New Bafang Crank-Drives

[Kepler]

Got a bit more done on the new bike this morning. Test fitted the drive to check clearances and started setting up head stem heights to suit my size and reach. Chainline is perfect with the 48 tooth clearing nicely and lining up with the middle gear on the cluster. Plenty of ground clearance on the drive with it tucked up nice and high.

I will be doing some changes to drive control also on this build. Plan to get rid of the thumb throttle and replace it with a push button that just gives a full throttle boost. Also will be using one of the brake switches and retrofit it so that it activates on up changes through the dead band of the rapid fire shifter. Still need to work out how to do this though :lol:

 

[wineboyrider]

Anyone try the bafang crank drive with a sram dual drive???

 

[dbaker]

I will be interested in your push button replacement for the throttle. My BBS-01 throttle does not appear to modulate. I use maximum PAS control and find average draw 10 amps at speed (50 volts). Using throttle I get 15 amps at same maximum speed. I would like to replace my throttle with a button as well. As a group we should investigate what it would take to get the programming software. We might be able to do a better job of programming that what we are experiencing

 

[Kai]

While ago I wrote here how I found some play in my Bafang cranks.
Tonight I checked and found out that the whole motor was loose at bottom bracket mount. Somehow the two thin nuts had loosened up (one is a lock nut).
I remember how I tightened them really hard. I tightened them again as tight I could with the right tool .
Maybe the reason for these loose parts is thermal expansion. My bike is used in -15 c temp outside and stored inside in +21 c temperatures. Another possible reason could be that my alu frame can't take the torgue of motor or the pressure of mounting.
Or maybe nuts and bolts allways get loose and I should check them more often

 

[Rusty123]

I will be interested in your push button replacement for the throttle. My BBS-01 throttle does not appear to modulate. I use maximum PAS control and find average draw 10 amps at speed (50 volts). Using throttle I get 15 amps at same maximum speed. I would like to replace my throttle with a button as well. As a group we should investigate what it would take to get the programming software. We might be able to do a better job of programming that what we are experiencing

It appears to me that the motor seems to have a distinct top speed (RPM), whether under PAS or throttle. On my bike, in low gear (46 x 34), top speed is about 9 MPH, even on the flats. In high gear (46 x 11), top speed is about 25 MPH. Fortunately, the top speed of the motor matches up quite well to the top speed of my legs, which means that my shifting pattern under power is about the same as without (I just reach the shift points sooner with the engine helping).

 

[Rusty123]

Rusty just tap one of the brake levers and the motor should stop instantly allowing a quick smooth change.

I've been experimenting with shifting while under (motor) power, with good results. My rear cassette is a 8 speed hyperglide, and I use friction shifters (no indexing). If I slowly slide the derailler across the cluster (as opposed to the normal click - click rapid fire type of shift), the chain uses the hyperglide ramps to smoothly transition from one to another. Much better than cutting power with brakes, particularly on a hill climb, since power doesn't come back instantly, which translates to momentum loss.

 

[Samd]

Kepler that ride looks awesome.
Let me know when you want an ally LiPo tank welded into the top bar

 

[Rassy]

I had my Nexus 8 speed IGH laced into a 26" rim, shortened the chain, and I'm real happy with the results. Just rode a few miles to test it and everything feels good. Climbs the 20% grade up the driveway with moderate pedal assist. This bike will be going to a sister that has a fair amount of hills over 15% grade between her house and town/work, a distance of 2 to 3 miles.

The Bafang is the 48V 500W version with no throttle. The manual says it can be set with from 2 through 9 assist levels, but if set for levels 6 through 9 it only ends of with 6 actual levels (plus 0) available from the control pad.

The battery in the rack is a 48V 10AH LiFePO4 from BMS Battery. I know the battery meters won't be accurate for this battery, there's actually one built into the battery case as well as the one on the Bafang unit, but I'm not going to add a Watt meter. I'll just have her relate the recharge time with the 2 amp charger to the AHs used, and try to keep it under 4 hours recharge time for an estimated max of 8 AH.

