Bafang BPM Motor internal slipping

[Toby82]

Hi Guys,

After receiving a dud crystalyte H series motor from crystalyte I decided to go back to the geared option as I have had no issues with my BMC and like the light weight and small size of the geared motors.
Not requiring a high power output I decided to go for a Bafang BPM front motor (350W) from BMS battery.
The motor is fitted into a 20" rim with a 36v 35amp controller.
The motor performed well for about 5 mins of easy riding but then began to slip internally as if the clutch is not engaging properly. When I apply a decent amount of throttle I can hear the motor spin up without much acceleration or change in speed so either the gears are stripped, unlikely due to the amount and type of use, or the clutch is not engaging properly under power.

With the motor/wheel off the ground I'm now able to hold the wheel steady and make the motor spin internally by apply some throttle.

Has anyone had or seen his problem with the BPM motor.

Cheers,

 

[dnmun]

what clutch?

 

[Wurly]

From what you describe, i would say its probably running backwards, hence clutch not engaging, but you say it ran ok for 5 minutes?
Try reversing 2 phase wires and see what happens.

 

[d8veh]

Could be a faulty clutch, but most likely it's going backwards. Which controller are you using? Are you running sensored or sensorless?

 

[knoxie]

yes my guess is the one way bearing in the freewheel assembly inside the motor although its amazing that it should go so soon though, folks often refer to it as a clutch which in many ways its the exact opposite a reverse clutch if you will.

Could also be the gears and it can sometimes be the sun gear pressed in to the hub, they can spin, the thing to do is take the motor apart and have a look, you can mark up the bits with a permanent pen then run the motor to see if you can spot what's spinning. Oh and sometimes the rotor can spin on the axle too! the bafangs are tough little motors though so I am a little surprised at this, we can assume that the phases are the right way around as the motor ran for 5 mins.

Good luck

 

[Toby82]

what clutch?

Clutch/freewheel/oneway bearing. Whatever you want to refer to it as. The mechanism that engages the motor to the gearing in fwd but allows the hub to freewheel with no power applied.

From what you describe, i would say its probably running backwards, hence clutch not engaging, but you say it ran ok for 5 minutes?
Try reversing 2 phase wires and see what happens.

Could be a faulty clutch, but most likely it's going backwards. Which controller are you using? Are you running sensored or sensorless?

Motor is running in fwd (correct) direction. It is a disc motor so you can't get it wrong. The motor/gearing was working initially (maybe 2kms) but is now slipping internally. Gives the same feeling you get when you ride the clutch in a car. I'm using a sensored infineon controller.

yes my guess is the one way bearing in the freewheel assembly inside the motor although its amazing that it should go so soon though, folks often refer to it as a clutch which in many ways its the exact opposite a reverse clutch if you will.

Could also be the gears and it can sometimes be the sun gear pressed in to the hub, they can spin, the thing to do is take the motor apart and have a look, you can mark up the bits with a permanent pen then run the motor to see if you can spot what's spinning. Oh and sometimes the rotor can spin on the axle too! the bafangs are tough little motors though so I am a little surprised at this, we can assume that the phases are the right way around as the motor ran for 5 mins.

Good luck

These problems sound more like what may have occured. Does anyone have any internal motor pictures or can link me to a thread which has. I'm guessing I'll need a puller to open the motor much the same as the crystalyte I have just had apart. I am curious to see the internals of a geared hub but I was hoping I would get a little more ride time first but.

Cheers.

 

[Toby82]

Opened up motor today and everything looks intact. No chewed gears so i think a slipping one way bearing is the problem. I'm going to mark the sun gear as suggested by Knoxie and power the motor just to check. I have contacted BMS battery to see what there input is also.
Where can I buy a replacement one way bearing/metal gears for this motor? Might also replace one nylon gear with a metal one if I can find these.

 

[heathyoung]

Yeah sounds like your one-way bearing (freewheel) is broken - it now freewheels in both directions.

Were you running excessive power through it? BMS battery are not known for their warantee

Another Novocastrian... I think that makes 3 active ones on here...

