Glueing magnet on disc rotor.

[Vetus Ossa]

I’m torn between posting this question here or on the ebike section but think here is more appropriate.
I own a Trek Powerfly ebike and have needed to buy a new rear wheel for it.
I chose a centre lock wheel, but finding a disc rotor to work with my Bosch motor is seemingly impossible to find.
I have been googling a little and it seems I am not alone here, one of the options as a fix seems to be bonding a magnet on the rotor with two pack glue. Does the team think this a trustworthy solution,I have my doubts.

[Jdsk]

What are the two surfaces?

Jonathan

[Vetus Ossa]

What are the two surfaces?

Jonathan

I think I am talking about a 10mm round magnet, such can can be found on Amazon or eBay, and I guess the rotor arms are made of aluminium.

[531colin]

IMG_5856 by 531colin, on Flickr

My Specialised Vado SL has a part for that.
the sensor is inside the chainstay, right next to the dropout.
Its a while since I took it off, but it looks to me like the centrelock lockring is the part which includes the magnet.
(it can get in the way re-fitting the wheel!)

Google comes up with loads of them!

[Brucey]

Colin's solution is very neat, but adhesive bonding might work too. Unfortunately. magnets, adhesives and even Al alloys all give up at high temps, depending on exactly what they are, so this route may be far from simple.

[Vetus Ossa]

Colin's solution is very neat, but adhesive bonding might work too. Unfortunately. magnets, adhesives and even Al alloys all give up at high temps, depending on exactly what they are, so this route may be far from simple.

I have seen a couple of gadgets as in colins picture and it is a decent option, as he said I am a mite concerned about wheel removal but may try it.
I may also have a go at bonding one on, some say it works well but the thought of a magnet falling off 30 miles from home doesn't bare thinking about.

[Brucey]

if you (say) wrap the Al part in thin steel (eg. from a coke can) this can allow some very strong (eg. Nd) magnets to effectively retain themselves in the event of adhesive failure. Add a mechanical restraint too and you can go belt, braces, and another belt.

[Vetus Ossa]

if you (say) wrap the Al part in thin steel (eg. from a coke can) this can allow some very strong (eg. Nd) magnets to effectively retain themselves in the event of adhesive failure. Add a mechanical restraint too and you can go belt, braces, and another belt.

Looking at this as well...
https://www.first4magnets.com/pot-clamp ... ps_1_15045

[531colin]

I suspect the magnet is glued into the retainer, so same problem?

[rjb]

If the centre lock lockring is steel then a neodymium magnet may well stay in situ by the magnetic attraction. On my tandem with it's Tongsheng set up I couldn't get the wheel spoke magnet close enough to the sensor so I placed a couple of small neodymium circular magnets on the existing wheel magnet to reduce the gap. Not lost anything so far after 8000 miles. . BTW the magnet is half way along the spoke so subject to a fair centrifugal force. At speeds up to 35mph. (Downhill of course)

[Vetus Ossa]

I’ll put the wheel and a rotor on the biketomorrow and give it a looking at.

[Brucey]

if you (say) wrap the Al part in thin steel (eg. from a coke can) this can allow some very strong (eg. Nd) magnets to effectively retain themselves in the event of adhesive failure. Add a mechanical restraint too and you can go belt, braces, and another belt.

Looking at this as well...
https://www.first4magnets.com/pot-clamp ... ps_1_15045

the magnet in that link is a ferrite magnet. This type of magnet has been rendered almost obsolete in a number of applications by the advent of super-powerful Nd magnets. A Nd magnet with the same holding power (0.8kg) would be a small fraction of that size and weight.

[Vetus Ossa]

If the centre lock lockring is steel then a neodymium magnet may well stay in situ by the magnetic attraction. On my tandem with it's Tongsheng set up I couldn't get the wheel spoke magnet close enough to the sensor so I placed a couple of small neodymium circular magnets on the existing wheel magnet to reduce the gap. Not lost anything so far after 8000 miles. . BTW the magnet is half way along the spoke so subject to a fair centrifugal force. At speeds up to 35mph. (Downhill of course)

I just tried fitting an old cat eye spoke magnet to roughly where it will need to go and it stuck like the proverbial to a blanket, so will play around with it tomorrow and fit the battery.

[Vetus Ossa]

if you (say) wrap the Al part in thin steel (eg. from a coke can) this can allow some very strong (eg. Nd) magnets to effectively retain themselves in the event of adhesive failure. Add a mechanical restraint too and you can go belt, braces, and another belt.

Looking at this as well...
https://www.first4magnets.com/pot-clamp ... ps_1_15045

the magnet in that link is a ferrite magnet. This type of magnet has been rendered almost obsolete in a number of applications by the advent of super-powerful Nd magnets. A Nd magnet with the same holding power (0.8kg) would be a small fraction of that size and weight.

Noted Brucey.

[tim-b]

Will a magnet fit on the disc?
Here's one that I prepared earlier... It's the magnet for a Garmin sensor, which I thought perfect because it uses double-sided tape backed up with a nylon tie. The only problem is that it won't fit through the gap between the disc and the fork!

I've taken the photo anyway, the blue arrow points to the exposed magnet, the red to a groove for a nylon tie