I found assist levels 3 or 4 most comfortable for my cadence. I put a 21 tooth cog on the Nexus, which gives it lower gears for hill climbing, but also dropped the top speed to a little over 15 MPH. I have an 18 tooth cog for the Nexus, but plan to leave it as is unless my sister wants more speed and is okay with less hill climbing ability. I think the little Bafang will be happy with the lower speed option.

Edit: Yes, it's a FS (Fake Suspension) bike from Wal-Mart. At $120 the bike is the cheapest part of the whole setup.

 

[Rusty123]

Has anyone noticed that the thumb throttle sometimes cuts power when it is activated and/or released? I usually just use PAS, but I occasionally give a little boost with the throttle on a hill to maintain speed. About 25% of the time, doing so causes power to cut off completely. It then ramps back up over the next second or two. Same thing when released.

Appears that the throttle overrides PAS (which is not surprising), but that my throttle may have a dead spot, such that between the two, power is cut for a moment.

Am I the only one who is experiencing this?

 

[teslanv]

Has anyone noticed that the thumb throttle sometimes cuts power when it is activated and/or released? I usually just use PAS, but I occasionally give a little boost with the throttle on a hill to maintain speed. About 25% of the time, doing so causes power to cut off completely. It then ramps back up over the next second or two. Same thing when released.

Appears that the throttle overrides PAS (which is not surprising), but that my throttle may have a dead spot, such that between the two, power is cut for a moment.

Am I the only one who is experiencing this?

That's actually what everone has noticed. Some suspect this is by design to aid in shifting.

 

[Tom L]

No Rusty you are not the only one experiencing this. Same goes for the half twist throttle.

There is a large deadband at the beginning of the throttle range and this overrides the PAS, cutting the motor off when the throttle is only engaged slightly. You can use it to disengage the motor when changing gears, though I prefer dabbing on the brakes.

Edit: Doh! Too slow.

 

[Kepler]

Managed to fabricate a mount to secure a brake cutout switch to my rapid fire shifter so when up shifting, the motor automatically cuts out. Downs changes under power don't seem to be too much of an issue .

The brake switch is a hall device that deactivates the motor when released. When riding single track with PAS, I sometimes find it necessary to tap the brake and momentarily cut the motor to stop getting pushed too hard into a corner. Having the cutout switch on the shifter lever will do the same thing by just pressing the shifter lever through its dead band before it starts placing pressure on the cable.

Looking forward to testing this one out as I think it is going to be a great riding asset.

 

[Tom L]

That's a neat solution Kepler. Like it a lot. I'm considering your idea of ditching the throttle for a "boost" button as I rarely use it and when I do it's 100%.

 

[teslanv]

Managed to fabricate a mount to secure a brake cutout switch to my rapid fire shifter so when up shifting, the motor automatically cuts out. Downs changes under power don't seem to be too much of an issue .

The brake switch is a hall device that deactivates the motor when released. When riding single track with PAS, I sometimes find it necessary to tap the brake and momentarily cut the motor to stop getting pushed too hard into a corner. Having the cutout switch on the shifter leave will do the same thing by just using pressing the shifter lever through its dead band before it starts placing pressure on the cable.

Looking forward to testing this one out as I think it is going to be a great riding asset.

Kepler, we need pics and detail. Sounds perfect for my rig.

 

[Kepler]

No problems. You will need to give me a few days as I am away from my workshop at the moment.

Here is a shot of the first part of the bracket that holds the actual switch. There is a second bracket hat then secures it to the shifter.

 

[--freeride--]

@ Kepler:

perfekt Solution with the shifter! But I would swap the thumbthrottle for a button. If you want to ride technical stuff you will need the throttle control.

Sooner or later somebody will come up with a solution to reprogramm that stupid controller settings and then the throttle is really usefull. I would prefer a mode with no PAS an Full Throttle for technical offroad sections... also I don't need that softstart in the throttle with this uge deadband. But that should be configurable to in the software.

