New Bafang Crank-Drives

[crossbreak]

My gf goes up to 29pkh max now. Guess she will go faster next year. so i will program speed limit a bit higher. I put a 13-32t sun race 9 speed freewheel on her bike. Original one was a 14..34 7speed. . had to add some washer. She always uses the 13t with a 52t chairing even at 29kph. So she pedals quite slow. She has a swxh hub.. Think about buying a 11..32t for her

 

[Warren]

If it is a 26" wheel she is pedaling under 60 rpm. A gearhub motor in the wheel would probably be more efficient.

 

[nukezero]

I suspect the reason you could tell the motor was warm is because you could actually put you hand on it. With the geared hub motor, you a feeling the outer aluminum hub shell, not the motor.

Part of the problem for a manufacturer offering different chainring options is that people would need to know what they are doing. As it is, if you ride around in high gear without pedaling, all the time, you will cook the motor on big hills, unless they have thermal protection.

If you ran a high enough gear, you could be pulling the full 18 amps at very low motor speeds...basically turning it into a toaster oven.

Yes you are correct. I told my girlfriend that when she encounters a hill, that she needs to go to gear 1 or 2 and let the motor do the work. I told her that if she is in gear 6 or 7, she cook burn out the motor. She used to drive stick shift so she has an idea of it.

But for the most part, she is mostly in gear 3 or 4 on flat land. If we do encounter some small ramps that are 15 feet long, I think gear 3 or 4 for 5 seconds up that ramp really has no time to burn out the motor.

Actually, gear 1 is too rediculous. It is the mega-range 34T. I told her use that when we go rock climbing. lol.

When I get home, I'm going to ride her bike more and adjust the derailleur a bit. Still having problem with it jumping gears and not going into highest gear sometimes.

 

[lcrewse]

BTW, someone mentioned that the 48V 750w is not that impressive than just the 48V 350watt or something. But if the 36V/350w can do 21mph (14T), then I reckon that the 48V/750w should bring you up close to 30mph easily, especially with a 11T in the back. My only gripe is that hopefully Bafang will come with various sized chainrings because I think the 44T is maybe a tad too large. 38T may be the sweet spot for my girlfriend. It also doesn't seem that hard to fabricate a custom chainring for this.

Here are some more pictures.

The person that commented about the 48v 750w not being impressive did not ride a production unit. With the speed limiter disabled it easily does 30mph (even on a fat bike). The 36v 350w ones that I had Bafang produce have different LCD, brake levers, a higher continuous current than standard, MPH readout on the LCD and a fully functioning throttle with PAS turned off (which as you mentioned isn't an option on standard units). The smallest chainring is a 46t (its printed on the inside of the chainring) with a 48t as an option and a 52t planned in the future. 44t is technically feasible retaining the 50mm chainline but Bafang won't produce it without significant demand for it. Anything smaller than a 44t will require the chainline to be moved out by several mm, making a conventional cassette useless. I already have adapters that fit this motor for mountain chainrings (designed for a fatbike) that result in a 60mm chainline. With a redesign it's possible to bring it in a bit but still is going to be only useful with an IGH like a Nuvinci.

 

[lcrewse]

The 48 volt, 25 amp, "750" can already pull over 1200 watts out of a battery, and possibly 1000 watts through the chain. A one kWh pack won't even get you 30 miles at that rate, and unless you run a BMX chain to a IGH, you will be replacing chains at a ridiculous rate. But over-stressing/breaking stuff seems to be a hobby for many on this site.

This is a really nice e-assist setup. Wanting to deliberately screw it up is lost on me.

The 750 motor is very hard on chains and conventional drivetrain components. I have snapped multiple chains already with the 750 and in order to make it truly useful when using a cassette, you need to use throttle only and apply it once you are firmly in gear. Shifting under load with the 750 motor is just asking for problems. Of course, the IGH solves all of these issues.

 

[crossbreak]

The 750 motor is very hard on chains and conventional drivetrain components.

