Bafang CST suppliers

[SwampRodent]

Hey all, anyone know where I can buy a new Bafang CST 36V 500W rear motor from?

I've been keeping an eye on Greenbike and BMS for months but they are constantly out of stock.

My motor has now completed more than18,000 miles of hard commuting abuse (off road use only of course), so need to be getting a replacement ready, it was originally supplied damaged from China so after removing / refitting the wheel some 100 times for puncture's the wiring is in danger of failing (already changed the plug / socket after one of the pins burnt out), the motor spends a good amount of time at full current when ploughing through deep mud for extended periods as well as some savage hill climbing, I had to ...erm.... lets say sprinkle some water on the motor in the recent 35 degree temperature as it was red hot and I had used all my drinking water on it.

As an alternative I might go AWD with a 250W mini hub front and rear, but the CST is such a great motor I would like the same again especially as the bike cruises nicely at 22 mph so I can complete my 14 mile homeward commute in 40 minutes.

 

[vfr400]

Two Q100Hs work very well at around 15 amps each. The drag from the motors isn't really noticeable. You can use a single pedal sensor and throttle as long as you use a common ground for both controllers. All you need is a branch off each of the signal wires to the second controller. In fact you mustn't branch the 5v wires. You can put a switch on the front motor's PAS signal wire so that you can ride with one or two wheel drive. You need the 260 rpm version that will give you a speed of around 20 mph. With two wheel drive, the bike goes like a Landrover. You can tackle the slipperiest surfaces. I think it would be a better solution than a single BPM/CST.

MXUS and Xofo make clones of the Bafang CST (same castings). They work equally well - maybe better. You can sometimes find them on Aliexpress.

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[SwampRodent]

OK thanks that's interesting, I think AWD would work better for me as it would move some of the weight from the rear wheel which currently gives a horrible ride over broken ground and it would help with a very long and very muddy uphill climb up the side of a slag heap where I have spun out and stalled more than once in the rain.

It will also give me some redundancy in the event of one motor failing and locating 2 x 250W controllers will be so much easier than locating the 500W 'house brick' of a controller.

It would be great to use a pedal sensor again, it's never worked properly with the 500W controller, I have to use a throttle and cruise control which has led to many an exiting moment when I've forgotten to switch it out!

 

[vfr400]

I've built several two wheel drive bikes, so if you need any more info, just ask.

One thing you need to think about is the power from the front motor. You set the rear up with normal throttle and PAS. I would use a normal 15 amp KT controller with LCD for it. You can then use that motor on its own for unchallenging tarmac and cycle tracks. You don't want two LCDs because you'd be pushing buttons all the time to get the right mix of power between the two motors. On mine, I controlled both motors with a single throttle, and no PAS on the front one, so I only used the front motor for extra power when doing steep climbs and difficult off-road stuff. I would guess that in your situation that you wouldn't want to use the throttle for extended periods.

I didn't try this, but you can set a KT controller to start on any particular level when you switch it on. My idea is that you set it to say level 3 with the LCD from the other controller, then run it without an LCD. You can share the PAS between the two controllers, so the front is always on level 3 or whatever you set it to (or switched off if you install a switch on the signal wire), and the back one can give power from level 1 to 5, which should cover most circumstances, then when you need max power, use the throttle. Bear in mind that the throttle with KT controllers and PAS fitted, gives only max power when you're pedalling. In effect, it becomes a level 5 switch; however, if you stop pedalling, it becomes a proportional throttle.

With that setup and a switch on the PAS signal wire to the front motor's controller, you get from the front motor max power with the throttle, level three with the PAS or nothing with it switched off, and you get normal operation of the back motor using the LCD and throttle. It all depends whether setting a controller to start on level three works without the LCD.. Without setting it, I'm not sure what you get - possibly level 1.

