Is my motor ****ed??

[Auldgit]

Hi all, the rear wheel motor in my daughter's bike has started making a loud metallic "whirring" noise when activated. It sounds as if something has come loose inside it. I've taken it out of the frame and it appears to be a completely sealed unit- I can't find any way in. The motor has "8FUN" written on it, and "Suzbon Bafang Motor Science Co Ltd." on a sticky label. Also states that it is brushless. It's also useless at the moment.....

Any suggestions as to how I can get into it- I can't see a joint anywhere- not even a pressed one?

Or am I looking at a new bike??

Any advice greatly appreciated. AG

 

[flecc]

Are you sure about that first name part, the most common make of 8fun motor is Suzhou Bafang?

They usually have a ring of crosshead bolts holding one side plate of the motor in place, and removing those gives access by removal of that side. The photo below of a motor hubshell shows the ring of bolt holes:

 

[neptune]

I have a similar problem on my Powabyke Euro . I have had one side

of the hub off to re grease the gearbox . I wanted to take a look at the brushes , but there does not seem to be any screws to take the right side off . I can only assume that you extract the whole guts of the hub from one side . I asked Powabyke if spare brushes are available but the answer seems to be no . If they need replacement , I will have to find something that fits .​

 

[Auldgit]

Are you sure about that first name part, the most common make of 8fun motor is Suzhou Bafang?

They usually have a ring of crosshead bolts holding one side plate of the motor in place, and removing those gives access by removal of that side. The photo below of a motor hubshell shows the ring of bolt holes:

Hi Flecc, yes you're right about the make, I've detached the label now and cleaned it and it is Suzhou as you suggest. However, no ring of bolts I'm afraid, nothing on either side. I'll try to take a couple of photos tomorrow and attach them. Thanks. AG

 

[shemozzle999]

Wonder if it is the new SZBAF motor - looks like it needs a special tool to unscrew:

Motors presentation

 

[jerrysimon]

Special tools can be made

Regards

Jerry

 

[Deleted member 4366]

First you need to remove the free-wheel and gears for which you need a free-wheel removal tool. Any bike shop should be able to remove it if you don't want to buy the tool. If you're very lucky and the free-wheel is on tight, the whole side of the motor will unscrew. The seam is right next to the spoke flange. If you're unlucky then you'll need to make a tool that engages with the three notches/holes for the special removal tool, which are hidden behind the gears.

Your problem will most likely be that water has got in through the wire hole or the disc screw holes if any of the 5 screws are missing.

Show us the photos when you get it apart.

You might be able to make a tool out of plywood by cutting a hole the size of the free-wheel thread and then drill three holes in line with the notches and then bolt in three bolts the right size. You might be able to do it with two long bolts clamped in a vice.

 

[Auldgit]

Loads of helpful info there chaps, and thanks a lot for it. I'll have a further look at it when I've more time tomorrow, take a few pics and get back to you. Bit more hopeful now!

Cheers AG

 

[Auldgit]

I've had a good look at it now, looks as if Shemozzle could be right, it may be the new design. I've taken two photos, hopefully attached, but still can't see how to get into it. The freewheel cogs are off but I can't see how the centre is removed- is it a threaded or on a spline? Tried holding the freewheel centre in the vice and turning the wheel but no joy. AG

 

[Auldgit]

I've made some progress and can now see how the freewheel centre comes off- need special tool as D8veh says, so off to find one. Is the centre on a LH or RH thread?

Cheers AG

 

[flecc]

RH thread.

 

[Auldgit]

Thanks Flecc. AG

 

[shemozzle999]

From you photo's it looks like after removing the freewheel as advised by d8veh you need a similar tool to the three pronged tool shown in the later posts in Jerry's thread.

 

[Auldgit]

Yes I've managed to dismantle it at last, but can't find anything that could cause the racket. All looks fine, and everything rotates freely. Do we know what the steel thingy on the end by the planet wheels is?? It may be there is something in there that has broken? It's seems to be sealed so can't examine.
Can I run the motor on the bench to test? There are three "power?" wires, green+blue+yellow, and five thin (sensor??) wires, and I have a spare battery, but which would I connect to?



Thanks for all the interest and advice so far. AG

 

[flecc]

That drum on the end of the planet gears is the freewheel that disconnects the motor drive when pedalling without power or beyond the motor drive limit. If you remove the circlip you can detach all those parts, but so long as the freewheel is disconnecting in one direction and locking firmly in the other it should be ok.

You can only run the motor from a controller like the bike's one, since that delivers the phase power pulses correctly timed.

Are all the magnets securely on the rotor drum, one of those adrift could create a noise and some rough running. Also check for anything between the magnets and stator poles.

The only other thing I can think of to possibly account for the whirring is a misalignment allowing the stator to touch the rotating side plate, you might see signs of rubbing if that was the case. As long as the spindle nut on the l/h side is fully tightened to draw the stator in that shouldn't happen.

 

[shemozzle999]

If it is not a mechanical failure I would also be inclined to check the end to end continuity of all the cables with a multimeter while you have got it apart.
A broken hall wire ( the 5 smaller wires ) would make the motor noisey and judder.
If any are broken it is usually at the point where the cable bends on entry into the shaft.
3 of the 5 wires go to the hall sensors which feedback motor position/direction information and control the pulses fed to the motor power wires ( 3 large wires ) the other 2 small wires are the +/-
supply for the hall sensors.
A defect hall sensor produces the same effect as a broken wire.
Hall sensors can be replaced but you would need to identify the code markings on the device first.
I can supply a replacement cable if you need one.

 

[Auldgit]

Hi Flecc, thanks for that, I've checked the freewheel and it's locking ok as you suggest. I ran the motor in the frame and it's running really roughly. Feels and sounds like a bearing has gone, don't know if I can get any further into it but I'll have a go tomorrow, out of time now.

Cheers AG

 

[Auldgit]

If it is not a mechanical failure I would also be inclined to check the end to end continuity of the cables with a multimeter while you have got it apart.
A broken hall wire ( the 5 smaller wires ) would make the motor noisey and judder.
If any are broken it is usually at the point where the cable bends on entry into the shaft.
I can supply a replacement cable if you need one.

Thanks shemozzle, something else to check tomorrow. They are very thin, watch this space as they say!

Cheers AG

 

[shemozzle999]

I have recently purchased a motor tester from China.
It has served its purpose for me as it identified a shorting output on one of my hall devices which I replaced and now have a smooth running motor again.
If you want I can post it out to you, just PM me your details.

 

[Auldgit]

I have recently purchased a motor tester from China.
It has served its purpose for me as it identified a shorting output on one of my hall devices which I replaced and now have a smooth running motor again.
If you want I can post it out to you, just PM me your details.

That's great, thanks for the offer. I'll let you know how I get on.

Cheers AG