That's why I propose the 14-42T cassette. Much less stress on gears and chain if a large chain ring is used.

If it is a 26" wheel she is pedaling under 60 rpm. A gearhub motor in the wheel would probably be more efficient

the swxh is a geared hub. the 52/13 is like the 44/11 I use on my MTBs. Just 4:1 overdrive. 60rpm is really slow, i'd like to "educate" her with the 52/11 setup. Let's see if this goes wrong When she had just a thumb throttle she didn't pedal at all most of the time. That is why her bike goes PAS only now

Then she had he 42/14 overdrive and would not go faster than 20pkh. Since she had to pedal too fast :?

I'm thinking of a Bosch bike with torque mode pedal assist also. Sadly they are so expensive, but I never really go hands on one. If the Bafang would have torque mode pedal assist that would be awesome.

Guess all "problems" will solve their selves as soon as she rides more often

 

[nukezero]

there must be a way to force cool this motor... maybe add air cooling using powerful 120mm fans or something

kind of like some kind of intake air duct like on cars. It could work! But you'd have to go fast enough.

BTW, someone mentioned that the 48V 750w is not that impressive than just the 48V 350watt or something. But if the 36V/350w can do 21mph (14T), then I reckon that the 48V/750w should bring you up close to 30mph easily, especially with a 11T in the back. My only gripe is that hopefully Bafang will come with various sized chainrings because I think the 44T is maybe a tad too large. 38T may be the sweet spot for my girlfriend. It also doesn't seem that hard to fabricate a custom chainring for this.

Here are some more pictures.

The person that commented about the 48v 750w not being impressive did not ride a production unit. With the speed limiter disabled it easily does 30mph (even on a fat bike). The 36v 350w ones that I had Bafang produce have different LCD, brake levers, a higher continuous current than standard, MPH readout on the LCD and a fully functioning throttle with PAS turned off (which as you mentioned isn't an option on standard units). The smallest chainring is a 46t (its printed on the inside of the chainring) with a 48t as an option and a 52t planned in the future. 44t is technically feasible retaining the 50mm chainline but Bafang won't produce it without significant demand for it. Anything smaller than a 44t will require the chainline to be moved out by several mm, making a conventional cassette useless. I already have adapters that fit this motor for mountain chainrings (designed for a fatbike) that result in a 60mm chainline. With a redesign it's possible to bring it in a bit but still is going to be only useful with an IGH like a Nuvinci.

Would it be possible to fabricate a 1-piece integrated chain-ring that sort of has an offset? Please see my cartoon drawing. The one piece chain ring would have 3 gear tooths and the proper negative offset towards the bottom bracket. Blue is the crank, brown is the pedal, red is the 1-piece integrated chainrings and black is the bottom bracket.

 

[crossbreak]

I see no reason why this should not work, except your chainline would be really weird.... the whole drivetrain would not very efficient/reliable in the slower (rear) gears.

Still there is no point in this:

Normally you use the 22T chainring on the steepest hill (without motor). A 250W motor adds the some torque as you can add. So you can use a 44T on the same hill at double the speed you go with the 22Twithout motor.

So everything is fine. why should anyone bother about more than 1 chainring?!?

 

[lcrewse]

Would it be possible to fabricate a 1-piece integrated chain-ring that sort of has an offset? Please see my cartoon drawing. The one piece chain ring would have 3 gear tooths and the proper negative offset towards the bottom bracket. Blue is the crank, brown is the pedal, red is the 1-piece integrated chainrings and black is the bottom bracket.

Something like that could be fabricated but you wouldn't be able to get a chainline even close to what is normal on a mountain bike. The issue is the final gear reduction unit that is enclosed behind the chainring mount. If you hold up a chainring to it you will see that anything less than a 44t will simply not fit over that part of the assembly. The Chainrings that come with the Bafang units are set in and over that circular assembly in order to get a 50mm chainline (which is roughly equivalent to a middle chainring in a standard triple). A 104mm bcd mountain chainring is much too small to clear and even a 130mm bcd road ring wont do it.

