Bafang 750W BBS02 w/ Nuvinci N360 & Gates Belt for Commuter?

[kmadd22]

Greetings! I have been lurking around these parts for better than 6 months and have found the community an invaluable resource for my first foray into electric propulsion.

Background: I intend to use my bike for commuting to work and generally around Seattle. My daily commute is less than 5 miles round trip and I don't anticipate many days where I would need to go more than 10-15 miles round trip. I already own what I consider an almost ideal commuter bike, the Novara Gotham, bone stock it includes a Gates Carbon Belt Drive, disc brakes, Nuvinci N360, 700C wheels, Shimano dynamo front hub, and all the other customary features and accoutrements.

Due to the mixte frame and a very strong recommendation against rack mount batteries, I decided to go with the Samsung Bottle box with the highest supported output from EM3EV.

I knew going into my build plans that I really wanted to keep the flexibility and smoothness of the drivetrain and that I wanted to build a as discrete of a bike possible. Those two things in mind, budget was not really a constraint, however I did want to keep the electrification and operation as dead simple as possible in terms of maintenance and operation (which fit primary constraints) so that anybody could ride with ease and appreciate it.

//Ed note: having had the opportunity to scoot around a bit on ebikes in the past I am very convinced that this is a serious and viable transportation option. Given that for many people my bike will be the first that they handle and experience, I really want to have as clean, maintenance free, and aesthetically pleasing a configuration as possible, as I want others to explore this wonderful hobby.

My travel needs around Seattle consist of mostly moving around at moderate speeds in dense urban traffic, longer but infrequent hill climbs, and mostly trail riding. Being able to move around like a SmartCar in traffic (~20 MPH, 3-4 sec. to get there) and strong assistance up some 10% 1mi hills is all I am really asking for in this project, but the ability to show off the capabilities of the technology to others is important.

Quickly realizing that a Bafang 750 was pretty much my only option if I wanted to keep my chainless drivetrain, I have placed an order via Paul at EM3 and should be receiving it within the next week or two. I went with the Bafang BBS002 750W and the 9.8Ah Frame Box and 25R cells with a BMS that will handle the 30A the cells are rated for when needed. I have also ordered a 130 BCD adapter for the Gates Carbon Drive chainring from CA ebikes.

After searching extensively I have seen little more than a picture of a Bafang with a belt drive and little conversation about the Nuvinci N360 here, but mostly N171 chatter here. In my great anticipation of my build in the coming weeks (and documentation shared here of course) I do have some questions that I would really appreciate the collective wisdom of this community on...

Will the Gates Belt (w/ center track alignment) be able to hold up without slipping when heavy throttle is applied?

Does anybody have experience with a Bafang and a belt drive whatsoever? Any thoughts on noise or performance?

Ditto the N360, any experiences would be insightful and if anybody has fried one, I would love to know what not to do with this tranny.

Chainline is critically important to my configuration and I have found little about the 103 BCD adapters on the forum. Bafang documentation shows stock centerline 10mm of the BB, I need 15mm to line up. Is it a safe assumption that as long as I have to move the chainring outward longer screws and more washers would suffice?

With the number of IGH hubs and Gates compatible frames coming out these days, how are these bikes not the ideal conversion candidates? Am I completely off base with this assumption?


Cheers! Your help is certainly appreciated!

 

[Warren]

The Gates belt should work fine. Optibike uses it on one of their models.

http://optibike.com/all-models/simbb-29r/

The chainring adaptor on CA ebikes website looks plenty thick enough to not flex.

 

[skitime]

I have a Bafang 750W with a Nuvinci N360 hub. The bike is a Diamondback Edgewood with 700C rims. It works great with one thing you have to get used to. When you change to higher gearing you have to stop pedaling for a moment to reduce the torque on the chain/Nuvinci 360. Once you get used to it you don't even think about it. Down shifting is not a problem. I also had to convert to a solid chain tensioner. Spring loaded tensioners would allow the chain to slip from the strong torque. I had to go though a few gears on the rear wheel to find the best ratio for my hilly terrain around here. I have muscle atrophy due to an old injury on my right leg and this bike setup has allowed me to enjoy riding bike again. Oh, and I used a bottle battery and like how the weight is nice and low.

