Bafang BPM II

C

cwah

100 MW
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Jul 24, 2011
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4,256
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Between paris and london
Hello there,

I've just seen the BPM 2:
2011829103004.jpg

http://www.szbaf.com/product.asp?id=11

From the BPM1 it has better efficiency (80 percent vs 78 for the BPM 1). It looks really similar to the previous one.

Anyone has idea what that worth and where to purchase it?
 
Mxer, they told me the same thing but apparently the new motor was the magic pie III

I sent an email to the manufacturer asking them where I could find it. Hoping to have an answer from them.. :)
 
Comparing their spec.s between the BPM II and the BPM, it's hard to see much difference between the two. The fore-mentioned 2 % increase in effecientcy and the cover seems a little cleaner in design, but that's about it.
So why the BPM II?
Both models have a listed RPM range of 285 to 300[I'm assuming at 36V], a nice mid-wind that seems to me to be more useful than the two ends of the spectrum winds that BMS Battery offers, so I can see the advantage of buying from the factory direct. Is there a price advantage as well?

At any rate, I would be interested in how the transaction goes, as I am interested in the CST when it comes available.

Thanx

EDIT Would you order the sensored or un-sensored version?
 
Great Scottyf :)

Momotech, I may get a sensored one as it's more efficient and has smoother start... but I'm not sure yet as with high voltage it may not be good to use sensored.

The BPM has been out since several years now, I believe the BPM II is a small upgrade to make it work sligthly better. If the price is similar, I don't see why I would get a BPM I instead of the II... even though the difference is difficult to spot. :lol:

ps: What's special about the CST version? Isn't a freewheel better?
 
It has a nice axle end in the picture. It looks like a big shoulder washer with tongue to grab more drop out. I set up an axle end like that by modifying a billet bicycle chain tensioner to fit a hub motor axle. The billet aluminum washer had a groove to engage the axle drop out and works well. I still run a torque arm for good measure.
 

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cwah said:
Great Scottyf :)

Momotech, I may get a sensored one as it's more efficient and has smoother start... but I'm not sure yet as with high voltage it may not be good to use sensored.

The BPM has been out since several years now, I believe the BPM II is a small upgrade to make it work sligthly better. If the price is similar, I don't see why I would get a BPM I instead of the II... even though the difference is difficult to spot. :lol:

ps: What's special about the CST version? Isn't a freewheel better?
Click to expand...


The CST will mount a real cassette. The splines can be seen in the pic.
 
Damn it, it seems the main difference with the bafang I is only the design... :(
The differences between the BPM and the BPMⅡis mainly the structure outside. For example, BPM's cover needs to be fixed using six bolts, while BPMⅡ's cover is processed thread on its edge, just need to screw it onto hub. This difference makes a different axiality tolerance, BPM2's axiality tolerance is smaller. So BPM is stronger, looks tough, while BPMⅡ is better appearance, looks beautiful. So there is only a llittle difference between two hubs according to the conver difference.
Click to expand...
 
BMS Battery has been shipping this new cover design for several months now, although they haven't changed the pictures accordingly. I have tested this motor (48V, 393 rpm, 10 turn winding) in 26 inch wheel and it's been very smooth and fairly quiet.
Since it no longer uses screws, I couldn't easily pull it apart to see if it's any different to the original design.
 
Would be nice if they fixed the seals / clutch and bearing issue compared to the older one.
 
I'm VERY interested in the cassette version - I'd love to convert my mtb but I don't want to lose the 11t at the rear.
 
I can't say either of those motors is stronger unless I look inside to see what's changed, but I prefer not to.. since the cover is press fit, I don't want to mess with it just to have a look. I'd choose either.
Interestingly, the hardware I got with the new style motor was same as the old style, nothing like the pic from mr.electric. Maybe I just got the old motor with new covers.
 
amigafan2003 said:
I'm VERY interested in the cassette version - I'd love to convert my mtb but I don't want to lose the 11t at the rear.
Click to expand...