 

[Hillhater]

The 48 volt, 25 amp, "750" can already pull over 1200 watts out of a battery, and possibly 1000 watts through the chain. A one kWh pack won't even get you 30 miles at that rate, and unless you run a BMX chain to a IGH, you will be replacing chains at a ridiculous rate. But over-stressing/breaking stuff seems to be a hobby for many on this site..

Warren, just because a drive can put 1+kW through the chain doesnt mean it will be doing that all the time.
My Aprilia crank drive pulls 1200W peak ( from a 250W motor !) and will do 30+mph and some nice acceleration /hill climbing, ...
....BUT,.. i have never broken a chain (or replaced one), and the 600Whr battery will keep me going for 30 miles of "spirited" stop/start city riding easily without going 80% DOD.
I guess the point is, unless you ride like a complete lunatic, you only actually use that 1+kW in rare situations.

 

[--freeride--]

The 48 volt, 25 amp, "750" can already pull over 1200 watts out of a battery, and possibly 1000 watts through the chain. A one kWh pack won't even get you 30 miles at that rate, and unless you run a BMX chain to a IGH, you will be replacing chains at a ridiculous rate. But over-stressing/breaking stuff seems to be a hobby for many on this site..

Warren, just because a drive can put 1+kW through the chain doesnt mean it will be doing that all the time.
My Aprilia crank drive pulls 1200W peak ( from a 250W motor !) and will do 30+mph and some nice acceleration /hill climbing, ...
....BUT,.. i have never broken a chain (or replaced one), and the 600Whr battery will keep me going for 30 miles of "spirited" stop/start city riding easily without going 80% DOD.
I guess the point is, unless you ride like a complete lunatic, you only actually use that 1+kW in rare situations.

Thats a controlls Problem, the PAS seems to pull with to much Power...

 

[Warren]

"Warren, just because a drive can put 1+kW through the chain doesnt mean it will be doing that all the time.
My Aprilia crank drive pulls 1200W peak ( from a 250W motor !) and will do 30+mph and some nice acceleration /hill climbing,"

I am not talking about instantaneous peak loads. A "250" crank drive, by definition, is designed to average 250 watts draw. A "750" is designed to average 750 watts draw. Some of the folks on here want to average a 1200 watt draw. That is why they are talking about running higher gears, and adding motor cooling fans.

Of course you can build a crank drive using mass and surface area, or forced air or liquid cooling for the motor for those kinds of loads. And of course you could gear it low enough that it never got pulled down into its efficient rpm range. But that would be pretty silly. Like people who drive SUV's in the city.

 

[Rollodo]

Of course you can build a crank drive using mass and surface area, or forced air or liquid cooling for the motor for those kinds of loads. And of course you could gear it low enough that it never got pulled down into its efficient rpm range. But that would be pretty silly. Like people who drive SUV's in the city.

Not entirely sure what you were referring to, so I'll give you a benefit of the doubt.

I have an SUV, live in Brooklyn, often drive to Manhattan, both are 'cities'. Just to clear things up a bit, the reason I choose an SUV is because NYC's roads are complete and utter shit, with potholes and otherwise deteriorated surface area accounting for more than half of that particular street. That's the main reason I choose thick (or just MTB) tires for my bike, aside from good suspension. I tried driving a sedan and damaged my lower bumper, felt driving over something, like a pipe that was left on the road, and 'felt the road' in general far more than I should have. Plus, being at an elevated level helps to see the traffic ahead.

 

[nukezero]

I'm planning to switch to a half twist throttle. Does anyone know if it is just as simple as cutting off the existing thumb throttle connector, soldering the wires, and then plug it back in? Would the signal wire's resistance between the thumb throttle and half twist throttle be the same?

The bbs-01 has their own proprietary connector , actually don't know how proprietary it is, but it's a circular shaped connector (kind of like ebikekit's) with one side flattened out.

 

[snowranger]

Interested in getting one.

Does anyone know if the regular 750 watt drives have unlimited speed control like icrewse's versions, or is there just some sort of programming changes to be done?