 

[scfoster]

kmadd22, any progress on your build? My specs look almost identical to yours; 5 mile commute each way with light hills.

Interested in how the 130 BCD adapter worked for you. Is the bottom bracket of the Novara Gotham 68mm or the larger 73mm? How is the alignment for the belt? That's my biggest concern.

I've got a Nuvinci N360 build going on right now; should have it in 2-3 weeks.

 

[amberwolf]

You might also look at this ongoing build:
http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=65590

 

[Voltron]

Totally doesn't answer your questions...but that isn't a mixte frame....the way the top tube meets the seatstays makes it a low top tube frame.. mixte has the weak, seatstays elevated above toptube frame. So the strength isn't an issue on this one re rack battery...And if you were going front motor it might work out...but mid drive would prob be too tail heavy with it back there.

 

[Voltron]

After rereading your requirements...you might consider a nice light geared front motor...with the weight of the Nuvinci back it would balance well, clean install, pretty quiet and dead simple to let friends use. The BBS02 units seem to be showing a lot of variation in quality control...the several I've ridden now are all over the place on the actual feel of the ride because of the hard for the simple home user to adjust programming. If maximizing your climbing or something is the goal it might be worth the extra complexity and noise? Also if either type fails, you could be waiting around a long time for some specialised parts on the mid drive compared to finding a replacement wheel motor or external controller.. not dissing mid drives...but they do have their issues just like anything.

 

[scfoster]

Doing some research on the Gotham from REI (here's a good review). Noticed there is no belt tensioner in the rear. Looks like it uses an elliptical bottom bracket (see picture). That would be a no-go for the BBS02 as there would be no way to tension the belt. Am I wrong?

No adjustment apparent at the hub.

What appears to be an eliptical bottom bracket tensioner.

 

[Voltron]

It looks as if it would still work as long as that eccentric BB accepts a regular standard cartridge...looks like enough clearance between the spindle and the motor body on the BBS02...unless maybe your belt was really short so the eccentric had to be towards the back too much?

 

[pjgold]

The 2 main issues I can see with the build will be belt alignment and the eccentric bottom bracket.

The chain alignment is perfect with the Nuvinci and the standard Bafang chain rings both at 49mm but the Gates "chainring" will not be offset so it will be out of alignment hopefully the adapter will correct it but it may may it worse. You may have to get a special offset adapter made to correct the alignment.

Second issue is the eccentric bottom bracket the BBS02 should fit with the adjustment in the forward position but you will loose the ability to adjust a lot of the the belt tension, so it will be by luck that it is in the right spot at the right tension.

Seeing that you have already ordered the BBS02 if you can't get the belt right then you should be able to go back to a chain and fit a tensioner to get you out of trouble.

 

[kmadd22]

The 2 main issues I can see with the build will be belt alignment and the eccentric bottom bracket.

Thanks all for the interest and feedback. I gave it a go and pretty much hit it on the head, and I have given up altogether on this bike and am moving on to another bike. EBB just wont work, chainline is a mess, adapter makes it worse.

Since I was unable to make the combination work, I thought I would document my struggles and findings so others in the future can have a resource when attempting to pair their Bafang BBSXX motor with a Gates Carbon Drive System and an IGH. A seemingly ideal combination, or at least I thought so...

For reference there are three key criteria to make a Gates belt drive work well and in a way all have become struggles when pairing with the Bafang BBS. Having a frame split, perfect chainline with an IGH or SS drive, and being able to set belt tension to the desired level.