 

[Toby82]

Good to hear from a local. I don't see to many ebikes around newcastle but hopefully things will change.

After marking various internal parts with marker, reassembling motor and powering it to slip I found it to be the sun gear rotating on the axle.

I have now brought two different motors (xlyte H2440 and Bafang BPM) which have both been faulty straight out of the box. very frustrating.

I have not dealt with BMS battery before but I have had a reply requesting footage of the problem so I'll wait and see. Have you had issues with them?

Cheers

 

[dnmun]

do you have pictures? i was able to epoxy the gear back onto the shaft of a heinzman with J-B weld and bearing retainer.

 

[miuan]

Sorry can't help with the failed sun gear / axle interface, but one thing: DO NOT mess with the nylon gears. They will hold up fine given your power levels, and will be more silent than any other option.
You mentioned it was a front motor and sensored controller. Does this mean BMSBattery ships sensored fronts? I got sensorless from them before.
I hope you get it right and enjoy your motor. The ones I've seen have been reliable so far.

 

[knoxie]

glad you found the problem, you can weld the sun gear against the rotor to stop it slipping, i have don this on a bmc but not on a bafang, i agree with the other poster on the metal gears you are better off sticking with the nylon ones.

 

[Wurly]

Welding would be a permenant fix, but what about trying some of this.

Loctite 648 High Strength High Temperature Fast Cure Retainer

 

[heathyoung]

JBWeld is a good alternative, Jaycar Electronics at Islington sell it - just make sure you clean the surfaces well with isopropyl alcohol.

 

[dnmun]

i bot some cheaper bearing retainer. same as loctite.

it is like rock when it sets up, but very thin outa the bottle, flows into the cracks and sets up like clear glass. i bet it is as strong as epoxy, but i used J-B WELD too.

use carb cleaner to get any grease or oil out.

 

[d8veh]

Isn't the sun gear held on a key in a slot? Is the key missing in which case you can get one from any engineering supplier?

 

[Toby82]

My understanding of how geared motors operate was not correct when I diagnosed the problem being a slipping sun gear. After sitting spinning and watching the various parts of the motor for a good period of time and getting my head around it, I have come back to the original conclusion that the one way bearing is failing.

Full-throttle has helped me out with a spare so will wait and see once bearing is replaced next week.

Cheers

 

[d8veh]

It's very easy to check whether the clutch (one way bearing) is working. You don't need to figure out how it works. Reassemble the motor and put the wheel on the bike. When you turn it backwards, you can feel the motor turning; when you turn the wheel forward, it should turn freely. If it turns freely both ways, then the clutch is stuck in the off position, which would be very unusual as it did work for a bit. When they jam, it's normally in the on position. If you can feel the motor turning when you turn the wheel backwards, but the motor still won't turn the wheel when it spins with power, then the motor is spinning backwards.

 

[knoxie]

they dont always fail like that though, i have had them work perfectly when you roll the wheel but they fail under power and I have also had another motor that did this exact same symptom and that turned out to be the sun gear slipping, so it is important to strip down the motor and check it, the OP one way bearing had not failed completely so the roll back test would have not helped.

 

[d8veh]

they dont always fail like that though, i have had them work perfectly when you roll the wheel but they fail under power and I have also had another motor that did this exact same symptom and that turned out to be the sun gear slipping, so it is important to strip down the motor and check it, the OP one way bearing had not failed completely so the roll back test would have not helped.

Are you taking about the BPM motor?

 

[miuan]

no matter if BPM or other, imho the geared motor designs are all similar and prone to the same failures

 

[d8veh]

no matter if BPM or other, imho the geared motor designs are all similar and prone to the same failures

I'm pretty sure that the BPM sun gear is keyed, while as the smaller ones aren't.

 

[dr_frost_dk]

Old thread but my myatu bike just did the same recently, will only take about 3-400W after that it slips, i can get it to 35km/h but takes extra time and clutch is heating up, slipping more after putting ATF in, but i ride on throttle 99.7% of the time so im going to take it apart in a few days and lock it down