Careers vengeance hard work pedalling!

[Sturmey]

If Rick's problem is the same as mine was, it's much worse than tyre resistance. And Rick doesn't say, but in my case, the problem would sometimes disappear which makes it much more likely that some kind of gear train was failing to disengage.
Mike

The other possibility is that the 'roller' type clutch mechanism is sticking. If you think about it, the rollers engage at the lower motor speeds and sometimes with a surge under high torque. This wedges the rollers. The disengagement on hub motors takes place at the higher speed/ lower torque end of the power curve and perhaps this may not be enough to dislodge the rollers. (photo below is a bafang clutch)

 

[MikeS]

The other possibility is that the 'roller' type clutch mechanism is sticking. If you think about it, the rollers engage at the lower motor speeds and sometimes with a surge under high torque. This wedges the rollers. The disengagement on hub motors takes place at the higher speed/ lower torque end of the power curve and perhaps this may not be enough to dislodge the rollers. (photo below is a bafang clutch)

I'm not technical Sturmey, but your explanation seems much more likely. It also sounds something like what the supposedly top man at Halfords (he ran a Suntour course for them) was saying. But by the time the message got back to me it was I think a bit distorted - something about a magnetic clutch failing to release?
IIRC it was also possible for me sometimes to correct the misbehaviour by switching on the motor and accelerating beyond the 15.5mph limit, after which when I switched off the power, pedalling was sometimes OK. This would seem to fit best with your theory.
Mike

 

[flecc]

The other possibility is that the 'roller' type clutch mechanism is sticking. If you think about it, the rollers engage at the lower motor speeds and sometimes with a surge under high torque. This wedges the rollers. The disengagement on hub motors takes place at the higher speed/ lower torque end of the power curve and perhaps this may not be enough to dislodge the rollers. (photo below is a bafang clutch)

I suggested that in this post, but as I observed there, Rick (and Mike since) say theirs spin freely by hand with the wheel lifted off the ground, even when the drag is happening. That would rule out the freewheel.

In any case this is a standard Bafang motor and freewheel jam was something they cured many years ago. It's very rare now and I haven't heard of it on any current motor, but in this thread we are told that this crops up on a number of Crosswires. Why not in the many other makes using this motor?
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[Sturmey]

I suggested that in this post, but as I observed there, Rick (and Mike since) say theirs spin freely by hand with the wheel lifted off the ground, even when the drag is happening. That would rule out the freewheel.

In any case this is a standard Bafang motor and freewheel jam was something they cured many years ago. It's very rare now and I haven't heard of it on any current motor, but in this thread we are told that this crops up on a number of Crosswires. Why not in the many other makes using this motor?
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I am speculating here but I am presuming that some wedging action of the rollers is to some extent how the clutch works (but is perhaps excessive in some cases), and whats best needed to release the wedge is a short sharp change in speed between motor and hub.
Now, I can see how this may not happen (clutch remains wedged) say if the rider exceeds 25 km/hr (or the motor is as max rpm) as the motor is already spinning (has inertia) and the rider is often quite slowly accelerating at this point.
I can also see the controller as possibly playing a part. (The more gently the disengagement, the more likely for clutch to stick?)
I can also see why lifting the bike and turning the wheel by hand might possibly (in some circumstances) free the clutch because the motor is stationary at this stage and turning the wheel by hand possibly accelerates the wheel momentarily more than when on the ground.
I can see this as a difficult discussion, as even without the clutch sticking, e-bikes without power are slower and heavier, and definitely feel that way once you have become accustomed to the power.

 

[MikeS]

Another symptom that might give you guys a clue. Often when travelling DOWN a long incline with power off, pedalling would actually slow the bike very noticeably. Stopping pedalling allowed it to continue to freewheel quite properly and in some cases even accelerate, but as soon as I started pedalling it would slow the bike down again.
Mike

 

[flecc]

Another symptom that might give you guys a clue. Often when travelling DOWN a long incline with power off, pedalling would actually slow the bike very noticeably. Stopping pedalling allowed it to continue to freewheel quite properly and in some cases even accelerate, but as soon as I started pedalling it would slow the bike down again.
Mike

I gathered that was a possibility from Rick's posts. If a motor without a freewheel, i.e. always engaged had it's controller phase wiring faulty it could produce that effect when pedalling triggered the controller. That's because in a different phase wiring mode the motor can act as an electronic brake. Indeed there's a Panasonic front hub motor e-bike (in Japan only) which has the motor doing both jobs, driving on pedalling but braking when the front brake lever is operated, this switching the controller connections.

I'd already considered this possibility, but it could only happen with two faults together on the Crosswire, the freewheel jammed solidly and the controller wiring switched. For those to happen to happen intermittently at the same time is highly unlikely to say the least, and for the same to happen on a number of the models even more improbable.

There seems to be a hidden factor present in this Suntour system that isn't revealed from user observation, it's very puzzling.
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[MikeS]

.... and another clue? I noticed sometimes that on level ground after using one of the power modes but then switching off, I could sometimes freewheel for several hundred yards. Almost as if the walk function was accidentally engaged, but then a slight incline would stop it happening and any freewheeling after that would be as normal and decay to a stop after 50 or 60 yards.
It's good to get some knowledgeable people seriously considering this, because I think it's a much more widespread problem with Halfords bikes than people realise. They are told they just need to get used to it, and since it's fine to ride in any of the power modes, they assume that it is a psychological problem they themselves have.
Mike

 

[Nealh]

I can't believe that all the issues with Bafang Carrera's is down to any hub issue as the motors are very much bullet proof, more likely to do with controller/software used.
If the hub freewheels by hand ok then the clutch is all fine .