 

[Tom L]

I was just re-reading every post in this thread because I thought someone was working on reverse engineering the controller programming protocol. Started skimming and nearly missed it.

...I'm even working at reverse engineering the CPU and EEPROM to decode the communications protocol and offer a open source software package for changing the settings...

Be patient
Mike

I'm being patient Mike, just wondering if you are having any luck with this project?

 

[Samd]

Hmmm, that with a servo controlled rear derailleur and an arduino to decide the gear choice based on current speed and rate of throttle change/acceleration and it'd be a cracker:
http://spectrum.ieee.org/geek-life/hands-on/diy-electronic-bicycle-derailleur

 

[samsavvas]

Hi Folks,

I've been (re)reading this thread compulsively for weeks. I'm strictly a commuter bicycle user (an aging one at that) and am primarily interested in ensuring I can continue to ride my bikes to work even on days when the legs and mind aren't so willing. I have one largish Big Dummy project on the boil but have also become quite interested in the BBS01/02 as a possible option for my old 20" wheel Moulton APB which is set up as a commuter with front and rear platform racks, baskets etc.

There seem to be a number of questions being pursued in this thread so I hope I am not derailing things to much if I ask those with experience with either unit to please try to list and explain some of the issues I would encounter in fitting a BBSxx to a 406 wheel bike.

I already run a 56 tooth chainwheel up front and an 11 tooth min sprocket at the back - standard practice really on the APB/TSR series Moultons. Occasionally I feel need for a bigger chainwheel on downhills in the country but not usually in city running (this might be different with assist!) I understand that there may be problems in fitting larger chainrings to the drive - correct? If I ordered a kit, what might I need to ask for in the way of 'programming' to ensure it will suit the smaller wheel? Any other issues? I already have some 48V batteries and would probably get one of the EM3ev 50v triangle batteries for the APB...

Many thanks,

Sam.

 

[Melbourne]

Hi Sam. I think the BBS02 will be faster than the BBS01 by 5 to 10kph. Melbourne and I travel the same route to the city when riding to work. I will shoot him a PM next week and see if we can meet up for back comparative testing.

Oopss Kepler is CORRECT.. my speedo is off by ~5kph...i have compared with my GPS, assuming my GPS is correct...lol

 

[rp3]

Got a bit more done on the new bike this morning.

Looking good, I'm keen for a test ride.

 

[Kepler]

That's a neat solution Kepler. Like it a lot. I'm considering your idea of ditching the throttle for a "boost" button as I rarely use it and when I do it's 100%.

I mostly use the throttle at 100% for a boost also. Plus I use the dead area at the start of the throttle range of movement when shifting up. With the shifter hopefully automatically taking care of dropping power when shifting, i think the 100% throttle button will suit me fine.

Freeride suggested that this might not be ideal for technical single track which is fair comment. However I have found using moderate PAS settings and either killing the PAS with a dab of the brake or boosting power with 100% throttle gave me all the control I needed. I am hoping this new setup will make control over power more intuitive.

Throttle button circuit should be straight forward to put together considering the drive works without the throttle connected. Means the controller is happy with zero volts at min throttle or open circuit in the case of a button type throttle. Simple voltage divider will then send 4v back to the controller when the throttle button is pressed.

Please excuse the finger painting diagram done on my iPad

 

[Tom L]

I wish I could justify the price of these: http://motogadget.com/en/griff-taster/push-button-controls-m-switch/m-switch-1/m-switch.html

Do you have a push-button in mind?

 

[Kepler]

I have done quite a few push button throttles now and had good success with this one from Jaycar http://www.jaycar.com.au/productView.asp?ID=SP0657. It's ip67 rated so no problems with a bit of moisture. Just
then need to fabricate a custom bracket to hold the switch.

 

[Racer_X]

This Bafang Crank-drives is getting more and more interesting. Looking forward to see how kepler solves this puzzle.

then need to fabricate a custom bracket to hold the switch.

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