1. Frame Split - You need a way to get the continuously looped belt through the chainstay and seatstay triangle on anything resembling a traditional frame, so you need some sort of frame split either on one of the drive-side stays or in the dropout. If your frame has a spit, proceed, otherwise you will need to see a local frame builder and convince them to take the work and cut your frame. This was quoted at $150 locally (Seattle) but would "seriously screw up" my paint and also require a teardown of my bike. Properly done (with paint and prep) expect ~$500 for the split and a new powder-coating.

2. Chain Line - Gates CenterTrack Belt Drive Systems supposedly have more tolerance for a wayward chainline than the older CDX, but my experimentation of moving my crankset laterally in the bottom bracket and trying to pedal showed significant resistance and noise beyond ~2mm in either direction. For a belt to make any sense at all, chainline must be perfect.

3. Belt Tension - Greater than 50 lbs. tension for IGHs in high torque applications is needed to prevent slippage. In order to do this you will need either horizontal / sliding rear dropouts or a eccentric bottom bracket to adjust the distance between the belt's cogs. Not only is this more difficult than it sounds to do precisely, but a frame that flexes will have slippage as well. I dont know for sure, but I can only imagine that flex would be exacerbated on a frame that was not designed around a split, but rather was literally cut, welded, and bolted back together.


With that preface, the process that ultimately led to the abandonment of my Bafang / Nuvinci / Gates concept ride. Here is my story....

My first clear complication was the eccentric bottom bracket which is used to adjust belt tension. I was fairly confident that I could manage to both fit the Bafang and set the tension properly as the desired tension actually put the eccentric hub in the front-bottom of the BB shell. With the 13mm of motor to BB spindle clearance provided I was confident that I could make a fit despite some passive mentions I discovered claiming that EBBs were not compatible with the bafang. Unfortunately little further detail was provided, which is why I am elaborating now.

To make it clear, EBBs are not compatible with the Bafang BBS.

My, like every other EBB I have seen has a spilt on the bottom which allows for rotation of the eccentric hub chainline length and latitude. The split is held together with tensioning bolts which protrude downward form the BB's center and effectively att 10 mm to the width of my BB. These bolts along with the protrusions on the motor's casing for the attachment plate and even the screws holding the unit together blocked the Bafang from even getting close to on the bike. Before quitting I even contemplated disassembling the motor then reassembling it on the bike frame, but even then tolerances would have been so tight that I would have been relegated to a fixed chain tension and no room for adjustment, which means it would be impossible to get the belt on or off; a showstopper.

My next line of logic was that I love this bike, especially it's drivetrain; how great would it be if I could just find a frame with rear-horizontal dropouts and just strip down the Gotham and its icky EBB frame and rebuild the new frame?

Or the logistics and feasibility of a Bafang / Gates Belt / Nuvinci bike

I am convinced that it is not possible to pair the Bafang BBS and a Nuvinci N360 IGH with a belt drive connection without seriously altering your bottom bracket or other deep fab.

Chainline, or the distance of a particular drive component from the center line of the bike is the crux of using a belt drive efficiently. Here are the respective chainline differences for all of the elements I encountered, in the most ideal situation front and rear drive element chainline measurements would be equal. For sprockets the chainline is measured to the centerline of the sprocket.

Chainlines in 135mm dropouts
-------------------------

Bafang BBS (stock ring): 50mm*
http://www.energiecycles.com/pdf/8FUNmanual.pdf
Nuvinci w/ Gates Sprocket: 46.45mm http://www.g-boxx.com/pdf/pdf-23-03-10/NuVinci-N360-belt-line-spec-drawing
Rohloff 500/14 w. Gates: 54.75mm
http://www.rohloff.de/en/technology/speedhub/technics/

*The stock bafang configuration considers the dished chainring that comes wit the kit. This chainring effectively removes 4mm from the overall chainline from the chainring's mounting point on the face of the reduction housing. As a belt is clearly not compatible with a "chain"-ring, an adapter will need to be used...