My bafang cst with kt electronics is faultless as is my Yose & Q128c.

If anyone has a Bafang Carrera and it is out of warranty with issues simply ditch the software and for $100 get a17a kt with lcd etc, then you will have a bike capable of 22/24mph ( dependant on winding speed) if unrestricted. With higher gearing and 48v it will go faster.

 

[MikeS]

That’s interesting neal Because when I was trying to work out what was wrong at one time I came to the conclusion that sometimes the controller was telling the motor it should engage (incorrect as it was switched to off) but then another part of the system was correctly refusing to supply power. Is that possible?
Mike

 

[anotherkiwi]

Unplug the controller from the wheel and go for a ride. Or two, or three... Ride far enough for the problem to either show up or not. If it doesn't then get a new controller.

 

[MikeS]

Unplug the controller from the wheel and go for a ride. Or two, or three... Ride far enough for the problem to either show up or not. If it doesn't then get a new controller.

Yes that would have been a good experiment. I think I tried it without the battery on the bike and still got the problem, but I lost patience and swapped it after 3 weeks for the Crossfuse. Halfords were proposing to change the hub motor on the Crossfire, but weren't able to tell me how long it was going to take
Mike

 

[anotherkiwi]

Yes that would have been a good experiment. I think I tried it without the battery on the bike and still got the problem, but I lost patience and swapped it after 3 weeks for the Crossfuse. Halfords were proposing to change the hub motor on the Crossfire, but weren't able to tell me how long it was going to take
Mike

If they insist on changing the motor it must be the clutch sticking and I am with flecc on this, why is the Bafang motor having faulty clutches only on those bikes? They make hundreds of thousands of motors every year.

Clutches do stick from time to time, the other day I turned the pedal on the GSM bike to change chainwheels and the light flicked on briefly. The battery wasn't on the bike...

 

[flecc]

Yes that would have been a good experiment. I think I tried it without the battery on the bike and still got the problem, but I lost patience and swapped it after 3 weeks for the Crossfuse. Halfords were proposing to change the hub motor on the Crossfire, but weren't able to tell me how long it was going to take
Mike

Changing the motor I'm sure wouldn't have solved the problem. As Neale has posted they are pretty much bomb proof after nearly two decades of refinement. It's more likely to be a controller problem, especially as it seems Suntour have created their own unique system and this happens on a few bikes.

Removing the battery wouldn't necessarily help diagnosis, since if the freewheel was jammed the revolving motor becomes a generator making current as Another Kiwi just showed with his momentary flicker of the light before the freewheel released. It's another of the complexities that a motor supplied with current drives, when turned without current it generates an output, but when wrongly wired it becomes a brake.
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[MikeS]

Removing the battery wouldn't necessarily help diagnosis, since if the freewheel was jammed the revolving motor becomes a generator making current as Another Kiwi just showed with his momentary flicker of the light before the freewheel released. It's another of the complexities that a motor supplied with current drives, when turned without current it generates an output, but when wrongly wired it becomes a brake.
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Exactly !!! That's exactly what it felt like - pedalling a powerful dynamo. But Halfords (and other forum members on other threads) were telling me and others with the problem that it was just a heavier bike.
Mike

 

[flecc]

Exactly !!! That's exactly what it felt like - pedalling a powerful dynamo. But Halfords (and other forum members on other threads) were telling me and others with the problem that it was just a heavier bike.
Mike

I think the best answer is for anyone suffering this to reject the bike and demand a full refund since they are legally entitled to it.

This is what Suntour say on their site about this ATS system:

"If your outing takes longer than planned or if you use the bike for training purposes, with the genuine free wheel function it rides like a normal bike if the battery is flat or the motor exceeds 25 km/h. No resistance, just pure freedom!"

Clearly the affected bikes as sold do not meet this specified "no resistance" performance and are therefore unfit for the described purpose.

I've submitted a technical query to Suntour to clear up one possibility. We'll see if they answer or just hope I go away..
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[Nealh]

Makes you wonder if they have developed the system with a regen function, which we know would be counter productive for ebikes. The last thing you need is more hinderance.

 

[flecc]

Makes you wonder if they have developed the system with a regen function, which we know would be counter productive for ebikes. The last thing you need is more hinderance.

I did wonder that, but it seems completely at odds with what they claim about no resistance to pedalling.

The Bafang motor they are using is branded with their name, so my query to Suntour is whether they are using a magnetic clutch in it, in combination with a three wire sensorless phase system.

That thought was prompted by their mention of an Active Torque Sensor and memories of the horrible Smiths magnetic clutch of long ago in the Standard 8 and 10 car models. Iron filings in a narrow gap locked by energising coils.

It could account for a controller ability to lock the freewheeling function.
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[egroover]

The vengeance uses a bafang system, the Crossfire and vulcan use the suntour system. Why are they being compared they don't share any parts ?

 

[peter.c]

I wonder if the returns will show up on ebay or they destroy them

 

[flecc]

The vengeance uses a bafang system, the Crossfire and vulcan use the suntour system. Why are they being compared they don't share any parts ?

The Suntour HESC system also uses a Bafang motor.
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