Alternative for epoxy resin in DIY coils

[Nightryder]

Hello everyone!

I just thought of sharing this idea with y'all to substitute epoxy filling for coils with candles wax!! Three things I'm sure about this wax are: it weighs a lot less than the epoxy, much cheaper, and it's waterproof. So what do you guys think of this? Has anyone tried it out already?

As y'all know epoxy most likely will off-balances IB coils as it solidifies. On the other hand, liquified candles can harden so fast that you can actually hold your coils (RX\TX) somehow with toothpicks or so until it does. Anyway, if you think candles' wax is not a good idea, could it at least be used as a fixing agent? I mean just a little amount to make a balanced coil steady enough for epoxy resin.

And what about Pi's mono coils? Can it be used for them at all? I read many times that epoxy is a bad idea for them, but there weren't explanation why. Frankly speaking, I never dug into the reason\s behind it since there are no beaches around me to worry about, so I just use spray foam instead.

[Carl-NC]

If you're talking about paraffin wax, I would think it's a poor choice. Heavy, low melting point, and poor rigidity. Low-shrinkage epoxy with microballoons works very well. Any coil movement during cure is fixed with a tweak wire. Never heard of a problem with epoxy-potted mono coils, I use them all the time.

[bbsailor]

If you're talking about paraffin wax, I would think it's a poor choice. Heavy, low melting point, and poor rigidity. Low-shrinkage epoxy with microballoons works very well. Any coil movement during cure is fixed with a tweak wire. Never heard of a problem with epoxy-potted mono coils, I used them all the time.

Another thing to consider is the dielectric constant of what you choose to use to secure your coil windings. If you choose something with a lower dielectric constant you will have a coil with less capacitance and a higher self resonant frequency. Less coil seen capacitance will allow a higher damping resistor value, steeper coil current discharge slope and potentially faster coil delay.

This is just a concept to better understand what coil builders can do to move some coil design variables in a particular direction.

Joseph J. Rogowski

[Nightryder]

Hi guys!

Carl-NC,
Thanks for sharing! I did not know that epoxy resins could be different shrinkage wise. I only thought they could be either fast or slow cure types. If you think you can provide me with a brand name that's low-shrinkage, so I can look where to buy, please do.


bbsailor
Thank you for your informative response!

[Carl-NC]

I've had good luck with Epoxy Seal 9000. Also Alumilite microballoons.

[Nightryder]

You actually gave me a better idea than mine in regard to shielding my coils with carbon! My idea is to mix some powdered activated carbon with some wood glue or paint and then apply it to paper strips to tape my coils with. Now you got me thinking; why don't I just mix the powder directly with the epoxy and and save the day? I have to figure out though how I'm going to make room for pure epoxy inbetween as a gap for the shield.



*For anyone reads this, please don't do this unless you know what you're doing as I'm not sure whether it works or not. I'm just experimenting at my own risk

[Carl-NC]

You could wrap the coil(s) with spiral wrap and then with vinyl tape to seal it. Mix up some test epoxy, let it cure, then see if the added carbon actually makes it conductive.

[Aleks85]

Hello, you can not fill the entire sensor with epoxy resin.I pour a thin layer, then put the foam, which does not dissolve with epoxy, then pour the resin again.The sensor turns out to be lightweight and durable.The archive contains photos of the manufacturing stages of the sensor.
https://disk.yandex.ru/d/00xvBCNrHagyaQ

[Nightryder]

Hello Aleks85

In terms of weight reduction, foam is a good option. However, in areas where temperature reaches above 40C or 100F, coil's specifications tend to slightly change due to the elasticity in foam, which allows the copper wire to stretch out a bit, although it is an excellent insulator against heat.

I would make it as an "epoxy sandwich" where the buns are the foam layers. This way the coil does not get much of a "wiggle room" to stretch.

This idea could work, or at least be tolerable only when making a PI mono coil. Not IB coil such that you need it to be balanced and fixed for life.

Thanks for sharing your opinion.

[Aleks85]

I forgot to add that when winding the coils, I also soaked them with epoxy resin and waited a week, during which time they dried well. A week or more passed between the filling stages, the foam only serves as a filler, if everything is filled with epoxy, then the sensor will be very heavy

[Aleks85]

These are my devices for winding coils, mandrels can be made of different diameters.I always impregnate with epoxy resin when winding, this allows me to avoid problems in the future, but this is only my opinion and it has never deceived me.
https://disk.yandex.ru/d/XL92fMLYS_bkZA

[Nightryder]

I have to say that I love your winding machine. Very neat job!!

[pito]

I am using it for a long time

only serves as a filler = or temperature stabilizer

[Nightryder]

Hi Pito,

I just googled this filler. The fact that it is non-shrinking and fast-curing formula makes quite interesting. If it's not too much trouble, could you please give me an idea about its weight compared to epoxy? and is it conductive at all?

The technical datasheet (attached) says it's not waterproof, which is currently no big deal for me, but for future reference and also to see if Aleks85's idea can be applied using it instead of the foam.


Thanks!

[pito]

• Body Filler
  
  Density at 20°C:
  putty 1.85 g/cm³
  hardener 1.15 g/cm³

epoxy
Density Part A - Resin (g/ml) 2.25 Density Part B - Hardener (g/ml) 0.94

1 milliliter (ml) is equal to 1 cubic centimeter (cm³)

says it's not waterproof = wrong, when is used for car repair it is last forever in winter and summer .................
is it conductive at all? = no,
using it instead of the foam = no, foam stay as on picture Post # 13, body filler is replacing epoxy.