No matter what, with the 130 BCD adapters currently available you can only increase the BBS's chainline by utilizing one. First you add ~4mm from the loss of the dished chainring, then depending on the adapter used can easily add another 2.5-6.5mm from the face of the housing to the center of the sprocket's spine.

http://california-ebike.com/product/ba130-bafang-chainring-adapter/

I tried the 130 BCD California Ebike Adapter which is a perfect fit for the drive and is very well machined. The adapter itself is 6mm thick and the outer bolt points are recessed so that they serve as 3mm thick mounting points. With the mounting recesses facing in, the mounting surface is out 3mm further (2.5mm effective w/ spine) from the surface of the drive than the original chainring. Adjusting for the stock ring's 4mm dish, with an adapter you have at least 6.5mm increased chainline distance from stock, or a actual chainline of 56.5mm.

** All of this assumes a 68mm BB, if you have a different size BB then take half the difference over 68 and add to the total chainline at the BB. EX: A custom chainring on a 73mm BB would be 59mm (56.5mm, per above + 2.5mm (73-67)/2) from the frame centerline.

A 9mm (21x tolerance) difference in chainline alignment from the nuvinci to the bafang is too much to overcome. The only options to use a belt drive & Nuvinci IMO would be:

Have enough bottom bracket (78mm?) to grind off 10.5mm on the drive side to bring the chainline in. Unfortunately you would risk ruining your frame to yet gamble with tire clearance with the wide belt, whether or not the reduction housing will actually have enough room to mount against the BB and clear the chainstay expansion.

Build/beg for a gates sprocket that is dished to move the chainline in and around the reduction housing.

To the later option of a custom chainring, the likelihood is slim as well since the inset would need to be on the perimeter of the ring to clear the reduction shaft and gears much like this guy:

http://www.alcedoitalia.it/shop/accessori-bbs/corona-42-denti-per-bafang-centrale-bbs01

With Gate's proprietary CenterTrack sprockets they look difficult to mill or render and can not be legally replicated without license. Poop!

So, no dice on the belt drive N360. I am currently investigating a Rohloff as well... I love the belt drive that much. A Rohloff with a Gates Sprocket conversion has a chainline of 54.75mm. The stock Rohloff is only 1.75mm closer to centerline than the modified BBS would be. 1.75mm is a more more realistic to shave off a BB or shim in my front chainring than the 10mm of the Nuvinci would have been. Most likely outcome here is the upside of the Nuvinci will lead me to a different chain drive rig, and I am pretty much OK with that since the Surly ECR that I have my sights on is a 73mm BB frame and my logic indicates that it is impossible to use a bafang/belt/IGH combo on a 73mm BB without throwing some sparks.

Interestingly Rohloff's decision to place their cable shifter interface outside of the rear dropouts rather than inside like Nuvinci, Shimano, etc, is what allows the drive such a large chainline distance and it's Bafang compatibility. It is actually Rohloff's defiance of a 50mm chainline convention that makes it unconventional and pair well with the extended Bafang, all the other IGHs I have looked at come in or slightly under 50mm which is pretty much the single speed frame convention that they were designed for.

 

[scfoster]

Thanks for the write-up. Too bad it didn't work out for you. I was VERY interested in the Gates belt drive.

 

[Toshi]

Bumping this thread because I had the same idea: BBS02 + Novara Gotham. I went so far as to test ride a Gotham at REI's Seattle flagship today, and was looking for info on Center Track's tolerances when I came upon this thread via Google.

That I found this through Google is amusing since I used to live in Seattle (when I built my first e-bike iteration) and have posted about it extensively in its own thread elsewhere: http://endless-sphere.com/forums/viewtopic.php?f=3&t=3999

 

[Toshi]

Grace has done what the original poster wished to do: combine a mid drive, carbon belt, and NuVinci:

http://www.grace-bikes.com/Bikes/Mx2

Starting at 3500 Euros. Ouch.

