Dismantling and repairing the motor :o

[jeff-jordan]

Looking at your pictures, I'm wondering if there was some kind of insulation or (double sided?) adhesive tape underneath the magnet which macerated due to the rust.
Maybe some kind of electric insulation is required, to avoid foucault currents? I don't know.

[dominik]

Magnets normaly get glued with high temperature glue, but if there gets water between the magnets and the housing, rust will grow and this will loosen the magnets.

I would ask QS or Yuma if they can sell fitting magnets to you.

[bob2.0]

I already asked QS for a quote for a new motor, but it came to more than these few EU sellers advertise for.

I then passed on images what has happened and asked them for their comments. They don't seem to want to know, or accept there are any problems here with their motors.

I think we are on our own.

[bob2.0]

I will use Loctite AA326. I think this is just the right stuff for this job. Not cheap glue.

But my glue-man is away at the moment, so I will have to wait to make the repair until he can send it to me.

I have asked QS for a replacement motor, because this magnet must have had some sort of plating damage or something. Apart from that second one, the other magnets look good, so this one should not have done this.

I would guess careless handling when fitting left a scratch on the thin end?

[bob2.0]

Nightmare.

I have measured a piece of magnet properly, now.

It is 2.5mm x 16mm (not sure exact, seem odd sizes. Imperial?)

So, what magnet to get?

I have made an enquiry on customized production.

Does anyone want to buy and hold any, in case they have the same?

[bob2.0]

I ordered 15mm square and 2mm thick magnets. These arrived today.

They are close, but as I posted before the original magnets are (45mm long) ~16mm wide and ~2.5mm thick (actually, they are slightly over that .. strange size. Imperial?).

I tried simply placing them in the gap, and they just get pulled in. It is easy to place them.

I suppose they would as the N/S faces align on each side.

They go in so well that they don't even repel each other (shown is all one pole, as it would be glued in).

You can see they are a bit small.

But the strength seems OK.

It was so easy to locate them. I thought I would be fighting them and losing skin!

I have not yet cleaned up the magnets, you can see this.

I have a Gaussmeter I will go find it. I will measure the strength at the magnetic faces, all the way around and report back.

[jeff-jordan]

...
I have a Gaussmeter I will go find it. I will measure the strength at the magnetic faces, all the way around and report back.

I'm really curious if the magnetic flux density is similar to the other ones.
If it is, there's nothing left to do than cleaning everything up and waiting for the Loctite guy to deliver the glue .

Anyway, it looks really promising so far!

[bob2.0]

An initial quick look, I was measuring surface flux of ~0.16T for the production magnets and ~0.14T for the ones I bought.

That is not bad, for 20% less thickness.

At approximately the radius of the stator poles, it was around 0.15T for normal and 0.13T for these replacements.

It did not seem to be strongly consistent. I think there are two batches of magnets in my motor, because the plating seems different on some to others, and the surface flux varies.

I have had a reply from a Chinese supplier, offering to make me the correct custom size. It is a fair price, however it is not justified if these replacements are 'good enough'.

But if others here wanted to hold spares in this size, then let me know. Maybe it is worth it for a number of us if we want to hold spare magnets.

They really are very easy to replace. There is no drama, they are strong but not that strong as they are quite thin.

[jeff-jordan]

That flux is pretty good for the replacement magnet(s).

I guess it's time now to reassemble the whole stuff, the weather will invite you for the next ride .

[bob2.0]

That flux is pretty good for the replacement magnet(s).

I guess it's time now to reassemble the whole stuff, the weather will invite you for the next ride .

I think so, it is sufficient.

I think the ones I bought must be higher grade than the original. Therefore are suitable in the thinner size. I hope their temperature resistance is adequate.

I did order some 40mm long x 15mm x 2mm a few weeks back which arrived from China yesterday. They were 'fake'. The surface flux was 0.02T! Barely any magnetic material in them. Enough for a fridge magnet. Fortunately I have a flux meter and asked for money back, now refunded. It would be difficult to know, or to argue, without the meter.

So, you cannot tell what you might get through these sorts of sellers.

Weather OK now, I have been riding my other bikes today. There was still salt around here, so not too much riding.

I will place order for glue, and should be ready in a week or so if all goes well.