If anyone is in the SF Bay Area and wants to go for a small group buy, let me know.

 

[nukezero]

alright just to clarify, the bbs-01 should have no problems on a 10-speed rear cassette on any bike?

also, it should fit 20" Dahon folding bikes too, no?

 

[lcrewse]

alright just to clarify, the bbs-01 should have no problems on a 10-speed rear cassette on any bike?

I haven't tried one on a 10 speed but on a 9 speed I would highly recommend using some sort of a chainguide. Especially under load the chain seems to come off the chainring easily when downshifting into the smallest two gears. I'm guessing a 10 speed would be similar.

 

[Warren]

Ten speed cassette cogs are 1.6-1.7 mm thick, 9 speed 1.75-1.8 mm, 8 speed 1.8-1.9 mm, 5-6-7 speed 1.85-2.0 mm, BMX 3.2 mm thick.

The upshot is that a ten speed cog will wear about twice as fast as a BMX cog. The chains themselves, on new cogs, will wear internally at the bushings and pins, based on the quality of the chain. But since the narrower cogs wear faster, this will indirectly accelerate chain wear.

On the jumping chainring issue, the flimsy plastic or sheet metal pants guards found on many single chainring bikes, similar to what the Bafang appears to have, are often too far from the chainring or too flimsy to prevent the chain being whipped off slideways during a shift. You can buy this very nice guide,

http://www.paulcomp.com/chainkeeper.html

Or just install a non-functioning front derailleur, as guys used to do on F1 bikes.

 

[nukezero]

Ten speed cassette cogs are 1.6-1.7 mm thick, 9 speed 1.75-1.8 mm, 8 speed 1.8-1.9 mm, 5-6-7 speed 1.85-2.0 mm, BMX 3.2 mm thick.

The upshot is that a ten speed cog will wear about twice as fast as a BMX cog. The chains themselves, on new cogs, will wear internally at the bushings and pins, based on the quality of the chain. But since the narrower cogs wear faster, this will indirectly accelerate chain wear.

On the jumping chainring issue, the flimsy plastic or sheet metal pants guards found on many single chainring bikes, similar to what the Bafang appears to have, are often too far from the chainring or too flimsy to prevent the chain being whipped off slideways during a shift. You can buy this very nice guide,

http://www.paulcomp.com/chainkeeper.html

Or just install a non-functioning front derailleur, as guys used to do on F1 bikes.

Interesting to know. I already have some shifting problems with my girlfriend's townie rear 7-speed freewheel. it keeps jumping gears. If I perfect the index on 6 and 7, then the big gears 1 and 2 keep jumping. If I fix 1 and 2, 6 and 7 goes back and has problems. I know my limits are correct and the index is fine but it's like it doesn't want to give me smooth shifting.

When I look down on the chain from the rear, it does seem a bit un-straight. I wonder if a un-straight chain causes poor shifting. Maybe it's time I buy her a new chain.

 

[kocoman]

is there any chainguard that can be used to hide the motor? thx

 

[crossbreak]

Interesting to know. I already have some shifting problems with my girlfriend's townie rear 7-speed freewheel. it keeps jumping gears. If I perfect the index on 6 and 7, then the big gears 1 and 2 keep jumping. If I fix 1 and 2, 6 and 7 goes back and has problems. I know my limits are correct and the index is fine but it's like it doesn't want to give me smooth shifting.

Sounds like a cheapo gripshift with too much friction in the cable. BTW I'm a SRAM ESP fan, it uses more cable per gear, less friction, better shift performance. Also available for 7-speed (SRAM comp 3.0 ESP gripshift). That was the first thing I swapped on my gf's bike as well on most of the others.

