of drag. On my drive, with chain off, a hard spin by hand will see the cranks turn about 10 to 15 times before stopping.

EDIT: A hard push on mine will see the cranks turn about 270 degrees, (forwards, without pedals)

 

[Kepler]

Something very wrong there. Presuming you didn't buy it locally and can easily return it, you will need to open it up. They come apart quite easily so hopefully you should be able to find the issue.

 

[nioko]

Keep in mind that calculator is based on actual power at the cranks.

The 750W unit on PAS only pulls about 550W. Subtract 100W to 150W for parasitic drag of the drive's internal gear system and motor efficiency losses. Put in a more realistic ebike weight like 45lb. Now see what you get. I think the figures will be more in line with what we are reporting the real world.

Good point about power at the cranks. About the weight, I've had 20kg in there (but that shouldn't matter too much as wind is the big factor), and then switched to American Units, must have mixed it up there..
But the best point would be, that from what you say it'll only provide 400-450W at the cranks.. definitely not what I was looking for to get my commute faster.

Have you ever ridden a BionX? Which one, and how does it compare to the BBS?

 

[bgraig]

Hi, I have a question for owners of BBS, I have not found an answer. someone has this logo on it will display the C 961, I did not, or it will not activate.
you know what that is? it is present in the manual but not in use.
greetings greg France.
ps: I have a 750w 48V Bafang BBS02

 

[samsavvas]

I've received today a BBS01, 250w, 36V. Bought as an experimental 'legal' alternative to my other 'illegal' project. Now I'm thinking hard about which bike to put it on (first!)

However I have an 'engineering' question. I note that although the freewheel on the crank clearly works, there seems to be more 'drag' involved in the freewheel action than I've encountered with a conventional rear screw-on sprocket freewheel or with a cassette-type freehub. If I hold the unit horizontally with a crank arm on the shaft and give it a decent spin in the 'freewheel' direction (ie; backwards), it stops within one revolution.

I presume that the BBS01 crank 'freewheel' is more akin to what we might call a Sprague one-way bearing. Is this correct? And if so, is the apparently greater drag normal for this type of freewheel?

Thanks,

Savvas.

 

[ErikDK]

I have issues with drag when pedaling without power, it sounds and feels like when I turn the chuck of my cordless drill by hand.

 

[samsavvas]

Hi Erik,

The 'drag' I'm referring is in the backwards rotation of the crank. In this situation there is no gearbox resistance that you refer to and as I would expect when turning a drill chuck, and the freewheel is definitely working because I can hear it clicking. I am just observing that there appears to be a little more drag than one would feel in a rear-wheel freewheel cluster or a free-hub.

However I hadn't thought of the forwards-pedaling situation where you're riding the bike without power. I've read somewhere in this thread that there are 2 freewheels inside the BBSxx - one for the crank and one for the motor. I assume that it's the latter than would disengage the motor in unpowered pedalling. I too notice that I'm 'turning gears' when I turn the crank forwards.

I'd be very interested to hear what owners experiences have, especially as the unit is 'run in'.

Savvas.

 

[Warren]

nioko,

"I don't know which calculation is more realistic"

That calculator is equivalent to motor watts, not battery watts. You can realistically hope to get 70-75% of battery watts to the wheel. Are you as small and light as the default values in the calculator? Will you be doing your commute on an expensive roadbike? if so, you might be able to average 28 mph for 8 miles, but if you aren't going to pedal like mad, it will depend on your battery maintaining high voltage and amperage the whole way.

 

[nioko]

@Warren, the calculations got mixed up when I switched from Metric to American units. But with my real values, i got 45kph at 750Watts.. which would be at the crank (as Keppler mentioned).
It's not about 45kph for the whole commute, that would be totally unrealistic, as there is a very steep part in it, which I manage to do at about 20kph with the bionX, and 12kph on my road bike.

As for the bike, I'm not going to use an expensive road bike, but similar geometry as a roadbike using a flat bar (therefore hands on the top in the calculation).
On the flat, (that's where I want to go up to 45kph / 28mph) I currently do reach the 31kph where the bionX stopps supporting me (at the Voltage that I have left when I get into that part of the commute). At this point I sustain on that speed without support, until it gets steep again.

I completely drain the ~260wh battery on each commute / charging twice a day with the bionx. However, I don't know how much capacity the battery has, I have 2 batteries, they perform the same, and have a total of 6000km on them.

The bosch drive unit seems to easily do 40kph on the flat, and 45kph doesn't seem to be unrealistic either...