Potting neodymium pickups

[Peteus]

So I'm planning on making some neodymium pickups with the neos magnets running down the centre of the bobbins (each side it's humbucking). I was wondering what can I use to pot the pickup due to the temperature limitations of neos around 80C. I have heard of people sealing with epoxy but, I know of very few epoxy systems which don't need heating to properly cure them. Any suggestions would be great

[big_teee]

80C is 176F.
I would pot them the regular way.
The magnets will hold up better than plastic bobbins at those temps.
Most of us try not to pot any hotter than 150F.
T

[Peteus]

I found that my wax won't melt until 100C but I will give it a shot. What wax you using I'm using a blend of paraffin and bees wax.

[mr fab]

I use a blend of paraffin and beeswax and get it to melt at around 80 - 85 degC. it takes a longer time to melt at this temp, so I usually set the initial heat to 100C and after melted reset the temperature to 80 or so and leave to 20 minutes or so to re-stabilise at the lower temperature

I don't believe neos have any issues with temperatures we use to pot; see here:

http://www.ndfeb-info.com/temperature_ratings.aspx

[big_teee]

I thin my wax with Lamp grade pure Paraffin oil. (Kerosene)
I add the oil until it melts at a temp I prefer, and it doesn't get as hard and brittle, as straight paraffin.
Others use mineral oil, and some still use bees wax.
Also I start with Gulf Canning wax, you can buy it at most grocery stores.
Here's a thread that covers most potting questions.
http://music-electronics-forum.com/t31683/
GL,
T

[Chuck H]

I can easily keep a pot of paraffin liquid and soupy at 155F. It's possible that the perception of "melting" and the all the temperature coefficients of the pot, wax and whatever else needs to come up to temperature are only making it seem as if the higher melting point is in order. If you get all your wax melted and the whole system stabilized with the wax at 150F-160F it'll work. No matter the temperature you "melt" at. I use paraffin with a poorly measured Tbsp. of Vaseline to a pound.

EDIT: Looking into it I see that "standard" neo's lose strength above 178F. There are more temperature stable grades available. but I don't know if this applies to what can be had for making pickups. Higher temp neo's probably come at a disproportionate premium. I think the 178F limit should be workable.

[big_teee]

I agree with Chuck.
I use a cooking thermometer, and while the wax is melting it will not get over 155-160f.
Right before it all melts, I turn down the heating elements, and let it idle at 145-155F.
IMO a good thermometer is a must.
T

[Joe Gwinn]

So I'm planning on making some neodymium pickups with the neos magnets running down the centre of the bobbins (each side it's humbucking). I was wondering what can I use to pot the pickup due to the temperature limitations of neos around 80C.

This seems a little low, unless this is a rubber magnet.

Rare-earth magnet - Wikipedia, the free encyclopedia

I have heard of people sealing with epoxy but, I know of very few epoxy systems which don't need heating to properly cure them. Any suggestions would be great

Lots of epoxy potting systems will cure at room temperature. It just takes longer. The high-temp cures are either for speed or for bond strength.

Call up a supplier of potting compounds, and have a talk with the application engineer. Do not use hardware-store epoxy.

[copperheadroads]

I looked that up & 80C /176F is the temp which Neo starts loosing its strength.... huh taken from the K & J link
https://www.kjmagnetics.com/neomaginfo.asp
Demagnetization
Rare Earth magnets have a high resistance to demagnetization, unlike most other types of magnets. They will not lose their magnetization around other magnets or if dropped. They will however, begin to lose strength if they are heated above their maximum operating temperature, which is 176°F (80°C) for standard N grades. They will completely lose their magnetization if heated above their Curie temperature, which is 590°F (310°C) for standard N grades. Some of our magnets are of high temperature material, which can withstand higher temperatures without losing strength.

[Joe Gwinn]

I looked that up & 80C /176F is the temp which Neo starts loosing its strength.... huh taken from the K & J link
https://www.kjmagnetics.com/neomaginfo.asp
Demagnetization
Rare Earth magnets have a high resistance to demagnetization, unlike most other types of magnets. They will not lose their magnetization around other magnets or if dropped. They will however, begin to lose strength if they are heated above their maximum operating temperature, which is 176°F (80°C) for standard N grades. They will completely lose their magnetization if heated above their Curie temperature, which is 590°F (310°C) for standard N grades. Some of our magnets are of high temperature material, which can withstand higher temperatures without losing strength.

Hmm. Other magnet types don't lose much until one is close to the Curie temperature.

Anyway, there are neo magnet grades with operating temperatures up to 200 C, so it ought to be possible to find one that can be wax potted without loss.

https://www.kjmagnetics.com/specs.asp

[big_teee]

A little demagnetization in a NEO, in a Pickup, may not be a bad thing.
It might warm the tone up a bit?
T

[salvarsan]

Curie (demagnetization) point on Neo mags is ~300C so 100C v.hot wax shouldn't be problem.

Thermal expansion coefficient is also low, ~5x10E-6 % per degree C so it probably won't crack either.

To be cautious, throw a single magnet in the wax pot and see what happens.

Should be fine.

[Peteus]

I looked that up & 80C /176F is the temp which Neo starts loosing its strength.... huh taken from the K & J link
https://www.kjmagnetics.com/neomaginfo.asp
Demagnetization
Rare Earth magnets have a high resistance to demagnetization, unlike most other types of magnets. They will not lose their magnetization around other magnets or if dropped. They will however, begin to lose strength if they are heated above their maximum operating temperature, which is 176°F (80°C) for standard N grades. They will completely lose their magnetization if heated above their Curie temperature, which is 590°F (310°C) for standard N grades. Some of our magnets are of high temperature material, which can withstand higher temperatures without losing strength.

Looks like I had better aim for keep my wax as cool as possible. Give it a shot if it doesn't work try again

[mr fab]

I make some pickups with neo magnets and have noticed no appreciable loss in volume or change in tone after potting, as I said I keep my pot at around 80 degrees C. maybe I am lucky, or maybe I don't leave them in long enough to demagnetise them to the point where it makes a difference.

I guess I should try to lower temp a little for neos

paraffin melt at 37 deg C and beeswax at 64 deg C so I don't think there would be a problem keeping a mixture of the two at say, mid to high 60's

[Peter Naglitsch]

If temperature is an issue, you can always try thin CA clue. It will penetrate the coil and cure well if you do it like every thousand turn and give it a light dusting of accelerator (OK, that need to be tested but it should work) I have done it with my first pickups (without the accelerator and only after a complete coil was done). It creates a rock solid coil and it didn't mess with insulation on poly wire.