 

[Warren]

It sounds to me like your derailleur hanger may be misaligned. Next to flats, straightening bent der. hangers was my most frequent task at the shop.

http://www.parktool.com/blog/repair-help/rear-derailleur-hanger-alignment

Steel frames with quality, forged hangers built into the rear dropout are pretty sturdy, but cheap department store bikes have thin sheet metal hangers that come crooked from the store. And modern aluminum and carbon bikes have soft aluminum hangers designed to bend. The idea is to save the expensive derailleur and frame in a crash. But it means, if you lay your bike on the right side, or somebody kicks the rear-end, your bike will shift as you describe. The hanger can often be straightened once or twice, but it will fatigue and break off eventually.

I have seen $6K boutique bikes, where the hanger broke, and threw the $250 derailleur into the $500 wheel, with disastrous results!

That said, I am constantly amazed at the garbage bikes on this site. There are some amazing builds, with world class components. But many are pure garbage big-box bikes. I get that many are only interested in hot rodding electric motors, and the bike is an afterthought. And with hub motors the drivetrain can be completely inoperable. But with a mid-drive, you really do need to have a decent bike and drivetrain.

There is absolutely nothing wrong with the Townie frame, but the derailleurs, chain and freewheel will see more use in a week than the maker expects that bike to see in a lifetime.

 

[nukezero]

Interesting to know. I already have some shifting problems with my girlfriend's townie rear 7-speed freewheel. it keeps jumping gears. If I perfect the index on 6 and 7, then the big gears 1 and 2 keep jumping. If I fix 1 and 2, 6 and 7 goes back and has problems. I know my limits are correct and the index is fine but it's like it doesn't want to give me smooth shifting.

Sounds like a cheapo gripshift with too much friction in the cable. BTW I'm a SRAM ESP fan, it uses more cable per gear, less friction, better shift performance. Also available for 7-speed (SRAM comp 3.0 ESP gripshift). That was the first thing I swapped on my gf's bike as well on most of the others.

It is a shimano 7-speed gripshift.

It sounds to me like your derailleur hanger may be misaligned. Next to flats, straightening bent der. hangers was my most frequent task at the shop.

http://www.parktool.com/blog/repair-help/rear-derailleur-hanger-alignment

Steel frames with quality, forged hangers built into the rear dropout are pretty sturdy, but cheap department store bikes have thin sheet metal hangers that come crooked from the store. And modern aluminum and carbon bikes have soft aluminum hangers designed to bend. The idea is to save the expensive derailleur and frame in a crash. But it means, if you lay your bike on the right side, or somebody kicks the rear-end, your bike will shift as you describe. The hanger can often be straightened once or twice, but it will fatigue and break off eventually.

I have seen $6K boutique bikes, where the hanger broke, and threw the $250 derailleur into the $500 wheel, with disastrous results!

That said, I am constantly amazed at the garbage bikes on this site. There are some amazing builds, with world class components. But many are pure garbage big-box bikes. I get that many are only interested in hot rodding electric motors, and the bike is an afterthought. And with hub motors the drivetrain can be completely inoperable. But with a mid-drive, you really do need to have a decent bike and drivetrain.

There is absolutely nothing wrong with the Townie frame, but the derailleurs, chain and freewheel will see more use in a week than the maker expects that bike to see in a lifetime.

Well, here's the thing. The derailleur cables go into the step-through frame and down exits the tube right at the bottom bracket. The bbs-01 motor sort of wedges that in. There's nothing I could do to move that cable out of the way because it would create too much tension. So I had no choice but to have the bbs-01 motor just sort of sandwich the cable against the bottom bracket. I'm wondering if this is causing the problem as well. But even if it were, why am I able to upshift (release tension) with no problems for several gears.

I will definitely read this on derailleur alignment. Need to figure it out.

 

[wojtek]

best way will always be internal gear hub... one chain line

 

[Warren]

You may need to run a new cable and a new continuous length of derailleur cable housing from the shifter to the rear derailleur, zip tying the housing securely to the frame at several places along the way. Make sure to keep as gentle bends as possible. I have done this more than a few times on new bikes which refused to shift properly, even with everything else perfect. Full suspension bikes are often terrible. Lots of short, tight bends in little pieces of housing, with too tight housing end caps binding on the cable.