You could still have an 11 tooth sm. cog on the standard on a screw-on type motor by using the DNP 7-speed freewheel. But if your Trek is a 9-speed like my Rocky Mountain and you want to be able to index that freewheel, you will also have to replace your chain, shifter and rear derailleur. The DNP is not highly thought of, but it's the only thing available with a 11T cog.
A budget alternative would be to keep all the 9-speed stuff, fix the derailleur to the 11T cog of the DNP and use the three gears of the chainring.
With a BPM, three on the frt. would probably be enough.
 
Scottyf said:
Would be nice if they fixed the seals / clutch and bearing issue compared to the older one.
Click to expand...
Seals are fine on BPM mark 1 - I'd say yours had a seal missing or broken. What are the issues with the clutch and bearing?

Looks like BPM II has an entirely different casting. The cover is no longer held by 6 screws but threaded and it's also smooth between flanges. Would be interesting to know what is different internally.

There' a report of freewheel falling off already, so there might be a bug introduced.. viewtopic.php?f=2&t=36597

I'd be also interested in trying out the cassette version.
 
Most people with the BPM have reported the clutch locking and not free wheeling as well as it should.
Ie full engaged.

The seals are a bit shit and only use a cheap "O" ring and rubber seal on the opposite side.

The axel is a weak point where the wires go though has cracked on a few members bikes (although this might be due to off roading).

The axel would also benefit from having a bearing where the cassete actually sits on the case to support the weight of the free wheel and closer to the actual load bearing of the bike on the free wheel side. Instead of having the bearing closer to the motor.

These are some points that could make a good motor into a fantastic motor. But i'm sure in the future there will be improvements and revisions that will help it along its way.
Don't get me wrong I'm not saying the motor is rubbish. Quite the opposite. Despite the issues i've had its never stopped working. Even when the bearings collapse it still going me home. The windings and gear's have been pushed with up to 2500w and it still works.
Its a stong motor and sensorless there's not much to go wrong at all.

But the above issues could be resolved with some cheap investment and getting a good motor to be great.
 
motomech said:
amigafan2003 said:
I'm VERY interested in the cassette version - I'd love to convert my mtb but I don't want to lose the 11t at the rear.
Click to expand...

You could still have an 11 tooth sm. cog on the standard on a screw-on type motor by using the DNP 7-speed freewheel. But if your Trek is a 9-speed like my Rocky Mountain and you want to be able to index that freewheel, you will also have to replace your chain, shifter and rear derailleur. The DNP is not highly thought of, but it's the only thing available with a 11T cog.
A budget alternative would be to keep all the 9-speed stuff, fix the derailleur to the 11T cog of the DNP and use the three gears of the chainring.
With a BPM, three on the frt. would probably be enough.
Click to expand...

The full sus is 7spd.

The Trek is 9spd but I'm keeing the Tongxin on the front for that one :)
 
Great motor. Running 10t on 15s in 26" wheel for some speed.

Any idea how to open Bpm 2?
 
Haste said:
Any idea how to open Bpm 2?
Click to expand...
You'd have to fab something like this
3784.jpg
but with 4 teeth

Scottyf said:
Most people with the BPM have reported the clutch locking and not free wheeling as well as it should.
Click to expand...
Link? Would be interested to know who these 'most' people are.

Seals are ok, better than any other hub motor I know of. If you watch carefully Justin's presentation you will realise that seals are not a problem.

The axle support on the RHS is poorly designed - mine snapped.. when hit by a car at 80kph.
 
got answers:
It's true that the BPM got clutch locking, and its axle cracked sometimes before, but we have been improving both. We have got new suppliers and changed technologise, you can see there is no any relief groove in axle. And now we seldom hear of these peoblems.
The seal will often be broken if you uninstall the cover, this problem happens to other motors also. Now we're looking for new rubber seal.
Do you have good suggestions about these problems? If yes, please give them. Thanks.
You're profession with the relation of bearing, free wheel and loading. Yes, now, the axle is just like you said, it's better.
Click to expand...

Apparently it's fixed now for all Bafang now.


I'm thinking about maybe getting the Bafang 2. Is it easy to open the BPM2? it looks difficult with special tools required.
 
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