 

[HDMW]

Hello List :
I was interested in using the Bafang 750 with the Nuvinci 360 until I talked to the Nuvinci rep in Europe. Apparently the hub is designed for 60 Nm of torque. The Bafang puts out 120 Nm. Even the 350 watt motor is rated at 80 Nm. I expect using the hub in this way would void the warranty.
The Rohloff on the other hand will accept 100 Nm. I'm talking to Rohloff at the moment about what might be done with a mid-drive.

Incidentally, HPVelotechnik tells me fitting any sort of mid-drive to my FS20 will void my warranty.

Best Wishes : Hubert Wagner
France

 

[eMax]

I have built a Trek Soho with a BBS02 750w and a belt drive. The key here is a centre track belt with tensioning in the frame rather than at the bottom bracket. Made for a very silent and smooth commute. The advantage of a hub gear is they reduce lateral pressure on the Bafangs driveshaft as the chainline is fixed. With a derailleur set up after a while the bearings will wear out which we have seen occur in a few units and some members have also reported. For the Soho see here
http://www.emax-ebikes.com.au/gallery.html

 

[Toshi]

Tempo appears to have two new offerings that have a mid-drive, belt drive, and a NuVinci hub all in one package:

Tempo Carmel, $3995: http://www.tempoebikes.com/carmel/index.html

Tempo Santa Barbara, also $3995: http://www.tempoebikes.com/santabarbara/index.html

 

[scfoster]

Finally got everything put together and have been commuting daily for a couple of months now. When I ordered the N360 I had the wheel built so it should have been a simple install. Well, the hub was bad (wouldn't cycle through the total gear range - only 50%). Took the better part of two months to get that sorted out. Now all is good.

My impression is that it does make "shifting" easier. I just know what adjustments to make and when, without the gear grinding associated with a derailleur setup. I don't notice much difference in efficiency.

I cannot shift while under high load and really don't mind that much. Only takes a split second to cut the power, adjust then reapply power.

Not sure if the experience is that extraordinary to justify the expense, but now that I have it I like it.

 

[AF7JA]

I just wanted to take a moment and also say, thanks for this write-up. I have a Novara Gotham that I have been using for commuting and this at least shows me that it is not compatible with the Bafang. Back to the front wheel motor idea (the forks are steel).

 

[Kai]

I have been usin a mid-drives @ 600-1000 watts with NuVinci n360 for few years and n360 is holding up just fine.
If the chainline can be made aligned then I see no reason why not to try belt drive.

I also used BBS-02 on my velomobile and in one month the bottom bracket boom broke off. Clearly not strong enough for such power.

 

[Lectric Cycles]

We have had recent success with the belt drive on a Spot Acme. Like the gentleman with the Trek Soho the key is the newer Center Track Technology from Gates.

 

[MelRider]

Hey Lectric Cycle, it's very cool to get that setup, good job!

Do you (or anyone else) have the experience building BBSHD + Gates Belt CDX Centertrack + Rohloff Speedhub?

One of the make/break factors is the chainline/beltline. Rohloff requires 54.75 beltline.

I wonder if BBSHD + Adapter + Gates Belt Ring would have it over 54.75. We could use some spacers if the beltline is (not much) less. But it will be really bad if it's over.

Thanks!

 

[JeremyCC]

Hi you say a rohloff hub works well with a Banfang hub. This is what I am trying to do. Could someone help and point me in the right direction for info? I have done a board search.

 

[kaister]

Came across this post by random.

I built the Rohloff / BBSHD / Gates combo.

https://electricbike.com/forum/foru...bullitt-cargo-bike-custom-rohloff-gates-bbshd

 

[Ttreshh]

I'm sorry in advance of my, may be stupid idea, but will try:

What about using kind of adapter to shift pulley-ring from Nuvinci to 56.5-59mm beltline that goes from BBS02?

It can be DIYed in some skilled service with lathe machine.

I'm far from reality, because didn't see bbs02 or N380, just ordering them on this week, but interested in belt drive too...

Don't judge too far.