 

[SwampRodent]

Loving the idea but unfortunately I cant use any sort of lcd as the ride is so brutal I can neither take my eyes of the track or my hands off the handle bars, plus for 6 moths of the year I'm riding in 100% darkness unless the moon is out.
My current setup has the thumb throttle on the left handle bar side so I can change gear at the same time as using the throttle, the gear lever from the left hand side has been relocated to the frame, kind of old school style. On the right side as well as the gear change I have a switch to disable the cruise control (or PAS if fitted) and the switch for high / low headlight beam, this way I can use everything purely by feel and in a fraction of a second.
I understand what you are saying about limiting the power to the front wheel, when I first started this commute I was running a front motor so had to balance pedal power to front wheel power, even so there was little to no steering in deep mud, I just have to follow where ever the front wheel is heading, with rear wheel drive only its a lot easier excent I regularly ride for a good 1/4 mile sideways with constant whelspin, once the front wheel jammed solid with mud and was just acting like a ski!
What I'm planning is controlling the rear wheel direct from the throttle but building in a traction control by comparing front and rear hall sensors then if the front is going faster than the rear to modulate the power.

 

[vfr400]

I rode one of my 2WDs in deep snow with a throttle giving equal power to both motors. It managed steep hills without any problems. The front wheel frequently lost traction and the rear one too, though not as much, but the gyroscopic affect of the spinning front wheel keeps the bike stable, so there's no tendency to topple. There is absolutely no way in the world that a rear wheel drive would have made it up those hills. In fact, I doubt that getting off and pushing would have worked either.

I also rode it many times on slippery mud and grass, where it managed itself with unbelievable ability. If you build one, you'll see what I mean. There's no comparison with a single rear wheel drive. It's like the difference between a Landrover and a BMW 325.

 

[egroover]

Loving the idea but unfortunately I cant use any sort of lcd as the ride is so brutal I can neither take my eyes of the track or my hands off the handle bars, plus for 6 moths of the year I'm riding in 100% darkness unless the moon is out.
My current setup has the thumb throttle on the left handle bar side so I can change gear at the same time as using the throttle, the gear lever from the left hand side has been relocated to the frame, kind of old school style. On the right side as well as the gear change I have a switch to disable the cruise control (or PAS if fitted) and the switch for high / low headlight beam, this way I can use everything purely by feel and in a fraction of a second.
I understand what you are saying about limiting the power to the front wheel, when I first started this commute I was running a front motor so had to balance pedal power to front wheel power, even so there was little to no steering in deep mud, I just have to follow where ever the front wheel is heading, with rear wheel drive only its a lot easier excent I regularly ride for a good 1/4 mile sideways with constant whelspin, once the front wheel jammed solid with mud and was just acting like a ski!
What I'm planning is controlling the rear wheel direct from the throttle but building in a traction control by comparing front and rear hall sensors then if the front is going faster than the rear to modulate the power.

Your off road commute sounds like it's a handful but a right laugh, I like it

 

[SwampRodent]

Yes its a pretty awesome comute, the alternative is sitting in a car for over an hour staring at someones brake lights...nah!

I have a second bike that is built as a full on ice bike, studded tires, front motor, heated battery etc, last year the weather was a bit boring but the year before we had a good bit of snow with a bit of drifting out in the sticks (beast from the east) the whole commute was out of this world but the best bit must have been climbing up a steep hill in a little hamlet, the road was hard packed ice that had been polished by all the cars that tried to climb it and failed, the bike just sailed up it.

I found with the studded tyres it was easier to ride on hard packed ice than though fresh snow as the front would slide about more in the snow especially with any sort of camber.
The only real issue I had was that in really deep snow the derailleurs were dragging in it so I lost a lot of the gears as they were encased in a block of ice, oh and then a couple of days later the front forks snapped... that was exiting

 

[KirstinS]

I rode one of my 2WDs in deep snow with a throttle giving equal power to both motors. It managed steep hills without any problems. The front wheel frequently lost traction and the rear one too, though not as much, but the gyroscopic affect of the spinning front wheel keeps the bike stable, so there's no tendency to topple. There is absolutely no way in the world that a rear wheel drive would have made it up those hills. In fact, I doubt that getting off and pushing would have worked either.

I also rode it many times on slippery mud and grass, where it managed itself with unbelievable ability. If you build one, you'll see what I mean. There's no comparison with a single rear wheel drive. It's like the difference between a Landrover and a BMW 325.

Totally agree with that gyroscope effect . I used to have a bike with a front wheel conversion and throttle only. Combined with human powered rear alfine hub

Still a 2wd system ! And yes, in snow and ice the fron wheel on throttle spinning like crazy and gentle pedalling lower through the back wheel was the only way that worked !